Question 1

An enzyme that is inhibited by the statin group of drugs (e.g.Lipitor®)is

Accepted Answer

Statin drugs inhibit HMG CoA reductase, which is an enzyme involved in the synthesis of cholesterol in the liver. This leads to a decrease in cholesterol production, which is why they are often used to treat high cholesterol.

Question 2

Which of the following is TRUE regarding the enzyme acetyl-CoA carboxylase?
(I)It catalyzes the first committed step in fatty acid oxidation.
(II)It requires S-adenosylmethionine.
(III)It produces malonyl CoA
(IV)It uses acetyl CoA

Accepted Answer

Acetyl-CoA carboxylase catalyzes the first committed step in fatty acid synthesis (not oxidation), producing malonyl-CoA from acetyl-CoA. It does not require S-adenosylmethionine; instead, it requires biotin as a cofactor.

Question 3

What is the net production of ATP from complete catabolism of the following fatty acid to CO₂ and H₂O?

Accepted Answer

The given fatty acid produces 15 acetyl-CoA molecules and 8 FADH2 and 8 NADH molecules through beta-oxidation. Each acetyl-CoA through the citric acid cycle produces 3 NADH, 1 FADH2, and 1 GTP (which can be converted to ATP). Therefore, the total ATP production through oxidative phosphorylation would be:
(15 x 3) + (8 x 1.5) + (8 x 2.5) = 45 + 12 + 20 = 77 ATP molecules
In addition, each FADH2 molecule would produce 1.5 ATP through oxidative phosphorylation, resulting in a total of 12 additional ATP molecules.
Therefore, the net production of ATP would be 77 + 12 = 89 ATP molecules, which falls between the range of 51-90.

Question 4

Which of the following best describes arachidonic acid?

Accepted Answer

Arachidonic acid is a 20-carbon fatty acid that is used for synthesis of prostaglandins.

Question 5

Cholesterol is a precursor to
(I)prostaglandins
(II)vitamin K
(III)steroid hormones such as androgens
(IV)bile acids

Accepted Answer

Cholesterol is a precursor to steroid hormones, such as androgens, and bile acids. It is not a precursor to prostaglandins or vitamin K.

Question 6

Sphinganine is an intermediate in the synthesis of which of the following?
(I)ceramides
(II)spingomyelins
(III)cerebrosides
(IV)prostaglandins

Accepted Answer

Sphinganine is an intermediate in the synthesis of ceramides, sphingomyelins, and cerebrosides. It is not involved in the synthesis of prostaglandins. Therefore, the correct option is C (I, II, III).

Question 7

Which of the following is the source of the two carbon fragments in fatty acids biosynthesis?

Accepted Answer

The answer of Which of the following is the source...

Question 8

In which location listed below does the following reaction take place?
HMG-CoA → acetoacetate + Acetyl-CoA

Accepted Answer

The conversion of HMG-CoA to acetoacetate and Acetyl-CoA occurs in the mitochondria of liver cells, as this is where ketone body synthesis occurs. The cytosol of cardiomyocytes and liver cells do not have the necessary enzymes for this conversion, and while ketone bodies can be produced in the mitochondria of heart cells, this specific reaction does not occur in that location. Therefore, the best choice is option D.

Question 9

Which of the following diets would most likely promote the formation of ketone bodies?

Accepted Answer

A diet high in fat and protein, with low carbohydrates, is most likely to promote the formation of ketone bodies. This is because in the absence of carbohydrates, the body turns to fat for energy and breaks it down into ketone bodies through a process called ketogenesis.

Question 10

Which of the following could be produced by the reaction of two or more of phosphatidic acids with two or more glycerol-3-phosphates?
(I)phosphatidylglycerol
(II)cardiolipin
(III)phosphatidylinositol
(IV)gangliosides

Accepted Answer

Phosphatidylglycerol and cardiolipin can be produced by the reaction of phosphatidic acids with glycerol-3-phosphates. Phosphatidylglycerol is a direct product, while cardiolipin, which consists of two phosphatidylglycerols linked by a glycerol, can also be formed through such reactions. Phosphatidylinositol and gangliosides, however, are derived from different biosynthetic pathways and do not form directly from the reaction of phosphatidic acids with glycerol-3-phosphates.

