Exam 1 - Biology 181 Sections 05/06! ! ! ! Lyons/Beilstein

Each question is worth 2.5 points.

1. A farmer wishes to develop a strain of high-yield corn that is also resistant to drought. He has the following individuals from the current year's crop:

Individual 1—Yield: 220 bushels/acre; drought resistance: highIndividual 2—Yield: 220 bushels/acre; drought resistance: lowIndividual 3—Yield: 185 bushels/acre; drought resistance: mediumIndividual 4—Yield: 140 bushels/acre; drought resistance: highIndividual 5—Yield: 200 bushels/acre; drought resistance: medium

Which of the following crosses would most likely produce the highest corn yield with the highest resistance to drought?! A. 1 and 2

B. 2 and 5C. 2 and 2D. 1 and 1E. 2 and 3

(D) Plants can be bred to themselves. One plant maximizes both yield and drought resistance.

2. The role of controls in scientific experiments is to _____,A. Keep conditions as constant as possible. B. Generate large sample sizes that reduce variation.C. Test for factors other than the one being investigated that might influence the

outcome of the experiment.D. Allow researchers to conduct experiments with the least possible amount of

materials.E. None Of The Above.

(C) Experimental “controls” control for variables other then one being tested.

3. Prokaryotic cells are found in the domain(s) _____.A. Bacteria and ArchaeaB. Bacteria and EukaryaC. Bacteria and ProtistaD. BacteriaE. Protista and Archaea

(A) Prokaryotic means “without nucleus”. Bacteria and Achaea cells lack a nucleus.

4. Looking at the graph above, which statements must be true:

1. Total crop yield has generally increased over time.2. Protein content has generally decreased over time.3. Protein content always increases with each generation.4. There has been selection for larger kernels.

A. 1 is trueB. 1 and 3 are trueC. 2 and 3 are trueD. 1, 3 and 4 are trueE. None are true

(E) The plot is about protein content only. Therefore, 1 and 4 are out. Protein content has increased over time (2 is out), but not with each generation (3 is out).

5. What is evolution?A. The tendency of organisms that are favorably adapted to their environment to survive

to reproduce.B. The reproductive isolation of a population that may form a new species.C. The family tree of organisms that describes the genealogical relationships among

species with a single ancestral species at its base.D. The accumulation of favorable adaptations in a population of organisms through

natural selection over thousands of generations.E. None Of The Above.

(D) Definition question.

6. In the above figure, group 1 sat closest to the front of the room and group 4 sat at the back of the room. Assuming that people were randomly assigned to groups, what does the graph show about the difference in behaviors between these groups.

A. People who liked to attend class preferentially sat in the front of the room.B. The distance from the front of the room made a difference in the grade people earned

in the class.C. There was no difference in attendance based on where people sat.D. People who sat in the front of the class were less likely to attend lectures than those

who sat in the back of the class.E. None Of The Above.

(E) The data in the graph shows that people who sat in the front of the class were more likely to attend lectures than those who sat in the back, regardless of whether it was the first or second half of the term (though the effect was larger in the second half of the term.)

7. What is the difference between a hypothesis and a scientific theory?A. A hypothesis is a scientific observation that has been repeatedly confirmed; a scientific

theory is a theory that has withstood repeated testing and is accepted as being true in all cases.

B. A hypothesis is a testable question developed by a scientist based on a series of observations; a scientific theory is a theory that has withstood repeated testing and is accepted as being true in all cases.

C. A hypothesis is a testable question developed by a scientist based on a series of observations; a scientific theory is an explanatory idea that is broad in scope and supported by the results from many experiments designed to test hypotheses.

D. A hypothesis is a theory that has withstood repeated testing and is accepted as being true in all cases; a scientific theory is a scientific observation that has been repeatedly confirmed.

E. None Of The Above.(C) Definition question.

8. Sodium chloride is held together by ____ bonds; Dihydrogen monoxide is held together by ____ bonds;

A. Ionic; Polar covalentB. Polar covalent; IonicC. Ionic; Nonpolar covalentD. Nonpolar covalent; IonicE. None Of The Above.

(A) Sodum cloride is NaCl or table salt. Na gives up an electron to be positively charged and Cl accepts an electron to become negatively charged. Dihydrogen monoxide is H2O, aka water. Its atoms are held together using polar covalent bonds.

