Deck 25: Biochemistry

Question 1

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

A)
B)
C)
D)
E)

Answer 1

Question 2

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.

Answer 2

Helices and sheets are common tertiary structures in proteins.

Question 3

Which of the following statements concerning carbohydrates is $\underline{\text{ not }}$ 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.

Answer 3

The acyclic (linear)form of monosaccharides predominates in aqueous solutions.

Question 4

Which of the following functional groups is not found in carbohydrates (sugars)?

A) carboxylic acid
B) alcohol
C) ketone
D) aldehyde
E) ether

Question 5

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

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

Question 6

What is the most prevalent form of the amino acid glycine (R = H)in an aqueous environment at a physiological pH.

A)
B)
C)
D)
E)

Question 7

Which of the following amino-acids is $\underline{\text{ not }}$ chiral?

A)
B)
C)
D)
E)

Question 8

The glycosidic bonds that form the link between sugars in disaccharides are formed by

A) an alkylation reaction.
B) a condensation reaction.
C) a hydrolysis reaction.
D) an addition reaction.
E) a substitution reaction.

Question 9

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 10

The sequence of the amino acids in a protein is termed the ____ structure.

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

Question 11

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 12

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 13

Which of the following statements concerning enzyme chemistry is/are correct?
1)Enzymes are biological catalysts.
2)A reaction occurs when substrate binds the enzyme active site.
3)Enzymes catalyze multiple types of reactions.

A) 1 only
B) 2 only
C) 3 only
D) 1 and 2
E) 1,2,and 3

Question 14

Nonpolar amino acid side chains contain substituents made mostly of what atoms?

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

Question 15

Which of the following statements concerning polysaccharides is/are correct?
1)Humans do not have enzymes that will break down cellulose.
2)Amylopectin and glycogen are both branched chains of glucose.
3)Amylose starch is a linear polysaccharide.

A) 1 only
B) 2 only
C) 3 only
D) 1 and 2
E) 1,2,and 3

Question 16

Which of the following is not a polysaccharide?

A) glycogen
B) lactose
C) cellulose
D) amylose starch
E) amylopectin starch

Question 17

Which of the following statements concerning proteins is $\underline{\text{ not }}$ 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 18

What is the functional group corresponding to a peptide bond?

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

Question 19

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

Question 20

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

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

Question 21

Which of the following statements concerning protein synthesis is/are correct?
1)Protein synthesis occurs in the ribosomes.
2)tRNA moves mRNA to the ribosome.
3)mRNA is cleaved more rapidly than DNA.

A) 1 only
B) 2 only
C) 3 only
D) 1 and 2
E) 1 and 3

Question 22

What is the complementary base which hydrogen bonds with thymine in double stranded DNA?

A) adenine
B) cytosine
C) guanine
D) thymine
E) uracil

Question 23

Which of the following statements concerning RNA is/are correct?
1)Retroviruses use RNA for storage of genetic information.
2)RNA can catalyze some reactions.
3)Translation of tRNA produces a protein.

A) 1 only
B) 2 only
C) 3 only
D) 1 and 2
E) 1 and 3

Question 24

How many RNA nucleotides comprise a codon?

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

Question 25

Which of the following is $\underline{\text{ not }}$ a step in protein synthesis?

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

Question 26

Which of the following units is $\underline{\text{ not }}$ 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 27

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 28

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

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

Question 29

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

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

Question 30

Which of the following statements concerning cell membranes is/are correct?
1)Bilayers are oriented head to tail.
2)Cholesterol in animal cell membranes provides greater rigidity.
3)Small polar molecules can readily cross a cell membrane by passive diffusion.

A) 1 only
B) 2 only
C) 3 only
D) 1 and 2
E) 1 and 3

Question 31

A hexose is a monosaccharide with six carbon atoms.The molecular formula of a hexose is

A) C₆H₁₂O₆
B) C₆H₆O₆
C) C₆H₁₂O₁₂
D) C₆H₆O₁₂
E) C₆H₅O₁₂

Question 32

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 $\underline{\text{ increasing }}$ melting point.

CH₃(CH₂)₁₆CO₂H CH₃(CH₂)₁₄CO₂H CH₃(CH₂)₁₁CO₂H

A) CH₃(CH₂)₁₁CO₂H < CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₆CO₂H
B) CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₁CO₂H < CH₃(CH₂)₁₆CO₂H
C) CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₆CO₂H < CH₃(CH₂)₁₁CO₂H
D) CH₃(CH₂)₁₆CO₂H < CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₁CO₂H
E) CH₃(CH₂)₁₁CO₂H < CH₃(CH₂)₁₆CO₂H < CH₃(CH₂)₁₄CO₂H

Question 33

How many five membered rings are found in a steroid molecule?

