Part 5 — Lipids: Types, Properties, Tests & Functions (Q101–125)

Q101.

Lipids are generally defined as:
A. Water-soluble biomolecules
B. Hydrophobic or amphipathic molecules soluble in organic solvents ✅
C. Polymers of amino acids
D. Polymers of nucleotides

Explanation:

A. Water-soluble: False — lipids are mostly insoluble in water.
**B. Correct — lipids are hydrophobic or amphipathic, soluble in organic solvents (ether, chloroform).
**C. Polymers of amino acids: proteins.
**D. Polymers of nucleotides: nucleic acids.

Q102.

The major storage form of lipids in animals is:
A. Phospholipids
B. Triacylglycerols ✅
C. Steroids
D. Waxes

Explanation:

A. Phospholipids: Structural role in membranes.
B. Triacylglycerols (Correct): Main energy storage lipids in adipose tissue.
C. Steroids: Regulatory (e.g., hormones).
D. Waxes: Protective coatings.

Q103.

Which test is used to detect lipids?
A. Biuret test
B. Benedict’s test
C. Sudan III stain ✅
D. Iodine test

Explanation:

**A. Biuret: proteins.
**B. Benedict’s: reducing sugars.
C. Sudan III (Correct): Stains lipids red.
**D. Iodine: starch.

Q104.

Which type of lipid makes up the major structural component of cell membranes?
A. Triacylglycerols
B. Phospholipids ✅
C. Waxes
D. Steroids

Explanation:

**A. Triacylglycerols: energy storage.
B. Phospholipids (Correct): Amphipathic molecules forming bilayers.
**C. Waxes: protective, not membrane.
**D. Steroids: modulate fluidity but minor.

Q105.

Which fatty acids have no double bonds?
A. Saturated fatty acids ✅
B. Unsaturated fatty acids
C. Polyunsaturated fatty acids
D. Essential fatty acids

Explanation:

A. Saturated (Correct): All single bonds.
**B. Unsaturated: contain double bonds.
**C. Polyunsaturated: many double bonds.
**D. Essential: cannot be synthesized by body (may be unsaturated).

Q106.

Which fatty acid is essential in humans?
A. Palmitic acid
B. Linoleic acid ✅
C. Stearic acid
D. Lauric acid

Explanation:

**A. Palmitic: synthesized by humans.
B. Linoleic acid (Correct): Essential fatty acid, must be obtained from diet.
**C. Stearic acid: saturated, synthesized.
**D. Lauric acid: synthesized.

Q107.

Which lipid has a steroid nucleus?
A. Phospholipid
B. Cholesterol ✅
C. Waxes
D. Triacylglycerol

Explanation:

**A. Phospholipid: glycerol backbone.
B. Cholesterol (Correct): Steroid with four fused rings.
**C. Waxes: esters of fatty acids & alcohols.
**D. Triacylglycerol: glycerol + fatty acids.

Q108.

Which lipid type provides waterproofing in plants?
A. Triacylglycerols
B. Waxes ✅
C. Phospholipids
D. Steroids

Explanation:

**A. Triacylglycerols: storage.
B. Waxes (Correct): Protective coatings on leaves/skin.
**C. Phospholipids: membranes.
**D. Steroids: hormones.

Q109.

Which is NOT a function of lipids?
A. Long-term energy storage
B. Hormone synthesis
C. Enzymatic catalysis ✅
D. Membrane structure

Explanation:

**A. Energy: yes.
**B. Hormones: steroid hormones.
C. Enzymatic catalysis (Correct): Role of proteins, not lipids.
**D. Membranes: phospholipids.

Q110.

Which vitamin is synthesized from cholesterol?
A. Vitamin A
B. Vitamin D ✅
C. Vitamin B12
D. Vitamin C

Explanation:

**A. Vitamin A: from beta-carotene.
B. Vitamin D (Correct): Synthesized in skin from cholesterol.
**C. B12: synthesized by microbes.
**D. C: ascorbic acid, not from cholesterol.

Q111.

Which lipoprotein is termed “bad cholesterol”?
A. HDL
B. LDL ✅
C. VLDL
D. Chylomicrons

Explanation:

**A. HDL: “good cholesterol”.
B. LDL (Correct): Deposits cholesterol in arteries.
**C. VLDL: triglyceride transport.
**D. Chylomicrons: dietary fat transport.

Q112.

Which lipid test involves acrolein formation?
A. Biuret test
B. Sudan III
C. Acrolein test ✅
D. Iodine test

Explanation:

**A. Biuret: proteins.
**B. Sudan: lipid staining.
C. Acrolein (Correct): Glycerol on dehydration → acrolein (acrid smell).
**D. Iodine: starch.

Q113.

