Make your own free website on
cruz lectures
bio course outline
Home | panspermia | activity one-gens102 | physics lectures | lec1-phylum chordata | lec2-vertebrate skeletal systems | chem course outline | physics course outline | bio3 course outline | bio course outline | earth science lecture one | for my rizal students | la salle syllabus-natsci2 | Contact Me | Calendar of Events | Students Page | Links | Respiratory System | endocrine system | cell division | cells | chemistry of living organisms | characteristics of living organisms | the unity and diversity of life | kingdoms of life | genetics | muscular system | Circulatory System | Digestive system | Integumentary System | Human Reproductive System | Skeletal System | Nervous System | chem rxns | chem bonds | gases | states of matter | periodic table of elements

Enter subhead content here

Course Module in NatSci2

Biological Science

Prepared by: Ms. Maria Eliza P. Cruz

Course Description:

      This is a course that covers fundamental concepts and theories of the life sciences. Topics include cell morphology and physiology, metabolism, genetics, evolution, ecology, and reproduction. Enrichment activities and discussions will reinforce and enhance understanding of lecture topics. Organisms of all five kingdoms will be studied, but emphasis will be placed on plants and animals.

Course Objectives:

At the end of the term, the student should be able to:

  1. Enhance his understanding of cellular structure and function as well as the chemistry and homeostatic mechanisms of cell metabolism.
  2. Develop an understanding of life at all levels of organization.
  3. Acquire an understanding of the interdependence that characterizes natural communities and evolutionary relationships that unite all living things.
  4. Be familiar with current developments in the life sciences by reading and reporting on articles that are of relevance to the field.

Course Outline:

    1. Introduction to Biological Science
      1. Etymology
      2. Definitions
      3. History
      4. Related Disciplines and Approaches
      5. Significance of studying Biology
      6. Scientific Method
    1. Characteristics of Life
      1. Organization.
      2. Metabolism
      3. Irritability or Response to Stimuli
      4. Reproduction
      5. Adaptation
    1. Chemical Basis of Life
      1. Some Basic Chemistry Facts
      2. Organic Compounds
      3. Inorganic Compounds
      4. Vitamins and Minerals
      5. Water
    1. Cellular Basis of Life
      1. Parts and Functions of Cells
      2. Differences between plant and animal Cells
      3. Cellular reproduction (Mitosis and Meiosis)
    1. Classification and Nomenclature
      1. History of Taxonomy
      2. Kingdom Monera
      3. Kingdom Protista
      4. Kingdom Fungi
      5. Kingdom Plantae
      6. Kingdom Animalia
      7. Viruses
    1. Organ Systems (emphasis on man)
      1. Integumentary System
      2. Endocrine System
      3. Musculo-skeletal System
      4. Digestive System
      5. Respiratory System
      6. Circulatory System
      7. Excretory System
      8. Reproductive System
      9. Nervous System
    1. Introduction to Evolution
      1. History of Evolution
      2. Evolution Theories and Principles
    1. Introduction to Ecology
      1. History of Ecology and Environmental Studies
      2. Ecology in the Philippine setting
    1. Medicine, Bio Issues and Recent Medical Breakthroughs
      1. History of Medicine
      2. Genetic Engineering
      3. Human Genome Project
      4. Biological Warfare

Course Content:

I. Introduction to Biological Science


  1. Identify the several definitions of biology;
  2. Compare and contrast the varied fields of study that are related to biological science.
  3. Trace the development and progress of biology in the world;
  4. Explain how scientists use the scientific method, how he generate observations, formulate and test hypothesis and make generalizations;
  5. Appreciate the value of biological study in your life.


   The word biology is formed by combining the Greek βίος (bios), meaning "life", and the suffix '-logy', meaning "science of", "knowledge of", "study of", based on the Greek verb λεγειν, 'legein' = "to select", "to gather" (cf. the noun λόγος, 'logos' = "word"). The term "biology" in its modern sense appears to have been introduced independently by :

   The word itself appears in the title of Volume 3 of Michael Christoph Hanov's Philosophiae naturalis sive physicae dogmaticae: Geologia, biologia, phytologia generalis et dendrologia, published in 1766.


  1. science of life
  2. study of structures, functions and relationships of living things or organisms
  3. realm of life
  4. a science that is linked to other sciences
  5. all processes associated with living organisms are the subject matter
  6. study of living things
  7. trascends such sciences as chemistry, physics, mathematics and geology
  8. field where all the sciences meet the social domains and the humanities such as economics, politics and environmental ethics due to man’s interaction with his environment
  9. draws on chemistry and physics for its foundation and applies these basic physical laws to living things
  10. begins with a search for answers to questions about our world


