Lipid Metabolism: A Comprehensive Guide
Q. Choose the true statement:
- There are two classes of phospholipids: those containing sphingosine and those containing glycerol as a backbone.
- Both classes are found as structural components of membranes and play a role in the generation of lipid signaling molecules.
Ethanolamine + PA = cephalin.
Choline + PA = lecithin.
Q. Two molecules of phosphatidic acid (PA) esterified through their phosphate group to glycerol are called:
Cardiolipin.
Q. The backbone of sphingomyelin is the amino alcohol:
Sphingosine.
Q. The precursor of many other phosphoglycerides is:
Phosphatidic acid (PA).
Q. Triacylglycerol synthesis occurs essentially only in the:
Liver.
Q. Lung maturity of a fetus is indicated by the ratio of:
Dipalmitoylphosphatidylcholine (DPPC) to sphingomyelin.
Q. Synthesis of phosphatidylcholine from phosphatidylserine occurs in the:
Liver.
Q. Which of the following statements is false?
Sphingomyelin, a glycerol-based phospholipid, is the major structural lipid in the nerve tissue.
Q. Which of the following statements is true?
Sphingomyelin is degraded by lysosomal phospholipase sphingomyelinase.
Q. Niemann-Pick disease is characterized by the inability to degrade:
Sphingomyelin.
Q. Sphingosine is a:
Glucolipid.
Q. A sphingolipid accumulates in the lysosomes if:
A specific hydrolase required for the degradation process is partially or totally missing.
Q. Synthesis of glycosphingolipids occurs primarily in the:
Golgi apparatus.
Q. A specific sphingolipidosis can be diagnosed by:
- Measuring specific enzyme activity in cultured fibroblasts or peripheral leukocytes.
- Analyzing DNA or performing a histologic examination of the affected tissue.
Q. Eicosanoids include:
Prostaglandins, thromboxanes, and leukotrienes.
Q. Eicosanoids have the following physiologic functions:
- Regulation of renal function.
- Regulation of smooth muscle contraction.
- Regulation of blood vessel diameter.
- Maintenance of platelet homeostasis.
Q. A deficiency in hematopoietic cells can lead to:
Paroxysmal nocturnal hemoglobinuria.
Q. The immediate precursor of prostaglandins is:
Arachidonic acid.
Q. Secondary bile acids are:
Deoxycholic acid and lithocholic acid.
Q. Bile is secreted into the intestine, and more than 95% of bile acids and salts are:
Efficiently reabsorbed.
Q. Cholelithiasis can occur if:
More cholesterol enters the bile than can be solubilized by the available bile salts and phosphatidylcholine.
Q. Plasma lipoproteins include:
- Chylomicrons
- Very-low-density lipoproteins (VLDL)
- Low-density lipoproteins (LDL)
- High-density lipoproteins (HDL)
Q. Cholesterol is the precursor of all classes of steroid hormones, including:
- Glucocorticoids and mineralocorticoids.
- Sex hormones (androgens, estrogens, progestins).
Q. Aromatase inhibitors are used in the treatment of breast cancer in women.
1) Select the correct sentence:
e) Answer B and C are correct.
- Lipids are the major source of energy for the body.
- Lipids play a major role in the control of the body’s homeostasis.
2) In the human body, digestion of lipids occurs in the:
b) Small intestine.
3) Name the compounds produced by the digestion of triacylglycerol:
Fatty acids and monoacylglycerol.
4) During the degradation of triacylglycerol (TAG):
a) Procolipase is activated by trypsin.
5) A model presents the structure of:
b) Cholesterol.
6) Mark (T) or (F) about lipoproteins:
- VLDL deliver cholesterol to the liver. (T)
- LDL are composed of low TAG and low cholesterol. (F)
- Chylomicrons deliver dietary triacylglycerol to the liver. (T)
7) The role of bile in the digestion of triglycerides is:
a) Emulsification of fat drops into droplets.
8) Select the correct answer:
During the digestion of dietary lipids, cholecystokinin decreases gastric motility and stimulates the secretion of bile.
9) Fatty acids are NOT:
c) Associated with proteins in membranes.
10) A substrate for PGH2 synthesis is:
b) Arachidonic acid.
11) In the human body, synthesis of fatty acids occurs in:
c) Adipocytes.
12) Complete the missing fields:
- Glycerol phosphate
- Acyltransferase
- Lysophosphatidic acid
- Acyltransferase
- Phosphatidic acid
- Phosphatase
- Diacylglycerol
- Acyltransferase
- Triacylglycerol
13) Beta-oxidation of very-long-chain fatty acids (VLCFA) occurs in:
e) Answer a and c are correct.
- Mitochondria
- Peroxisomes
14) Replace Ketone Bodies with:
- Acetoacetate
- 3-hydroxybutyrate
- Acetone
15) The question is too long.
16) Niemann-Pick disease is caused by:
c) Deficiency of sphingomyelinase.
17) Mark (T) or (F) about Tay-Sachs disease:
- Accumulation of gangliosides. (T)
- Muscular weakness and blindness. (T)
- Skeletal deformities. (T)
18) Oxidation of LDL is (stimulated/inhibited) by:
- Inhibited by ascorbic acid. (T)
- Stimulated by hydrogen peroxide. (T)
- Inhibited by vitamin E. (T)
19) Synthesis of cholesterol:
d) Answer a and c are correct.
- Is regulated by HMG CoA reductase.
- Is produced from mevalonic acid.
