Deck 25: Biochemistry

Question 1

A polypeptide is

A) an addition polymer of amino acids.
B) a condensation polymer of amino acids.
C) a polymer of sugar molecules.
D) a part of nucleic acids.
E) a polymer of nucleic acids.

Answer 1

a condensation polymer of amino acids.

Question 2

Which statement concerning the twenty different α-amino acids widely found in nature is true?

A) Each α-amino acid has a different number of carbon atoms.
B) Each α-amino acid has one amino (−NH₂)group.
C) Each α-amino acid has one carboxylic acid (−COOH)group.
D) These α-amino acids differ in the R groups attached to the α-carbon.
E) None of these α-amino acids are aromatic compounds.

Answer 2

These α-amino acids differ in the R groups attached to the α-carbon.

Question 3

A disaccharide is formed when two monosaccharides are linked by the elimination of a molecule of water and the formation of an ether bond.The newly formed C⎯O bond linking the monosaccharides is called the ____ bond.

A) aldose
B) ketose
C) glycogen
D) cyclic
E) glycosidic

Answer 3

glycosidic

Question 4

Which of the following reactions is responsible for the formation of glycosidic bonds in disaccharides?

A) An alkylation reaction
B) A condensation reaction
C) A hydrolysis reaction
D) An addition reaction
E) A substitution reaction

Question 5

What is the general formula for carbohydrates?

A) (CH₂O)_n
B) C_n(H₂O)_n+2
C) C(H₂O)_n
D) C_n(H₂O)_m
E) C_n(H₂O)_n+1

Question 6

The side chains of nonpolar amino acids contain _____.

A) carbon and hydrogen
B) nitrogen and oxygen
C) carbon and nitrogen
D) carbon and oxygen
E) nitrogen and hydrogen

Question 7

What is the most prevalent form of the amino acid glycine (R = H)in an aqueous environment when mixed with an excess of strong acid.

A)
B)
C)
D)
E)

Question 8

Which of the following amino-acids is not chiral?

A)
B)
C)
D)
E)

Question 9

What carbohydrate is the form in which plants store glucose for future use as cellular fuel?

A) starch
B) cellulose
C) glycogen
D) sucrose
E) fructose

Question 10

The sequence of amino acids linked by peptide bonds is called the _____ structure of a protein.

A) isomeric
B) primary
C) secondary
D) tertiary
E) quaternary

Question 11

Which of the following functional groups is not found in naturally occurring proteins or their amino acid building blocks?

A) carboxylic acid
B) alcohol
C) ketone
D) amide
E) amine

Question 12

A triose is a monosaccharide with three carbon atoms.The molecular formula of a triose is _____.

A) C₃H₆O₃
B) C₃H₃O₃
C) C₃H₆O₆
D) C₃H₃O₆
E) C₃H₂O₆

Question 13

Which of the following is not a polysaccharide?

A) Glycogen
B) Lactose
C) Cellulose
D) Amylose starch
E) Amylopectin starch

Question 14

Which of the following represents the linkage connecting amino acids in proteins?

A)
B)
C)
D)
E)

Question 15

Which of the following statements concerning carbohydrates is not correct?

A) Carbohydrates are also known as sugars.
B) Monosaccharides,the simplest sugars,have the general formula C_x(H₂O)_x.
C) Almost all sugars are chiral and many possess more than one chiral carbon.
D) The acyclic (linear)form of monosaccharides predominates in aqueous solutions.
E) Sugars are found in RNA and DNA.

Question 16

Which of the following concerning protein structure is not correct?

A) The primary structure of a protein is the sequence of amino acids linked together by peptide bonds.
B) Hydrogen bonds between amide linkages in the protein backbone define protein secondary structure.
C) Helices and sheets are common tertiary structures in proteins.
D) How a protein folds into its overall 3-dimensional shape is referred to as the protein tertiary structure.
E) In cases where more than one polypeptide chain makes up the protein,the interaction of the different chains is referred to as the quaternary structure.

Question 17

How many unique tripeptides can be made from two molecules of valine (val)and one molecule of alanine (ala)?