  • As early as between 3000 and 2000 BC, major civilizations of China, Egypt, and India had knowledge of certain biological processes, primarily with the practical aspects of agriculture and medicine.
  • During the Renaissance era (1300-1650 AD), serious study of anatomy emerged through the efforts of Leonardo da Vinci and Andreas Vesalius
  • In 1750’s, a major advance in Biology was the publication of Carolus Linnaeus’ classification scheme for organisms
  • In 1859, Charles Darwin published his theory of evolution in a book entitled “On the Origin of Species by Means of Natural Selection”.
  • In 1865, Gregor Mendel published evidence that garden peas inherited characteristics from their parents (introducing fundamental genetic principles)
  • Mapping, or more properly, assignment of human genes to locations on various chromosomes proceeded when Mohr noted in 1951 that a gene for a blood protein factor, Lutheran, in some families appeared to be associated with another gene controlling salivary secretion of a red blood cell protein. In other families it was not associated with the secretion gene. Thus "secretor" and Lutheran appeared linked and presumably close together on the same chromosome. Both of these are now assigned to Chromosome 19, physically corroborating the earlier family linkage studies of Mohr.
  • The major contribution of Watson and Crick came in 1953, the description of the molecular structure of the genetic material, the double helix.
  • Tijo and Levan in 1956 found human beings had 46 and not 48 chromosomes, and several years later, Lejeune noted a 47th chromosome in individuals with Down syndrome.
  • By 1995, the entire 1,830,137 base pairs of the bacterium, Haemophilus influenzae , had been sequenced and its genes mapped by a large team headed by J. Craig Venter at the Institute for Genomic Research (TIGR) in Gaithersburg, MD (Venter, 1995). It has served as a superb model for how an animal's genome programs itself from a single fertilized cell into a multi-celled adult.

Timeline of Biology

Before 1600

  • c. 520 B.C. - Alcmaeon of Croton distinguished veins from arteries and discovered the optic nerve.
  • c. 500 B.C.1 - Sushruta - wrote Sushruta Samhita describing over 120 surgical instruments, 300 surgical procedures and classified human surgery in 8 categories. Performed cosmetic surgery.
  • c. 500 B.C. - Xenophanes examined fossils and speculated on the evolution of life.
  • c. 350 B.C. - Aristotle attempted a comprehensive classification of animals. His written works include Historia Animalium, a general biology of animals, De Partibus Animalium, a comparative anatomy and physiology of animals, and De Generatione Animalium, on developmental biology.
  • c. 320 BC - Theophrastos (or Theophrastus) begins the systematic study of botany.
  • c. 300 B.C. - Herophilos dissected the human body.
  • c. 300 B.C. - Diocles wrote the first known anatomy book and was the first to use the term anatomy.
  • c. 50-70 - Historia Naturalis by Pliny the Elder (Gaius Plinius Secundus) was published in 37 volumes.
  • 130-200 - Claudius Galen wrote numerous treatises on human anatomy.
  • c. 1010 - Avicenna (Ibn Sina or Abu Ali al Hussein ibn Abdallah) published his Canon of Medicine (Kitab al-Qanun fi al-tibb).






** Source:

Related Disciplines and Approaches

Biological Sciences (life sciences)

  1. Zoology: study of animals
  2. Botany: study of plants
  3. Biological Psychology: use of biology in psychological studies
  4. Biomathematics: use of math in the study of living things
  5. Biophysics: use of physics in the study of living things
  6. Physiology: Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms.
  7. Biochemistry: use of chemistry in the study of living things
  8. Anatomy: study of internal structures of living things
  9. Pathology: study of diseases (particularly animal diseases)
  10. Phytopathology: study of plant diseases
  11. Taxonomy: study of systematic classification
  12. Ecology: study of man’s interaction with his environment
  13. Genetics: study of heredity
  14. Microbiology: study of microorganisms
  15. Bacteriology: study of bacteria
  16. Virology: study of viruses
  17. Mammalogy: study of mammals
  18. Ornithology: study of birds
  19. Herpetology: study of reptiles and amphibians
  20. Ichthyology: study of fishes
  21. Entomology: study of insects
  22. Helminthology: study of worms
  23. Protozoology: study of unicellular organisms
  24. Mycology: study of fungi
  25. Phycology/ Algology: study of algae
  26. Lichenology: study of lichens
  27. Biosociology: the study of the evolution of social forms and the development of social behavior in terms analogous to or correlated with biological studies.
  28. Parasitology: study of parasites
  29. Epidemiology: study of epidemics
  30. Gnotobiotics: study of organisms in a germ-free environment
  31. Biogeography: study of geographical distribution of living things
  32. Phytogeography: study of the land and its plants
  33. Zoogeography: study of the land and its animals
  34. Biological limnology: the scientific study of bodies of fresh water, as lakes and ponds, with reference to their physical, geographical, biological, and other features.
  35. Embryology: study of the formation and development of living things from fertilization to birth as independent organisms
  36. Pharmacology: study of the actions of chemicals on and in living things
  37. Endocrinology: study of hormones and their actions
  38. Cytology: study of cells
  39. Histology: study of tissues
  40. Bryology: study of mosses
  41. Malacology: study of mollusks

Physical Sciences (concerned mainly with the nature of the universe)

  1. Astronomy: the science that deals with the material universe beyond the earth's atmosphere
  2. Chemistry: the science that deals with the composition and properties of substances and various elementary forms of matter
  3. Geology: science of the earth's history, composition, and structure, and the associated processes.
  4. Meteorology: branch of science that deals with the atmosphere of a planet, particularly that of the earth, the most important application of which is the analysis and prediction of weather.
  5. Climatology: the science that deals with the phenomena of climates or climatic conditions
  6. Physics: branch of science traditionally defined as the study of matter, energy, and the relation between them

Social Sciences (concerned with the study of man and society)

  1. Anthropology: classification and analysis of humans and their society, descriptively, culturally, historically, and physically

2. Geography: the science of place, i.e., the study of the surface of the earth, the location and distribution of its physical and cultural features, the aerial patterns or places that they form, and the interrelation of these features as they affect humans

3. Physiogeography: the systematic description of nature in general.

4. Oceanography: the systematic description of sea animals in oceans.

  1. Biogeography: the systematic description of animals abundant in the air
  2. Linguistics of Philology: systematic study of similarities and differences of languages
  3. Political Science: study of the nature and existence of governments

Significance of studying Biology

      A good grasp of the biological perspective and the development of appreciation on how biological knowledge works on one’s life are important elements of good citizenship especially in an era when issues on environmental problems, health conditions and biotechnology are more crucial than ever. Let us identify some of the usefulness of biology in your life.

