BioChem exam 3

What is ΔG for transport of a solute into the cell when the extracellular concentration is 10 mM, the intracellular concentration is 0.1 mM, and T = 20°C?

-11.2 kj mol-1

for a cell with [Na+]out = 150 mM and [Na+]in= 15mM at 37 0C, what is the free energy for movement of sodium ions from outside the cell to inside if the potential across the membrane is -60mV?

-11.7 kj/mol

delta G* for a reaction is 800 what is delta G at 37 C when the ration of product to reactant concentration is 0.6

-520 J mol -1

What is the membrane potential created by a sodium gradient where [Na+]out =145 mM and [Na+]in=12 mM at 37 0C?

-67mV

when a reaction is at equilibrium, the G is equal to ____

0

A sample of cells has a total receptor concentration of 24 mM, and 40% of the receptors are occupied with ligand. The concentration of free ligand is 10 mM. Calculate Kd.

15 μM

hydrolysis of ATP by the Na,K-ATPase moves_____ while hydrolysis of the phosphate moves_____

3 Na+; 2 K+

Calculate the intracellular concentration of Na+ when the extracellular concentration is 160 mM and the membrane potential (due entirely to Na+) is -100 mV at 20°C

3.3 mM

calculate delta G* for a reaction at 25C when Keq=0.25

3400 J mol-1

What is the ratio [Na+]in/[Na+]out created by depolarization in a nerve cell if the final potential is +50 mV at 37 0C

6.5

An uncatalyzed reaction has a rate of 4.2 × 10-7 sec-1. When an enzyme is added the rate is 3.2 × 104 sec-1. Calculate the rate enhancement caused by the enzyme.

7.6 x 1010

which molecule is most reduced

A

receptor tyrosine kinases all use ____ as a substrate

ATP

the delta G* for the hydrolysis of acetyl CoA is most similiar to the delta G* for the hydrolysis of ____

ATP

which sentence best describes ATP's role as a source of energy

ATP is less stable than its hydrolysis reaction products

primary active transport is usually driven by _____, and secondary active transport by _____

ATP; an ion gradient

Which of the following is not an accurate description of an event in a G protein signaling system?

Adenylate cyclase is activated by phosphorylation-Adenylate cyclase is activated by its interation with the α subunit of certain G proteins.

Which of the following does NOT occur in biological signaling systems?

All of the above processes may occur.

N-linked oligosaccharides can be covalently linked to proteins at the amino acid ____

Asn

which structure represents an acetyl group

B

which of the monosaccharides seen below are L sugars?

C and D

which elements are most abundant in carbohydrates?

C, H, O

the ___-terminus of ubiquitin is linked to a ____ residue of proteins to be degraded

C; lys

at a nerve-muscle synapse,

Ca2+ flow in the neuron triggers the release of acetylcholine

the molecular formula for a monosaccharide is ____ where _____

CnH2nOn; n>3

which monosaccharide seen below is the enantiomers of A?

D

which of the following Haworth projections correctly shows the alpha-anomer of galactose

D

in the following structure, which carbon is the anomeric carbon

E

the two main types of receptor systems involve

G proteins and receptor tyrosine kinases

activation of a G protein in response to hormone binding requires binding of _____ to the ____ subunit

GTP, alpha

The imidazole side chain of histidine can function as either a general acid catalyst or a general base catalyst because

I, II

Which of the following amino acid residues would not provide a side chain for acid-base catalysis at physiological pH? (Assume pK values of each amino acid are equal to the pK value for the free amino acid in solution.)I. leucineII. lysineIII. aspartic acidIV. histidine

I, II, III

If you add enzyme to a solution containing only the product(s) of a reaction, would you expect any substrate to form?

It depends on the energy difference between E + P and the transition state.You got it right

which substance is not a second messenger

K+

the oxidized form of NADH is

NAD+

which of the following does not serve as a cellular energy currency?

NAD+

Which of the following statements concerning receptors is FALSE?

Receptors bind signal molecules specifically and irreversibly.-Receptors interact with their ligands in a reversible manner.

A new serine protease was discovered that preferentially cleaves a peptide bond adjoining a negatively charged side chain. Which of the following is true?

The specificity pocket is likely lined with amino acids such as Arg and Lys.

Which of the following statements concerning receptors is CORRECT?

They have a ligand binding site on the extracellular side of the membrane.

what two amino acid residues are the targets of protein kinase A?

