Deck 25: Biochemistry

Question 1

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

Answer 1

A condensation reaction

Question 2

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 2

glycosidic

Question 3

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

Answer 3

ketone

Question 4

Which of the following is not a polysaccharide?

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

Question 5

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

A)
B)
C)
D)
E)

Question 6

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 7

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 8

What is the functional group corresponding to a peptide bond?

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

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 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 12

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 13

Which of the following amino-acids is not chiral?

A)
B)
C)
D)
E)

Question 14

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.

Question 15

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 16

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

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

Question 17

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 18

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.

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

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 21

Which of the following is not a component of DNA?

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

Question 22

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 23

Aerobic respiration links the oxidation of glucose with the production of ATP form ADP. Given the following thermodynamic data,
$$\begin{array} { l l } \mathrm { C } _ { 6 } \mathrm { H } _ { 12 } \mathrm { O } _ { 6 } ( \mathrm {~s} ) + 6 \mathrm { O } _ { 2 } ( \mathrm {~g} ) \rightarrow 6 \mathrm { CO } _ { 2 } ( \mathrm {~g} ) + 6 \mathrm { H } _ { 2 } \mathrm { O } ( \ell ) & \Delta _ { \mathrm { r } } \mathrm { H } ^ { \circ } = - 2803 \mathrm {~kJ} / \text { mol-rxn } \\\mathrm { ATP } + \mathrm { H } _ { 2 } \mathrm { O } ( \ell ) \rightarrow \mathrm { ADP } + \mathrm { HPO } _ { 4 } {}^ { 2 - } ( \mathrm { aq } ) & \Delta _ { \mathrm { r } } \mathrm { H } ^ { \circ } \approx - 24 \mathrm {~kJ} / \text { mol-rxn }\end{array}$$
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) ?_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 24

Which of the following pairs of compounds form a nucleoside?

A) A single sugar and a nitrogenous base
B) A phosphate group and a lipid
C) A lipid and a starch molecule
D) A lactose molecule and a phosphate group
E) An mRNA molecule and a lactose molecule

Question 25

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

Question 26

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 27

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 28

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

Question 29

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 30

Which DNA or RNA base is guanine?

A)
B)
C)
D)
E)

Question 31

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 32

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 33

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

Question 34

What is the role of tRNA in protein synthesis?

Question 35

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

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

Question 36

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?

Question 37

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 ?_rG°? = ?
Given the following thermodynamic data,
PEP + H₂O(l) ? pyruvate + HPO₄^2-(aq) ?_rG°? = ?61.9 kJ/mol-rxn
ATP + H₂O(l) ? ADP + HPO₄^2-(aq) + H⁺(aq) ?_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 38

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 39

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⁺ ?_rG°? = ?
Given the following reduction potentials,
NAD⁺ + H⁺ + 2e? ? NADH ?°? = ?0.320 V
Pyruvate + 2H⁺ + 2e^? ? lactate ?°? = ?0.190 V
Calculate the standard Gibbs free energy (at pH 7) for the reduction of pyruvate to lactate by NADH. (?_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 40

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?