Lc.7 (ch 6-ch7.4)

Question 1

Which of the following analogies best describes the induced-fit model of enzyme-substrate binding?
a) a hug between two people
b) a key fitting into a lock
c) a square peg fitting through the square hole and a round peg fitting through the round hole of a children’s toy
d) the fitting together of two jigsaw puzzle pieces

Answer 1

a) a hug between two people

the enzyme slightly changes shape to better accommodate the substrate, similar to how people adjust their arms to fit each other during a hug.

Question 2

An allosteric inhibitor does which of the following?
a) Binds to an enzyme away from the active site and changes the conformation of the active site, increasing its affinity for substrate binding.
b) Binds to the active site and blocks it from binding substrate.
c) Binds to an enzyme away from the active site and changes the conformation of the active site, decreasing its affinity for the substrate.
d) Binds directly to the active site and mimics the substrate.

Answer 2

c) Binds to an enzyme away from the active site and changes the conformation of the active site, decreasing its affinity for the substrate.

An allosteric inhibitor binds to a site other than the active site (the allosteric site), causing a change in the enzyme’s shape, which reduces its ability to bind to the substrate effectively

Question 3

Which of the following is not true about enzymes:
a) They increase ∆G of reactions.
b) They are usually made of amino acids.
c) They lower the activation energy of chemical reactions.
d) Each one is specific to the particular substrate(s) to which it binds.

Answer 3

a) They increase ∆G of reactions.

They only lower the activation energy, making the reaction proceed faster, but they do not alter the overall energy balance between reactants and products.

Question 4

The energy currency used by cells is ________.
ATP
ADP
AMP
adenosine

Answer 4

ATP

Question 5

A reducing chemical reaction ________.
a) reduces the compound to a simpler form
b) adds an electron to the substrate
c) removes a hydrogen atom from the substrate
d) is a catabolic reaction

Answer 5

b) adds an electron to the substrate

Question 6

During the second half of glycolysis, what occurs?
a) ATP is used up.
b) Fructose is split in two.
c) ATP is made.
d) Glucose becomes fructose.

Answer 6

c) ATP is made.

Question 7

What is removed from pyruvate during its conversion into an acetyl group?
a) oxygen
b) ATP
c) B vitamin
d) carbon dioxide

Answer 7

d) carbon dioxide

During the conversion of pyruvate into an acetyl group (a process called pyruvate oxidation), a carbon dioxide (CO₂) molecule is removed from pyruvate. This step occurs in the mitochondrial matrix and is catalyzed by the pyruvate dehydrogenase complex, producing acetyl-CoA and NADH.

Question 8

What do the electrons added to NAD+ do?
a) They become part of a fermentation pathway.
b) They go to another pathway for ATP production.
c) They energize the entry of the acetyl group into the citric acid cycle.
d) They are converted to NADP.

Answer 8

b) They go to another pathway for ATP production.

Question 9

How many NADH molecules are produced on each turn of the citric acid cycle?
one
two
three
four

Answer 9

three

Question 10

Chemiosmosis involves ________.
a) the movement of electrons across the cell membrane
b) the movement of hydrogen atoms across a mitochondrial membrane
c) the movement of hydrogen ions across a mitochondrial membrane
d) the movement of glucose through the cell membrane

Answer 10

c) the movement of hydrogen ions across a mitochondrial membrane

process where hydrogen ions (protons) move across the inner mitochondrial membrane through the ATP synthase enzyme, creating a proton gradient.

Question 11

Consider the reaction below.
CO2 + H2 —-> 2 CO + H2O

a) Which part of the reaction is a reduction?
b) Which part of the reaction is an oxidation?
c) Which molecule gains and oxygen?
d) Which molecule loses an Oxygen?

Answer 11

a,d) CO2 –> CO

b,c) H2 –> H2O

Question 12

Where does the electron transport chain occur in a eukaryotic cell?
a) matrix of the mitochondria
b) inner membrane of the mitochondria
c) cytoplasm

Answer 12

b) inner membrane of the mitochondria

Question 13

Where does the citric acid cycle occur in a eukaryotic cell?
a) matrix of the mitochondria
b) cytoplasm
c) inner membrane of the mitochondria

Answer 13

a) matrix of the mitochondria

Question 14

Is the conversion of phosphoenolpyruvate to pyruvate endergonic or exergonic?

Answer 14

exergonic

Question 15

How many net ATP are created by glycolysis (sum of all reactions)?

Answer 15

2