A) One
B) Two
C) Three
D) Four
E) >Five

Question 18

What is the functional group corresponding to a peptide bond?

A) amine
B) ether
C) amide
D) hemiacetal
E) carboxylic acid

Question 19

Which of the following statements concerning proteins is not correct?

A) Some proteins provide structural support in the form of muscle and collagen.
B) Some proteins provide storage and transport.
C) Some proteins regulate chemical reactions that take place in the body.
D) Some proteins act as catalysts.
E) Nucleic acids are the building blocks of proteins.

Question 20

Which of the following functional groups are not found in carbohydrates?

A) Carboxylic acids
B) Alcohols
C) Ketones
D) Aldehydes
E) Ethers

Question 21

An important reaction in the production of energy from sugars (glycolysis)is the reduction of pyruvate to lactate by NADH. pyruvate + NADH + H⁺(aq)→ lactate + NAD⁺ Δ_rG°′ = ?
Given the following reduction potentials,
NAD⁺ + H⁺ + 2e− → NADH
Ε°′ = −0.320 V
Pyruvate + 2H⁺ + 2e⁻ → lactate
Ε°′ = −0.190 V
Calculate the standard Gibbs free energy (at pH 7)for the reduction of pyruvate to lactate by NADH.(Δ_rG°′ = −nFE°′; F = 96485 C/mol electrons)

A) 98.4 kJ/mol-rxn
B) −98.4 kJ/mol-rxn
C) −12.6 kJ/mol-rxn
D) 25.1 kJ/mol-rxn
E) −25.1 kJ/mol-rxn

Question 22

Saturated fats and oils have ___ melting points than unsaturated fats and oils because of greater ___ forces between molecules.

A) lower,hydrogen bonding
B) higher,London dispersion
C) higher,hydrogen bonding
D) higher,dipole-dipole
E) lower,London dispersion

Question 23

Which of the following is the product of transcription in protein synthesis?

A) ATP
B) Protein
C) tRNA
D) mRNA
E) DNA

Question 24

How many rings are found in a steroid molecule?

A) < 3
B) 3
C) 4
D) 5
E) > 5

Question 25

Which of the following is not a lipid?

A) triglycerides
B) fatty acids
C) glycerol
D) steroids
E) phospholipids

Question 26

A compound which contains both a positive and negative charge is called a ____.

Question 27

Aerobic respiration links the oxidation of glucose with the production of ATP form ADP. Given the following thermodynamic data,
C₆H₁₂O₆(s)+ 6O₂(g)→ 6CO₂(g)+ 6H₂O(l)
Δ_rH° = −2803 kJ/mol-rxn
ATP + H₂O(l)→ ADP + HPO₄^2-(aq)
Δ_rH° ≈ −24 kJ/mol-rxn
Calculate the enthalpy of reaction for the aerobic production of 25 ATP shown below.
C₆H₁₂O₆(s)+ 6O₂(g)+ 25ADP + 25HPO₄^2-(aq)→ 6CO₂(g)+ 25ATP + 31H₂O(l)Δ_rH° = ?

A) 2827 kJ/mol-rxn
B) -3403 kJ/mol-rxn
C) -2779 kJ/mol-rxn
D) -2203 kJ/mol-rxn
E) -2827 kJ/mol-rxn

Question 28

Given the following reduction potentials, NAD⁺ + H⁺ + 2e− → NADH
Ε° = −0.105 V
2H⁺ + 2e⁻ → H₂
Ε° = 0.000 V
Calculate the standard reduction potential and identify the reducing agent in the following reaction.
NAD⁺ + H₂ → NADH + 2H⁺

A) 0.105 V,NAD⁺
B) −0.105 V,NAD⁺
C) −0.105 V,H₂
D) 0.105 V,H₂
E) −0.105 V,NADH

Question 29

Which of the following base forms hydrogen bonds with adenine in double-stranded DNA molecule?

