1
Q
- Lipids are best defined as biomolecules that are:
a. Water soluble and polymeric
b. Hydrophobic or amphipathic and insoluble in water
c. Always composed of repeating monomers
d. Primarily composed of peptide bonds
A
Answer: b. Lipids are hydrophobic or amphipathic and insoluble in water.
2
Q
- Which element is the most fundamental for organic molecules and lipids?
a. Nitrogen
b. Oxygen
c. Carbon
d. Phosphorus
A
Answer: c. Carbon forms the backbone of organic molecules.
3
Q
- Fatty acids are characterized by:
a. A phosphate head and two hydrocarbon tails
b. A glycerol backbone with three phosphates
c. A terminal carboxylic acid and a long hydrocarbon chain
d. A steroid four-ring structure
A
Answer: c. Fatty acids have a terminal –COOH and a long hydrocarbon chain.
4
Q
- As fatty-acid chain length increases, melting point generally:
a. Decreases
b. Increases
c. Is unchanged
d. Becomes unpredictable
A
Answer: b. Longer chains increase van der Waals interactions → higher melting point.
5
Q
- The presence of cis double bonds in fatty acids causes:
a. Straighter chains and higher melting point
b. Kinks in the chain and lower melting point
c. Formation of steroid rings
d. Conversion to glycerol
A
Answer: b. Cis double bonds introduce kinks that lower melting point and increase fluidity.
6
Q
- Which fatty acid type most increases membrane fluidity?
a. Long-chain saturated
b. Trans monounsaturated
c. Cis polyunsaturated
d. Medium-chain saturated
A
Answer: c. Cis polyunsaturated fatty acids introduce multiple kinks → highest fluidity.
7
Q
- Essential fatty acids that humans must obtain from diet include:
a. Palmitic acid and stearic acid
b. Linoleic acid (ω-6) and α-linolenic acid (ω-3)
c. Oleic acid only
d. Arachidonic acid only
A
Answer: b. Linoleic and α-linolenic acids are essential (we lack certain desaturases).
8
Q
- In delta (Δ) fatty-acid nomenclature, numbering starts from:
a. Methyl end (ω end)
b. Carboxyl end
c. Middle carbon
d. It’s arbitrary
A
Answer: b. Δ system numbers from the carboxyl (–COOH) end.
9
Q
- Omega-3 designation (ω-3) refers to a double bond located how many carbons from the methyl end?
a. 2
b. 3
c. 6
d. 9
A
Answer: b. ω-3 means first double bond is 3 carbons from methyl end.
10
Q
- Triacylglycerols (TAGs) are composed of:
a. Glycerol + 3 fatty acids (esterified)
b. Sphingosine + 2 phosphates
c. Cholesterol + fatty acids
d. Two fatty acids + phosphate
A
Answer: a. TAGs = glycerol backbone esterified with three fatty acids.
11
Q
- Which process yields glycerol + free fatty acids from TAGs?
a. Lipogenesis
b. Lipolysis (hydrolysis)
c. Hydrogenation
d. Saponification only
A
Answer: b. Lipolysis breaks TAGs into glycerol and free fatty acids (via lipases).
12
Q
- The energy yield of lipids per gram (approx) is:
a. 4 kcal/g
b. 7 kcal/g
c. 9 kcal/g
d. 2 kcal/g
A
Answer: c. Lipids yield ~9 kcal/g, higher than carbohydrates/proteins.
13
Q
- Which physical change occurs when hydrogenating vegetable oils?
a. Increase in cis double bonds
b. Conversion of unsaturated → more saturated (and often trans)
c. Creation of glycerol backbone
d. Formation of phospholipids
A
Answer: b. Hydrogenation saturates double bonds and can create trans fats.
14
Q
- Saponification of triglycerides produces:
a. Fatty acids and glycerol
b. Fatty acid salts (soap) and glycerol
c. Cholesterol and bile acids
d. Phospholipids
A
Answer: b. Strong base hydrolysis yields fatty acid salts (soap) + glycerol.
