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Unit 2: Lipids and Amino acids - Practice Quiz

BTY501 — Biomolecules And Metabolism 60 Questions
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1 Which of the following best describes a saturated fatty acid?

Lipids: fatty acids and their properties Easy
A. A fatty acid with one carbon-carbon double bond
B. A fatty acid with no carbon-carbon double bonds
C. A fatty acid containing a hydroxyl group
D. A fatty acid with many carbon-carbon double bonds

2 As the chain length of a saturated fatty acid increases, its melting point generally:

Lipids: fatty acids and their properties Easy
A. Drops to zero
B. Increases
C. Remains constant
D. Decreases

3 The presence of a cis double bond in an unsaturated fatty acid causes the melting point to:

Lipids: fatty acids and their properties Easy
A. Decrease compared to saturated ones
B. Increase compared to saturated ones
C. Stay exactly the same
D. Become undefined

4 Lipids that yield fatty acids and alcohol on hydrolysis are called:

Lipids: classification of lipids Easy
A. Simple lipids
B. Non-saponifiable lipids
C. Nucleic lipids
D. Derived lipids

5 Which of the following is classified as a derived lipid?

Lipids: classification of lipids Easy
A. Triacylglycerol
B. Lecithin
C. Cholesterol
D. Beeswax

6 A triacylglycerol is formed by the esterification of glycerol with how many fatty acid molecules?

Lipids: triacylglycerol Easy
A. Three
B. One
C. Two
D. Four

7 The main biological function of triacylglycerols is:

Lipids: triacylglycerol Easy
A. Genetic information storage
B. Long-term energy storage
C. Oxygen transport
D. Enzyme catalysis

8 The backbone alcohol present in a triacylglycerol molecule is:

Lipids: triacylglycerol Easy
A. Glycerol
B. Cholesterol
C. Sphingosine
D. Ethanol

9 Chemically, waxes are esters of long-chain fatty acids with:

Lipids: waxes Easy
A. Glycerol
B. Sphingosine
C. Long-chain monohydric alcohols
D. Phosphoric acid

10 Which property makes waxes useful as protective coatings on leaves and skin?

Lipids: waxes Easy
A. They dissolve readily in water
B. They are highly water-repellent
C. They are strongly acidic
D. They conduct electricity

11 Which component distinguishes a phospholipid from a simple triacylglycerol?

Lipids: phospholipids and glycolipids Easy
A. Fatty acid chains
B. Ester bonds
C. A phosphate group
D. A glycerol backbone

12 Glycolipids are characterized by the presence of which group attached to the lipid?

Lipids: phospholipids and glycolipids Easy
A. A metal ion
B. A phosphate group
C. A steroid ring
D. A carbohydrate group

13 Phospholipids are described as amphipathic because they possess:

Lipids: phospholipids and glycolipids Easy
A. Only hydrophobic regions
B. Both hydrophilic and hydrophobic regions
C. Only hydrophilic regions
D. No functional groups

14 Cholesterol belongs to which class of lipids?

Lipids: cholesterol and its significance Easy
A. Waxes
B. Phospholipids
C. Triacylglycerols
D. Steroids

15 Cholesterol serves as a precursor for the synthesis of:

Lipids: cholesterol and its significance Easy
A. Steroid hormones
B. Polysaccharides
C. Proteins
D. Nucleic acids

16 Every standard amino acid contains which two functional groups attached to the central carbon?

Amino acids: structure and classification of amino acids Easy
A. A hydroxyl group and a phosphate group
B. Two amino groups
C. An amino group and a carboxyl group
D. Two carboxyl groups

17 Amino acids are commonly classified based on the properties of their:

Amino acids: structure and classification of amino acids Easy
A. Alpha carbon
B. Amino group
C. R group (side chain)
D. Carboxyl group

18 The amino acids found in naturally occurring proteins are predominantly of which configuration?

Amino acids: stereochemistry of amino acids Easy
A. L-configuration
B. R-configuration only
C. Racemic mixture
D. D-configuration

19 Which amino acid is not optically active because it lacks a chiral center?

Amino acids: stereochemistry of amino acids Easy
A. Serine
B. Glycine
C. Alanine
D. Valine