Question 11

Knoop's experiments with fatty acids

Accepted Answer

The answer of Knoop's experiments with fatty acids
...

Question 12

The mechanism of the condensing enzyme (KS)of fatty acid synthase is best described as

Accepted Answer

The mechanism of the condensing enzyme (KS) of fatty acid synthase is covalent catalysis using a cysteine (Cys) residue in the active site. KS catalyzes the formation of a thioester bond between two acyl substrates. The Cys residue in the active site of KS forms a transient thioester bond with one of the substrates, which is then transferred to the other substrate to form the final product. This covalent catalysis involves the temporary formation of an acyl-enzyme intermediate, which is crucial in the overall mechanism of fatty acid synthesis.

Question 13

Which enzyme catalyses the key regulatory step of cholesterol synthesis?

Accepted Answer

HMG-CoA reductase catalyses the key regulatory step of cholesterol synthesis, which is the conversion of HMG-CoA to mevalonate. This step is a rate-limiting step and is tightly regulated by feedback inhibition.

Question 14

Which of the following compounds are required to make sphingosine?
(I)palmitoyl-CoA
(II)serine
(III)acetyl-CoA
(IV)isoprene
(V)arachidonic acid

Accepted Answer

Sphingosine is synthesized from palmitoyl-CoA and serine, making options I and II correct.

Question 15

Which statement concerning fatty acid synthesis is TRUE?
(I)The process occurs in the cytosol.
(II)In eukaryotes,the process occurs on a single large protein.
(III)The growing acyl chain is carried on an acyl carrier protein instead of coenzyme A.
(IV)The process requires two NADPH per acetyl group (2 carbons)added.

Accepted Answer

Fatty acid synthesis occurs in the cytosol, involves a large multi-enzyme complex in eukaryotes, uses an acyl carrier protein, and requires two NADPH per acetyl group added.

Question 16

In which cellular compartment does the following reaction take place? HMG-CoA + 2 NADPH → mevalonate + 2 NADP⁺ + Acetyl-CoA

Accepted Answer

The reaction converting HMG-CoA to mevalonate, which is a key step in cholesterol biosynthesis, takes place in the cytosol of liver cells. This process is crucial for the production of cholesterol and other isoprenoids.

Question 17

Pain and inflammation are triggered by ___ which are synthesized by an enzyme inhibited by ____.

Accepted Answer

Pain and inflammation are often triggered by prostaglandins, which are synthesized by an enzyme called cyclooxygenase (COX). Aspirin and other NSAIDs inhibit the activity of COX, thereby reducing the production of prostaglandins and alleviating pain and inflammation. Cardiolipins, analgesics, and statins are not directly involved in the process of pain and inflammation. COX-1 is an isoform of the cyclooxygenase enzyme that plays a role in normal physiological functions such as protecting the stomach lining, while COX-2 is an inducible isoform that is primarily responsible for the production of prostaglandins during inflammation.

Question 18

Which of the following statements about peroxisomes is FALSE?

Accepted Answer

Long chain fatty acids are transported into the mitochondria via a carnitine carrier protein, not into the peroxisome. Peroxisomes primarily facilitate the breakdown of very long chain fatty acids and other lipid molecules through beta oxidation.

Question 19

An important structural lipid found in nerve cell membranes,______,is a type of ______.

Accepted Answer

Sphingomyelin is a type of phospholipid that is an important structural lipid found in nerve cell membranes. Palmitate is a fatty acid and not a phospholipid, while phosphatidylcholine is also a phospholipid but not known to be specifically important in nerve cell membranes. Glucagon is a hormone and not a lipid at all.

Question 20

Which statement concerning phospholipid synthesis is true?

Accepted Answer

The addition of polar "head groups" to diacylglycerol usually involves CDP derivatives, which are activated forms of the head group that allow it to be attached to the diacylglycerol molecule. This process is known as phospholipid synthesis. The other answer choices are incorrect.

Quiz 20: Lipid Metabolism

An enzyme that is inhibited by the statin group of drugs (e.g.Lipitor®) is

Which of the following is TRUE regarding the enzyme acetyl-CoA carboxylase? (I) It catalyzes the first committed step in fatty acid oxidation. (II) It requires S-adenosylmethionine. (III) It produces malonyl CoA (IV) It uses acetyl CoA

What is the net production of ATP from complete catabolism of the following fatty acid to CO₂ and H₂O?

