Quantitative Human Physiology An Introduction 1st Edition Feher Test Bank Full Download:http://alibabadownload.com/product/quantitative-human-physiology-an-introduction-1st-edition-fehe
CHAPTER 2.1 CELL STRUCTURE EXAMINATION QUESTIONS
1.
The concentration of solutes in the cytoplasm of most cells follows which of the following order, from grea test to least: A. B. C. D. E.
2.
The boundary between the inside and outside of a cell is provided by the A. B. C. D. E.
3.
Myosin Desm in Ac tin Tu bu lin Interm ediate filam ents
Intermediate filaments differ from the other cytoskeletal filaments in that A. B. C. D. E.
5.
Cell membrane Endoplasmic reticulum mem brane Mitochondrial membrane Nuclear Envelope Cytoskeleton
Kinesin and dynein move vesicles and other cargo along tracts composed of A. B. C. D. E.
4.
Na>K>ATP>Ca K>Na>ATP>Ca Na>K>Ca>ATP Na>ATP>K>Ca ATP>Na>K>Ca
Intermediate filaments have a polarity (+ and - ends) Intermediate filaments are dynamic along their entire length, not just the ends They are approximately 100 nm in diameter Intermediate filaments are polymers of globular monom eric proteins Interm ediate filam ents do not differ from the other c ytosk eletal elem ents exc ept in s ize
Proteasomes degrade proteins that are “tagged” by A. B. C. D. E.
Myristoylation Palmitoylation Formation of disulfide bonds Farnesylation Ubiquitinylation
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6.
All of the following organelles of the cell have mem branes that enclose a space except A. B. C. D. E.
7.
Cells adhere to each other through all of the following junctions EXCEPT A. B. C. D. E.
8.
Electron microscopy Differential centrifugation Free zon e electrophoresis Light microscopy Bouyant density centrifugation
The relative centrifugal force is given as A. B. C. D. E.
11.
Cytosol Peroxisomes Lysosomes Nucleus M itocho nd ria
Purified subcellular organelles are most often isolated by A. B. C. D. E.
10.
Desm osomes Gap junctions Zonula adherens Zonula occludens Zonula cad hera
Most of the oxygen consumption of human cells occurs in the A. B. C. D. E.
9.
Mitoc hondria Peroxisomes Cytoskeleton Lysosomes Nucleus
kT /D 6B0a T 2r / g (dr/dt) / T 2r -$ v
The Svedberg is defined as A. B. C. D. E.
kT /D 6B0a T 2r / g (dr/d t) / T 2r -$ v
2
12.
The endosymbiotic hypothesis proposes that A. B. C. D. E.
13.
W hich of the fo llowing supports th e endosym biotic hypothe sis A. B. C. D. E.
14.
Integrins Cadherins Desm oplak in Co nn exin Pla ko philin
W hich are NO T one of the ways that cells connect to each other? A. B. C. D. E.
17.
Rough endoplasmic reticulum Smooth endoplasmic reticulum Golgi apparatus Peroxisome E ndosom e
Gap junctions are formed by A. B. C. D. E.
16.
Mitochondria contain circular DNA separate from nuclear DNA Mitochondria consume oxygen Lysosomes contain hydrolytic enzymes Mitochondria import proteins from the cytoplasm Ribosomes contain RNA
Of the following, the organelle most involved in the synthesis of lipids is the A. B. C. D. E.
15.
Lysosomes fuse with endocytotic vesicles to form secondary lysosomes Phagocytosis was a precursor to the gastrointestinal system Secon dary active transpo rt is neces sary for life M itocho nd ria originated from eng ulfm ent of aerobic b acte ria The nucleus was once a separate c ell
Gap junction Adherens junction D esm osom e Zonula occludens C o nn ec to so m e
Of the following, the organelle most involved with packaging and pro cessing of s ecreted pro tein s is the A. B. C. D. E.
Endoplasmic reticulum Peroxisome Golgi apparatus Nucleus Mitoc hondria
3
18.
Doub le mem branes a re part of the structure of A. B. C. D. E.