15
Q
- Waxes differ from TAGs because they contain:
a. Glycerol with three fatty acids
b. Long-chain alcohols esterified to fatty acids
c. Steroid nucleus
d. Phosphate head groups
A
Answer: b. Waxes = fatty acid + long-chain alcohol esters (R-COO-R’).
16
Q
- Major roles of phospholipids include:
a. Energy storage only
b. Membrane structure and signaling
c. Hormone storage
d. Carrying oxygen in blood
A
Answer: b. Phospholipids form bilayers and produce signaling molecules (IP3, DAG).
17
Q
- Waxes differ from TAGs because they contain:
a. Glycerol with three fatty acids
b. Long-chain alcohols esterified to fatty acids
c. Steroid nucleus
d. Phosphate head groups
A
Answer: b. Waxes = fatty acid + long-chain alcohol esters (R-COO-R’).
18
Q
- Which phospholipid is a major component of lung surfactant?
a. Phosphatidylserine
b. Phosphatidylethanolamine
c. Phosphatidylcholine (lecithin)
d. Cardiolipin
A
Answer: c. Dipalmitoyl-phosphatidylcholine (lecithin) is critical for surfactant.
19
Q
- Which lipid class is especially important in nervous tissue and myelin?
a. Triacylglycerols
b. Sphingolipids (sphingomyelin, gangliosides)
c. Waxes
d. Sterols only
A
Answer: b. Sphingolipids (sphingomyelin, gangliosides) are abundant in nervous tissue.
20
Q
- A child with cherry-red macula and neurodegeneration most likely has accumulation of:
a. Glucocerebroside
b. GM2 ganglioside
c. Sphingomyelin
d. Ceramide
A
Answer: b. GM2 ganglioside accumulates in Tay-Sachs disease (Hexosaminidase A deficiency).
21
Q
- The parent sterol for steroid hormones and bile acids is:
a. Ergosterol
b. Phytosterol
c. Cholesterol
d. Lanosterol only
A
Answer: c. Cholesterol is the sterol precursor for steroid hormones and bile acids.
22
Q
- HMG-CoA reductase catalyzes which step?
a. Conversion of acetyl-CoA → HMG-CoA
b. Rate-limiting reduction of HMG-CoA → mevalonate in cholesterol synthesis
c. Final conversion of mevalonate → cholesterol
d. Hydrolysis of cholesterol esters
A
Answer: b. HMG-CoA reductase is the rate-limiting enzyme converting HMG-CoA to mevalonate.
23
Q
- Statins lower cholesterol primarily by:
a. Preventing dietary cholesterol absorption
b. Inhibiting HMG-CoA reductase (cholesterol synthesis)
c. Increasing bile acid reabsorption
d. Stimulating lipoprotein lipase to degrade HDL
A
Answer: b. Statins inhibit HMG-CoA reductase, reducing endogenous synthesis.
24
Q
- Which lipoprotein transports dietary triglycerides from intestine to tissues?
a. HDL
b. LDL
c. Chylomicrons
d. VLDL
A
Answer: c. Chylomicrons carry dietary TAGs from the gut to peripheral tissues.
25
24. Which lipoprotein is richest in protein (highest density)?
a. Chylomicron
b. VLDL
c. LDL
d. HDL
Answer: d. HDL is smallest and most protein-dense (highest density).
26
25. LDL’s primary physiological role is:
a. Export triglycerides from liver
b. Reverse cholesterol transport
c. Deliver cholesterol to peripheral tissues
d. Digest dietary fat in the gut
Answer: c. LDL transports cholesterol from liver to peripheral cells.
27
26. HDL is best known for:
a. Delivering triglycerides to adipose tissue
b. Reverse cholesterol transport (tissue → liver)
c. Causing atherosclerotic plaques
d. Carrying fat-soluble vitamins only
Answer: b. HDL mediates reverse cholesterol transport to the liver.
Good cholesterol
28
27. VLDL primarily transports:
a. Cholesterol esters only
b. Endogenously synthesized triglycerides
c. Phospholipids for membranes
d. Bile acids
Answer: b. VLDL carries triglycerides synthesized in the liver to tissues.