  1. You possess all the manifestations of being alive and of living with other forms. A study of biology enables you to understand and value your place in the earth’s environment as well as your relationship with other life forms.
  2. As a conscious being, you are confronted with making choices on how to sustain your own life and health. Biology helps you understand the basic mechanisms of bodily processes; hence, it enables you to make choices and decisions for yourself as a food and medical consumer, as well as energy user.
  3. You live in an era of critical issues like abortion, human life preservation over population explosion, drug addiction and environmental degradation. Your knowledge of biology will enable you to form learned opinions and scientifically guided decisions and actions on such issues.
  4. You live in an era of escalating dimensions of science and technology. Knowledge of significant developments in biology and biotechnology will eliminate confusing and threatening views bothering your mind and help you develop positive approaches.
  5. A solid foundation in biological science is necessity for your future life as a life partner and parent, as well as a professional in any field. A scientifically literate person progresses in his practices, beliefs and attitudes in life. (Hafalla, p.13)

Scientific Method

Event Activity Example
Observation Recognize something has happened and that it occurs repeatedly. (empirical evidence is gained from experience or observation) Students in a classroom are stricken with a disease that causes red rashes on their faces. This same situation has been described in several schools in your region. Skin cultures taken from the students indicate that there are some unusual bacteria present.
Question formulation Write many different kinds of questions about the observation, evaluate the questions and keep the ones that will be answerable. Is the disease psychosomatic? (i.e., is this a case of hysteria in which there is nothing organically wrong?)

Is the rash caused by a bacterium?

Is the disease caused by a virus?

Exploration of alternative resources Go to the library to obtain information about this observation. Also, talk to others who are interested in the same problem. Visits to other researchers or communication via letter, fax or computer will help determine if your question is a good one or if others have already explored the topic. A search through the medical literature reveals that physicians who used antibiotic X in similar circumstances reported cures, even though they never found a bacterium to be present. Attend scientific meetings where this disease outbreak will be discussed. Contact scientists who are reported to be interested in the same problem.
Hypothesis formation Pose a possible answer to your question. Be sure that it is testable and that it accounts for all the known information. Recognize that your hypothesis may be wrong. Antibiotics do not usually affect viruses. Further, the disease has been reported elsewhere, which tends to rule out psychosomatic disease. Therefore, your hypothesis is that the disease is caused by a bacterium and that antibiotic X can cure the disease by controlling the rate of growth of the bacterial population.
Experimentation Set up an experiment that will allow you to test your hypothesis using a control group and an experimental group. Be sure to collect and analyze the data carefully. To test the cause-and-effect relationship between administering antibiotic X and curing the illness, you set up 2 groups. A control group will be given a placebo (a pill with no active ingredient). The experimental group will receive pills containing antibiotic X. The pills will look identical and will be coded so that neither the person receiving the pill nor the person administering the pill will know which individuals receive the medication and which receive the placebo. This is called a “double-blind” test. After five days, you collect the data and find that 90% of those receiving antibiotic X no longer have the rash. By contrast, only 10% of those receiving the placebo have recovered. You conclude that the disease is not psychosomatic and that a bacterium is probably the cause. You publish your results.
Theory formation Repeat the experiment and share the information with others over a long period of time. Your results support the generally held theory that many kinds of diseases are caused by microorganisms.

This generalization is called the germ theory of disease.

Law formation If your findings are seen to fit with many other major blocks of information that tie together many different kinds of scientific information, they will be recognized by the scientific community as being consistent with current scientific laws. If there is a major new finding, a new law may be formulated. Your experimental results are consistent with the biogenetic law that states that all living things come from previously living things. Your results strongly suggest that the disease was caused by the multiplication of certain bacteria, and that the antibiotic stopped their multiplication.

(Ross, p.4)

Healthy Living

tips, facts, news you can use

Cell phone “shields” useless, says US agency

      Not only do some of the commercially available shields that claim to protect users from cells phone radiation not work as promised, they in fact, may cause the phone to emit even more energy. The US Federal Trade Commission (FTC) has filed charges against the makers of two such devices, saying the only “shield” at work is one of misrepresentation to consumers about the products’ effectiveness, the Associated Press reports. The two companies named in the lawsuits are Stock Value 1 Inc., of Boca Raton, Florida and Comstar Communications Inc., of West Sacramento, California. The FTC says both companies made false claims about scientific tests about their products, and it hopes to close both down once customers are given refunds. In fact, says the FTC, there are no known products that reduce cell phone radiation exposure to users. The coin- sized devices are designed to cover phone earpieces and were sold for about $20 each.

            Source: Health Today, June 2002 Edition

How much have you learned?