A) Thymine
B) Guanine
C) Uracil
D) Cytosine
E) None of these

Question 30

One way our bodies produce ATP is to couple the formation of ATP from ADP with the hydrolysis of phosphoenopyruvate (PEP),as shown below. PEP + ADP + H⁺(aq)→ pyruvate + ATP Δ_rG°′ = ?
Given the following thermodynamic data,
PEP + H₂O(l)→ pyruvate + HPO₄^2-(aq)
Δ_rG°′ = −61.9 kJ/mol-rxn
ATP + H₂O(l)→ ADP + HPO₄^2-(aq)+ H⁺(aq)
Δ_rG°′ = −30.5 kJ/mol-rxn
Calculate the standard Gibbs free energy of reaction for the formation of ATP from the hydrolysis of PEP.

A) 92.4 kJ/mol-rxn
B) −31.4 kJ/mol-rxn
C) −92.4 kJ/mol-rxn
D) 31.4 kJ/mol-rxn
E) −46.7 kJ/mol-rxn

Question 31

Which of the following units is not found in a DNA molecule?

A) a phosphate group
B) a peptide bond
C) an organic base
D) a five-membered ring
E) a ribose sugar

Question 32

A fragment of a DNA molecule has the base sequence GACT.Which of the following is the complementary sequence of the DNA fragment?

A) TACG
B) TCAG
C) CTAG
D) CTGA
E) GACT

Question 33

Classification of a compound as a lipid is based on the _____ of the compound.

A) polarity
B) pH
C) size
D) hydrophobicity
E) solubility

Question 34

The fully protonated form of the amino-acid glycine (R=H)may be simply written as H₂Gly⁺.Write the balanced acid dissociation equilibria (K_a1 and K_a2)for this acid.

Question 35

Which of the following is not a step in protein synthesis?

A) translation
B) transcription
C) replication
D) A and B
E) A,B,and C

Question 36

A phospholipid may include all of the following except

A) ester functional groups.
B) one or more alkene functional groups.
C) a net negative charge.
D) a polar tail.
E) a phosphodiester linkage.

Question 37

Which DNA or RNA base is guanine?

A)
B)
C)
D)
E)

Question 38

Which of the following is not a component of DNA?

A) Cytosine
B) Phosphodiester group
C) ß-D-ribose
D) Guanine
E) Thymine

Question 39

The melting point of lipids depends on the strength of the intermolecular forces present in the solid.Rank the following fatty acids in order of increasing melting point. CH₃(CH₂)₁₄CO₂H CH₃(CH₂)₁₅CO₂H CH₃(CH₂)₁₁CO₂H

A) CH₃(CH₂)₁₁CO₂H < CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₅CO₂H
B) CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₁CO₂H < CH₃(CH₂)₁₅CO₂H
C) CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₅CO₂H < CH₃(CH₂)₁₁CO₂H
D) CH₃(CH₂)₁₅CO₂H < CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₁CO₂H
E) CH₃(CH₂)₁₁CO₂H < CH₃(CH₂)₁₅CO₂H < CH₃(CH₂)₁₄CO₂H

Question 40

How many RNA nucleotides comprise a codon?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 41

What is the role of tRNA in protein synthesis?

Question 42

The amide linkages in a protein are also called _____ bonds.

Question 43

The oxygen that bridges two sugars in a disaccharide is known as a ___ bond.

Question 44

Starch and cellulose are polysaccharides made up long chains of glucose linked by glycosidic bonds.Despite the identical composition,why can humans digest starch but not cellulose?

Question 45

The principal compound used to store and transport energy in a cell is called adenosine 5'-triphosphate.

Question 46

The process by which a double stranded of DNA is copied is called ___.In the process,a ___ strand of DNA is produced from each single strand of the original double-stranded DNA.

Question 47

In the context of polymerase chain reaction,if you start with a single double-stranded DNA molecule,how many double-strabded DNA molecules will you have after 10 amplification cycles?

Question 48

When a drop of the fatty acid oleic acid (CH₃(CH₂)₇CH=CH(CH₂)₇CO₂H)is added to water it forms a molecule thick layer on the surface of the water.What is the likely orientation of the acid on the water surface?