The endoplasmic reticulum Th e m itocho nd ria The peroxisome The Golgi apparaturs The cytoskeleton
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CHAPTER 2.2 DNA AND PROTEIN SYNTHESIS EXAMINATION QUESTIONS
1.
Th e ou tward appea ranc e or b eha vior of an organ ism is called its A. B. C. D. E.
2.
The set of alleles of a particular pe rson is called the person’s A. B. C. D. E.
3.
Alte rnate form s of prote ins expressed by cells Protein formed by alternate splicing of DNA Alte rnate form s of som atic cells Alte rnate form s of ge rm cells Alternate forms of genes
W hich of the following is NOT a building block of a nucleotide? A. B. C. D. E.
5.
Genotype Som atotype Phenotype Proteome G enom e
Alleles are A. B. C. D. E.
4.
Genotype Som atotype Phenotype Proteome G enom e
A base such as adenine, guanine, thymine or cytosine Phosp hate Deoxyribose 2-deoxy Glucose All of the above are components of nucleotides
Nucleotides consist of A. B. C. D. E.
Deoxyribose, phosphate and a base such as adenine Glycerol, fatty acid and a polar head group such as choline Glycerol, phosphate and a base such as adenine Glyce rol, fatty acid and a polar head g roup suc h as pho sph ate Deoxyribose, choline and a base such as adenine
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6.
The “backbone” of a single DNA nucleotide chain consists of A. B. C. D. E.
7.
Adenine on one strand of D NA form s A. B. C. D. E.
8.
DNA has deoxyribose, RNA has ribose DNA uses thymine, RNA uses uracil to pair with guanine DNA is double-stranded, RNA is single-stranded DNA is replicated from DNA, but RNA is not replicated from RNA All of the above are true differences between RNA and DNA
The 3' to 5' direction o n on e DNA stran d be ing op pos ite to the 5' to 3' direction in the opposing strand is called A. B. C. D. E.
11.
Three hydrogen bonds with thymine on the opposite DNA strand Three hydrogen bonds with thymine on tRNA Three hydrogen bonds with cytosine on the opposite DNA strand Two hydrogen bonds with thymine on the opposite DNA strand Two hydrogen bonds with cytosine on the opposite DNA strand
W hich of the following are NOT differences between RNA and DNA? A. B. C. D. E.
10.
Three hydrogen bonds with guanosine on tRNA Covalent bonds with rRNA Two hydrogen bonds with thymine on tRNA Two hydrogen bonds with cytosine on tRNA Two hydrogen bonds with uracil on tRNA
Gua nine on one s trand of DN A form s A. B. C. D. E.
9.
Deoxyribose units bonded together with phosphate groups hanging off one side and bases hanging off the other side Altern ate p ho sphate an d deoxyrib ose pa rts bon ded co valently Phosphate chains to which deoxyribose units with bases are attached Nucleotides attached by hydrogen bonds Nucleotides attached to each other by covalent bonds
Antiparallel Double helix Reverse strands Helicase Ok azak i fragm ents
DNA polymerase A. B. C. D. E.
Adds nucleotides only to the 3' end of deoxyribose Uses the base on the existing strand as a guide to which nucleotide to add Uses nucleotide triphosphates as substrates Adds nucleotides to the complementary strands of both halves of unwound DNA All of the above are true
2
12.
The unwin ding of DNA is accom plished by A. B. C. D. E.
13.
The only RN A th at is not m ade from DN A is A. B. C. D. E.
14.
Ma kes m RN A fro m a DNA tem plate Ma kes m RN A fro m an R NA tem plate M akes p re t-RNA from a DN A temp late Makes ribosomal RNA in the nucleolus Makes snRNA
mR NA is made by A. B. D. E. E.
17.
Synthesis of proteins in the cytosol Syn the sis of p rotein s in the m itoc hondria Synthesis of proteins on the ER mem brane Synthesis of mRNA from DNA in the nucleus The formation of aminoacyl tRNA
RN A Polym eras e III A. B. C. D. E.
16.
messenger RNA ribosomal RNA transfer RNA small nuclear RNA None of the above
“Transcription” refers to the A. B. C. D. E.
15.