Enrichment activities, exercises to keep you on your toes…


  1. Cite 3 definitions of biological science. Why is it significant to include it in your curriculum?
  2. Analyze the timeline of biology presented and discussed previously. What do you think are the five (5) major inventions or discoveries of all time? Prove your point.
  3. Name five (5) approaches/disciplines that are related to biology and make connections why you consider them as related to biology.

Activity: Scientific Investigation

Concept: The Power of Observing and Hypothesizing


   1. Recognize the steps in scientific investigations

  1. Formulate a problem and hypothesis for scientific investigation
  2. Draw procedures applicable to the problem and the hypothesis.


  1. Magazines
  2. pair of scissors
  3. glue
  4. bond paper/s


  1. Form groups of five students and arrange chairs in a circular fashion to facilitate the discussion.
  2. Scan the pages of the magazine. Choose a picture on environmental changes or technological trends and the like that attracts you most.
  3. Cut and paste the picture/s on the clean bond paper.
  4. List some observed situations and scenes. (Note: record observations but not perceptions)
  5. Analyze the situations or scenes shown in the picture.
  6. Formulate scientific problem that can be tested based on the observed situations.
  7. The following activities can help you in the formulation of the problem:
    1. Brainstorming of ideas and topic related to the situations;
    2. Listing down some related situations that are actually happening in life;
    3. Narrowing the problems into specific ones.
  8. Formulate a hypothesis that will serve as the temporary answer or solution to the problem.
  9. Conceptualize the procedure to determine if your hypothesis can be tested or not.
  10. Make generalization on how problems and hypotheses are formulated.
  11. Submit output 15-20 minutes before the end of the class hour for critiquing and evaluation.

II. Characteristics of Life


  1. Discuss the attributes of manifestations of the living state;
  2. Infer what life is from the manifestations of the living state.
  3. Analyze some significant biological principles and concepts, which form basic conclusions about living things.


      Living things are made of cells, which are assembled into interrelated system for performing the life processes. They rearrange and combine the chemical elements for their need. Non-living things on the other hand cannot recombine materials and their structure depends on chemicals present and mode of formation (Ditan, p.1 )


      Metabolic processes involve the total of all chemical reactions and associated energy changes that take place within an organism. This set of reactions is often simply referred to as metabolism (=Greek metaballein, to turn about, change, alter). There are three essential aspects of metabolism: (1) nutrient uptake (2) nutrient processing, and (3) waste elimination. (Ross, p.11).

Two phases of metabolism:

    1. anabolism: constructive or building up phase
    2. Catabolism- destructive or breaking down phase.

Irritability or Response to Stimuli

      Irritability is an excessive response to stimuli. Irritability takes many forms, from the contraction of a unicellular organism when touched to complex reactions involving all the senses of higher animals. In plants response is usually different from that found in animals but is nonetheless present. The term irritability is both used for the physiological reaction to stimuli and for the pathological, abnormal or excessive sensitivity to stimuli.


      Biological reproduction is the biological process by which new individual organisms are produced. Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction by an antecedent. The known methods of reproduction are broadly grouped into two main types: sexual and asexual reproduction.

      In asexual reproduction, an individual can reproduce without involvement with another individual of that species. The division of a bacterial cell into two daughter cells is an example of asexual reproduction. Asexual reproduction is not, however, limited to single-celled organisms. Most plants have the ability to reproduce asexually.

      Sexual reproduction requires the involvement of two individuals, typically one of each sex. Normal human reproduction is a common example of sexual reproduction. In general, more-complex organisms reproduce sexually while simpler, usually unicellular, organisms reproduce asexually.


      A biological adaptation is an anatomical structure, physiological process or behavioral trait of an organism that has evolved over a period of time by the process of natural selection such that it increases the expected long-term reproductive success of the organism. The term adaptation is also sometimes used as a synonym for natural selection, but most biologists discourage this usage.

      Adaptation can be viewed as taking place over geological time, or within the lifetime of one individual or a group.

   Organisms that are adapted to their environment are able to:

  • get air, water, food and nutrients
  • cope with physical conditions such as temperature, light and heat
  • defend themselves from their natural enemies
  • reproduce
  • respond to changes around them

   Adaptations are the way living organisms cope with environmental stresses and pressures. One common form of physical Adaptation involves acclimatization. Acclimatization allows the organism to be able to exist in its new environment. Adaptation can be structural or behavioural. Structural adaptations are special body parts of an organism that help it to survive in its natural habitat, for example, its skin color, shape and body covering. Behavioral adaptations are special ways a particular organism behaves to survive in its natural habitat. Organisms that are not suitably adapted to their environment will either have to move out of the habitat or die out. The term die out in the context of adaptation simply means a specieces' death rate excedes its' birth rate for a long enough period for the species to disappear.

   It is possible for an adaptation to be poorly selected or become less appropriate or even become on balance more of a dysfunction than a positive adaptation over time; this is known as maladaptation and can apply to both humans and animals in such fields as biology, psychology (where it applies to behaviors and other learned survival mechanisms) and other fields.

   There is a great difference between adaptation and acclimation. Adaptation occurs over many generations; it is generally a slow process caused by natural selection. Acclimation occurs generally in a single lifetime and copes with issues that are less threatening. For example, if a human was to move to a higher altitude, respiration and physical exertion would become a problem, but after spending a duration of time in high altitude conditions one will soon acclimate to the pressure and function and no longer notice the change.

Healthy Living

tips, facts, news you can use

Your Faith Will Heal You…

      Participants of “Spirituality and Healing in Medicine”, a seminar held at Harvard University six years ago, declared that “prayer… could have astounding therapeutic effects.”