20 At its isoelectric point (pI), an amino acid exists predominantly as a:

Amino acids: titration curve of amino acids Easy
A. Positively charged ion
B. Zwitterion with no net charge
C. Neutral molecule with no charges at all
D. Negatively charged ion

21 Two fatty acids have identical chain lengths of 18 carbons, but one is oleic acid () and the other is stearic acid (). Which statement correctly explains their difference in melting point?

fatty acids and their properties Medium
A. Stearic acid has a lower melting point because saturated chains pack loosely
B. Both have identical melting points since chain length is the same
C. Oleic acid has a lower melting point because its cis double bond introduces a kink that prevents tight packing
D. Oleic acid has a higher melting point due to stronger van der Waals forces

22 A fatty acid is designated . How many carbon atoms and double bonds does it contain, and what is this fatty acid commonly called?

fatty acids and their properties Medium
A. 20 carbons, 4 double bonds; arachidonic acid
B. 18 carbons, 4 double bonds; linolenic acid
C. 20 carbons, 5 double bonds; eicosapentaenoic acid
D. 24 carbons, 4 double bonds; nervonic acid

23 Which of the following is classified as a saponifiable lipid?

classification of lipids Medium
A. Vitamin A
B. Prostaglandin
C. Cholesterol
D. Triacylglycerol

24 Sphingomyelin is classified as both a phospholipid and a sphingolipid. What structural feature justifies its dual classification?

classification of lipids Medium
A. It contains a phosphate group attached to a ceramide backbone
B. It contains a steroid nucleus with a phosphate ester
C. It contains glycerol esterified to two fatty acids
D. It contains a sugar directly bonded to glycerol

25 Complete saponification of one mole of a simple triacylglycerol with NaOH yields which products?

triacylglycerol Medium
A. One mole of glycerol and one mole of fatty acid salt
B. Two moles of glycerol and two moles of fatty acid salts
C. Three moles of glycerol and one mole of fatty acid salt
D. One mole of glycerol and three moles of fatty acid sodium salts

26 Why are triacylglycerols more efficient for long-term energy storage than glycogen?

triacylglycerol Medium
A. They contain many charged groups that store ionic energy
B. They are highly oxidized and hydrated, releasing water on storage
C. They are highly reduced and anhydrous, storing more energy per gram
D. They dissolve readily in the cytosol for rapid mobilization

27 What is the general chemical structure of a biological wax?

waxes Medium
A. A phosphodiester linking two fatty alcohols
B. An amide of a fatty acid with sphingosine
C. A triester of glycerol with three fatty acids
D. An ester of a long-chain fatty acid with a long-chain alcohol

28 Which property makes waxes suitable as waterproof protective coatings on leaves and animal fur?

waxes Medium
A. Their amphipathic nature allowing bilayer formation
B. Their extreme hydrophobicity and high melting points due to long saturated chains
C. Their high water solubility enabling even spreading
D. Their charged head groups repelling water molecules

29 In a biological membrane, why do phospholipids spontaneously form a bilayer in aqueous solution?

phospholipids and glycolipids Medium
A. Their fully hydrophilic nature keeps them dissolved as monomers
B. Their positive charge attracts them into stacked sheets
C. Their amphipathic structure orients hydrophilic heads outward and hydrophobic tails inward
D. Their fully hydrophobic nature causes them to precipitate as droplets

30 What structural feature distinguishes a glycolipid from a phospholipid such as phosphatidylcholine?

phospholipids and glycolipids Medium
A. A glycolipid lacks any hydrophobic tail region
B. A glycolipid contains a steroid ring in its head group
C. A glycolipid has three fatty acids instead of two
D. A glycolipid has a sugar residue as its polar head group instead of a phosphate

31 How does cholesterol modulate the fluidity of an animal cell membrane at body temperature?

cholesterol and its significance Medium
A. It converts the bilayer into a rigid crystalline sheet at all temperatures
B. It has no effect since it lacks a hydrophobic region
C. It reduces fluidity by restraining phospholipid motion while preventing tight packing
D. It increases fluidity by displacing all phospholipids

32 Cholesterol serves as the biosynthetic precursor for all of the following EXCEPT:

cholesterol and its significance Medium
A. Steroid hormones
B. Sphingosine
C. Vitamin D
D. Bile acids

