Exam 1: chapters 1-3 & 5

Which of the following statements is not true of most cellular redox reactions? The electron acceptor is reduced. The reactant that is oxidized loses electrons. Changes in potential energy can be released as heat. A hydrogen atom is transferred to the atom that loses an electron.

A hydrogen atom is transferred to the atom that loses an electron.

A(n) _____ reaction occurs spontaneously. kinetic endergonic chemical exergonic anabolic

exergonic

The energy for an endergonic reaction comes from a(n) _____ reaction. glucose + glucose --> maltose ADP + P --> ATP anabolic synthesis exergonic

exergonic

The reaction A --> B + C + heat is released in a(n) _____ reaction. exergonic anabolic endergonic exchange dehydration synthesis

exergonic

Select the INCORRECT association. enzyme ... protein exergonic ... spontaneous potential energy ... positional energy kinetic energy ... motion exergonic ... uphill

exergonic ... uphill

The unequal sharing of electrons within a water molecule makes the water molecule _____. hydrophobic polar ionic have a low surface tension change easily from a liquid to gaseous form

polar

In this molecule, what type of bond is found between the oxygen and hydrogens? hydrophilic polar covalent hydrophobic ionic nonpolar covalent

polar covalent

Why isn't this insect drowning? It is difficult to change the temperature of water. Surface tension. The insect is very light. The insect is swimming. The insect is flying just above the water surface.

surface tension

In this reaction _____. AC is a reactant CD is a product the products have been rearranged to form reactants the products have less potential energy than the reactants entropy has decreased

the products have less potential energy than the reactants

What is energy coupling? a description of the energetic relationship between the reactants and products in an exergonic reaction the use of an enzyme to reduce EA a barrier to the initiation of a reaction the hydrolysis of ATP to ADP + P the use of energy released from an exergonic reaction to drive an endergonic reaction

the use of energy released from an exergonic reaction to drive an endergonic reaction

Under standard conditions, a given reaction is endergonic (i.e., ΔG >0). Which of the following can render this reaction favorable: using the product immediately in the next step, maintaining a high starting-material concentration, or keeping a high product concentration? maintaining a high starting-material concentration keeping a high product concentration using the product immediately in the next step using the product immediately in the next step and maintaining a high starting-material concentration

using the product immediately in the next step and maintaining a high starting-material concentration

An ionic bond involves _____. no atoms other than sodium and chlorine an attraction between ions of opposite charge the unequal sharing of an electron pair the sharing of a single pair of electrons water avoidance

an attraction between ions of opposite charge

Atoms with the same number of protons but with different electrical charges _____. are different ions have different atomic masses are different isotopes have different numbers of neutrons have different atomic numbers

are different ions

The tendency of an atom to pull electrons toward itself is referred to as its _____. polarity electronegativity covalency ionic potential tonicity

electronegativity

Calculate the value of pKa for an acid when Ka = 2.6 × 10-4. -8.25 +3.59 -3.59 +8.25

+3.59

Calculate the ΔG°' for the reaction: fructose-6-phosphate → glucose-6-phosphate given the equilibrium constant is 1.97 and the physiological relevant temperature is 37°C. -0.21 kJ/mol -1.75 kJ/mol +1.75 kJ/mol +0.21kJ/mol

-1.75 kJ/mol

What is the pH of a 0.1 M phosphate buffer (pKa = 6.86) that contains equal amounts of acid and conjugate base? 5.61 6.86 5.86 8.11

6.86

Which of the following statements about noncovalent bonding interactions are true? 1) All noncovalent bond interactions are inherently electrostatic in nature. 2) A charge may induce formation of a dipole in a nearby polarizable molecule. 3) Charge-induced dipole interactions are inversely proportional to the square of the distance between the two atoms. 4) Van der Waals interactions, also known as dispersion forces, are the weakest of the attractive noncovalent bonding interactions.

1, 2, 4

Which statements about buffers are true? 1) The principle behind a buffering solution is that the pH changes the least per added increment of acid or base at the p K a. 2) A buffer solution is an aqueous solution of a weak acid and its conjugate base. 3) The Henderson-Hasselbalch equation does not apply to buffering solutions. 4) Buffered solutions can minimize the change in pH, because the conjugate acid and conjugate base of the buffer are present in sufficient concentration to combine with and neutralize added H+ or OH- All statements are true 1, 2, and 4 are correct

1, 2, and 4 are correct

The energy of a noncovalent interaction is dependent on their range. Organize the following types of noncovalent interactions from longest range to shortest range interactions. Van der Waals interaction (dispersion force) Charge-charge interaction Dipole-induced dipole interaction Dipole-dipole interaction

2 > 4 > 3 > 1

Weak acids dissociate only partially. In an aqueous solution of a weak acid, there is a measurable equilibrium between the acid and its conjugate base. Which of the following acids are weak? Hydrochloric acid (HCl) Formic acid (HCOOH) Carbonic acid (H2CO3) Acetic acid (CH3COOH) 2 and 4 3 and 4 2, 3, and 4 All listed acids are weak.