Which lipid functions as an emulsifier in bile?
A. Cholesterol
B. Bile salts ✅
C. Waxes
D. Steroid hormones

Explanation:

**A. Cholesterol: precursor, not emulsifier.
B. Bile salts (Correct): Amphipathic, emulsify fats.
**C. Waxes: protective coatings.
**D. Steroids: regulatory hormones.

Q114.

Which fatty acid is monounsaturated?
A. Oleic acid ✅
B. Linoleic acid
C. Linolenic acid
D. Stearic acid

Explanation:

A. Oleic acid (Correct): One double bond (C18:1).
**B. Linoleic: polyunsaturated.
**C. Linolenic: polyunsaturated.
**D. Stearic: saturated.

Q115.

Which lipid serves as precursor for prostaglandins?
A. Cholesterol
B. Arachidonic acid ✅
C. Oleic acid
D. Stearic acid

Explanation:

**A. Cholesterol: steroid hormones.
B. Arachidonic acid (Correct): Polyunsaturated fatty acid precursor of prostaglandins.
**C. Oleic acid: MUFA.
**D. Stearic: saturated FA.

Q116.

Which test is used to detect unsaturation in fatty acids?
A. Baeyer’s test ✅
B. Biuret test
C. Millon’s test
D. Iodine test

Explanation:

A. Baeyer’s (Correct): Decolorization of KMnO₄ indicates unsaturation.
**B. Biuret: proteins.
**C. Millon’s: tyrosine.
**D. Iodine: starch.

Q117.

Which lipid is an important component of myelin sheath?
A. Phospholipids
B. Sphingolipids ✅
C. Waxes
D. Steroids

Explanation:

**A. Phospholipids: present, but main is sphingolipids.
B. Sphingolipids (Correct): Form myelin sheath around neurons.
**C. Waxes: protective only.
**D. Steroids: signaling.

Q118.

Which lipid type has both glycerol and fatty acids?
A. Triacylglycerols ✅
B. Steroids
C. Terpenes
D. Cholesterol

Explanation:

A. Triacylglycerols (Correct): Glycerol + 3 fatty acids.
**B. Steroids: fused rings.
**C. Terpenes: isoprene units.
**D. Cholesterol: steroid nucleus.

Q119.

Which steroid regulates sodium and water balance?
A. Cortisol
B. Aldosterone ✅
C. Estrogen
D. Testosterone

Explanation:

**A. Cortisol: stress hormone.
B. Aldosterone (Correct): Mineralocorticoid controlling Na⁺ reabsorption.
**C. Estrogen: female sex hormone.
**D. Testosterone: male sex hormone.

Q120.

Which lipid is solid at room temperature?
A. Oil
B. Fat ✅
C. Phospholipid
D. Sterol

Explanation:

**A. Oil: liquid (unsaturated).
B. Fat (Correct): Saturated, solid at room temp (butter).
**C. Phospholipids: membranes, not physical state term.
**D. Sterols: regulatory, not storage lipids.

Q121.

Which molecule is amphipathic?
A. Triacylglycerol
B. Phospholipid ✅
C. Cholesterol
D. Wax

Explanation:

**A. TAG: hydrophobic.
B. Phospholipid (Correct): Hydrophilic head + hydrophobic tails.
**C. Cholesterol: mostly hydrophobic.
**D. Wax: hydrophobic.

Q122.

Which test detects cholesterol specifically?
A. Liebermann-Burchard test ✅
B. Biuret test
C. Benedict’s test
D. Iodine test

Explanation:

A. Liebermann-Burchard (Correct): Green-blue color test for cholesterol.
**B. Biuret: proteins.
**C. Benedict’s: reducing sugars.
**D. Iodine: starch.

Q123.

Which fatty acids raise risk of atherosclerosis?
A. Unsaturated fatty acids
B. Saturated fatty acids ✅
C. Polyunsaturated fatty acids
D. Essential fatty acids

Explanation:

**A. Unsaturated: protective.
B. Saturated (Correct): Excess intake → atherosclerosis.
**C. Polyunsaturated: heart-healthy.
**D. Essential: required, beneficial.

Q124.

Which steroid hormone controls glucose metabolism?
A. Cortisol ✅
B. Aldosterone
C. Estrogen
D. Progesterone

Explanation:

A. Cortisol (Correct): Glucocorticoid regulating glucose metabolism.
**B. Aldosterone: Na⁺ balance.
**C. Estrogen: reproduction.
**D. Progesterone: pregnancy hormone.

Q125.

Which lipid derivative acts as a second messenger in cells?
A. Triacylglycerol
B. Phosphatidylinositol derivatives (IP₃, DAG) ✅
C. Cholesterol
D. Waxes

Explanation:

**A. TAG: storage.
**B. Correct — PIP₂ cleavage forms IP₃ and DAG → second messengers.
**C. Cholesterol: structural/hormones.
**D. Waxes: protective.

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Part 5 — Lipids: Types, Properties, Tests & Functions (Q101–125)