33 All standard amino acids found in proteins are of the L-configuration. To which reference molecule are they related in the D/L system?

stereochemistry of amino acids Medium
A. D-glucose
B. L-glyceraldehyde
C. L-tartaric acid
D. D-ribose

34 Which standard amino acid is NOT optically active (achiral)?

stereochemistry of amino acids Medium
A. Glycine
B. Alanine
C. Serine
D. Threonine

35 Isoleucine and threonine each contain two stereocenters. How many total stereoisomers are theoretically possible for such an amino acid?

stereochemistry of amino acids Medium
A. 8
B. 4
C. 1
D. 2

36 4-Hydroxyproline is an uncommon amino acid abundant in collagen. How is it generated?

un-common amino acids Medium
A. By methylation of lysine residues
B. By deamination of glutamate residues
C. By direct incorporation during translation via a specific codon
D. By post-translational hydroxylation of proline residues

37 Which uncommon amino acid is a key intermediate in the urea cycle but is not found in proteins?

un-common amino acids Medium
A. Pyroglutamate
B. Selenocysteine
C. Hydroxylysine
D. Ornithine

38 For glycine with (carboxyl) and (amino), what is its isoelectric point (pI)?

titration curve of amino acids Medium
A. 7.00
B. 5.95
C. 2.30
D. 9.60

39 At which point on its titration curve does an amino acid function best as a buffer?

titration curve of amino acids Medium
A. At extremely high pH only
B. At its isoelectric point only
C. At pH values equal to its values
D. Midway between two equivalence points where it cannot resist pH change

40 At physiological pH (), which amino acid side chain carries a net negative charge?

structure and classification of amino acids Medium
A. Aspartate
B. Phenylalanine
C. Lysine
D. Alanine

41 Two fatty acids, stearic acid () and oleic acid (), have the same carbon count. Which statement best explains why oleic acid has a markedly lower melting point?

fatty acids and their properties Hard
A. Oleic acid is more polar and forms stronger dipole interactions in the solid state
B. The cis double bond introduces a kink that prevents tight molecular packing, weakening van der Waals interactions
C. The double bond increases hydrogen bonding between adjacent chains
D. Oleic acid has a lower molecular weight due to the loss of two hydrogen atoms

42 A fatty acid is described by the shorthand notation . Using the (omega) nomenclature, this fatty acid is classified as:

fatty acids and their properties Hard
A. An -9 fatty acid
B. An -7 fatty acid
C. An -3 fatty acid
D. An -6 fatty acid

43 Which of the following correctly distinguishes a saponifiable lipid from a non-saponifiable one?

classification of lipids Hard
A. Saponifiable lipids are insoluble in ether, non-saponifiable are soluble
B. Saponifiable lipids are steroids, non-saponifiable are triacylglycerols
C. Saponifiable lipids contain ester bonds hydrolyzable by alkali, whereas non-saponifiable lipids lack them
D. Saponifiable lipids are always solid at room temperature, non-saponifiable are liquid

44 A mixed triacylglycerol contains one palmitic, one oleic, and one stearic acid esterified to glycerol. Considering the prochiral nature of glycerol, how many distinct positional/stereoisomeric arrangements are possible?

triacylglycerol Hard
A. 12
B. 3
C. 6
D. 9

45 The saponification value of a fat is inversely related to the average molecular weight of its fatty acids. A fat rich in short-chain fatty acids (like butter) compared to one rich in long-chain fatty acids will show:

triacylglycerol Hard
A. A zero saponification value
B. An identical saponification value
C. A lower saponification value
D. A higher saponification value

46 Why are biological waxes such as those in bird feathers and plant cuticles highly effective as waterproofing agents?

waxes Hard
A. They contain phosphate groups that repel water electrostatically
B. They are unsaturated and form a fluid barrier that excludes water
C. They are esters of long-chain fatty acids with long-chain alcohols, making them extremely hydrophobic and chemically inert
D. They contain glycerol backbones that trap water molecules

47 Phosphatidylinositol 4,5-bisphosphate () plays a signaling role distinct from its structural role. Upon activation of phospholipase C, which two second messengers are generated?

phospholipids and glycolipids Hard
A. cAMP and cGMP
B. Arachidonic acid and choline
C. Inositol 1,4,5-trisphosphate () and diacylglycerol (DAG)
D. Phosphatidic acid and glycerol