Thr and Ser

which of the following statements regarding G proteins is true?

When activated, the α-subunit can cause adenylate cyclase to synthesize cAMP.

arrestin helps terminate G protein signaling by binding to

a G protein-coupled receptor

a nucleotide consists of

a base linked to a phosphorylated ribose

In affinity labeling, a technique used to study enzyme mechanisms,

a compound designed to bind at the active site reacts with and therefore permits the identification of a nearby group

a fatty acid can be linked to glycerol by ____ reaction

a condensation

an ion transport protein constructed entirely from beta strands is most likely to be

a porin

in endocytosis

a vesicle buds inward from the plasma membrane

which of the following is more highly oxidized than acetaldehyde?

acetic acid

The following diagram shows a portion of a reaction sequence of an enzyme. What type(s) of catalysis is (are) occurring in this first step?

acid-base catalysis

what enzyme is activated by association with an active G protein

adenylate cyclase

the bulk of triaclyglycerols in the human body are stored in _____

adipocytes

the molecule shown here is a

aldopentose

which of the following is true regarding SNARE complex formation?

all of the above

which of the following can be regulared by eicosanoids

all of the above -blood pressure -blood coagulation -inflammation -fever

Which of the following can be a hormone?

all of the above -amino acid derivatives -steroids -polypeptides -eicosanoids

the cellular effects of signaling via receptor tyrosine kinases may include

all of the above -phosphorylation of proteins -changes in gene expression -activation of G proteins

amino acids can be converted to ____

all of the above -carbohydrates -fatty acids -nucleotides -peptides

why can histidine NOT act as a base in the lysosome (an organelle where the pH is close to 4.5)?

all of the above are correct

which of the following will cause the opening or closing of a gated ion channel?

all of the above: pH change phosphorylation voltage change ligand binding

which of the following are characteristics of cellulose

all of the above: -highly extended fibers -beta (1->4) glycosidic bonds -extensive hydrogen bonding -between individual molecules unbranched polymer

a transporters activity can be described in terms of

all of the above: -velocity of solute transport -K M for the solute -the maximum rate of transport

amylopectin contains primarily ____ glycosidic bonds with _____ glycosidic bonds as branch points

alpha (1 ->4); alpha (1->6)

an allosteric regulator

alters an enzymes activity

the transformation of a monosaccharide into its _____ occurs easily and does not require the assistance of a catalyst

anomer

the Na,K-ATPase is an ______ that moves Na+ ions from _____ and K+ ions from _____

antiporter; inside to out; outside to in

what type of transported is responsible for moving water across membranes?

aquaporin

the eicosanoids are derived from the membrane fatty acid

arachidonic acid

eicosanoids

are derived from membrane lipids

N-linked oligosaccharides

are modified by glycosidases

which of the following is an inhibitor of cyclooxygenase

aspririn

the conformation changes responsible for ion transport in the Na,K-ATPase are triggered by

attachment and release of a phosphoryl group

lactase, the enzyme responsible for breaking lactose into its monomers, is a ____ enzyme

beta-galactosidase

the following is a ____ disaccharide with a _____ glycosidic bond

beta; alpha (1 ->4

an enzyme does all of the following except

bind a wide variety of substrates

lipid hormones

bind to intracellular receptors

which of the following would be the first to occur following opening of Ca2+ channels during acetylcholine-mediated neurotransmission to a muscle cell?

binding of SNARE complex to synaptic vesicles and pre-synaptic membrane

which of the following is glucose-6-phosphate?

c

protein kinase A is activated by

cAMP and phosphorylation

a protein with two stable conformations

can alternate between conformations

energy is generated during ____, the breakdown of larger molecules into smaller while energy is consumed during ____, the building of larger molecules from smaller ones

catabolic reactions; anabolic reactions

generally speaking, ATP is produced by ____ reactions and used by ____ reactions

catabolic; anabolic

the oligosaccharides of glycoproteins do all of the following except

catalyze chemical reactions

in a metabolic pathway, the reactions that control flux through the pathway

catalyze irreversible reactions

the fusion of a vesicle membrane with the plasma membrane depends on

changes in membrane curvature

ion channels select their solutes by

charge and size

Acid-base catalysis may be accomplished by:

charge delocalization

Since proteins are limited in their abilities to catalyze oxidation-reduction reactions, enzymes often employ ________ to assist with catalysis

coenzymes

which of the following is TRUE regarding cofactors?