      “I am not a religious person,” said Dr. Herbert Benson, a Harvard Medical School cardiologist and founder of the Mind-Body Institute at Beth Israel Deaconess Hospital. But study after study convinced him that prayer was good for his patients. His research showed that:

  • Two 10-minute prayer sessions per day could lower the heart rate, slow down breathing, and stabilize brain wave activity
  • Prayer could avert the need for invasive surgery and substantially reduce the need for visits to a doctor.
  • Thirty-five percent of couples with fertility problems with in six months of beginning prayer sessions.

      Source: Health Today, June 2002 Edition

      Lydia Strohl and Elena Serocki, citing results of hundreds of studies, revealed that people with strong religious faiths and prayed regularly:

  • have longer lives
  • have fewer health problems
  • have three times better chance of surviving open-heart surgery
  • are 70% less prone to coronary heart disease
  • have lower rates of depression and anxiety

   Source: “The Healing Power of Faith”, Readers Digest September 2002

How much have you learned?

Enrichment activities, exercises to keep you on your toes…


  1. Formulate a concept map indicating all the manifestations of the living state how these are interrelated and what principles govern them.
  2. How can you operationally define “life”?
  3. Discuss the differences of the form and structure between plants and animals.

Make connections:

      Life is a fragile state totally dependent on its environment. How committed are you in conserving the Earth’s resources that sustain life?

III. Chemical Basis of Life


  1. Define basic terms in the study of the chemical basis of the living state.
  2. Compare and contrast organic from inorganic compounds.
  3. Discuss the vast uses and potentials of vitamins, minerals and water.

Some Basic Chemistry Facts

Chemistry: science that is concerned with matter, its composition, its properties, the changes in composition that it will undergo, its relationship to energy, and the laws, principles, theories, and concepts that describe, interpret, and predict its behavior and basic nature

Matter: anything that has mass and occupies space

Composition: refers to what matter is made of

Properties: characteristics that identify substances

Physical properties: can be observed or measured without changing the composition of the substance

Chemical properties: can be observed or measured only when it undergoes a change in composition

Chemical changes: changes in the composition of substances

Chemical reaction: the process of chemical change

Fact: a piece of information about nature that is based on observation, often a measurement that can be repeated

Law: a general statement that sums up a number of facts

Organic Compounds: compounds that contain carbon (and usually hydrogen and oxygen)

Inorganic Compounds: compounds that do not contain carbon (except carbon dioxide and carbon monoxide)

Vitamins: organic nutrients that are necessary in small amounts for normal metabolism and good health

Water: from the Old English waeter; c.f German "Wasser", from PIE *wod-or, "water"), in its pure form, is a tasteless, odorless substance that is essential to all known forms of life and is known also as the most universal solvent. It appears colorless to the naked eye in small quantities, though it can be seen to be blue in large quantities or with scientific instruments

Organic Compounds

a. Carbohydrates

b. Vitamins

    1. Nucleic Acids
    2. Lipids

a. Carbohydrates: group of chemicals that include sugars, starches and cellulose.

     Carbohydrates are the main energy source for the human body. Chemically, carbohydrates are organic molecules in which carbon, hydrogen and oxygen bond together in the ratio: Cx(H2O)y where x and y are whole numbers that differ depending on the specific carbohydrate to which we are referring.  Animals (including humans) break down carbohydrates during the process of metabolism to release energy.  For example, the chemical metabolism of the sugar glucose is shown below:

C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy

     Animals obtain carbohydrates by eating foods that contain them, for example potatoes, rice, breads, etc.  These carbohydrates are manufactured by plants during the process of photosynthesis.  Plants harvest energy from sunlight to run the reaction described above in reverse:

6 CO2 + 6 H2O + energy (from sunlight) C6H12O6 + 6 O2  

b. Vitamins

      Vitamins are nutrients you must get from food.

      You need only small amounts (that's why they are often referred to as micronutrients) because the body uses them without breaking them down, as happens to carbohydrates and other macronutrients. So far, 13 compounds have been classified as vitamins. Vitamins A, D, E, and K, the four fat-soluble vitamins, tend to accumulate in the body. Vitamin C and the eight B vitamins-biotin, folate, niacin, pantothenic acid, riboflavin, thiamin, vitamin B6, and vitamin B12-dissolve in water, so excess amounts are excreted.

      The "letter" vitamins sometimes go by different names. These include:

Vitamin A = retinol, retinaldehyde, retinoic acid 
Vitamin B1 = thiamin 
Vitamin B2 = riboflavin 
Vitamin B6 = pyridoxine, pyridoxal, pyridoxamine 
Vitamin B12 = cobalamin 
Vitamin C = ascorbic acid 
Vitamin D = calciferol 
Vitamin E = tocopherol, tocotrienol 
Vitamin K = phylloquinone

Vitamin A:

Vitamin A does much more than help you see in the dark. It stimulates the production and activity of white blood cells, takes part in remodeling bone, helps maintain the health of endothelial cells (those lining the body's interior surfaces), and regulates cell growth and division. This latter role had researchers exploring for years whether insufficient vitamin A caused cancer. Several studies have dashed this hypothesis,(1) as have randomized trials of supplements containing beta carotene, a precursor of vitamin A.