48 Which statement correctly differentiates a sphingomyelin from a phosphatidylcholine?

phospholipids and glycolipids Hard
A. Sphingomyelin is a glycolipid while phosphatidylcholine is a phospholipid
B. Sphingomyelin lacks a phosphate group whereas phosphatidylcholine contains one
C. Sphingomyelin has a sphingosine backbone with one fatty acid via an amide bond, while phosphatidylcholine has a glycerol backbone with two ester-linked fatty acids
D. Sphingomyelin contains two sphingosine chains and no fatty acids

49 Gangliosides are complex glycolipids characterized by the presence of:

phospholipids and glycolipids Hard
A. A phosphate diester linkage to choline
B. An ergosterol nucleus
C. One or more sialic acid (N-acetylneuraminic acid) residues
D. A glycerol backbone with two acyl chains

50 Cholesterol modulates membrane fluidity in a dual manner. At temperatures above the phase transition temperature (), cholesterol:

cholesterol and its significance Hard
A. Has no effect on fluidity above
B. Converts the bilayer entirely into a gel phase
C. Increases fluidity by disrupting acyl chain packing
D. Decreases fluidity by restraining phospholipid acyl chain motion

51 Cholesterol is the biosynthetic precursor of several important molecules. Which of the following is NOT derived from cholesterol?

cholesterol and its significance Hard
A. Steroid hormones
B. Sphingosine
C. Vitamin D
D. Bile acids

52 L-cysteine, despite having the same spatial arrangement as other L-amino acids, is assigned the (R) configuration in the CIP system, whereas most L-amino acids are (S). This is because:

stereochemistry of amino acids Hard
A. Cysteine lacks a true stereocenter
B. The sulfur atom in the side chain has higher priority than the carboxyl carbon, reversing the priority order
C. Cysteine is a D-amino acid disguised as L
D. The thiol group forms a disulfide that alters chirality

53 Threonine and isoleucine each contain two stereocenters. How many total stereoisomers are theoretically possible for threonine, and how many are typically found in proteins?

stereochemistry of amino acids Hard
A. 4 total possible; 1 (L-threonine) found in proteins
B. 2 total possible; 2 found in proteins
C. 8 total possible; 2 found in proteins
D. 4 total possible; 4 found in proteins

54 4-Hydroxyproline is an uncommon amino acid abundant in collagen. It is formed by:

un-common amino acids Hard
A. Direct incorporation from a dedicated codon during translation
B. Post-translational hydroxylation of proline by prolyl hydroxylase, requiring vitamin C
C. Transamination of glutamate in the mitochondria
D. Enzymatic methylation of lysine residues

55 Selenocysteine, often called the '21st amino acid,' differs from the standard genetic code because it:

un-common amino acids Hard
A. Is encoded by a UGA stop codon reinterpreted via a SECIS element and specialized machinery
B. Is inserted only during post-translational modification of serine
C. Requires no tRNA for its incorporation
D. Uses a unique AUA codon not used elsewhere

56 For glycine ( for , for ), the isoelectric point (pI) is calculated as:

titration curve of amino acids Hard
A.
B.
C.
D.

57 For histidine with values of , , and , the isoelectric point is:

titration curve of amino acids Hard
A.
B.
C.
D.

58 At its isoelectric point, a solution of an amino acid shows the poorest buffering capacity. This is because at the pI:

titration curve of amino acids Hard
A. The amino acid precipitates and stops ionizing
B. All molecules are fully protonated and cannot accept protons
C. The buffering capacity is actually maximal at the pI
D. The pH is far from either , so little conjugate acid/base pair is available to resist pH change

59 At physiological pH (~7.4), which amino acid's side chain is most likely to carry a partial positive charge and act as an effective buffer, given its side-chain near 6?

structure and classification of amino acids Hard
A. Aspartate
B. Arginine
C. Lysine
D. Histidine

60 Among the standard amino acids, which pair would be classified together as aromatic and also capable of absorbing UV light strongly near 280 nm?

structure and classification of amino acids Hard
A. Histidine and proline
B. Tryptophan and tyrosine
C. Tyrosine and serine
D. Phenylalanine and leucine
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