DNA polymerase DNA unw inding enzym e Helicase DNA ligase DNA primase
RNA RNA RNA RNA RNA
polymerase I acting on DNA polymerase II acting on DNA polymerase III acting on DNA polymerase III acting on RNA polymerase I acting on RNA
The “codon” refers to a triplet sequence of nu cleotid es in A. B. C. D. E.
DNA mRNA tRNA complementary DNA rRNA
3
18.
Th e fun ction o f t-RN A is to A. B. C. D. E.
19.
The genetic code is located A. B. C. D. E.
20.
At the end of the response element In betwee n res pon se e lem ents Expressed Excised in the making of mRNA Promotes expression of the DNA
A region of the DNA that is expressed is called A. B. C. D. E.
23.
A site, P site, E site A site, E site, P site E site, P site, A site E site, A site, P site P site, A site, E site
An exon is a reg ion of D NA th at is A. B. C. D. E.
22.
On the mRNA On the tRNA On the DNA On the amino acyl transferases Non e of the ab ove ; it is a system prope rty
The sequential order of b inding of tRNA to the ribo som e is A. B. C. D. E.
21.
Covalently link to an amino acid and also recognize and bind the codon on mRNA Structurally stabilize ribosomes Bind mRNA to the ribosome Elongate the amino acid chain by creating the peptide bond Transfer proteins into the ER
An intron A response element A promoter An exon A spliceosome
Regions of DNA that bind receptors for steroid hormones, for example, are called A. B. C. D. E.
Exons Introns Splices Resp onse eleme nts Promoters
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24.
Histones are A. B. C. D. E.
25.
W hich reaction is NOT part of the “histone code” A. B. C. D. E.
26.
Histone acetylation Histone methylation Histone phosphorylation Histon e prote olysis Histone ubiquitinylation
Transcription requires A. B. C. D. E.
27.
Proteins that bind DNA and make it inaccessible to transcription Proteins that prevent DNA from being translated Enzymes that mark cells for histology Enzymes that ubiquinylate DNA Enzymes that methylate DNA
Unraveling of DNA from the histones Activation of DNA polymerase Activation of RNA polymerase I Duplication of DNA Nucleosome formation
The codon on mRN A 5' to 3' is UCA, which codes for serine. The amino acid sequence complem entary to the codon on the tRNA, 5' to 3' is what sequence of nucleotides? UGA
28.
If the DN A sequence in a gene is 5' to 3' is T GA, w hat is the sequence in the codon, 5' to 3'? UCA
29.
How many possible codons are there? How many different amino acids are there? From this, what can you conclude about the genetic code? Th ere are 4 possibilities for nucleotides in the first position, 4 in the second, and 4 in the third, giving a total of 64 p ossible cod on s. Sin ce th ere a re only 20 amino acids, the genetic code is redundant: several different codons may specify a given amino acid.
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6
CHAPTER 2.3 PROTEIN STRUCTURE EXAMINATION QUESTIONS
1.
All am ino acids conta in A. B. C. D. E.
2.
In a naturally occurring amino acid at neutral pH A. B. C. D. E
3.
Ac idic am ino acid Ba sic amino acid Non-polar am ino acid Po lar am ino acid Arom atic am ino acid
An exam ple of a polar am ino acid is A. B. C. D. E.
5.
The amino group is -NH 3+ and the carboxyl group is -COOH The amino group is -NH 2 and the carboxyl group is -COO The amino group is -NH 3+ and the carboxyl group is -COO The amino group is -NH 2 and the carboxyl group is COOH It is impossible to say the ionization of the groups because they vary among the differeent amino acids
Arginine is an exam ple of a A. B. C. D. E.
4.
An amino group (-NH 2) An asymm etric carbon A carboxyl group (-COOH) A, B and C A and C
Tryptophan Arginine As partic acid Serine Phenylalanine
An exam ple of a non-polar am ino acid is A. B. C. D. E.
Tyrosine Histidine Threonine Gluta m ic acid Leucine
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6.
Non-polar amino acids include all of the following EXCEPT A. B. C. D. E.
7.
“Hydrophobicity” of an amino acid describes A. B. C. D. E.