cofactor is a broad term used for all enzyme "helpers"

Simultaneous stimulation of a reaction by general acid and general base catalysis is defined as

concerted acid-base catalysis

the ability for some receptor tyrosine kinases to ultimately activate phospholipase C is an example of _____

cross talk

olfactory receptors generate _____ as a second messenger

cyclic AMP

which of the following factors contributes to the highly exergonic nature of ATP hydrolysis?

decrease in negative-ion repulsion in ATP

a cells response to a hormone signal diminishes as a result of

desensitization

The action of phospholipase C on phosphatidylinositol-4,5-bisphosphate generates two important signalling molecules. What are they?

diacyl glycerol and inositol-1, 4, 5- trisphosphate

what is the only monosaccharide that is achiral?

dihydroxyacetone

Curved arrows are conventionally used to illustrate the movement of

electron pairs

changing the configuration of C3 of glucose generates an

epimer

glucose and galactose are ____ of each other

epimers

the conversion of a carbohydrate into CO2 is a ____ process; the conversion of CO2 into a carbohydrate is a ____ process

exergonic; endergonic

Alcohol dehydrogenase catalyzes the conversion of methanol to _________ and is, therefore, classified as a(an)________.

formaldehyde; oxiodoreductase

an autophagosome

forms following membrane fusion

which of the following describes glycosaminoglycans?

found in extracellular space

starch and glycogen function as

fuel storage molecules

this molecule is derived from

galactose

Proton transfer from an acid, lowering the free energy of a reaction's transition state, is characteristic of

general acid catalysis

proton transfer from an acid, lowering the free energy of a reactions transition state, is characteristic of

general acid catalysis

which of the following would be positively charged at physiological pH

glucosamine

the three-carbon monosaccharide ____ is a _____

glyceraldehyde; aldose

which of the following is mobilized for energy use by a phosphorolysis reaction, not a hydrolysis

glycogen

which type of stored metabolic fuel is not mobilized by hydrolysis

glycogen

which of the following is the major difference between glycogen and amylopectin

glycogen contains about twice the number of branch points as amylopectin

the reaction between an alcohol and an anomeric carbon of a carbohydrate forms a ____ bond

glycosidic

monosaccharide residues in polysaccharides are linked by

glycosidic bonds

a transmembrane protein

has regular secondary structure in its transmembrane segments

choose the true statement about autotrophs and heterotrophs

heterotrophs obtain nutrients from autotrophs

The catalytic mechanism of bovine pancreatic RNase A relies upon acid-base catalysis involving the amino acid __________.

histidine

The complex formed between a lipid hormone and its receptor binds to _____ which are specific DNA sequences.

hormone response elements

compounds containing hydroxyl groups interact with water molecules via

hydrogen bonds

digestion of food utilizes enzymes that catalyze ____ reactions

hydrolysis

which is not a function of lipids

information storage

the second messenger ____ opens Ca2+ channels in the endoplasmic reticulum

inositol trisphosphate

the ____ receptor is a receptor tyrosine kinase

insulin

cellulose is a rigid molecule as a result of

interchain hydrogen bonds

the interior of a lipid bilayer

is completely nonpolar

the transition state of an enzyme and substrate reaction

is stabilized due to the specificity of the active site for the substrate

Which of the following amino acid residues would provide a side chain capable of increasing the hydrophobicity of a binding site?

isoleucine

which amino acid side chain is most likely to be found on a membrane-spanning helix?

isoleucine

before a G protein can activate adenylate cyclase

it dissociates into two parts

in a G protein signal-transduction system, what role does the G protein play?

it transmits the signal from the receptor to other components of the signaling system

Research scientists are trying to clone a gene. In order to accomplish this task they join two pieces of DNA. Which class of the enzymes below might accomplish this task?

ligase

which of the following is used to move lipids around the blood stream?

lipoproteins

the ____ stores glucose as glycogen and converts excess glucose to _____

liver; fatty acids

On a transition state diagram for a one-step very spontaneous reaction a large peak (high deltaG) would imply a ______ rate for the reaction

low

inside a nerve cell at rest, [Na+] is _____ and [K+] _____ relative to the concentrations seen outside the cell

low; high

degradation of proteins within a cell can occur within the ____ or by use of ____

lysosome; a proteasome

which of the following molecules is in the most reduced state?

methane

Which of these amino acid groups would not make a good nucleophilic catalyst?