29
28. Enterohepatic circulation reabsorbs approximately what percentage of bile salts?
a. 5%
b. 25%
c. 50%
d. 95%
Answer: d. About 95% of bile salts are reabsorbed in the ileum and returned to the liver.
30
29. Bile salts are conjugated with which amino acids to increase detergent effectiveness?
a. Lysine or arginine
b. Glycine or taurine
c. Glutamate or aspartate
d. Serine or threonine
Answer: b. Bile acids are conjugated with glycine or taurine to make bile salts.
31
30. Bile acid sequestrants (e.g., cholestyramine) lower cholesterol by:
a. Inhibiting HMG-CoA reductase
b. Binding bile acids in gut → increased fecal loss → liver uses more cholesterol to make bile
c. Blocking dietary fat absorption directly
d. Stimulating LDL receptor degradation
Answer: b. They bind bile acids, increasing fecal excretion and driving hepatic cholesterol conversion to bile acids.
32
31. Which vitamin(s) require bile acids for intestinal absorption?
a. Vitamin C only
b. Vitamin B12 only
c. Fat-soluble vitamins A, D, E, K
d. Water-soluble vitamins B & C
Answer: c. ADEK require bile salts for micelle formation and absorption.
33
32. A high dietary cholesterol: bile salt ratio predisposes to:
a. Pancreatitis
b. Gallstone (cholelithiasis) formation
c. Rickets
d. Steatorrhea
Answer: b. Too much cholesterol or too little bile salts can cause cholesterol gallstones.
34
33. Which is the main route for cholesterol elimination from the body?
a. Urine excretion of cholesterol
b. Conversion to bile acids and fecal excretion
c. Exhalation as CO2
d. Sweat secretion
Answer: b. Conversion to bile acids and excretion in feces is the primary elimination route.
35
34. Which statement about cholesterol’s effect on membrane fluidity is TRUE?
a. Cholesterol only decreases fluidity at all temperatures
b. Cholesterol only increases fluidity at all temperatures
c. Cholesterol buffers membrane fluidity: rigidifies at high T and prevents freezing at low T
d. Cholesterol creates micelles in membranes
Answer: c. Cholesterol stabilizes membrane fluidity across temperatures.
36
35. Which enzyme is rate-limiting for bile acid synthesis from cholesterol?
a. HMG-CoA reductase
b. Cholesterol 7α-hydroxylase
c. Lipoprotein lipase
d. Acetyl-CoA carboxylase
Answer: b. Cholesterol 7α-hydroxylase is the rate-limiting enzyme for bile acid synthesis.
37
36. Eicosanoids (prostaglandins, leukotrienes) are derived from which precursor?
a. Cholesterol
b. Arachidonic acid (20:4)
c. Phosphatidylcholine exclusively
d. Bile salts
Answer: b. Arachidonic acid is the precursor for eicosanoids.
38
37. Which lipid disorder is due to LDL-receptor defects and causes very high LDL?
a. Tangier disease
b. Familial hypercholesterolemia
c. Gaucher disease
d. Tay-Sachs disease
Answer: b. Familial hypercholesterolemia results from LDL receptor defects → elevated LDL.
39
38. Phosphoester bonds are important in:
a. ATP and signaling molecules (cAMP)
b. Triacylglycerol hydrophobic tails
c. Steroid nucleus formation
d. Bile salt conjugation
Answer: a. Phosphate esters are found in ATP and second messengers like cAMP.
40
39. Which enzyme class adds phosphate groups to molecules?
a. Kinases
b. Phosphatases
c. Hydrolases
d. Isomerases
Answer: a. Kinases catalyze phosphorylation (transfer of phosphate groups).
41
40. Which statement about sphingomyelin is true?
a. It contains glycerol backbone exclusively
b. It’s a sphingolipid with sphingosine backbone and is abundant in myelin
c. It’s the main bile acid in humans
d. It’s the primary storage form of triglycerides in adipose
Answer: b. Sphingomyelin has a sphingosine backbone and is concentrated in myelin sheaths.