8.
C. D. E.
The am ino gro up of a lysine R chain and the carboxyl group of a n aspartic R chain The carboxyl group on the carboxyl terminus of the growing chain and the amino gro up of th e ne xt am ino acid The amino group on the amino terminus of the growing chain and the carboxyl group of the next a m ino acid Am ino and carboxyl groups of adjacent amino acids in the interior of the polypeptide The alpha carbon and the R group
Th e linear seq uen ce o f am ino ac ids tha t m ake up a sing le polype ptide c hain is called its A. B. C. D. E.
11.
Lysine As partic acid Serine Tyrosine Isoleucine
Peptide bonds form on the ribosome between A. B.
10.
The num ber of hydrocarbons in its R group Its ability to dissolve in water Its preference for non-polar solvents over water The num ber of polar gro ups on the am ino acid The num ber of charged groups on the am ino acid
W hich of the following amino acids is most hydrophobic? A. B. C. D. E.
9.
Tryptophan Phenylalanine Leucine Lysine Valine
Prim ary structure Secon dary structure Tertiary structure Qua rternary structure Code
W hich of the following is NOT one of the non-covalent interactions that stabilize protein structure? A. B. C. D. E.
Hydrogen bonding Electrostatic attraction/repulsion Hydrophobic interactions Quantum tunneling Steric hindrance
2
12.
The final three-dimensional structure of proteins is important because A. B. C. D. E.
13.
Post-translational modifications of proteins includes A. B. C. D. E.
14.
As partic acid Serine Tryptophan Phenylalanine Proline
N-link ed g lycosylation occ urs whe n ca rboh ydrate grou ps a re ad ded to A. B. C. D. E.
17.
Phosphorylation Methylation Ubiquitinylation Acetylation Transesterification
Phosphorylation of proteins typically occurs at which of the following amino acids? A. B. C. D. E.
16.
Elongation Replication Transcription Proteolytic cleavage Initiation
Chemical post-translational modifications include all of the following EXCEPT A. B. C. D. E.
15.
The pictures are awesome Protein function occurs through interactions on the surfaces of the proteins They are not two-dimensional structures Am ino acids nearby in the 3D structure are us ually not adjacent in the primary structure The structure is dictated by the function
The side chain NH 2 of asparagine The side chain NH 2 of lysine The side chain N of histidine The side chain N of N-acetylglucosamine The side chain NH 2 of serine
O-linked glycosylation o ccu rs when carb ohydrate g roup s are add ed to A. B. C. D. E.
The hydroxyl group of threonine The hydroxyl group of hydroxyproline The hydroxyl group of serine The hydroxyl group of tyrosine Both A and C are correct
3
18.
Proteins can be anchored to mem branes by A. B. C. D. E.
19.
20.
Co valent attachment of th e protein to GP I (glycosyl phosph atidyl ino sitol) Covalent attachment to retinal in membranes Linkage to myristic acid through the carboxyl terminal COOH Linkage to myristic acid through cysteine Linkage to farnesyl through the N-terminus
After the am ino acid sequence of a p rotein is assem bled, th e protein often undergoes a number of post-translational m odificatio ns. There are fou r m ajo r classes of po st-translational m odifications. List three of these. A.
Proteolytic cleavage
B.
Disulfide bond formation
C.
Chemical modification
D.
Protein folding
The ratio of the concentratio n of an unkn ow n am ino acid in octanol compared to its concentration in water was 10:1. Calculate the free energy of transfer from the water to the octanol phase. Use T = 310°K and R = 8.314 joule mol -1 K -1. )G 0T =
- RT ln [X] octanol / [X] H2O = =
21.
- 8.314 joule mol -1 K -1 x 310°K x ln 10
5.93 kj mol -1
Briefly describe the difference between integral and peripheral proteins. Integral prote ins are tightly bound to membranes and can be removed only by usin g drastic means. Periphe ral proteins are loo sely bou nd to me mb ranes an d can be extracted relatively easily.
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CHAPTER 2.4 BIOLOGICAL MEMBRANES EXAMINATION QUESTIONS
1.
Fatty acids consist of A. B. C. D. E.