methyl

is this molecule more oxidized or more reduced than glyceraldehyde-3-phosphate

more oxidized

which of the following is correct regarding metabolic pathways?

none of the above are correct

which of the following is a ligand of the 2-adrenergic receptor?

norepinephrine

which class of biological molecule is not a major metabolic fuel?

nucleic acids

unlike proteins and oligonucleotides, polysaccharides _____

often have branched structures

the signal molecule shown below would need a receptor that is located

on the cell surface, because the signal is a hydrophilic molecule

which of the following best describes the relationship between the following molecules?

one is a D sugar, one is an L sugar

the correct order of events during nerve cell signaling is

opening Na+ channels, depolarization, opening K+ channels, repolarization

Metal ion cofactors offer various _______ states that allow enzymes to accomplished oxidation reduction reactions.

oxidation

Metal ion cofactors offer various ________ states that allow enzyme,es to accomplished oxidation reduction reactions

oxidation

a reaction that results in the loss of electrons from a molcule is a ___

oxidation

Enzyme X catalyzes the addition of a hydroxyl group to substrate Y. In the process a metal cofactor is reduced and then reoxidized. What class of enzyme is X?

oxiodoreductase

the movement of glucose into a cell when blood sugar is high is accomplished by____. The movement of K+ ions against its concentration gradient is accomplished by______

passive transport; active transport

which of the following is a heteropolysaccharide?

pectin

in a protein, amino acids are linked by

peptide bonds

bacterial cells are surrounded by a cell wall made from

peptidoglycan

which of the following has the most spontaneous hydrolysis?

phosphoenolpyruvate

plants are considered ____

photoautotrophs

In a G protein signaling pathway, what would happen if phosphodiesterase were inactivated?

protein kinase A would remain active

in a ____, the carbohydrate is responsible for most of the mass; in a ____ the protein is responsible for most of the mass

proteoglycan; glycoprotein

A pH versus rate curve with an inflection point at pH~4 suggests the involvement of a(n) ________ in the catalytic step.

proton transfer with a pK close to 4

choose the true statement

receptor tyrosine kinases undergo autophosphorylation

any sugar that has a free aldehyde group is call a

reducing sugar

cAMP binds to the ____ subunits of protein kinase A allowing the tetramer to dissociate into _____

regulatory subunits; two active monomers and an inactive dimer

A small molecule produced inside a cell in response to a hormone binding to its receptor is called a(n) _____.

second messenger

in G protein signal transduction systems, what role does cAMP play?

second messenger

choose the most accurate statement about vitamins

some vitamins are the precursors of enzyme cofactors

which of the following disaccharides has both anomeric carbons involved in the glycosidic bond?

sucrose

what is a transporter that moves two different molecules or ions in the same direction?

symporter

Transport of glucose from the intestine into the intestinal cells is accomplished by a _____. This is an example of ______

symporter; secondary active transport

the oligosaccharide groups of glycoproteins

tend to be located outside the cell

a primary active transport protein moves a solute in only on direction because

the ATP -> ADP reaction is not reversible

ion transport in the Na, K-ATPase is driven by

the ATP hydrolysis reaction

at equilibrium in solution, D-glucose consists of a mixture of its anomers. Which statement most accurately describes the solution?

the beta-anomer predominates over the alpha-anomer by a ratio of approximately 2:1

choose the true statement about metabolic pathways

the products of one pathway are substrates for another pathway

in a spontaneous reaction

the reactants have higher free energy than the products

the main difference between starch and cellulose is that

the residues are connected differently in starch and cellulose

the main difference between active and passive transport systems is

the source of free energy that drives the transport

which property of proteoglycans allows them to function as shock absorbers?

their hydrophilicity

O-linked oligosaccharides are commonly attached to the oxygen of ____

threonine

an ion will spontaneously move

to an area where it is less concentrated

_____ metals are the most common metallic enzyme cofactors

transition

the monomeric products of digestive polymers are mostly

transported to the liver

digestion of food by mammals converts ____ into ____ which can be absorbed from the intestines

triacylglycerols; fatty acids

an allosteric regulator

triggers shape changes in the protein

all known porins are _____ proteins composed of _______

trimeric; beta barrels

which of the following is a lipid-soluble electron carrier in its reduced state?

ubiquinol

the GLUT transporter changes conformation

when glucose binds and when glucose dissociates

lactose can be described as

β-galactose (1->4) glucose