question

Each of the following is a noncovalent interaction EXCEPT

answer

A) a hydrogen bond. B) a carbon-hydrogen bond. C) the interaction between an amino and a carboxylate group. D) a van der Waals interaction. E) an interaction between —NH3+ and a water molecule. Answer: B

question

The most important noncovalent interaction in biochemistry is the ________ bond.

answer

Hydrogen

question

Which of the following is FALSE when considering van der Waals interactions?

answer

A) The van der Waals radius represents the most stable distance between two interacting centers. B) Van der Waals radii can determine molecular surfaces. C) Molecules that interact by van der Waals forces do not interpenetrate. D) The total interaction energy is the sum of the attractive and repulsive forces. E) They are not important in determining the stability of three-dimensional structures of proteins. Answer: E

question

Which of the following in biological compounds are sufficiently electronegative to serve as strong donors in a hydrogen bond?

answer

A) Hydrogen and oxygen B) Oxygen and nitrogen C) Nitrogen and hydrogen D) Hydrogen and carbon E) Nitrogen and carbon Answer: B

question

Hydrogen bonds share features of both covalent and noncovalent bonds.

answer

TRUE

question

Which of the following is TRUE of hydrophobic molecules?

answer

A) They have limited solubility in water. B) Water forms a cage-like structure around them. C) Dissolving in water decreases the entropy of the mixture. D) They self-associate by releasing some of the surrounding water molecules. E) All of the above Answer: E

question

Water is both a hydrogen bond donor and acceptor.

answer

TRUE

question

Amphipathic molecules are not able to interact via van der Waals forces.

answer

FALSE

question

Ionic compounds can be readily dissolved in water because the high dielectric constant of water screens and decreases the ________ force between the oppositely charged ions.

answer

Electrostatic

question

The ________ describes the tendency for hydrophobic molecules to aggregate because of the exclusion of water with the consequent increase of entropy of the solvent.

answer

Hydrophobic Effect

question

Glycine cannot serve as a buffer because it has two ionizable groups.

answer

FALSE

question

The average charge on an amino acid below its pI will be positive.

answer

TRUE

question

Calculate the acid dissociation constant Ka of a 0.2 M solution of weak acid that is 0.1% ionized.

answer

Answer: 2 × 10-7

question

Calculate the pH of a 0.1 M phosphate buffer (pKa = 6.86) that contains equal amounts of acid and conjugate base.

answer

6.86

question

Calculate the pH of a 0.2 M acetate buffer (pKa = 4.77) that contains twice as much acid as conjugate base.

answer

4.47

question

The pKa of each amino acid residue in a protein will not be influenced by the adjacent residue.

answer

FALSE

question

Calculate the pH at the end of an enzyme-catalyzed reaction if it were carried out in a 0.1 M phosphate buffer, pH 6.86 and 0.005 M of acid was produced during the reaction?

answer

6.77

question

If hydroxide is added to an amino acid it will become increasingly ________ charged.

answer

Negatively

question

Calculate the pH of a weak acid that is 0.2% ionized in a 0.2 M solution.

answer

3.39

question

The net charge on an amino acid at its isoelectric point (pI) is ________.

answer

Zero

question

Many proteins interact with DNA at physiological pH because:

answer

A) proteins are naturally attracted to DNA regardless of the pH. B) the negatively charged DNA is electrostatically attracted to positively charged regions on proteins. C) the positively charged DNA is electrostatically attracted to negatively charged regions on proteins. D) proteins and DNA interact using mainly hydrophobic interactions. E) both proteins and DNA are at their isoelectric points at physiological pH and tend to aggregate. Answer: B

question

Small ions in biological fluids:

answer

A) encourage strong electrostatic interactions between oppositely charged macroions at low ionic strengths. B) encourage strong electrostatic interactions between oppositely charged macroions at high ionic strengths. C) have no effect on the interactions between oppositely charged macroions. D) tend to cluster around macroions of the same charge. E) have large effects on pH. Answer: A

question

The water content in the human body is approximately

answer

70%

question

The Four most abundant chemical elements in living systems are:

answer

Hydrogen, Carbon, Nitrogen and Oxygen

question

Nearly all proteins contain

answer

Sulfur

question

Which of the following statements is FALSE?

answer

Proteins are the only biological polymer that can catalyze biochemical reactions

question

Which of the following is NOT classed as a lipid?

answer

Glycerol

question

Amino acids and simple organic compounds like carbon dioxide and hydrogen cyanide cannot be produced without the use of enzymes

answer

False

question

Oxidation reduction reactions, which are the basis of many biochemical reactions and pathways, cannot take place in the absence of oxygen

answer

False

question

Many biochemical reactions that form biopolymers from monomeric units involve the removal of water

answer

True

question

The principle component of a biological membrane is a triglyceride

answer

False

question

The chemical element __________ has a role in both transfer of energy as well as in the structure of nucleic acids

answer

Phosphorus

question

List the four major classes of biological macromolecules.

answer

Lipids, Carbohydrates, Proteins and Nucleic Acids

question

An amphiatic molecule provides the foundation for biological membranes because they have both ____ and ____ functions

answer

Hydrophobic and Hydrophilic

question

Genomics is concerned with the entire _____, while ______ is focused on identifying all of the proteins of a cell

answer

Genome, proteomics

question

Which of the following statements is FALSE?

answer

Organisms are open systems as they can create energy from their environments

question

Which of the following statements is FALSE?

answer

Biological systems are highly ordered so entropy changes are not relevant

question

A biochemical reaction will proceed in the direction as written if:

answer

G < 0

question

Life is an irreversible process, such that it never comes to equilibrium

answer

True

question

The equilibrium constant of a reaction:

answer

Is related to the change in free energy of the reaction

question

The change in enthalpy (?H) for the complete oxidation of a fatty acid is different depending on whether it occurs via a biochemical path combustion to CO2 and H2O

answer

False

question

A reaction at its lowest energy state for the system and with equal rates in the forward and reverse directions is said to be at _______

answer

Equilibrium

question

A reaction at equilibrium can be driven in one direction or the other by changing the ______ of reactants or products

answer

Concentration

question

A thermodynamically unfavorable reaction can become favorable if the mass action ratio is _________ than the equilibrium mass action ratio

answer

Less

question

Calculate the equilibrium constant for the enzymatic hydrolysis of 0.1 M glucose-6-phosphate to glucose and inorganic phosphate given 0.05% of the original glucose-6-phosphate remained after reaching equilibrium and the activity of water is unity

answer

199.8

question

The ?Go of a reaction:

answer

Can be used to calculate whether a reaction is thermodynamically favorable under defined non-standard conditions

question

Calculate the ?G?' for the reaction Fructose-6-phosphate ? glucose-6-phosphate Given the equilibrium constant is 1.97 and the physiological relevant temperature is 37 C

answer

-1.75 kj/mol

question

A thermodynamically unfavorable reaction can become favorable when coupled to a highly endergonic reaction

answer

False

question

A reaction with a large negative free energy of hydrolysis can be coupled to the synthesis of ATP from ADP and Pi

answer

True

question

In a general redox reaction, the reductant becomes oxidized and the oxidant becomes reduced

answer

True

question

The standard reduction potential is a measure of the ability of a reductant to _____ an electron

answer

Lose

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