2.
Fa tty ac id Glycerol Phosp hate Choline Cholesterol
In phospholipids, the phosphate is generally bonded between A. B. C. D. E.
5.
Bind proline Have a trans double bond in the hydrocarbon chain Ha ve a cis do ub le bo nd in the hydro carb on cha in Are saturated Are esterified to cholesterol
W hich of the following is not a constituent of a phospholipid? A. B. C. D. E.
4.
hydrocarbon chain and an alcohol group on one end hydrocarbon chain and an ester bond at the far end hydrocarbon chain and an ether bond at the far end hydrocarbon chain and an carboxylic acid group at the far end hydrocarbon chain and an SH group at the far end
Kinks are formed in hydrocarbon chains that A. B. C. D. E.
3.
A A A A A
Fatty acid and glycerol Glycerol and hydrophilic group such as choline Fatty acid and serine Glycerol and glucose Fatty acids and glucose
Th e m ajor h ydrophob ic part of a phos pho lipid is its A. B. C. D. E.
Glycerol Phosp hate Fatty ac id Inositol Choline
1
6.
Th e m ajor h ydrophilic part o f a ph osp hatidylinositol is its A. B. C. D. E.
7.
W hich of the following is NOT a polar group used in phospholipids? A. B. C. D. E.
8.
Sphingomyelin with attached carbohydrate molecules Two sphingosine molecules linked by a glycerol Tw o ph osp hatidyl ch oline m olecules linked by a ph osp hate Two phosphatidic acid molecules linked by a glycerol Tw o ce ram ide m olecules linked by a ph osp hate
Surface tension is best described as A. B. C. D. E.
11.
Phospholipids Cholesterol Free fatty acids Triglycerides Cardiolipin
Cardiolipin consists of A. B. C. D. E.
10.
Serine Inositol Choline Ethanolamine Alanine
The m ain ingredient of the lipid bilayer in m ost biological m em branes is A. B. C. D. E.
9.
Glycerol Phosp hate Cis F atty a cid Inositol Trans fatty ac id
The Th e The The The
surface energy per unit area su rface en ergy per un it length force or tension per unit area force per unit volume surface energy per unit volume
Consider a spherical cell with surface area 4Br 2 with surface tension (. what would be the change in surface energy? A. B. C. D. E.
+ + + +
1.050 ( 1.050 r ( 1.050 r ( 1.288 r2 ( 0.628 r2 (
2
If we increase r b y 5%,
12.
The orig in of the surface tension of wate r at the water-air interface is A. B. C. D. E.
13.
Am phipathic molecules A. B. C. D. E.
14.
12 dyne cm -1 132 dyne cm -1 0.166 dyne cm -2 0.20 dyne cm -2 Cannot be determined from the information given
Integral proteins A. B. C. D. E.
17.
Am bivalent Am ph ipathic Zw itterionic Integral Peripheral
The surface tension of pure water is 72 dyne cm -1. Addition of surfactant lowers the surface tension to 60 dyne cm -1. W ith th e surfacta nt, the surface pre ssure is A. B. C. D. E.
16.
Prefer organic solvents such as chloroform or CCl4 as a solvent Prefer water as a solvent Have spatially separated lipophilic and hydrophilic regions Have spatially separated positive and negative charges on their surface Are solub le in neither water n or lipid so lvents
Molecules having a lipophilic part spatially separated from a hydrophilic part are called A. B. C. D. E.
15.
Air pressure pushing on the water surface Water molecules attracting other water molecules more than the air attracts them W ater in the bulk phase being at a higher energy than water at the surface Attractive forces of air molecules that tend to exclude the water The hydrophilic nature of air molecules
Have irreducible functions Are loosely bound to mem branes Are constituents of ribosomes Are tightly bound to mem branes Require high salt for removal from mem branes
Motio n of lipid s in a biological m em brane is A. B. C. D. E.
Slow in all directions Slow across the membrane, but fast in the plane of the membrane Rapid in all directions Fast across the mem brane, but slow in the plane of the mem brane Re stricted ex cep t in lipid rafts
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18.
