Understanding Lipid Metabolism: From Digestion to Diseases
Q. Choose True:
– Two classes of phospholipids contain sphingosine and 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 PA esterified through their phosphate group to glycerol is 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:
Liver
Q. Lung maturity of the fetus is determined by the ratio of:
DPPC to Sphingomyelin
Q. Synthesis of phosphatidylcholine from phosphatidylserine occurs in:
Liver
Q. False Statement:
Sphingomyelin, a glycerol-based phospholipid, is the major structural lipid in nerve tissue.
Q. True Statement:
Sphingomyelin is degraded by lysosomal phospholipase sphingomyelinase.
Q. Niemann-Pick Disease is characterized by the inability to degrade:
Sphingomyelin
Q. Sphingosine is a:
Sphingolipid
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:
Golgi
Q. A specific sphingolipidosis can be diagnosed by:
- Measuring specific enzyme activity in cultured fibroblasts or peripheral leukocytes.
- Analysis of DNA or histologic examination of the affected tissue.
Q. Eicosanoids include:
Prostaglandins and related compounds, thromboxanes, and leukotrienes.
Q. Physiological functions of eicosanoids include:
- 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 and lithocholic acids
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, VLDL, LDL, and HDL
Q. Cholesterol is the precursor of all classes of steroid hormones:
- Glucocorticoids and mineralocorticoids
- Sex hormones (androgens, estrogens, progestins)
Aromatase inhibitors are used in the treatment of breast cancer in women.
1) Select the correct sentence:
b) Lipids are the major source of energy for the body.
c) Lipids play a major role in the control of the body’s homeostasis.
e) Answers B and C are correct.
2) In the human body, digestion of lipids occurs in:
b) Small intestine
3) Name the compounds that are produced by the digestion of triacylglycerol:
2-Fatty acids and 2-Monoacylglycerol
4) During the degradation of TAG:
a) Procolipase is activated by trypsin.
5) The image presents the structure of:
b) Cholesterol
6) Mark (T) or (F) about lipoproteins:
VLDL deliver cholesterol to the liver. F
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 to 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, the 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:
a) Mitochondria
c) Peroxisomes
e) Answers a and c are correct.
14) Ketone Bodies:
a) Acetoacetate
b) 3-hydroxybutyrate
c) Acetone
15) What is the process by which arachidonic acid is converted to prostaglandins and thromboxanes?
a) Prostaglandin synthesis
16) Niemann-Pick disease is caused by:
c) Deficiency of sphingomyelinase
17) Mark (T) or (F) about Tay-Sachs disease:
a) Accumulation of gangliosides T
b) Muscular weakness and blindness T
c) Skeletal deformities T
18) Oxidation of LDL is (stimulated/inhibited) by:
a) Inhibited by ascorbic acid
b) Stimulated by hydrogen peroxide
c) Inhibited by vitamin E
19) Synthesis of cholesterol:
a) Is regulated by HMG-CoA reductase
c) Is produced from mevalonic acid
d) Answers a and c are correct.
20) Write the basic structure of a fatty acid:
CH3(CH2)nCOOH
21) Mark (T) or (F) about plasma lipoproteins:
a) Chylomicrons are the lipoproteins with the highest percentage of protein. F
b) LDLs are denser than VLDL. T
c) 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:
a) Is inhibited by epinephrine and glucagon
c) Is inhibited by AMP-activated protein kinase
e) Answers a and c are correct.
24) Select the correct sentence:
a) Fatty acid synthesis occurs in the cytosol.
c) Fatty acid biosynthesis takes place via different pathways than degradation.
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:
a) Are formed in the liver as a result of a multi-stage process.
b) Are transported in plasma with albumin as a protein carrier.
d) Answers a and b are correct.
The digestion of lipids begins in the stomach, catalyzed by lingual and gastric lipases that are:
b) Acid-stable lipases
A near or complete absence of pancreatic lipase may be due to: Cystic fibrosis (CF), which is caused by a mutation in the gene for the CF transmembrane conductance regulator (CFTR) protein. This protein functions as a chloride channel on the epithelium. The mutation leads to decreased hydration, resulting in thickened secretions that prevent pancreatic enzymes from reaching 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) Structure of fatty acids:
CH3(CH2)nCOO-
Hydrophobic Hydrocarbon chain
Hydrophilic Carboxyl group (ionized at pH 7)
11) 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:
a) 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 synthase 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) β-Oxidation is the major pathway for the 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. It 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 errors of metabolism, which causes a decrease in fatty acid oxidation, resulting in hypoketonemia and severe hypoglycemia.
27) The energy yield from the β-oxidation of one molecule of palmitoyl-CoA to CO2 and H2O is:
c) 129 ATP
28) Select the correct sentence:
b) The compounds categorized as ketone bodies are acetoacetate, 3-hydroxybutyrate, and acetone.