9. Approximately how many hydrogen bonds does it take to yield the same strength (kJ/mol) of a covalent bond? A. 1 B. 10 C. 100 D. 1000 E. None Of The Above.(B) This chart was shown multiple times in lecture: Strength of bonds: (kJ/mol) Covalent: 100-400 Ionic: 50-200 Hydrogen: 10-65

10._____ causes water to form droplets; ____ causes water to stick to other things.A. Adhesion; cohesionB. Surface tension; cohesionC. Surface tension; adhesionD. Cohesion; surface tensionE. None Of The Above.

(E) Cohesion is the ability of water to stick to itself. Adhesion is the ability of water to stick to other things.

11. A mole of sodium chloride weighs approximately 58 grams. How much sodium chloride is needed to make 4 liters of 0.5M table salt solution?

A. 29 gramsB. 58 gramsC. 87 gramsD. 116 gramsE. None Of The Above.

(D) 58g/mol * .5 mol/L * 4 L = 116g

12. _____ atoms give organic molecules their overall shape; _____ atoms determine the overall chemical behavior of organic molecules.

A. Hydrogen; C, N, and OB. H, N, and O; carbonC. Carbon; H, N, and OD. Carbon; waterE. None Of The Above.

(C) Carbon is used as the skeleton of an organic molecule, H, N, O provide charge to a molecule which greatly influences their chemical behavior.

13. Why do chemical reactions tend to speed up when the temperature of the reactants is increased? What type of energy is this?

A. The reactants collide more frequently; potentialB. The electronegativity of the reactants is decreased; kineticC. The specific heat is increased; freeD. The heat of vaporization is decreased; covalent E. None Of The Above.

(E) Heat causes molecules to move faster which is molecular kinetic energy. This results in more collisions per second and increase the likelihood of a productive reaction.

14. Which of the following statements most accurately describes the relative locations of the covalently bonded electrons in methane (CH4) and ammonia (NH3)?

A. Electrons are shared unequally in both molecules.B. Electrons are shared equally in both molecules.C. Electrons are shared equally in CH4 and unequally in NH3.D. Electrons are shared equally in NH3 and unequally in CH4.E. None Of The Above.

(C) C and H have a similar electronegativity. N is more electronegative than H.

Consider the molecule above when answering questions 15 – 16.

15. The Carbon atom, attached to another carbon atom and a nitrogen, is known as the ______________ carbon.! A. central

B. primary C. alpha

! D. #1E. none of the above

(C) the alpha carbon

16. The OH group is part of a(n) _______________ because it donates it’s ____________ion, which is accepted by the _________ atom. The entire molecule thus has ______________ charge and is known as a Zwitterion.

A. aldehyde, oxygen, hydrogen, a negativeB. carboxylic acid, hydrogen, oxygen, a positiveC. aldehyde, hydrogen, nitrogen, no netD. carboxylic acid, hydrogen, nitrogen, a negativeE. none of the above

(E) The OH is part of a carboxylic acid because it donates its hydrogen ion, which is accepted by the nitrogen atom. The entire molecule thus has no net charge and is known as a Zwitterion.

17. What aspects of amino acid structure vary among different amino acids?A. the long carbon-hydrogen tails of the moleculeB. the presence and location of the primary carbon atomC. the glycerol molecule that forms the backbone of the amino acidD. the components of the R-groupE. both B and D

(D) R-groups vary among amino acids and give different amino acids different chemical properties.

A B

C D

? ?

18. Consider the image above. Which of the following correctly represent the contents of boxes A – D?

1. A: N-terminus; B: C-terminus; C: acidic amino acid; D: primary structure 2. A: NH3+; B: COO-; C: peptide; D: polymer3. A: N-terminus; B: C-terminus; C: hydrophobic amino acid; D: protein4. A: NH3+; B: COO-; C: monomer; D: polypeptide

A. 1, 2, 3 B. 2, 3, 4 C. 1, 3, 4 D. 1, 2, 4 E. 1, 2, 3, 4

(D) The amino acid in box C is aspartic acid and is hydrophilic due to its negative charge.

19. You are studying a protein that is shaped like a doughnut. The shape is a function of which level(s) of protein structure?

A. tertiary onlyB. primary onlyC. secondary and tertiary onlyD. secondary onlyE. primary, secondary, and tertiary

(E) Primary structure influences secondary structure which influences tertiary structure.

