Describe the general properties of each of the four major classes of organic molecules, including the
major roles of each of them in cells.
What will be an ideal response?
The four major classes of organic molecules are carbohydrates, lipids, proteins, and nucleic acids.
Carbohydrates contain carbon, hydrogen, and oxygen at or near the ratio of (CH2O). Their major roles
in cells are as energy sources and energy storage molecules, and as structural molecules. Lipids are
primarily nonpolar, mainly hydrophobic organic molecules. Their main functions in cells are as
structural components of cell membranes, as energy sources, as energy storage molecules, and as
hormones. Proteins are polymers of amino acids that fold into specific structures that allow each type
of protein to carry out its specific role or roles. Proteins play many major roles in cells. Some
examples: enzymes that catalyze cellular reactions; motile molecules involved in movement of and
within cells as well as for specialized groups of cells; transport of material across cell membranes;
receptor molecules at cell surfaces; and regulation of the activity of other cellular molecules such as
other proteins and DNA. Nucleic acids are polymers of nucleotides. There are two main types of
nucleic acids, DNA and RNA. These differ from each other chemically in the exact type of sugar in
their nucleotides (deoxyribose for DNA and ribose for RNA) and in whether thymine or uracil is used
as a nitrogenous base (DNA uses thymine, RNA uses uracil). DNA is typically found as two strands
connected by hydrogen bonds to form a double helix, while RNA is typically single-stranded.
Hereditary information in cells is stored in DNA. There are many different types of RNA, but nearly
all RNA molecules play either a direct or indirect role in the production of proteins using the
information stored in DNA.
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a. cuticle b. protoplast c. stoma d. trichome e. bark
The electrons for photosynthesis come from:a
ATP. b. glucose. c. NADP+. d. chlorophyll a. e. H2O
Anaerobes can be cultured in a CO2 rich environment, as long as O2 gas is excluded.
Answer the following statement true (T) or false (F)
Graft rejection can be reduced by
A. preventing B cell activation. B. antiphagocytic factors. C. stimulating B cells. D. preventing T cell proliferation. E. suppressing macrophage activity.