42
41. Gangliosides are glycosphingolipids that:
a. Contain sialic acid (NANA) residues and function in neural recognition
b. Lack carbohydrates entirely
c. Are triglyceride derivatives
d. Serve as bile acid precursors
Answer: a. Gangliosides have oligosaccharides with sialic acid and are important in neural cell recognition.
43
42. Which clinical condition is associated with deficiency of dipalmitoyl phosphatidylcholine in the lungs?
a. Asthma
b. Respiratory distress syndrome (RDS) in premature infants
c. COPD
d. Pneumonia
Answer: b. Lack of surfactant (dipalmitoyl-PC) causes neonatal RDS.
44
43. Which of the following increases the melting point of a triglyceride?
a. More cis double bonds in constituent fatty acids
b. Shorter fatty acid chain length
c. Greater proportion of long saturated fatty acids
d. Presence of unsaturation only in ω-3 position
Answer: c. Long saturated fatty acids pack tightly → higher melting point.
45
44. Which process traps dietary monosaccharides inside cells via phosphorylation?
a. Saponification
b. Phosphorylation (e.g., glucose → G6P) by kinases
c. Esterification of fatty acids
d. Bile acid conjugation
Answer: b. Kinase-mediated phosphorylation (glucose → G6P) traps sugars intracellularly.
46
45. Phosphatidylinositol derivatives are important in signaling because they:
a. Form structural waxes
b. Produce second messengers (IP3, DAG) when cleaved
c. Directly carry oxygen to tissues
d. Are the main transport form of cholesterol
Answer: b. PI derivatives are cleaved to produce IP3 and DAG, key second messengers.
47
46. Which lipoprotein remnant is formed after VLDL delivers triglycerides?
a. Chylomicron
b. LDL
c. IDL (intermediate density lipoprotein)
d. HDL
Answer: c. VLDL → IDL after TG removal; IDL can be further processed to LDL.
48
47. Which is NOT a role of cholesterol?
a. Precursor for steroid hormones
b. Component of cell membranes modifying fluidity
c. Primary energy storage used immediately like glucose
d. Precursor for bile acids and vitamin D
Answer: c. Cholesterol is not used primarily as immediate energy storage.
49
48. Which reaction converts fatty acyl-CoA to fatty alcohols during wax biosynthesis?
a. Fatty acyl-CoA reductase action
b. HMG-CoA reductase action
c. Lipoprotein lipase action
d. Cholesterol 7α-hydroxylase action
Answer: a. Fatty acyl-CoA reductase reduces acyl-CoA to fatty alcohols in wax biosynthesis.
50
49. Elevated plasma triglycerides (hypertriglyceridemia) are most strongly associated with an increased risk of:
a. Atherosclerotic plaque calcification only
b. Pancreatitis (especially when very high)
c. Gallbladder hypomotility
d. Hypoglycemia
Answer: b. Very high TAGs increase pancreatitis risk; also associated with metabolic syndrome.
51
50. Rancidity of fats is primarily due to:
a. Complete hydrogenation
b. Oxidation of double bonds in unsaturated fatty acids
c. Conversion to cholesterol
d. Micelle formation
Answer: b. Oxidative breakdown of unsaturated fats causes rancidity.
52
51. Which of the following best describes the amphipathic nature of phospholipids?
a. Entire molecule is hydrophobic
b. Contains both hydrophilic head and hydrophobic tails → forms bilayers
c. Entire molecule is hydrophilic
d. Forms crystals in water
Answer: b. Amphipathic phospholipids have polar heads and nonpolar tails and form bilayers.
53
52. During fasting, adipose hormone-sensitive lipase is activated primarily by:
a. Insulin
b. Glucagon and epinephrine via cAMP cascade
c. High dietary glucose
d. Bile salts
Answer: b. Glucagon and epinephrine activate HSL via cAMP → lipolysis.
54
53. Which lipoprotein class has the greatest lipid:protein ratio (most lipid-rich)?
a. HDL
b. LDL
c. VLDL
d. Chylomicrons
Answer: d. Chylomicrons are largest and most lipid-rich (high TG content).
