Deck 3: The Chemical Building Blocks of Life

Question 1

High temperatures can cause proteins in a cell to denature. This can be reversed by heat shock proteins that function as _______.

A) catalysts
B) chaperones
C) proteasomes
D) ribosomes
E) polymerases

Answer 1

chaperones

Question 2

What is the difference in the bonding between alpha-helix and beta sheets?

A) Hydrogen bonding between the amides only occurs in one of these two types of secondary structures.
B) Hydrogen bonding occurs between the amides of adjacent chains in the sheets instead of between the amides in different parts of the helices.
C) Sulfur bridges allow the spring like turns in alpha helices and van der Waals dispersion allows the folds in beta sheets.
D) Hydrogen bonding always occurs in the alpha helices but only occurs in parallel beta sheets.

Answer 2

Hydrogen bonding occurs between the amides of adjacent chains in the sheets instead of between the amides in different parts of the helices.

Question 3

Fructose and galactose both have six carbon atoms, twelve hydrogen atoms and six oxygen atoms, just like glucose. A friend of yours says: "Since those sugars have the same number of atoms, they should have the same name." You answer: "While they do have the same number and type of atoms,

A) they are named differently because one is found in RNA and the other in DNA."
B) they are named differently because they cannot be converted into glucose."
C) they are named differently because they have different secondary structure."
D) they are named differently because they are isomers of the monosaccharide, glucose."
E) they are all polysaccharides and have slightly different functions within organisms and therefore have different names."

Answer 3

they are named differently because they are isomers of the monosaccharide, glucose."

Question 4

Which reaction illustrates a dehydration reaction?

A) A + H₂O $\rightarrow$ B + C
B) A + B $\rightarrow$ C + H₂O
C) A $\rightarrow$ B + C+ H₂O
D) A + B + H₂O $\rightarrow$ C

Question 5

Which reaction illustrates a hydrolysis reaction?

A) A $\rightarrow$ B + C+ H₂O
B) A + B + H₂O $\rightarrow$ C
C) A + H₂O $\rightarrow$ B + C
D) A + B $\rightarrow$ C + H₂O

Question 6

L-lysine is an essential amino acid and must be supplied in the diet. By comparison, the stereoisomer D-lysine is not biologically active. Why can your body only utilize one form?

A) Since the L form and D form are enantiomers, they will bind together and inhibit utilization of the D form.
B) Since the L form and D form are chiral molecules, they will bind together and inhibit utilization of the D form.
C) Antibodies recognize the D form and destroy it before your body can use it for nutritional purposes.
D) Enzymes can only recognize a single, specific stereoisomer.

Question 7

People who are lactose intolerant can often consume some products made from milk such as cheese and yogurt. By comparison, people with a true milk allergy, which involves an immune response to milk protein, cannot consume milk or products made from milk. Given this information, what can you conclude about milk?

A) The protein that causes a true milk allergy is lactose.
B) All people who are lactose intolerant are also allergic to milk.
C) Yogurt contains live and active cultures of Lactobacillus acidophilus bacteria and therefore prevents an allergic response in people with a true milk allergy.
D) Lactose is a carbohydrate, not a protein and is therefore not the cause of true milk allergies.

Question 8

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

A) Hydrogenation of fats changes them from unsaturated to saturated, which are more solid.
B) Hydrogenation of fats changes them from saturated to unsaturated, which are more solid.
C) Trans fatty acids are changed from saturated to unsaturated, allowing them to solidify.
D) Trans-fatty acids are changed from unsaturated to saturated, allowing them to solidify.

Question 9

Hemoglobin transports oxygen in the blood and consists of a chain of 146 amino acids. If amino acids were incorporated into hemoglobin in the same proportions, approximately how many alanine residues would you predict to find in hemoglobin?

A) 2
B) 7
C) 20
D) 36
E) 146

Question 10

In a phospholipid, the phosphate would be found in which part of a membrane?

A) In the bilayer, interacting with water.
B) On the surface of the membrane, shielded from water.
C) In the bilayer, shielded from water.
D) On the surface of the membrane, interacting with water.

Question 11

Which type of RNA is used as a template for translation of proteins?

A) ribosomal RNA
B) micro RNA
C) transfer RNA
D) messenger RNA

Question 12

Benedict's reagent is a chemical that is used as a test for the presence of a free aldehyde functional group on glucose. The aldehyde is used when glucose and fructose bind together to form sucrose, and the Benedict's test is negative. Starch contains a great deal of glucose but gives a negative Benedict's test because:

A) only the glucose at the end of a chain of starch will have an exposed aldehyde functional group to react with Benedict's reagent.
B) starch is not soluble in water and cannot react with Benedict's reagent.
C) all of the aldehyde groups on the starch are oxidized and cannot react with the Benedict's reagent.
D) glucose in starch has lost a carbon atom and cannot react with Benedict's reagent.

Question 13

$\alpha$ - glucose is present in potatoes and $\beta$ - glucose is present in wood. Both are glucose molecules but one can be used by humans to synthesize ATP and one cannot. Based on this information, what is the best explanation on why humans can only digest one of the glucose types?

A) $\alpha$ - glucose is a chain and $\beta$ - glucose is a ring.
B) Only $\alpha$ - glucose can form polysaccharides.
C) $\alpha$ - glucose is C₆H₁₂O₆ and $\beta$ - glucose is C₅H₁₂O₆.
D) $\alpha$ - glucose and $\beta$ - glucose are stereoisomers with OH groups oriented differently.