Cyclins and cyclin-dependent kinases (CDKs) are:
1. Two key classes of regulatory molecules that determine a cell's progress through the cell cycle
2. The products of the proto oncogenes in a eukaryotic cell
3. Two very important promoters that are involved in oncogenes
4. Mediators of apoptosis

Consider the following statements:
I. In animals, meiosis always results in the formation of gametes, while in other organisms it can give rise to spores.
II. Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes (including single-celled organisms) that reproduce sexually.
III. Meiosis does not occur in archaea or bacteria, which reproduce via asexual processes such as binary fission.
The correct statements are:
1. I, II, and III
2. II and III
3. I and III
4. I and II

Which of the following is an essential amino acid?
1. Phenylalanine

2. Aspartic acid

3. Glutamic acid

4. Serine

Most abundant organic compound on earth is
1. Cellulose

2. Protein

3. Lipids

4. Steroids

Why is cellulose so difficult for most animals to digest?
1. they don’t have the proper enzyme to break the bonds between subunits
2. cellulose is made up of chitin, which is indigestible
3. the bonds holding cellulose subunits together are extremely strong, stronger than in any other macromolecule
4. there are many hydrogen bonds holding the subunits together

Which statement regarding enzyme inhibition is correct?
1. Competitive inhibition occurs when a substrate competes with enzyme for binding to inhibitor protein
2. Competitive inhibition occurs when a substrate and the inhibitor compete for active site on the enzyme
3. Non-competitive inhibition of an enzyme can be overcome by adding a large amount of substrate
4. Non-competitive inhibitors often bind to the enzyme irreversibly

The structure that helps in cell wall formation, DNA replication and respiration in bacteria is :
1. Mesosome

2. Chromatophores

3. Pilus

4. Nucleoid

Cell membrane carbohydrates participate in
1. transporting substances between two protein layers
2. cell-to-cell recognition
3. attaching the membrane to cytoskeleton
4. cell adhesions

A molecule of ATP is structurally most similar to :
1. RNA nucleotide

2. DNA nucleotide

3. amino acid

4. fatty acid

The unique properties of each amino acid is determined by its particular :
1. R group
2. amino group
3. finds of peptide bond
4. number of bonds to other amino acids