55
54. Which enzyme defects cause sphingolipidoses like Tay-Sachs and Gaucher’s?
a. Kinase overactivity
b. Lysosomal enzyme deficiencies leading to sphingolipid accumulation
c. Increased HMG-CoA reductase activity
d. Lack of bile salt synthesis
Answer: b. Lysosomal hydrolase deficiencies → sphingolipid accumulation (lysosomal storage diseases).
56
55. A drug that blocks the enterohepatic reabsorption of bile acids will:
a. Decrease fecal cholesterol loss
b. Increase hepatic conversion of cholesterol to bile acids and lower serum cholesterol
c. Increase intestinal absorption of fat-soluble vitamins
d. Inhibit HMG-CoA reductase directly
Answer: b. Blocking reabsorption causes more bile acid excretion; liver uses more cholesterol to make bile.
57
56. Which describes the steroid nucleus common to steroid hormones?
a. Three-ring phenanthrene only
b. Four fused carbon rings (cyclopentanoperhydrophenanthrene)
c. Single benzene ring
d. Long linear hydrocarbon chain
Answer: b. Steroids share a four-ring fused sterol nucleus (cyclopentanoperhydrophenanthrene).
58
57. Which process forms triglycerides from glycerol and fatty acids?
a. Saponification
b. Esterification (lipogenesis)
c. Deamination
d. Oxidative phosphorylation
Answer: b. Esterification of glycerol by fatty acids forms TAGs (lipogenesis).
59
58. Which lipid is key for controlled-release drug coatings and ointments (industrial/medical)?
a. Free cholesterol
b. Waxes (long-chain esters)
c. HDL particles
d. Sphingomyelin
Answer: b. Waxes are used in drug coatings and ointments for controlled release.
60
59. Which fat-soluble vitamin is synthesized from a cholesterol derivative after UV exposure?
a. Vitamin A
b. Vitamin B12
c. Vitamin D3 (from 7-dehydrocholesterol)
d. Vitamin K
Answer: c. Vitamin D₃ is formed from 7-dehydrocholesterol in skin under UV light.
61
60. Which is the major storage form of lipids in adipose tissue?
a. Cholesterol esters
b. Free fatty acids
c. Triacylglycerols (TAGs) stored as anhydrous droplets
d. Phospholipids
Answer: c. TAGs stored as anhydrous droplets are the major adipose storage form.
62
A patient on statin therapy shows increased hepatic LDL-receptor expression. What is the physiological purpose of this change?
a. Increase cholesterol synthesis
b. Enhance uptake of LDL from blood to reduce plasma cholesterol
c. Promote bile acid reabsorption
d. Stimulate VLDL release
Answer: b. Statins lower intracellular cholesterol, upregulating LDL receptors to pull LDL from plasma.
63
2. A newborn with respiratory distress has alveoli that collapse after exhalation. Which lipid deficiency explains this?
a. Cholesterol
b. Dipalmitoyl phosphatidylcholine
c. Sphingomyelin
d. Ceramide
Answer: b. Surfactant deficiency → RDS.
64
3. A man with xanthomas and high LDL since childhood likely has a mutation in:
a. HMG-CoA synthase
b. HMG-CoA reductase
c. LDL receptor
d. Lecithin–cholesterol acyltransferase (LCAT)
Answer: c. Familial hypercholesterolemia → LDL receptor defect.
65
4. In bile-acid malabsorption (ileal resection), which vitamin deficiency is most likely?
a. Vitamin C
b. Vitamin B12
c. Vitamin A
d. Vitamin B6
Answer: c. Fat-soluble vitamins A, D, E, K need bile salts for absorption.
66
A 45-year-old develops gallstones after rapid weight loss. Mechanism?
a. Increased bile acid synthesis
b. Decreased bile salts relative to cholesterol
c. Overproduction of phospholipids
d. Increased bilirubin
Answer: b. Supersaturated cholesterol with insufficient bile salts → stones.
67
Deficiency of carnitine or CPT-I impairs:
a. Fatty-acid synthesis
b. Fatty-acid oxidation and ketone production
c. Glycolysis
d. Cholesterol esterification
Answer: b. Carnitine shuttle is required for β-oxidation in mitochondria.