Although it's relatively easy to get too little vitamin A, it's also easy to get too much. Intake of up to 10,000 IU, twice the current recommended daily level, is thought to be safe. However, there is some evidence that this much preformed vitamin A might increase the risk of hip fracture (2) or some birth defects.(3)

Optimal Intake: The current recommended intake of vitamin A is 5,000 IU for men and 4,000 IU for women. Many breakfast cereals, juices, dairy products, and other foods are fortified with vitamin A. Many fruits and vegetables, and some supplements, also contain beta-carotene and other vitamin A precursors, which the body can turn into vitamin A. In contrast to preformed vitamin A, beta-carotene is not toxic even at high levels of intake. The body can form vitamin A from beta-carotene as needed, and there is no need to monitor intake levels, as there is with preformed vitamin A. Therefore, it is preferable to choose a vitamin supplement that has all or the vast majority of its vitamin A in the form of beta-carotene. Another reason to avoid too much preformed vitamin A is that it may interfere with the beneficial actions of vitamin D.

The 3 Bs: Vitamin B6, Vitamin B12, and Folic Acid

One of the advances that changed the way we look at vitamins was the discovery that too little folic acid, one of the eight B vitamins, is linked to birth defects such as spina bifida and anencephaly. Fifty years ago, no one knew what caused these birth defects, which occur when the early development of tissues that eventually become the spinal cord, the tissues that surround it, or the brain goes awry. Twenty five years ago, British researchers found that mothers of children with spina bifida had low vitamin levels.(4) Eventually, two large trials in which women were randomly assigned to take folic acid or a placebo showed that getting too little folic acid increased a woman's chances of having a baby with spina bifida or anencephaly and that getting enough folic acid could prevent these birth defects.(5,6)

Enough folic acid, at least 400 micrograms a day, isn't always easy to get from food. That's why women of childbearing age are urged to take extra folic acid. It's also why the US Food and Drug Administration now requires that folic acid be added to most enriched breads, flour, cornmeal, pastas, rice, and other grain products, along with the iron and other micronutrients that have been added for years.(7)

The other exciting discovery about folic acid and two other B vitamins is that they may help fight heart disease and some types of cancer. It's too early to tell if there's merely an association between increased intake of folic acid and other B vitamins and heart disease or cancer, or if high intakes prevent these chronic diseases.

B Vitamins and Heart Disease

In 1968, a Boston pathologist investigaed the deaths of two children from massive strokes. Both had inherited conditions that caused them to have high levels of a protein breakdown product called homocysteine in their blood, and both had arteries as clogged with cholesterol as those of a 65-year-old fast food addict.(8) Putting one and one together, he hypothesized that high levels of homocysteine contribute to the artery-clogging process of atherosclerosis. Since then, some-but not all-studies have linked high levels of this breakdown product, called homocysteine, with increased risks of heart disease and stroke.(9,10)

Folic acid, vitamin B6, and vitamin B12 play key roles in recycling homocysteine into methionine, one of the 20 or so building blocks from which the body builds new proteins. Without enough folic acid, vitamin B6, and vitamin B12, this recycling process becomes inefficient and homocysteine levels increase. Several observational studies show that high levels of homocysteine are associated with increased risks of heart disease and stroke. Increasing intake of folic acid, vitamin B6, and vitamin B12 decreases homocysteine levels. And some observational studies show lower risks of cardiovascular disease among people with higher intakes of folic acid, those who use multivitamin supplements, or those with higher levels of serum folate (the form of folic acid found in the body). However, other prospective studies show little or no association between homocysteine and cardiovascular disease.

The first large trial of homocysteine to be completed ended with negative results. In the Vitamin Intervention for Stroke Prevention trial, 3680 adults who had had nondisabling strokes took a pill containing high doses of vitamins B6, B12, and folic acid or one containing low doses of these three B vitamins. After two years, second strokes, heart attacks and other coronary heart disease events, and deaths were the same in the two groups. However, in that trial, high levels of homocysteine at baseline were associated with higher risk of cardiovascular disease. Other ongoing randomized trials, such as the Women's Antioxidant Cardiovascular Study (11) and the Vitamin Intervention in Stroke Prevention Study (12) should yield more definitive answers regarding homocysteine, B vitamins, and cardiovascular risk.

Folic Acid and Cancer

In addition to recycling homocysteine, folate plays a key role in building DNA, the complex compound that forms our genetic blueprint. Observational studies show that people who get higher than average amounts of folic acid from their diets or supplements have lower risks of colon cancer(13) and breast cancer.(14) This could be especially important for those who drink alcohol, since alcohol blocks the absorption of folic acid and inactivates circulating folate. An interesting observation from the Nurses' Health Study is that high intake of folic acid blunts the increased risk of breast cancer seen among women who have more than one alcoholic drink a day.(14)

Optimal Intake: The definition of a healthy daily intake of B vitamins isn't set in stone, and is likely to change over the next few years as data from ongoing randomized trials are evaluated. Because only a fraction of U.S. adults currently get the recommended daily intake of B vitamins by diet alone, use of a multivitamin supplement will become increasingly important.

Folic Acid: The current recommended intake for folic acid is 400 micrograms per day. There are many excellent sources of folic acid, including prepared breakfast cereals, beans, and fortified grains.

Vitamin B6: A healthy diet should include 1.3 to 1.7 milligrams of vitamin B6. Higher doses have been tested as a treatment for conditions ranging from premenstrual syndrome to attention deficit disorder and carpal tunnel syndrome. To date, there is little evidence that it works.

