Where are the enzymes of the citric acid cycle primarily situated?
Răspuns
(A)
The central region of mitochondria
2
What is the first reaction in the citric acid cycle?
Răspuns
(B)
Combining acetyl-CoA with oxaloacetate
3
Which molecule acts as a catalyst in the citric acid cycle?
Răspuns
(A)
Oxaloacetate
4
Which citric acid cycle enzyme can also be found outside the mitochondria?
Răspuns
(C)
a-Ketoglutarate dehydrogenase
5
What is necessary for the α-ketoglutarate dehydrogenase enzyme to function in the citric acid cycle?
Răspuns
(A)
NAD
6
Assuming a solution contains all citric acid cycle components, excess acetyl-CoA, and is at the right pH, which factor would limit the cycle's speed?
Răspuns
(D)
Cofactor reduction
7
In the TCA cycle, what enzyme changes oxalosuccinate into α-ketoglutarate?
Răspuns
(B)
Isocitrate dehydrogenase
8
Which cofactor is essential for the enzyme -ketoglutarate dehydrogenase in the citric acid cycle?
Răspuns
(A)
Lipoate
9
In the citric acid cycle, which reaction produces a high-energy phosphate through substrate-level phosphorylation?
Răspuns
(D)
Succinyl CoA ⇌†† α-Succinate
10
Fluoroacetate prevents which reaction in the citric acid cycle?
Răspuns
(C)
Citrate ⇌†† α-cis-aconitate
11
What substance inhibits the conversion of α-Ketoglutarate into succinyl-CoA?
Răspuns
(B)
Arsenite
12
How many ATP molecules are produced in a single cycle of the citric acid cycle?
Răspuns
(B)
12
13
What is the net ATP yield from the complete oxidation of one glucose molecule?
Răspuns
(D)
38 ATP
14
Which metabolic intermediate can serve as both a starting material and an end product in glucose metabolism?
Răspuns
(A)
Lactate
15
Which of the following molecules can freely pass through the mitochondrial membrane?
Răspuns
(B)
Malate
16
Which reaction in the Kreb's cycle does not require a cofactor from the vitamin B group?
Răspuns
(A)
Citrate ‡† isocitrate
17
Which coenzyme is NOT used in the formation of acetyl-CoA from pyruvate?
Răspuns
(B)
Biotin
18
In the citric acid cycle, which molecule acts as a carrier?
Răspuns
(C)
Oxaloacetate
19
Which substance specifically inhibits succinate dehydrogenase?
Răspuns
(B)
Arsenite
20
Which enzyme in the citric acid cycle is regulated by allosteric control?
Răspuns
(C)
Fumarase
21
What is the net ATP production from the Rapport-Leubering pathway in red blood cells?
Răspuns
(A)
0
22
Under aerobic versus anaerobic conditions, what is the approximate ratio of net ATP molecules formed per glucose molecule?
Răspuns
(C)
18:1
23
Glycogen synthesis utilizes a specific nucleotide of glucose. In the following reaction, what does NuDP represent? NuDP Glucose + glycogen,→ NuDP + glycogen+1
Răspuns
(C)
UDP
24
Which describes the state of the enzyme phosphoglucomutase during the conversion of glucose 6-phosphate to glucose 1-phosphate?
Răspuns
(D)
Phosphorylated-dephosphorylatedrephosphorylated
25
Approximately what percentage of the liver's weight is glycogen?
Răspuns
(A)
6%
26
Which enzyme creates branch points during glycogenesis?
Răspuns
(A)
Amylo [1→ 4] [1→ 6] transglucosidase
27
In glycogenolysis, which enzyme facilitates the transfer of a trisaccharide unit, exposing a 1→6 branch point?
Răspuns
(B)
α-[14] α-[14] Glucan transferase
28
Which step in the synthesis of glycogen from glucose is reversible?
Răspuns
(B)
Glucose 6-phosphate glucose 1-phosphate
29
In which of the following tissues is the enzyme glucose-6-phosphatase, which converts glucose 6-phosphate to glucose, not present?
Răspuns
(B)
Muscle
30
Which molecule acts as an allosteric activator of glycogen synthase?
Răspuns
(B)
Glucose-6-Phosphate
31
Which factor suppresses the function of glycogen synthase?
Răspuns
(C)
Mg2+
32
Which hormone stimulates glycogen synthase function?
Răspuns
(A)
Insulin
33
What are the distinguishing traits of an active site?
Răspuns
(D)
Both (A) and (B)
34
A deficiency in which enzyme defines Von Gierke's disease?
Răspuns
(A)
Glucose-6-phosphatase
35
What enzyme's absence causes Cori disease (Limit dextrinosis)?
Răspuns
(B)
Debranching enzyme
36
Mc Ardle's syndrome is caused by the lack of which enzyme?
Răspuns
(B)
Muscle phosphorylase
37
Which enzyme deficiency is associated with Pompe's disease?
Răspuns
(A)
Lysosomal α-1→4 and 1→6-glucosidase
38
What enzyme deficiency results in Amylopectinosis?
Răspuns
(B)
Branching enzyme
39
What enzyme is deficient in Her's disease?
Răspuns
(B)
Liver phosphorylase
40
Tarui disease is linked to the lack of which enzyme?
Răspuns
(C)
Muscle and erythrocyte phosphofructokinase
41
Which enzyme is involved in the hexose monophosphate pathway?
Răspuns
(D)
Glucose-6-phosphate dehydrogenase
42
Which molecule accepts hydrogen in the pentose phosphate pathway?
Răspuns
(B)
NADP
43
Where are the enzymes of the pentose phosphate pathway located?
Răspuns
(A)
Cytosol
44
What enzyme converts D-ribulose-5-phosphate to D-ribose-5-phosphate in the pentose phosphate pathway?
Răspuns
(B)
Ketoisomerase
45
Which B vitamin is required by the transketolase enzyme in the pentose phosphate pathway?
Răspuns
(B)
Thiamin
46
In a reaction, Xylulose-5-phosphate donates active glycolaldehyde. Which molecule acts as the acceptor?
Răspuns
(A)
Erythrose 4-phosphate
47
What is a significant product generated by the pentose phosphate pathway?
Răspuns
(A)
NADPH for reductive synthesis
48
The pentose phosphate pathway helps protect erythrocytes from hemolysis by supporting which enzyme?
Răspuns
(C)
Glutathionic peroxidase
49
What enzyme deficiency in the pentose phosphate pathway is often associated with hemolytic anemia?