2,3,4

Which of the following statements about acids and bases are true? 1) Acetic acid is a strong acid. 2) A strong acid has a weak conjugate base. 3) A Brønsted base is a proton acceptor. 4) Bases need not contain -OH directly; instead, they can increase the concentration of -OH by deprotonating water.

2,3,4

Check all that apply. 1) A hydrogen bond is equivalent to a covalent bond. 2) Hydrogen bonding occurs when a hydrogen atom is covalently bonded to an N, O, or F atom. 3) The CH4 molecule exhibits hydrogen bonding. 4) A hydrogen bond is possible with only certain hydrogen-containing compounds. 5) A hydrogen atom acquires a partial positive charge when it is covalently bonded to an F atom.

2,4,5

What is the approximate pH of a 0.10 M solution of a weak acid that has a Ka of 5 × 10-5 M? 2.7 5.3 11.3 4.8

2.7

The pKa of lactic acid is 3.9. A lactate buffer will be useful from pH values ________. 3.5 through 4.4 3.8 through 4.0 2.9 through 4.9 3.0 through 4.5

2.9 through 4.9

The pH of a 10-4 M solution of HCl is ________. 4.0 3.5 3.0 4.5

4.0

Pure water has a concentration of ________. 55 M 1000 g/ml 1 g/ml 18 g/ml

55M

Eukaryotic cells are compartmentalized. Assign a function to each organelle. A) Vacuole 1) Waste removal and digestion B) Golgi complex 2) Intracellular secretion, excretion, storage, and digestion C) Lysosome 3) Membrane-bound chambers that function in secretion and the transport of newly synthesized proteins to their destination D) Chloroplast 4) Photosynthesis

A:2 B:3 C:1 D:4

In cells, what is usually the immediate source of energy for an endergonic reaction? glucose ATP sugar ADP as spontaneous reactions, endergonic reactions do not need an addition of energy

ATP

This graph illustrates a(n) _____ reaction. catabolic hydrolysis endergonic exergonic spontaneous

endergonic

Which statements about lipid bilayers are true? 1) Their formation is driven by the hydrophobic effect. 2) The amphipathic molecules that make up the bilayers orient themselves such that their polar head groups point out toward the aqueous solvent and their hydrophobic tails are pointed toward the interior of the bilayer. 3) They serve the role of physical compartmentalization of components within a cell. 4) They can be made up of phospholipids. All answers are correct. 1, 3, and 4 are true. 1, 2, and 4 are true. 1, 2, and 3 are true.

All answers are correct.

Noncovalent interactions are critically important to the function of biomolecules. Which of the following statements is/are (a) valid reason(s) for this importance? The energies of weak, noncovalent interactions are cumulative, i.e. together they are strong. Noncovalent bond energies are ~10-100 times weaker than ordinary covalent bonds. Noncovalent interactions are made up of hydrogen bonding, electrostatic interactions, and dispersion forces. All of the listed statements are valid reasons for this importance.

All of the listed statements are valid reasons for this importance

Which statements about adenosine triphosphate (ATP) are true? ATP can be hydrolyzed to adenosine monophosphate and pyrophosphate. ATP is a carrier of cellular energy. ATP can be hydrolyzed to adenosine diphosphate and inorganic phosphate. ATP has two phosphoanhydride bonds. All statements are true. 3 and 4 1 and 2 2, 3, and 4

All statements are true.

Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other? Anion and cation. Polar and nonpolar. Ionic and covalent. Proton and electron.

Anion and cation.

Which of these reactions requires a net input of energy from its surroundings? hydrolysis ATP --> ADP + P exergonic catabolic endergonic

endergonic

When a reduction half-reaction is ________ (negative, positive), electrons flow to the more readily reduced substance which is ________ (negative, positive) in value. Negative; positive Negative; negative Positive; negative Positive; positive

Negative; positive

For molecules with more than one ionizable groups, such as glycine, which of the following statements is true? At pH near the pI, nearly all the molecules carry no net charge. At a pH near the pI, nearly all the molecules carry a net positive charge. At a pH near the pI, nearly all the molecules carry a net negative charge. When the pH is near the pI, the solution is near its maximum buffering ability.

At pH near the pI, nearly all the molecules carry no net charge.

Which of the following statements is TRUE? Biological systems are highly ordered so entropy changes are not relevant. Entropy is a measure of order. The entropy of an isolated system will tend to level to a minimum value. Biological systems expend energy to overcome entropy.

Biological systems expend energy to overcome entropy.

The reaction ADP + P --> ATP is a(n) _____ reaction. hydrolysis exergonic endergonic spontaneous chemical

ENDERGONIC

Which term describes the degree to which an element attracts electrons? Polarity. Electronegativity. Oxidation. Reduction.

Electronegativity

If hydroxide is added to an amino acid, how will this affect the charge on the amino acid? It will become more negatively charged. It will become more neutrally charged. It will become more positively charged. It will have a higher charge than before the OH group was added.

It will become more negatively charged.

What name is given to the bond between water molecules?