Vitamin B12: The current recommended intake for vitamin B12 is 6 micrograms per day. Vitamin B12 deficiency can be caused by pernicious anemia, due to a lack of "intrinsic factor" (a substance secreted by gastric cells that binds to vitamin B12 and enables its absorption). A more common cause of deficiency is often diagnosed in older people who have difficulty absorbing vitamin B12 from unfortified foods; such people can typically absorb vitamin B12 from fortified foods or supplements, however, providing yet another reason to take a multivitamin. Symptoms of B12 deficiency include memory loss, disorientation, hallucinations, and tingling in the arms and legs. Some people diagnosed with dementia or Alzheimer's disease are actually suffering from the more reversible vitamin B12 deficiency.

Vitamin C: Vitamin C has been in the public eye for a long time. Even before its discovery in 1932, nutrition experts recognized that something in citrus fruits could prevent scurvy, a disease that killed as many as 2 million sailors between 1500 and 1800.(15) More recently, Nobel laureate Linus Pauling promoted daily megadoses of vitamin C (the amount in 12 to 24 oranges) as a way to prevent colds and protect the body from other chronic diseases.

There's no question that vitamin C plays a role in controlling infections. It's also a powerful antioxidant that can neutralize harmful free radicals, and it helps make collagen, a tissue needed for healthy bones, teeth, gums, and blood vessels.(16) The question is, do you need lots of vitamin C to keep you healthy?

No. Vitamin C's cold-fighting potential certainly hasn't panned out. Small trials suggest that the amount of vitamin C in a typical multivitamin taken at the start of a cold might ease symptoms, but there's no evidence that megadoses make a difference, or that they prevent colds.(17) Studies of vitamin C and heart disease, cancer, and eye diseases such as cataract and macular degeneration also show no clear patterns.

Optimal Intake: The current recommended dietary intake for vitamin C is 90 mg for men and 75 mg for women (add an extra 35 mg for smokers). There's no good evidence that megadoses of vitamin C improve health. As the evidence continues to unfold, 200 to 300 mg of vitamin C a day appears to be a good target. This is easy to hit with a good diet and a standard multivitamin. Excellent food sources of vitamin C are citrus fruits or citrus juices, berries, green and red peppers, tomatoes, broccoli, and spinach. Many breakfast cereals are also fortified with vitamin C.

Vitamin D: If you live north of the line connecting San Francisco to Philadelphia, odds are you don't get enough vitamin D. The same holds true if you don't, or can't, get outside for at least a 15-minute daily walk in the sun. African-Americans and others with dark skin tend to have much lower levels of vitamin D, due to less formation of the vitamin from the action of sunlight on skin. A study of people admitted to a Boston hospital, for example, showed that 57% were deficient in vitamin D.(18)

Vitamin D helps ensure that the body absorbs and retains calcium and phosphorus, both critical for building bone. Laboratory studies also show that vitamin D keeps cancer cells from growing and dividing.

Some preliminary studies indicate that insufficient intake of vitamin D is associated with an increased risk of fractures, and that vitamin D supplementation may prevent them.(19) It may also help prevent falls, a common problem that leads to substantial disability and death in older people.(20) Other early studies suggest an association between low vitamin D intake and increased risks of prostate, breast, colon, and other cancers.(21)

Optimal Intake: The current recommended intake of vitamin D is 5 micrograms up to age 50, 10 micrograms between the ages of 51 and 70, and 15 micrograms after age 70. Optimal intakes are higher, though, with 25 micrograms (1000 IU) recommended for those over age 2. Very few foods naturally contain vitamin D. Good sources include dairy products and breakfast cereals (which are fortified with vitamin D), and fatty fish such as salmon and tuna. For most people, the best way to get the recommended daily intake is by taking a multivitamin, but the level in most multivitamins (10 micrograms) is too low.

Vitamin E: For a time, vitamin E supplements looked like an easy way to prevent heart disease. Promising observational studies, including the Nurses' Health Study(22) and Health Professionals Follow-up Study,(23) suggested 20% to 40% reductions in coronary heart disease risk among individuals who took vitamin E supplements (usually containing 400 IU or more) for least two years.(24)

The results of several randomized trials have dampened enthusiasm for vitamin E's ability to prevent heart attacks or deaths from heart disease among individuals with heart disease or those at high risk for it. In the GISSI Prevention Trial, the results were mixed but mostly showed no preventive effects after more than three years of treatment with vitamin E among 11,000 heart attack survivors.(25) Results from the Heart Outcomes Prevention Evaluation (HOPE) trial also showed no benefit of four years worth of vitamin E supplementation among more than 9,500 men and women already diagnosed with heart disease or at high risk for it.(26) Based on these and other studies, the American Heart Association has concluded that "the scientific data do not justify the use of antioxidant vitamin supplements [such as vitamin E] for CVD risk reduction." (27)

A recent scientific analysis raised questions about whether high doses of vitamin E supplements might increase the risk of dying.(28) The authors gathered and re-analyzed data from 19 clinical trials of vitamin E, including the GISSI and HOPE studies; they found a higher rate of death in trials where patients consumed more than 400 IU of supplements per day. While this meta-analysis drew headlines when it was released online in November 2004, there are limitations to the conclusions that can be drawn from it. Some of the findings are based on very small studies; furthermore, many of the high-dose trials of Vitamin E included in the analysis were done on people who had chronic diseases, such as heart disease or Alzheimer's disease. So it is not clear that these findings would apply to healthy people.

