biochem final

Question 1

What happens in feedback inhibition?

Answer 1

A product slows its own production when it is present in ample supply.

Question 2

Which functional group is circled in the structure of histidine? (2)

Answer 2

carboxyl

Question 3

Which cellular component is the site of protein synthesis?

Answer 3

ribosome

Question 4

What is the Henderson-Hasselbalch equation?

Answer 4

pH = pKa + log [A−]/[HA]

Question 5

Which statement is false regarding osmolarity?

Answer 5

A 1 mM NaCl solution has the same osmolarity as a 1 mM glucose solution.

Question 6

Why is it important for cells to maintain a specific and constant pH close to pH 7?

Answer 6

Biomolecules, such as enzymes, must be kept at their optimal ionic state to
allow for proper structure and function

Question 7

Which of the listed amino acids has an uncharged polar side chain at pH 7?

Answer 7

Thr

Question 8

Which level of protein structure describes the covalent backbone of a protein,
including the sequence of amino acids?

Answer 8

primary

Question 9

Which of the following proteins would elute first from a gel filtration column?

a) protein D, with Mr 15,600
b) protein C, a homodimer in which the protomer has an Mr of 11,300
c) protein B, with Mr 58,400
d) protein A, with Mr 27,000

Answer 9

protein B, with Mr 58,400

Question 10

Some mutations can reduce protein stability, but not completely destroy it. In the
Siamese cat, a G→R transition, changing glycine to arginine (G302R), makes the
tyrosinase enzyme in skin cells sensitive to temperature. This enzyme takes part in
the synthesis of melanin, the dark pigment in hair and skin. It is properly folded at
low body temperatures but denatured at high body temperatures. What can we then
say about the Siamese cat?

Answer 10

The dark areas around its paws, nose, and ears are slightly cooler than the
rest of the cat.

Question 11

What did Christian Anfinsen use to break the disulfide bonds in ribonuclease A?

Answer 11

reducing agent

Question 12

What metal ion is critical in muscle contraction?

Answer 12

Ca2+

Question 13

Which statement about myoglobin is FALSE?

Answer 13

It has four sites to bind oxygen

Question 14

What is the first step in immunoblotting?

Answer 14

protein separation by gel electrophoresis

Question 15

The heme prosthetic group:

Answer 15

consists of protoporphyrin and an iron (II) ion.

Question 16

An arrow points to part of the immunoglobulin structure. What is the name of this
portion of the structure? (16)

Answer 16

FAB

Question 17

Which experiment demonstrated that enzymes are proteins?

Answer 17

fermentation of sugar to alcohol by cell-free yeast extracts

Question 18

Consider the reaction:
E + S ⇌ ES ⇌ EP ⇌ E + P
What do ES and EP represent in the reaction?

Answer 18

reaction intermediates consisting of transient complexes of the enzyme with the
substrate and with the product, respectively

Question 19

A regulatory enzyme whose activity is affected/controlled by the reversible,
noncovalent binding of small metabolites or other compounds at a site other than
the enzyme’s active site is called an _____ enzyme.

Answer 19

Allosteric

Question 20

What is the steady state?

Answer 20

the reaction period where [ES] is constant

Question 21

Which enzyme class does this enzyme belong?? (21)

Answer 21

ligase

Question 22

Which class of enzymes relocates molecules or ions across membranes?

Answer 22

translocases

Question 23

What is the current theory behind the substrate-enzyme interaction in the enzyme’s
active site?

Answer 23

The active site is complementary to the transition state.

Question 24

How is chitin different from cellulose?

Answer 24

Chitin has acetylated amino groups on C-2 of the glucose units, cellulose does
not.

Question 25

What type of monosaccharide is depicted? (25)

Answer 25

aldohexose because the carbonyl is on an end carbon and there are six carbons

Question 26

Amylose and Starch are:

Answer 26

glucose homopolysaccharides joined by (α1→4) links.

Question 27

What are the components of a nucleotide?

Answer 27

nitrogenous base, pentose, and phosphate

Question 28

Compare the energy released by hydrolysis of phosphate groups from a nucleotide.
Then choose the correct answer.

Answer 28

Release of the γ phosphate releases more energy than the release of
the α phosphate.

Question 29

What is the name of the phosphate group indicated by the arrow on the ATP (29)

Answer 29

α

Question 30

The structure in the figure can BEST be described as a (30):

Answer 30

deoxyribonucleotide.

Question 31

What would be expected for the electrophoresis of DNA at pH 7

Answer 31

DNA migrates toward the positive electrode because the phosphates carry
negative charges.

Question 32

. What must be bound to the intracellular side of the G protein–coupled receptor to
initiate a secondary messenger?

Answer 32

G protein

Question 33

Which signaling feature does the figure depict? (33)

Answer 33

integration

Question 34

What is an advantage of using bacteria as a host for an expression vector?

Answer 34

Bacteria can be grown in huge amounts in commercial fermenters.

Question 35

Which statement about green fluorescent protein (GFP) is false?

Answer 35

GFP requires molecular oxygen and additional proteins and cofactors to
fluoresce.

Question 36

What is the defining feature of lipids?

Answer 36

Lipids are insoluble in water.

Question 37

Lipids that contain simple sugars or complex oligosaccharides at the polar ends are
called:

Answer 37

glycolipids.

Question 38

Consider the fatty acid described by the abbreviation 18:2. How many double bonds
does this compound have?

Answer 38

2

Question 39

Which does NOT apply to the fatty acid structure shown? (39)

Answer 39

Δ-fatty acid

Question 40

Which enzymes contribute to the asymmetric distribution of phospholipids in the
plasma membrane?

Answer 40

flippase and floppase

Question 41

Membrane proteins that speed the passage of solutes across membranes by
providing an aqueous path across the membrane are called:

Answer 41

ion channels