Exam 2

Question 1

Enzyme Inhibitors: True or False:

An allosteric inhibitor binds to the active site of the enzyme.

Answer 1

False

Question 2

the process by which an end product of a pathway devoted to the synthesis of a compound acts as an inhibitor of an earlier step in a metabolic pathway is called:

Answer 2

Feedback inhibition

Question 3

An allosteric enzyme inhibitor…

Answer 3

Changes the shape of the enzyme.

Question 4

True or False:

All enzymes have the same optimal temperature.

Answer 4

False

Question 5

What do the sign and the magnitude (numerical value) of the delta G of a reaction tell us about the speed of the reaction?

Answer 5

Neither the sign not the magnitude of delta G have anything to do with the speed of the reaction.

Question 6

True or False:

Only proteins made of two or more polypeptide chains have quaternary structure.

Answer 6

True

Question 7

The tertiary structure of a protein is the:

Answer 7

Unique three-dimensional shape of the fully folded polypeptide that results from hydrogen bonding, ionic bonding, disulfide bonding, and hydrophobic interactions between amino acids

Question 8

Protein secondary structure elements such as the alpha-helices and beta-sheets constitute the major regular folding patterns in proteins. with regard to these elements of the secondary structure:

Answer 8

The folding pattern that result from hydrogen-bonding between the N-H and C=O groups in the protein backbone.

Question 9

In an aqueous solution, protein conformation is determined by two major factors. One is the formation of the maximum number of bonds. The other is:

Answer 9

Placement of hydrophobic amino acid side chains within the interior of the protein.

Question 10

In the first law of Thermodynamics, “conservation of energy” refers to the fact that ___.

Answer 10

Energy cannot be created or destroyed but can be converted from one form to another.

Question 11

True or False:

Enzymes convert endergonic reactions into exergonic reaction.

Answer 11

False

Question 12

True or False:

Rough endoplasmic reticulum produces lipids

Answer 12

False

Question 13

What kind of cell junction helps ensure that the epithelial lining of the stomach prevents stomach contents from leaking out into the body?

Answer 13

Tight junction

Question 14

A ____ can bud off of the membrane of any organelle within the endomembrane system and then fuse with the membrane of another organelle, thereby carrying materials from one organelle to another.

Answer 14

Transport vesicle

Question 15

What happens to a red blood cell in a hypotonic solution? What about a hypertonic solution?

Answer 15

cell expands and can burst; the cell shrivels

Question 16

what happens to a red blood cell in an isotonic solution?

Answer 16

Nothing, the cell remains its shape

Question 17

A/an ____ is a cytoskeletal fiber made from the protein “actin: that is involved in muscle contraction, ameboid movement and maintaining the shape of the plasma membrane.

Answer 17

Microfilament

Question 18

A vesical containing proteins from the ER fuses with the ___ region of the Golgi apparatus.

Answer 18

cis

Question 19

Which of the following is/are found in prokaryotic cells and eukaryotic cells.

a. Chloroplasts
b. Plasma membrane
c. Nuclear membrane
d. Mitochondria

Answer 19

b. Plasma membrane

Question 20

Which of the following tends to limit cell size?

• Surface area- to - volume ratios
• The difficulty in maintaining a continuous large membrane
• The difficulty of reproduction in a large cell
• All of the above
• None of the above

Answer 20

Surace area-to-volume ratios

Question 21

What factors would increase membrane fluidity?

Answer 21

A greater proportion of phospholipids with unsaturated fatty acids and a high temperature.

Question 22

Which type of organism from the list below have the highest % of unsaturated fatty acid chains in its membranes?
Reptile in the desert 
Thermophilic bacterium in hot springs
Antartic fish
Human

Answer 22

Antartic fish

Question 23

Which of the following molecules or ions will diffuse across a phospholipid bilayer the fastest, assuming that there are no proteins associated with the bilayer?
Na+
O2
H2O
C2H3O0-
NH4+

Answer 23

O2

Question 24

Some proteins that are on the surface of mammalian cells contain carbohydrates. These proteins are synthesized by ___ and the sugars added in the ___.

Answer 24

Rough endoplasmic reticulum; Golgi apparatus and/or the rough endoplasmic reticulum

Question 25

The outside of a cell wall is ___ and the inside of a cell wall is ____.

Answer 25

Hydrophilic; Hydrophobic

Question 26

Which of the following is not involved in secondary active transport?

• Coupling to another transport system
• The plasma membrane
• Use of an existing concentration gradient
• Direct use of ATP

Answer 26

The direct use of ATP

Question 27

Which of the following mutation might cause familial hypercholesterolemia?

• A mutant LDL receptor that cannot make it from the rough endoplasmic reticulum to the Golgi apparatus.
• A mutant LDL receptor that cannot bind
• A mutant LDL receptor that can bind LDL but cannot trigger the formation of a clathrin-coated pit.
• A mutant LDL receptor that is trafficked to the lysosome and cannot be recycled back to the surface of the cell
• All of the above

Answer 27

All of the above

Question 28

The process of receptor-mediated endocytosis consists of several steps. Referring to the specific example of LDL uptake by cells, what is the fourth step in the sequence?

Answer 28

After LDL is separated from the receptors and the receptors are sorted out, the endosome containing the LDL molecules fuses with a lysosome.

Question 29

What is the difference between active and facilitated diffusion?

Answer 29

Active transport requires energy, and facilitated does not.

Question 30

The binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

Answer 30

Ion channel receptor

Question 31

The process of receptor-mediated endocytosis True or False:

Coated vesicles eventually become part of the endoplasmic reticulum.

Answer 31

False

Question 32

True or False:
Active protein kinase A phosphorylates multiple target proteins. some proteins are activated, while other proteins are inhibited.

Answer 32

True

Question 33

Suppose the concentration of epinephrine in the bloodstream of an animal drops. Assuming that the cyclic AMP phosphodiesterase activity in liver cells remains constant, the cyclic AMP concentration in liver would be expected to ______ because ___ activity would _____

Answer 33

Decrease; adenylyl cyclase; decrease

Question 34

What would happen to a liver cell exposed to both epinephrine and caffeine at the same time?

Answer 34

The effect of the epinephrine would be enhanced by the caffeine because the caffeine would inhibit cAMP phosphodiesterase, which would allow cAMP levels in the cell to stay high for an extended amount of time

Question 35

Vitamin A is a relatively small, lipid-soluble molecule that can behave as a hormone. Most likely its receptor:

Answer 35

Is found within the cytoplasm

Question 36

For each molecule of ATP consumed during active transport if sodium and potassium, there is an import of ____ ion(s) and an export of ____ ion(s).

Answer 36

Two K+; three Na+

Question 37

Suppose you’re studying the transport of a certain small polar molecule across the plasma membrane of cells in culture. Over a period of time, you measure the concentration of the polar molecule inside and outside of the cells. You find that the concentration of the molecule is lower inside of the cell but is gradually increasing. You also measure the ATP concentration inside the cell and find that it is not changing. What type of transport is used?

Answer 37

Facilitated diffusion

Question 38

Suppose you’re studying the transport of a certain small polar molecule across the plasma membrane of cells in culture. Over a period of time, you measure the concentration of the polar molecule inside and outside of the cells. You find that the concentration of the molecule is higher inside of the cell and is gradually increasing. You isolate the transporter responsible for moving the molecule across the membrane and find that is cannot bind or hydrolyze ATP concentration inside the cell and find that it is not changing. What type of transport is used?

Answer 38

Secondary active transport