It's entirely possible that in secondary prevention trials, the use of drugs such as aspirin, beta blockers, and ACE inhibitors mask a modest effect of vitamin E, and that it may have benefits among healthier people. Ongoing randomized trials of vitamin E, such as the Women's Health Study (29) and SU.VI.MAX (30) will tell us more about its possible benefits in the coming years.

Optimal Intake: The recommended daily intake of vitamin E from food now stands at 15 milligrams from food. That's the equivalent of 22 IU from natural-source vitamin E or 33 IUs of the synthetic form. Researchers are still writing the book on vitamin E. Some small studies have suggested that vitamin E supplements might interfere with statins, but this hypothesis was refuted in a large trial. While the data are sparse and conflicting, evidence from some observational studies suggests that at least 400 IU of vitamin E per day, and possibly more, are needed for optimal health. Since standard multivitamins usually contain around 30 IU, a separate vitamin E supplement is needed to achieve this level. Current guidelines say that consuming more than 1000 mg of supplemental vitamin E per day is not considered safe; that's the equivalent of a supplement with 1,500 IU of natural-source vitamin E or 1,100 IU of synthetic vitamin E.

Vitamin K: Vitamin K helps make six of the 13 proteins needed for blood clotting. Its role in maintaining the clotting cascade is so important that people who take anticoagulants such as warfarin (Coumadin) must be careful to keep their vitamin K intake stable.

Lately, researchers have demonstrated that vitamin K is also involved in building bone. Low levels of circulating vitamin K have been linked with low bone density, and supplementation with vitamin K shows improvements in biochemical measures of bone health.(31) A report from the Nurses' Health Study suggests that women who get at least 110 micrograms of vitamin K a day are 30% less likely to break a hip as women who get less than that.(32) Among the nurses, eating a serving of lettuce or other green leafy vegetable a day cut the risk of hip fracture in half when compared with eating one serving a week. Data from the Framingham Heart Study also shows an association between high vitamin K intake and reduced risk of hip fracture.(33)

Optimal Intake: The recommended daily intake for vitamin K is 80 micrograms for men and 65 for women. Because this vitamin is found in so many foods, especially green leafy vegetables and commonly used cooking oils, most adults get enough of it. According to a 1996 survey, though, a substantial number of Americans, particularly children and young adults, aren't getting the vitamin K they need.(34)


Our cells must constantly contend with nasty substances called free radicals. They can damage DNA, the inside or artery walls, proteins in the eye--just about any substance or tissue imaginable. Some free radicals are made inside the body, inevitable byproducts of turning food into energy. Others come from the air we breathe and the food we eat.

We aren't defenseless against free radicals. We extract free-radical fighters, called antioxidants, from food. Fruits, vegetables, and other plant-based foods deliver dozens, if not hundreds, of antioxidants. The most common are vitamin C, vitamin E, beta-carotene and related carotenoids. Food also supplies minerals such as selenium and manganese, which are needed by enzymes that destroy free radicals.

During the 1990s, the term antioxidants became a huge nutritional buzz word. Antioxidants were promoted as wonder agents that could prevent heart disease, cancer, cataracts, memory loss, and a host of other conditions.

It's true that the package of antioxidants, minerals, fiber, and other substances found in fruits, vegetables, and whole grains help prevent a variety of chronic diseases. Whether high doses vitamin C, vitamin E, or other antioxidants can accomplish the same feat is an open question.

The evidence accumulated so far isn't promising. Randomized trials of vitamin C, vitamin E, and beta-carotene haven't revealed much in the way of protection from heart disease, cancer, or aging-related eye diseases. Ongoing trials of other antioxidants, such as lutein and zeaxanthin for macular degeneration and lycopene for prostate cancer, are underway.

The Bottom Line

A standard multivitamin supplement doesn't come close to making up for an unhealthy diet. It provides a dozen or so of the vitamins known to maintain health, a mere shadow of what's available from eating plenty of fruits, vegetables, and whole grains. Instead, a daily multivitamin provides a sort of nutritional safety net.

While most people get enough vitamins to avoid the classic deficiency diseases, relatively few get enough of five key vitamins that may be important in preventing several chronic diseases. These include:

  • Folic acid
  • Vitamin B6
  • Vitamin B12
  • Vitamin D
  • Vitamin E

Reference: World Cancer Research Fund. Food, Nutrition and Cancer. Washington, DC: American Institute for Cancer

c. Nucleic Acids

d. Lipids

Inorganic Compounds

Vitamins and Minerals

Water and Solutions

      Most vitamins must be provided by the diet or by supplements; only three vitamins (D, K, and the B vitamin biotin) can be manufactured in the body from nondietary sources. Vitamins are not sources of energy as are carbohydrates, fats, and proteins. Instead, vitamins serve as chemical partners for the enzymes involved in the body's metabolism, cell production, tissue repair, and other vital processes. Vitamins are either fat soluble or water soluble. The fat-soluble vitamins, which include A, D, E, and K, are absorbed by the body using processes that closely parallel the absorption of fat. They are stored in the liver and used up by the body very slowly. The water-soluble vitamins include C and the B complex vitamins. The body uses these vitamins very quickly; excess amounts are eliminated in urine.

Enter supporting content here