1. Unit 2, Lesson 3 – DNA and Proteins
B – The molecule contains a nitrogen atom and an R group, therefore it is an amino acid.
A – Deoxyribose is the sugar found in DNA not RNA.
C – Nucleotides contain a phosphate group, 5-carbon sugar, and a nitogenous base. The nirotgenous bases come in 4 varieties and participate in hydrogen bonding interactions.
A – Proteins do not encode genetic information (nucleic acids do)

2. Unit 2, Lesson 3 – DNA and Proteins
Part A Answer:
Proteins and nucleic acids are both long unbranched polymers made up of monomers. Proteins are made of amino acids and nucleic acids and made of nucleotides. Both types are joined be dehydrated synthesis.

3. Unit 2, Lesson 3 – DNA and Proteins
Part B Answer:
Nucleotides are variable, the sequence of nucleotides allowing DNA or RNA to encode genetic information. Hydrogen bonding between nucleotides allows different nucleic acids strands to bond (for example, in a DNA double strand)

4. Unit 2, Lesson 3 – DNA and Proteins
Part C Answer:
Amino acids are variable with 20 different types. The variable R groups of amino acids allow for a large variety of proteins to be made. The R groups have different chemical and physical properties that allow the protein to take on a specific 3D shape.

5. Unit 2, Lesson 4 - Enzymes
B – Enzymes are proteins, which are composed of amino acids and contain an active site. The substrate in the reactant the enzyme acts on (not part of the enzyme)
D – Catalase is the enzyme which is not consumed in the reaction. Hydrogen peroxide is the substrate. Water and oxygen are the products of the reaction.
C – Galactose increases and lactase remains the same.
D – Substrate is already in excess and not the limting factor in the reaction.

6. Unit 2, Lesson 4 – Enzymes Part A Answer:
The graph shows that pepsin functions best in low pH (acidic environment) suggesting that the stomach has a pH between 2 and 3. Trypsin functions best at a pH of about 6 or 7, suggesting that the pH of the small intestine is about neutral.

7. Unit 2, Lesson 4 – Enzymes Part B Answer:
When it travels to the small intestine, pepsin will become denatured by the high pH level. It will no longer catalyze the breakdown of protein.

8. Unit 2, Lesson 4 – Enzymes Part C Answer:
The advantage to having two enzymes is that each enzyme can function in the specific environments of the stomach and small intestine. At least one enzyme functions in each part of the digestive tract ensuring the complete digestion of the proetein in food.