Hydrogen

The brackets are indicating a(n) _____ bond. A bond between two identical molecules. Each molecule consists of two small atoms connected to a bigger one. This bond is formed between one small atom from one molecule and the big atom from the other molecule. This small atom has a delta plus charge, and the big atom has a delta minus charge. This bond is marked by three points.

Hydrogen - A hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.

Gaseous hydrogen burns in the presence of oxygen to form water: 2H2 + O2 → 2H2 O + energy Which molecule is oxidized and what kind of bond is formed? Oxygen, nonpolar. Oxygen, polar. Hydrogen, nonpolar. Hydrogen, polar.

Hydrogen, polar.

What is the fate of the phosphate group that is removed when ATP is converted to ADP? It is broken down into one phosphorus and four oxygen atoms. It is used to convert an ATP into an AQP. It is acquired by a reactant in an endergonic reaction. It is acquired by a reactant in an exergonic reaction. It is acquired by a reactant in a spontaneous reaction.

It is acquired by a reactant in an endergonic reaction.

Examine the biochemical reaction below: CH3CH2OH + NAD+ ↔ CH3CHO + NADH + H+ Which of the following molecules is reduced in the aforesaid reaction? EtOH NAD+ NADH Acetaldehyde

NAD+

Which of the following statements is true of the bonds in a water molecule? There is equal sharing of the electrons between the oxygen atom and the two hydrogen atoms, and the net charge is zero. The electron in each hydrogen atom is completely transferred to the oxygen atom, and each hydrogen atom has a net charge of +1. Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero. Oxygen acts as the electron acceptor and is oxidized.

Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero.

The endergonic conversion of ADP to ATP requires more than 30 kJ/mol. The hydrolysis of phosphoenolpyruvate to pyruvate drives the conversion of ADP to ATP. What must be true about this hydrolysis? The hydrolysis reaction is more endergonic than the conversion of ADP is exergonic. The hydrolysis reaction is more endergonic than the conversion of ADP is endergonic. The hydrolysis reaction is less exergonic than the conversion of ADP is endergonic. The hydrolysis reaction is more exergonic than the conversion of ADP is endergonic.

The hydrolysis reaction is more exergonic than the conversion of ADP is endergonic.

The hydrolysis reaction is more endergonic than the conversion of ADP is exergonic. The hydrolysis reaction is more endergonic than the conversion of ADP is endergonic. The hydrolysis reaction is less exergonic than the conversion of ADP is endergonic. The hydrolysis reaction is more exergonic than the conversion of ADP is endergonic.

The hydrolysis reaction is more exergonic than the conversion of ADP is endergonic.

Do you predict that this salt bridge will become stronger, become weaker, or be unaffected as pH increases from pH=7.1 to pH=7.6? The salt bridge will become stronger. The salt bridge will become weaker. The salt bridge will be unaffected.

The salt bridge will become weaker.

The terms Q and K describe mass action for reactions at non-equilibrium and equilibrium conditions, respectively. For a forward reaction to be favored in a living cell, which of the following statements must be true? The value of Q must be less than that of K. None of the listed statements are true; cells are at equilibrium. No conclusion can be drawn about Q and K for a favorable process. The value of K must be less than that of Q.

The value of Q must be less than that of K.

Consider the following reaction: NADH + FAD + H+ → NAD+ + FADH2. Which of the following statements is correct? This reaction is favorable because it has a positive ΔE°. The reaction is not favorable because the ΔE° is negative. FAD is the reductant. NADH is the oxidant

This reaction is favorable because it has a positive ΔE°.

From the standpoint of entropy, consider the following processes: water boiling, mixing cola and root beer sodas, and assembling a house of cards. Based on your understanding, which of the following statements is true? Water boiling and mixing cola and root beer sodas are not favorable processes, but assembling a house of cards is. Water boiling and mixing cola and root beer sodas are favorable processes, but assembling a house of cards is not. Water boiling is a favorable process, but mixing cola and root beer sodas and assembling a house of cards are not. All of the listed processes are favorable.

Water boiling and mixing cola and root beer sodas are favorable processes, but assembling a house of cards is not.

Each water molecule is joined to _____ other water molecules by ____ bonds. two ... hydrogen two ... polar covalent four ... polar covalent three ... ionic four ... hydrogen

four ... hydrogen

A reduction reaction is characterized by a... gain of hydrogens gain of electrons Loss of hydrogen loss of electrons

gain of electrons

In this reaction _____. entropy has decreased disorder has decreased the chemical energy of the products is greater than that of the reactants the kinetic energy of the reactants is less than that of the products heat has been released to the environment

heat has been released to the environment

In salt, what is the nature of the bond between sodium and chlorine? polar covalent nonpolar covalent ionic hydrophobic hydrogen

ionic

What kind of bond is formed when lithium and fluorine combine to form lithium fluoride? Nonpolar covalent. Redox. Polar covalent. ionic

ionic

A certain reaction is unfavorable at RT. You increase the temperature and find that the reaction becomes favorable. What can you say about ΔS of the reaction? From the information given, we cannot determine if ΔS is positive, negative, or 0. ΔS must be zero. ΔS must be negative. ΔS must be positive.

ΔS must be positive.