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

Question 34

Which of the following is not a lipid?

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

Question 35

Which of the following statements concerning lipids is/are correct?
1)Phospholipids are most prevalent in cell membranes.
2)Triglycerides are formed from fatty acids and glycerol.
3)A major function of lipids in the body is energy storage.

A) 1 only
B) 2 only
C) 3 only
D) 1 and 2
E) 1,2,and 3

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 of the following is $\underline{\text{ not }}$ a component of RNA?

A) cytosine
B) phosphodiester groups
C) ( $\beta$ )-D-ribose
D) guanine
E) thymine

Question 38

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 39

The product of transcription in protein synthesis is

A) ATP
B) protein
C) tRNA
D) mRNA
E) complementary,single stranded DNA

Question 40

Which DNA or RNA base is uracil?

A)
B)
C)
D)
E)

Question 41

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

Question 42

Which of the following statements concerning metabolism is/are correct?
1)Breaking a phosphodiester linkage (P-O bond)in ATP is an endothermic process.
2)Aerobic respiration produces ATP by glucose oxidation.
3)In cells the hydrolysis of ATP is linked to many reactant favored processes to make them product favored.

A) 1 only
B) 2 only
C) 3 only
D) 1 and 2
E) 1,2,and 3

Question 43

=nFE ^{$\circ$ '}; F

-An important reaction in the production of energy from sugars (glycolysis)is the reduction of pyruvate to lactate by NADH.

pyruvate + NADH + H⁺(aq) $\to$ lactate + NAD⁺ $\Delta$ _rG ^{$\circ$ '}=?

Given the following reduction potentials,
NAD⁺ + H⁺ + 2e^- $\to$ NADH $~~~~~~~~$ E ^{$\circ$ '} = -0.320 V
Pyruvate + 2H⁺ + 2e^- $\to$ lactate $~~~~~~~~$ E ^{$\circ$ '} = -0.190 V

Calculate the standard Gibbs free energy (at pH 7)for the reduction of pyruvate to lactate by NADH.( $\Delta$ _rG ^{$\circ$ '}=nFE ^{$\circ$ '}; 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 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

Aerobic respiration links the oxidation of glucose with the production of ATP form ADP.Given the following thermodynamic data,
C₆H₁₂O₆(s)+ 6O₂(g) $\to$ 6CO₂(g)+ 6H₂O( $\ell$ ) $~~~~~~~~$$\Delta$ _rH ^$\circ$ = -2803 kJ/mol-rxn
ATP + H₂O( $\ell$ ) $\to$ ADP + HPO₄^2-(aq) $~~~~~~~~$$\Delta$ _rH ^$\circ$ $\approx$ -24 kJ/mol-rxn

Calculate the enthalpy of reaction for the aerobic production of 28 ATP shown below.C₆H₁₂O₆(s)+ 6O₂(g)+ 28ADP + 28HPO₄^2-(aq) $\to$ 6CO₂(g)+ 28ATP + 34H₂O( $\ell$ ) $\Delta$ _rH ^$\circ$ = ?

A) 2827 kJ/mol-rxn
B) -3475 kJ/mol-rxn
C) -2779 kJ/mol-rxn
D) -2131 kJ/mol-rxn
E) -2827 kJ/mol-rxn

Question 46

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 47

If you start with a single duplex DNA molecule,how many duplex DNA molecules will you have after 10 amplification cycles by the polymerase chain reaction?

Question 48

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) $\to$ pyruvate + ATP $~~~~~~~~$$\Delta$ _rG ^{$\circ$ '}=?

Given the following thermodynamic data,
PEP + H₂O( $\ell$ ) $\to$ pyruvate + HPO₄^2-(aq) $~~~~~~~~$$\Delta$ _rG ^{$\circ$ '} = -61.9 kJ/mol-rxn
ATP + H₂O( $\ell$ ) $\to$ ADP + HPO₄^2-(aq)+ H⁺(aq) $~~~~~~~~$$\Delta$ _rG ^{$\circ$ '} = -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 49

What is the role of tRNA in protein synthesis?

Question 50

Given the following reduction potentials,
NAD⁺ + H⁺ + 2e^- $\to$ NADH $~~~~~~~~$ E ^$\circ$ = -0.105 V
2H⁺ + 2e^- $\to$ H₂ $~~~~~~~~$$~~~~~~~~$$~~~~~~~~$ E ^$\circ$ = 0.000 V

Calculate the standard reduction potential and identify the reducing agent in the following reaction.
NAD⁺ + H₂ $\to$ 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 51

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

Question 52

The amide linkages in a protein and also called ___ bonds.

Question 53

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 54

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.