68
A patient with pancreatitis has markedly elevated plasma triglycerides. Which lipoprotein is most increased?
a. LDL
b. HDL
c. VLDL and chylomicrons
d. IDL
Answer: c. Severe hypertriglyceridemia = ↑ chylomicrons & VLDL.
69
8. In abetalipoproteinemia, which apolipoprotein is missing?
a. ApoA-I
b. ApoB-48 and ApoB-100
c. ApoC-II
d. ApoE
Answer: b. ApoB absence → no chylomicrons or VLDL → fat malabsorption, steatorrhea.
70
9. In familial LCAT deficiency, what happens to HDL particles?
a. They enlarge and become cholesterol-rich
b. They remain small, discoidal, and ineffective at reverse cholesterol transport
c. They convert to LDL
d. They disappear entirely
Answer: b. LCAT esterifies cholesterol → without it, HDL cannot mature.
71
A diet high in saturated fats causes which lipid change?
a. Increased HDL
b. Decreased VLDL
c. Increased LDL and total cholesterol
d. Increased bile-acid synthesis
Answer: c. Saturated/trans fats raise LDL levels.
72
Why do omega-3 fatty acids reduce plasma triglycerides?
a. They inhibit hepatic VLDL synthesis and promote β-oxidation.
b. They increase cholesterol synthesis.
c. They block bile-acid absorption.
d. They stimulate HMG-CoA reductase.
Answer: a. ω-3 FAs down-regulate TG synthesis and VLDL secretion.
73
12. A diabetic patient with ketosis shows elevated acetone, acetoacetate, and β-hydroxybutyrate. These are derived from:
a. Glycerol
b. Acetyl-CoA from fatty-acid oxidation
c. Citrate
d. Pyruvate
Answer: b. Excess acetyl-CoA from β-oxidation → ketone-body synthesis in liver.
74
13. Which laboratory pattern suggests cholestasis (bile-flow obstruction)?
a. Low bile acids and low cholesterol
b. Elevated alkaline phosphatase, conjugated bilirubin, and cholesterol
c. Low HDL and high TAG
d. Normal bile salts with high LDL
Answer: b. Obstructed bile flow traps bile salts/cholesterol → ↑ ALP, bilirubin, cholesterol.
75
15. An individual taking cholestyramine complains of bleeding gums. The underlying reason is decreased absorption of:
a. Vitamin C
b. Vitamin K
c. Vitamin E
d. Vitamin A
Answer: b. Loss of bile acids → poor vitamin K absorption → ↓ clotting factors.
76
During fasting, the main fuel for cardiac muscle is:
a. Glucose
b. Fatty acids
c. Ketone bodies exclusively
d. Amino acids
Answer: b. Heart primarily oxidizes fatty acids for ATP during fasting.
77
Which enzyme releases fatty acids from circulating chylomicrons and VLDL at capillary beds?
a. Lipoprotein lipase (LPL)
b. Hormone-sensitive lipase
c. HMG-CoA reductase
d. Pancreatic lipase
Answer: a. LPL hydrolyzes TAGs in circulating lipoproteins.
78
In atherosclerosis, oxidized LDL is taken up by:
a. Hepatocytes via LDL receptor
b. Macrophages via scavenger receptors forming foam cells
c. Endothelial cells via HDL receptor
d. Pancreatic acinar cells
Answer: b. Oxidized LDL → foam cells in arterial wall → plaques.
79
A 2-year-old with hepatosplenomegaly and bone pain has accumulated glucocerebroside. The defective enzyme is:
a. Glucocerebrosidase
b. Hexosaminidase A
c. Arylsulfatase A
d. Sphingomyelinase
Answer: a. Gaucher disease = glucocerebrosidase deficiency.
80
Which fatty acid property most affects membrane fluidity at body temperature?
a. Number of carbon atoms and degree of unsaturation
b. Presence of ester linkages
c. Type of alcohol in ester
d. Oxidation potential
Answer: a. Longer and more saturated → less fluid; shorter and unsaturated → more fluid.
Biochemistry I
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