The thickness of biological membranes is about A. B. C. D. E.
19.
Th e first part of a sec reted prote in to be trans lated is called its A. B. C. D. E.
20.
23.
By diffusion By active transport Through a channel provided by a translocon By osm osis Through a channel made by the SRP
The signal recognition peptide A. B. C. D. E.
22.
Initiation sequence Origin Signal sequence Target sequence Recognition sequence
Secreted proteins cross the mem brane of the ER A. B. C. D. E.
21.
10 :m 1 :m 100 nm 10 nm 1 nm
Binds to the signal sequence and to the SRP receptor Binds to the signal sequence and to the translocon Binds to the SRP and to the translocon Binds to the signal sequence inside the ER lumen Helps fold up proteins inside the ER
Nam e three ways that proteins can be anchored into mem branes: A.
Hydrophobic interactions of amino acids with the lipid interior
B.
Co valently attachment of p alm itic or myristic acid
C.
Covalent attachment of a farnesyl group
D.
Covalent attachment to glycosylphosphatidylinositol
Briefly describe the difference between integral and peripheral proteins. Integral prote ins are tightly bound to membranes and their release requires drastic measures such as deterg ents. Periph eral proteins are loo sely bou nd to membranes and can be released by washing in salt solutions or other relatively mild treatments.
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CHAPTER 2.5 PASSIVE TRANSPORT AND FACILITATED DIFFUSION EXAMINATION QUESTIONS
1.
In the microporous model of a mem brane, solutes diffuse across the mem brane by A. B. C. D. E.
2.
In the microporous mem brane model, transport flux is increased by A. B. C. D. E.
3.
n Ba 2 D / * J / )C k s D lipid / * D/* (n B a 2 D + k s D lipid) / *
W hen a solute penetrates through a mem brane by dissolving in the lipid, the perm eability is dire ctly proportional to the A. B. C. D. E.
5.
Increasing the thickness of the mem brane Increasing the length of each pore Decreasing the difference in concentration across the mem brane Incre asing the size of the solute Increasing the number of pores per unit area of membrane
Permeability is best defined for any mem brane as A. B. C. D. E.
4.
Dissolving in the lipid and diffusing across the lipid phase Diffusing through water-filled channels, or pores Being bound to carriers that diffuse across the mem brane Obtaining enough energy through splitting of ATP Riding down the electrochemical gradient of Na +
Size of the s olute Partition coefficient Tem perature Thickness of the mem brane Concentration difference across the mem brane
In th e lipid-dissolution m odel of pa ssive transport, the ra te-lim iting ste p in the perm eation is A. B. C. D. E.
Dissolution of the solute in the lipid phase on the source side of the mem brane Dissolution of the solute in the aqueous phase on the sink side of the mem brane Diffusion of the solute through the lipid interior of the membrane Conformational changes in the carrier The num ber of pores in the mem brane.
1
6.
Permeability through the lipid bilayer A. B. C. D. E.
7.
A mem brane separates a solution with a concentration C L on the left and C R on the right. The free energy change for movem ent of solute to the right is zero when A. B. C. D. E.
8.
It is the solute con centration at one-h alf the ma ximu m tran sport rate It is the X -interc ept on a plot of 1 /Q aga inst 1 / S It is the Y-intercept on a plot of 1/Q against 1/ S It is the solute concentration when Q = Q max It is -R tim es the slop e of the plot of ln Q vs 1/T
Facilitated diffusion differs from simple passive permeability in all of the following EXCEPT A. B. C. D. E.
11.
0.25 Q max 0.5 Q max 0.67 Q max 2 Q max Q max
You have the ability to measure the transport rate, Q, across a mem brane as a function of the concentration of tran spo rted s olute on the source side, S. How would you experimentally determine the Km for transp ort? A. B. C. D. E.
10.
CL < CR C L = RT Ln C L / C R C R = RT Ln C L / C R CL = CR p=0
A facilitated diffusion carrier has a K m = 5 m M an d a m axim um transport rate of Q max. At a solute concentration of 10 mM, its transport rate is about A. B. C. D. E.
9.
