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