Question 1

Muscle contraction is accomplished by a mechanism known as the cross-bridge cycle,in which myosin heads bind to actin and cause the actin filaments to move across the myosin filaments.Which of the following is capable of providing the energy needed for this process?

Accepted Answer

ATP is the primary source of energy for muscle contraction. The ATP molecule provides energy to the myosin heads, which bind to the actin filaments and cause them to slide across the myosin filaments. FAD and NADH are involved in the process of cellular respiration, but they do not directly provide energy for muscle contraction. Enzymes catalyze chemical reactions but do not provide energy.

Question 2

You arrive late to a biological seminar.However,just as you enter the room,you hear the speaker referring to the "five-prime end" and the "three-prime end" of a macromolecule.Immediately,you know that they are talking about a

Accepted Answer

The terms "five-prime end" and "three-prime end" are used to describe the ends of a DNA molecule. The terms refer to the carbon atoms on the deoxyribose sugar ring in the DNA backbone. The 5' end has a phosphate group attached to the 5' carbon atom, while the 3' end has a hydroxyl group attached to the 3' carbon atom. This orientation is important for DNA replication and transcription.

Question 3

Vitamin D can be synthesized by the body from a derivative of cholesterol.Given this information,which of the following statements about the solubility of vitamin D is true?

Accepted Answer

Since vitamin D is synthesized from a derivative of cholesterol, which is a lipid or fat molecule, it is also fat-soluble. This means it dissolves in fats and oils, and not in water.

Question 4

You have recently identified a novel protein.After obtaining the protein sequence you realize that this protein contains several motifs and domains.How might this information help you to determine the function of your new protein?

Accepted Answer

Motifs and domains are patterns in protein structure that are often associated with particular functions. Identification of these patterns in the new protein can provide insight into possible functions of the unknown protein. Therefore, the presence of motifs and domains can aid in determining the function of the new protein. However, it is important to note that the presence of a particular motif or domain does not necessarily determine the protein's function with certainty. Additional experimentation, such as functional assays, would be necessary to confirm the protein's function.

Question 5

The digestive enzyme pepsin works in the acidic environment of the stomach to hydrolyze peptide bonds.On which of the following macromolecules does pepsin act?

Accepted Answer

Pepsin is a digestive enzyme that works to break down proteins by hydrolyzing peptide bonds. It does not work on carbohydrates, DNA, or lipids.

Question 6

Margarine is made by hydrogenating vegetable oils so that they take on the consistency of butter.Which of the following is the chemical basis for this change from a liquid to a solid?

Accepted Answer

Hydrogenation involves adding hydrogen to unsaturated fatty acids to make them more saturated. The more saturated the fatty acids, the more solid the product will be. Therefore, A is the correct answer as it correctly describes the chemical process of hydrogenation and the resulting change in consistency from liquid to solid.

Question 7

Which of the following would not contain polymers of b-glucose?

Accepted Answer

Amylose is a polymer of alpha glucose, not beta glucose. The other options contain polymers of beta glucose.

Question 8

The human immunodeficiency virus (HIV)uses RNA,rather than DNA,to encode genetic information.During infection,however,HIV uses an enzyme known as reverse transcriptase to generate double-stranded DNA.Generally speaking,how would the enzyme generate a double strand of DNA from a single strand of RNA?

Accepted Answer

Reverse transcriptase catalyzes the synthesis of a DNA copy from the viral RNA, but this DNA copy is only single-stranded. The enzyme then uses the newly synthesized DNA as a template to synthesize a second strand of DNA that is complementary to the first one, resulting in a double-stranded DNA molecule. This process is known as reverse transcription.

Question 9

You arrive late to a biological seminar.However,just as you enter the room,you hear the speaker referring to the "amino end" and the "carboxyl end" of a macromolecule.Immediately,you know that they are talking about a

Accepted Answer

Amino and carboxyl ends are terms used to describe the two ends of a protein molecule. The amino end has a free amine group (-NH2) while the carboxyl end has a free carboxylic acid group (-COOH). This terminology is not applicable to carbohydrates, DNA, or lipids.

Question 10

Egg whites consist primarily of water and the protein albumin.When you fry an egg,why does the egg white turn from clear to white?

Accepted Answer

When an egg is fried, heat causes the protein albumin to undergo a process called denaturation. This means that the protein's normal structure is disrupted, causing it to unfold and reorganize into a new structure. This new structure reflects and scatters light in a way that makes the egg white appear opaque (white) rather than translucent (clear). Therefore, the correct answer is C) The protein becomes denatured.

Quiz 3: The Chemical Building Blocks of Life