Requires an input of metabolic energy Saturate s with highe r con cen tration o f solute Always involves mo vem ent of solute from low to high osm otic pressure Depends directly on the partition coefficient Is increas ed b y ionization o f the s olute
Facilitated diffusion is saturable, passive permeability is not Facilitated diffusion uses metabolic energy, passive permeability does not Facilitated diffusion is specific, passive permeability is not Facilitated diffusion displays competitive inhibition, passive permeability does not Facilitated diffusion uses a carrier, passive permeability does not
In carrier kinetics, saturation means that A. B. C. D. E.
All of the ca rriers are b usy a nd transport is limited by the num ber o f carriers No m ore transport is possible Equilibrium has been reached Th e m em bran e ca n ho ld no m ore s olute There are no free C=C double bonds 2
12.
An ionophore is a substance that A. B. C. D. E.
13.
W hich of the following is NOT a characteristic of biological ion channels? A. B. C. D. E.
14.
Specificity of ion con duc tanc e is de term ined by a ga te Ch annels appear to have gates that are opened sometimes, and closed at other times Channels behave like sieves Channels are like circular pipes with pressure-operated valves Opening of the channels is metabolically controlled
Voltage-gate d ch ann els chan ge their open p roba bility in res pon se to A. B. C. D. E.
16.
Th ey display specificity They often display gating The y are passive They are integral proteins Th ey are c arriers
Gating of ion channels means that the A. B. C. D. E.
15.
Increases the permeability of a mem brane to glucose Separa tes proteins on the basis of their charge a nd s ize Carries water across mem branes Increases the permeability of a membrane to ions Enlarges the size of water pores
Chem icals that bind to the channel Current that flows through the channel Th e loc al electrica l field Binding of ions to the channel Phosphorylation of the channel
A mem brane separates two solutions of glucose. The outside concentration of 5 mM and the inside has a concentration of 20 mM. Consider that there is an efflux of 1 pmol of glucose to the outside of the cell . How m uch energy does the transport of 1 pmol of glucose involve? Is the free energy change positive or negative? R = 8.314 joule mol -1 oK -1 , T = 37oC The free energy of transport per mole is given as : final - : initial = : 0outside + RT ln C outside - : 0inside - RT ln C inside 8.314 joule mol -1 oK -1 x 310 oK ln [ 5 x 10-3M / 20 x 10 -3 M] The free energy is )G
= n ):
=
RT ln C outside / C inside =
= - 3.57 kJ mol -1
= 1 x 10-12 mol x -3.57 x 10 3 joule mol -1 = -3.57 x 10 -9 joules
W here does the energy for passive transport come from? It comes from the solutions themselves.
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17.
The concentration of solute on the left side of a mem brane was 5 :M and the concentration on the other side was 0. The flux across the mem brane was determined to be 0.2 pmol cm -2s -1.
A.
W hat is the permeability of the mem brane to the solute?
Perm eab ility is de term ined as p = J / )C = 0.2 x 10 -12 mol cm -2 s -1 / 5 x 10 -9 mol cm -3 p = 4 x 10-5 c m s-1 B.
The thickness of the mem brane is 10 :m, and the free water diffusion coefficient of the solute is 1 x 10 -5 cm 2s -1. W e want to find out if transport across the mem brane is faster than it would be across water. W hat wo uld the diffusive flux be for a water barrier the thickness of the m em brane? Is the flux th rough the m em brane fa ste r or slowe r than for sim ple diffusion through water?
The diffusive flux across a water barrier this thick wou ld be given by Fick’s First Law of Diffusion: J = - D )C/)x =
- 1 x 10 -5 cm 2s -1 x [(5 x 10 -9 - 0 ) mol cm -3 ] / [0 - 10 x 10 -4 cm ] =
J = 5 x 10-11 mol cm -2 s -1 This is much faster than the flux across the membrane, 0.2 x 10 -12 mol cm -2 s -1
18.
Explain w hy at ste ady-s tate the con cen tration g radient in a pore m ust be co nsta nt. Because if the conce ntration gradient were not constant in time, then the concentrations w ou ld be changing with time, and the flux would be changing w ith time, and there would not be a steady-state.
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