Biology 1A    Sept 1, 1998
Lecture 2 - The Nature of Life

Page Contents :

• Reading Assignment
• Overview of Lecture
• Overview of Lab
• Lecture Outline
• Vocabulary
• Study Questions
• Related Websites

Stern: Chapter 2

Overview of Lecture:

Attributes of living organisms.
Living organisms are composed primarily of six elements.
Water is the medium for the chemical reactions of life.
Lipids, carbohydrates, proteins, and nucleic acids.

Overview of Lab:

(A bullet indicates a handout.)
• Biochemical evaluation of selected cellular products
  Benedict's evaluation of carbohydrates
  Starch evaluation
  Lipid spot test
  Amylase activity

A. Growth and Development.
1. Growth is an increase in sixe, resulting from an increase in mass and/or volume.
2. The process by which most growth occurs is called development.
B. Reproduction.
1. Reproduction is the production of new organisms (offspring).
2. Offspring resemble their parents, and share the features of their biology.
C. Responsiveness -- Life responds to stimuli.
1. Behavioral responses - short-term response of an individual.
     Examples: homeostasis, response to injury.
2. Acclimatization - seasonal response of an individual, usually developmental.
     Examples: dormancy, deciduousness.
3. Adaptation - long-term response of a population; equals evolution.
D. Metabolism
1. Metabolism is the result of the chemical reactions of life.
2. The major reactions of life include: digestion, assimilation, respiration, photosynthesis.
E. Movement
1. Locomotion (motility) - movement of the entire organism. (e.g. phototaxy)
2. Tropisms - directional response to a stimulus (e.g. phototropism, geotropism)
3. Nastic Movement - hydrostatic movement in response to a stimulus. (e.g. thigmonasty)
F. The common structure of all life -- cells (next lecture).
G. The common chemical composition of all life. . .

A. Elements versus Compounds
1. Elements are composed of a single kind of atom. (e.g. oxygen, iron)
2. Compounds are composed of more than one kind of atom. (e.g. salt, water)
3. The compounds of life consist primarily of six elements. (CHONPS)
B. Carbon is the basis of organic chemistry
C. Hydrogen, Oxygen
1. Components of water (H2O)
2. Necessary for organic acids (COOH) and alcohols (OH)
D. Nitrogen - essential component of proteins, nucleic acids, and pigments
E. Phosphorus
1. Essential component of nucleic acids (DNA, RNA)
2. Essential component of ATP, used in energy exchange
F. Sulfur - important in many amino acids & proteins

A. Water high an enormous capacity to absorb heat energy.
1. Water is a fluid at typical land and ocean temperatures.
2. Water buffers the physical environment.
3. Water buffers the internal environment.
B. Water is polar.
1. Water molecules are angled, with positive and negative regions.
2. Polarity makes it an excellent solvent for polar molecules and ions.
3. High cohesion
C. Water is a reactant or product in many biochemical reactions.
1. hydrolysis - "splitting with water"; requires water.
2. dehydration synthesis - linking of two molecules by release of water.
3. Biological importance of linking: monomers, polymers

A. Lipids
1. Fats, waxes, oils.
2. Mostly C & H; insoluble in water; nonpolar
3. fats and oils - glycerol plus three fatty acids (mostly 16-18C)
4. waxes - long-chain fatty acids and long-chain alcohol
5. phospholipids - like fats, but with two fatty acids and a phosphate group (PO4)
6. Many vertebrate hormones
B. Carbohydrates
1. The most abundant organic compounds in nature
2. C:H:O = approx. 1:2:1
3. monosaccharides - simple sugars of 3-7 carbon atoms
4. disaccharides - two monosaccharides bonded by dehydration synthesis
5. polysaccharides - several monosaccharides bonded by dehydration synthesis
     Examples: starch, cellulose, chitin, immune system
C. Proteins
1. Hundreds to thousands of different kinds in each cell
2. Mostly C,H,O,N, and some S
3. Often very large and complicated molecules
4. Polymer of the 20 amino acids
5. peptide is two or more AAs bonded together.
6. polypeptide - exceptionally large peptides.
     Examples: Enzymes, cytoskeleton, flagellae, hemoglobin.
D. Nucleic acids
1. Exceptionally large polymers of nucleotides.
2. Each nucleotide includes a nitrogenous base, 5C sugar, and phosphate group.
3. DNA & RNA
4. Related compounds important in energy exchange (ATP, NADH, NADPH)
E. Other biological compounds
1. Coenzymes (vitamins) - cannot be synthesized by vertebrates, and so must be ingested.
2. Pigments - complex molecules that can absorb or release light energy.

• What is the difference between growth and development?
• Explain homeostasis. Why is homeostasis important for life?
• Of the following, which are examples of acclimatization?
  a) A tree loses its leaves during the dry season.
  b) A dog pants to reduce excess heat.
  c) An arctic fox has a brown coat in summer and a white coat in winter.
  d) An arctic flower bends to follow the location of the sun.
• What are the four major reactions of metabolism?
• How are phototropism and phototaxy different? How are they similar?
• Why is water necessary for life?
• Explain hydrolysis and deyhdration synthesis. Which is important in digestion? Which is necessary for assimilation? Which class of compounds catalyzes these reactions?
• Why do we have to "take our vitamins"?
• What are the four major classes of organic compounds? What is an example of an organic compound that is NOT in one of those four classes?
• Why is vegetable oil liquid at room temperature, but animal fat is solid?
• Why are polyunsaturated fats more common in plants than in animals? (Hint: What is different about the way in which plants deal with their environment?)
• What important structural role do phospholipids play in cells?
• What role does starch play in the biology of plants? Of what monomer is it composed? What is the usual form for transporting this monomer within the plant?
• How many amino acids are there?
• What is the importance of ATP for the cell? What class of biological molecule is it?
• Which of the following compounds typically contain nitrogen? phosphorous? sulfur?
  carbohydrates
  lipids
  nucleic acids
  proteins

• JENA Image Library of Biological Macromolecules
• UCMP Glossary Vol. 3 : Biochemistry