20) Write the basic structure of a fatty acid:
CH3(CH2)nCOO-
Hydrophobic hydrocarbon chain (ionized at pH 7) – Hydrophilic carboxyl group
21) Mark (T) or (F) about plasma lipoproteins:
- Chylomicrons are the lipoproteins with the highest percentage of protein. (F)
- LDLs are denser than VLDL. (T)
- HDLs are the lipoproteins with the lowest percentage of protein. (F)
22) Mark the true answer about hypertriacylglycerolemia:
c) Is caused by a deficiency of lipoprotein lipase.
23) Activation of acetyl CoA carboxylase:
e) Answer a and c are correct.
- Is inhibited by epinephrine and glucagon.
- Is inhibited by AMP-activated protein kinase.
24) Select the correct sentence:
c) Fatty acid biosynthesis takes place in pathways other than the degradation pathways.
25) A palmitoyl-ACP is formed as a result of:
a) Five-cycle repetition of fatty acid synthesis.
26) The most common compounds of bile acids are:
c) Cholic acid and chenodeoxycholic acid.
27) Bile acids:
d) Answer a and b are correct.
- Are formed in the liver as a result of a multi-stage process.
- Are transported in plasma with albumin as a protein carrier.
The digestion of lipids begins in the stomach, catalyzed by lingual and gastric lipases that are:
b) Acid-stable lipases.
The reason for a near or complete absence of pancreatic lipase may be:
Cystic fibrosis (CF) is caused by a mutation to the gene for the CF transmembrane conductance regulator (CFTR) protein, which functions as a chloride channel on epithelium. This leads to decreased hydration, resulting in thickened secretions such that pancreatic enzymes are not able to reach the intestine, leading to pancreatic insufficiency.
The critical process of emulsification of dietary lipids occurs:
In the duodenum.
Colipase (secreted by the pancreas) is secreted as the zymogen, procolipase, which is activated in the intestine by:
Trypsin.
5) Cholesteryl esters are hydrolyzed by:
Pancreatic cholesteryl ester hydrolase (cholesterol esterase), which produces cholesterol plus free fatty acids.
6) Pancreatic secretion of the hydrolytic enzymes that degrade dietary lipids in the small intestine is hormonally controlled by:
c) A small peptide hormone – cholecystokinin (CCK, formerly called pancreozymin).
7) Triacylglycerol in chylomicrons is degraded to free fatty acids and glycerol by:
b) Lipoprotein lipase.
8) Glycerol that is released from TAG is used:
Almost exclusively by the liver to produce glycerol 3-phosphate.
9) Which one of the following statements about the absorption of lipids from the intestine is correct?
Dietary triacylglycerol is partially hydrolyzed and absorbed as free fatty acids and monoacylglycerol.
10) Sing the structure of the fatty acids:
CH3(CH2)nCOO-
Hydrophobic hydrocarbon chain (ionized at pH 7) – Hydrophilic carboxyl group
11) Fill in the gaps of the names and structures of fatty acids:
- Palmitic acid – 16:0
- Palmitoleic acid – 16:1(9)
- Stearic acid – 18:0
- Oleic acid – 18:1(9)
- Linoleic acid – 18:2(9,12)
12) Essential fatty acid (linoleic acid and alpha-linolenic acid) deficiency can result in:
Scaly dermatitis as well as visual and neurologic abnormalities.
14) In adult humans, fatty acid synthesis occurs primarily in:
b) The liver and lactating mammary glands, and to a lesser extent, in adipose tissue.
15) The first step in de novo fatty acid synthesis is:
The transfer of acetate units from mitochondrial acetyl CoA to the cytosol.
16) Mitochondrial acetyl CoA is produced by:
b) The oxidation of pyruvate, the catabolism of fatty acids, ketone bodies, and certain amino acids.
17) The carboxylation of acetyl CoA to form malonyl CoA is catalyzed by:
Fatty acid synthase.
19) Palmitate, a 16-carbon fully saturated long-chain fatty acid (16:0), is the primary end product of fatty acid synthesis activity. It can be further elongated by the addition of:
b) Two-carbon units in the endoplasmic reticulum (ER) and the mitochondria.
20) Enzymes present in the ER are responsible for desaturating fatty acids (that is, adding cis double bonds). Termed mixed-function oxidases, the desaturation reactions require NADH, cytochrome b5 reductase, and O2.
21) The initial acceptor of fatty acids during TAG synthesis is:
b) Glycerol phosphate.
23) Beta-oxidation is the major pathway for catabolism of saturated fatty acids, in which:
b) Two-carbon fragments are successively removed from the carboxyl end of the fatty acyl CoA, producing acetyl CoA, NADH, and FADH2.
24) Select the correct sentence:
c) Carnitine is responsible for the transport of long-chain acyl groups from the cytosol into the mitochondrial matrix.
25) Carnitine:
Can be obtained from the diet, where it is found primarily in meat products, and can also be synthesized from the amino acids lysine and methionine by an enzymatic pathway found in the liver and kidney.
26) medium-chain fatty acyl CoA dehydrogenase (MCAD) deficiency:
b) is one of the most common inborn error of metabolism, which causes a decrease in fatty acids oxidation, resulting in hypoketonemia and severe hypoglycemia.
27) the engery yield from the B-oxidation of a molecule of palmitoyl CoA to CO2 and H2O:
c) be generated 129 ATP.
28) select the correct sentence: b) the compounds categorized as ketone bodies are acetoacetate, 3-hydroxybutyrate and acetone
29) when the rate of formation of ketone bodies is greater then the rate of their use, their levels begin to rise in the blood. It is ketonemia.Eventually their levels begin to rise in urine. It is Ketonuria
30) a frequent symptom of diabetic ketoacidosis is a fragity odow on the breath ,which result from increased production of acetone