In which cellular compartment does the lengthening of fatty acid chains primarily take place in the mammalian liver?
Răspuns
(D)
Microsomes
2
Which enzyme is crucial for facilitating the movement of acetyl-CoA, the primary building block of fatty acids, from the mitochondria to the cytosol?
Răspuns
(C)
Citrate lyase
3
The process of fatty acid synthesis is often described as a reductive process. Which of the following molecules provides the necessary reducing power for this process?
Răspuns
(D)
NADPH
4
Which complex functions as a multifunctional enzyme in higher organisms, playing a key role in fatty acid synthesis?
Răspuns
(D)
Fatty acid synthase
5
The fatty acid synthase complex carries out how many distinct enzymatic steps?
Răspuns
(B)
6 sequential enzymatic steps
6
What is the major pathway that generates the reducing equivalents (NADPH) required for the synthesis of fatty acids?
Răspuns
(A)
Pentose phosphate pathway
7
ACP (acyl carrier protein), a component of fatty acid synthase in both bacteria and mammals, contains which vitamin?
Răspuns
(D)
Pantothenic acid
8
Which enzyme catalyzes the reaction that converts acetyl-CoA to malonyl-CoA?
Răspuns
(A)
Acetyl-CoA carboxylase
9
In the pathway of fatty acid synthesis, what is the step that most significantly controls the rate of the overall process?
Răspuns
(A)
Acetyl-CoA carboxylase step
10
To create an acylCoA derivative with two additional carbon atoms from fatty acyl-CoA, which molecule serves as the source of acetyl units?
Răspuns
(D)
Malonyl-CoA
11
What cofactor is necessary for the transformation of acetyl-CoA to malonyl-CoA during fatty acid synthesis outside of mitochondria?
Răspuns
(A)
Biotin
12
Where does the glycerol used for fatty acid esterification primarily originate in fat cells?
Răspuns
(A)
Primarily from glucose
13
What is the initial intermediate formed in the process of synthesizing triglycerides from glycerol 3-phosphate and acyl-CoA?
Răspuns
(D)
Phosphatidic acid
14
In which of the following tissues is the activity of the enzyme glycerol kinase notably low?
Răspuns
(D)
Adipose tissue
15
What is the shared precursor in the creation of both triacylglycerol and phospholipids?
Răspuns
(A)
1, 2-Diacylglycerol phosphate
16
Which enzyme systems are involved in the synthesis of polyunsaturated fatty acids?
Răspuns
(A)
Acyl transferase and hydratase
17
Which factor promotes the desaturation and chain elongation system of polyunsaturated fatty acids?
Răspuns
(A)
Insulin
18
A higher rate of fat production (lipogenesis) is linked to what dietary or hormonal state?
Răspuns
(A)
High proportion of carbohydrate in diet
19
Which of the following exemplifies enzyme specificity?
Răspuns
(D)
All of these
20
Phospholipase C cleaves the ester bond, releasing 1, 2-diacylglycerol and a phosphoryl base at which position?
Răspuns
(D)
3
21
What enzyme facilitates the creation of phosphatidylinositol by attaching inositol to CDP diacylglycerol?
Răspuns
(C)
CDP-diacylglycerol inositol transferase
22
Which cofactor is necessary for the creation of sphingosine?
Răspuns
(C)
NADPH+
23
What two molecules combine to create ceramide?
Răspuns
(B)
Acyl-CoA
24
Where does the synthesis of the amino alcohol sphingosine primarily occur?
Răspuns
(D)
Endoplasmic reticulum
25
Which hormone decreases the release of free fatty acids from fat tissue?
Răspuns
(A)
Insulin
26
What is the main way insulin affects fat tissue, specifically regarding enzyme activity?
Răspuns
(A)
Hormone sensitive lipoprotein lipase
27
In the process of non-shivering thermogenesis, what is the primary mechanism?
Răspuns
(B)
Fatty acids uncouple oxidative phosphorylation
28
What best characterizes brown adipose tissue?
Răspuns
(B)
Characterised by high content of mitochondria
29
What substance accumulates in the liver, leading to fatty liver disease?
Răspuns
(D)
Triacylglycerol
30
What is an example of a lipotropic factor?
Răspuns
(A)
Choline
31
Which of the following substances is linked to the development of fatty liver?
Răspuns
(B)
CCl4
32
Where are all the enzymes necessary for cholesterol production primarily located?
Răspuns
(D)
Endoplasmic reticulum and cytosol
33
What is the primary source of all the carbon atoms in cholesterol?
Răspuns
(A)
Acetyl-CoA
34
What enzyme facilitates the condensation of two acetyl-CoA molecules into acetoacetyl-CoA?
Răspuns
(A)
Thiolase
35
What molecule is formed when acetoacetyl-CoA combines with another acetyl-CoA molecule?
Răspuns
(D)
3-Hydroxy 3-methyl-glutaryl-CoA
36
What enzyme catalyzes the conversion of HMG-CoA to mevalonate through reduction?
Răspuns
(B)
HMG-CoA reductase
37
What cofactor is essential for the enzyme HMG-CoA reductase during the reduction process?
Răspuns
(A)
NADPH
38
Which step in cholesterol biosynthesis is key for controlling the rate and site of metabolic regulation?
Răspuns
(C)
HMG CoA → mevalonate
39
What sterol is directly produced by the cyclization of squalene in mammals?
Răspuns
(B)
Lanosterol
40
Which enzyme is the rate-limiting factor in the biosynthesis of cholesterol?
Răspuns
(C)
HMG-CoA reductase
41
Which enzyme's activity is suppressed by cholesterol through a regulatory loop?
Răspuns
(B)
HMG-CoA reductase
42
Which of the following is known to suppress the function of HMG-CoA reductase?
Răspuns
(A)
A fungal-derived compound related to mevastatin
43
What is the primary mechanism by which clofibrate, a lipid-lowering medication, achieves its effect?
Răspuns
(B)
Lowering the release of VLDL particles, which transport triacylglycerol and cholesterol, by the liver
44
In the production of cholesterol, which enzyme's function is disrupted by triparanol?
Răspuns
(A)
Δ24 Reductase
45
Which hormone's presence is associated with increased activity of HMG-CoA reductase?
Răspuns
(A)
Insulin
46
Which of the following sterols is the primary one found in fecal matter?
Răspuns
(A)
Coprostanol
47
The most crucial, or rate-limiting, process in the creation of bile acids involves which of the following?
Răspuns
(A)
7-Hydroxylase reaction
48
Which of the following conditions is often associated with elevated cholesterol levels?
Răspuns
(A)
Xanthomatosis
49
In which of these conditions is a decrease in cholesterol levels typically observed?
Răspuns
(A)
Thyrotoxicosis
50
What is the main source of cholesterol outside of cells that is available for human tissues?