Which of the following best describes arachidonic acid?

Cholesterol is a precursor to (I) prostaglandins (II) vitamin K (III) steroid hormones such as androgens (IV) bile acids

Sphinganine is an intermediate in the synthesis of which of the following? (I) ceramides (II) spingomyelins (III) cerebrosides (IV) prostaglandins

Which of the following is the source of the two carbon fragments in fatty acids biosynthesis?

In which location listed below does the following reaction take place? HMG-CoA → acetoacetate + Acetyl-CoA

Which of the following diets would most likely promote the formation of ketone bodies?

Which of the following could be produced by the reaction of two or more of phosphatidic acids with two or more glycerol-3-phosphates? (I) phosphatidylglycerol (II) cardiolipin (III) phosphatidylinositol (IV) gangliosides

Knoop's experiments with fatty acids

The mechanism of the condensing enzyme (KS) of fatty acid synthase is best described as

Which enzyme catalyses the key regulatory step of cholesterol synthesis?

Which of the following compounds are required to make sphingosine? (I) palmitoyl-CoA (II) serine (III) acetyl-CoA (IV) isoprene (V) arachidonic acid

In which cellular compartment does the following reaction take place? HMG-CoA + 2 NADPH → mevalonate + 2 NADP⁺ + Acetyl-CoA

Pain and inflammation are triggered by _ which are synthesized by an enzyme inhibited by __.

Which of the following statements about peroxisomes is FALSE?

An important structural lipid found in nerve cell membranes,,is a type of .

Which statement concerning phospholipid synthesis is true?

Quiz 20: Lipid Metabolism

An enzyme that is inhibited by the statin group of drugs (e.g.Lipitor®) is

Which of the following is TRUE regarding the enzyme acetyl-CoA carboxylase? (I) It catalyzes the first committed step in fatty acid oxidation. (II) It requires S-adenosylmethionine. (III) It produces malonyl CoA (IV) It uses acetyl CoA

What is the net production of ATP from complete catabolism of the following fatty acid to CO2 and H2O?

Which of the following best describes arachidonic acid?

Cholesterol is a precursor to (I) prostaglandins (II) vitamin K (III) steroid hormones such as androgens (IV) bile acids

Sphinganine is an intermediate in the synthesis of which of the following? (I) ceramides (II) spingomyelins (III) cerebrosides (IV) prostaglandins

Which of the following is the source of the two carbon fragments in fatty acids biosynthesis?

In which location listed below does the following reaction take place? HMG-CoA → acetoacetate + Acetyl-CoA

Which of the following diets would most likely promote the formation of ketone bodies?

Which of the following could be produced by the reaction of two or more of phosphatidic acids with two or more glycerol-3-phosphates? (I) phosphatidylglycerol (II) cardiolipin (III) phosphatidylinositol (IV) gangliosides

Knoop's experiments with fatty acids

The mechanism of the condensing enzyme (KS) of fatty acid synthase is best described as

Which enzyme catalyses the key regulatory step of cholesterol synthesis?

Which of the following compounds are required to make sphingosine? (I) palmitoyl-CoA (II) serine (III) acetyl-CoA (IV) isoprene (V) arachidonic acid

In which cellular compartment does the following reaction take place? HMG-CoA + 2 NADPH → mevalonate + 2 NADP+ + Acetyl-CoA

Pain and inflammation are triggered by ___ which are synthesized by an enzyme inhibited by ____.

Which of the following statements about peroxisomes is FALSE?

An important structural lipid found in nerve cell membranes,______,is a type of ______.

Which statement concerning phospholipid synthesis is true?

What is the net production of ATP from complete catabolism of the following fatty acid to CO₂ and H₂O?

In which cellular compartment does the following reaction take place? HMG-CoA + 2 NADPH → mevalonate + 2 NADP⁺ + Acetyl-CoA

Pain and inflammation are triggered by _ which are synthesized by an enzyme inhibited by __.

An important structural lipid found in nerve cell membranes,,is a type of .