20. Which of the following statements are true?

1. An alpha-helix is a type of secondary structure created by hydrogen bonds formed along the backbone atoms of an amino acid chain.

2. Tertiary structures are created by ionic bonds, hydrogen bonds, sulfur bridges, hydrophobic interactions and Van der Waals forces.

3. Quaternary structure is achieved when a protein has multiple sub-units.4. Once a protein has achieved tertiary structure, it is referred to as “folded”.

A. 1,2 onlyB. 2,3 onlyC. 1,2,3 onlyD. 2,3,4 onlyE. 1,2,3,4

(E) All statements are true.

21. In cells, the activity of enzymes is often regulated by other molecules. Why is this necessary?

A. because it is unlikely that all reaction products are required all of the timeB. because other molecules are necessary to prevent enzymes from denaturingC. because every enzyme has multiple functionsD. because all enzymes require some help from another molecule to function correctlyE. because most enzymes function as trans-membrane channels

(A) It is inefficient for cells to catalyze reactions when products are not required or when substrates are not present.

22. HIV is the virus that causes AIDS. In the mid-1990s, researchers discovered an enzyme in HIV called protease. Once the enzyme's structure was known, researchers began looking for drugs that would fit into the active site and block it. If this strategy for stopping HIV infections were successful, it would be an example of what phenomenon?

A. allosteric activationB. allosteric deactivationC. co-factor mediated regulationD. competitive inhibitionE. none of the above

(D) In competitive inhibition, molecules compete for the active site of the enzyme.

23. An enzyme has a total of four active sites. When you denature the molecule and study its composition, you find that each active site occurs on a different polypeptide. Which of the following hypotheses does this observation support?

A. The enzyme requires a cofactor to function normally.B. The protein has a quaternary structure.C. The protein’s structure is affected by temperature and pH.D. The enzyme is subject to allosteric regulation.E. none of the above

(B) Enzymes composed of more than one polypeptide have quaternary structure.

a. _

____

____

____

__

b. _______________

c. _______________

d. _______________

e. _______________

Consider the graph above when answering questions 24.

24. Which of the following represents a correct labeling of elements a-e of the graph? A. a: free energy; b: reaction progress; c: activation state; d: ∆G; e: activation ! ! energy B. a:time; b: ∆G; c: transition state; d: activation energy; e: free energy C. a: free energy; b: reaction progress; c: transition state; d: activation energy; ∆G D. a: time; b: free energy; c: activation state; d: activation energy; e: ∆G E. none of the above(C) The graph depicts free energy (y-axis) during a reaction progression (x-axis). The activation energy is the energy required to achieve the transition state, which is unstable. When the product is formed from the substrate, the change in free energy is the ∆G, which is the same whether the reaction takes place in the presence or absence of a catalytic enzyme.

Consider the following paragraph and figure and answer questions 25 – 28.Since structure correlates so well with function, biochemists are constantly looking for new ways to probe the complex structure of proteins in order to understand what they do and how they do it. One of the most powerful techniques in existence today is X-ray crystallography. The main difficulty with this technique is getting the protein to crystallize. Once crystallized, the protein is bombarded with X-rays to create a pattern that can be analyzed mathematically to determine the three-dimensional structure of the protein. This analysis has been performed by Krzysztof Palczewski on the protein rhodopsin, which is a light-sensitive protein found in species ranging from ancient bacteria (archaea) to humans. The structure (schematically shown below, where each letter represents an amino acid) is characterized by a single polypeptide chain with several α-helical segments that loop back and forth across the cell membrane. Another notable feature is the disulfide bond (-S-S-) that can be seen at the bottom of the third transmembrane segment. [Figure adapted from K. Palczewski et al., Science 289 (2000): 739.]

25. If you were reading off the sequence of amino acids in the figure to a biologist friend, what should the first three letters be?

A. APAB. MNGC. it doesn’t matter, the protein has no polarity or direction

(B) MNG. Proteins begin at the amino (NH2) terminus and end at the carboxyl (COOH) terminus.

26. Identify the location of the disulfide bond in the figure. What is the name of the amino acids that are forming this bond?

A. cytosineB. glycineC. aspartic acidD. cysteineE. none of the above

(D) Disulfide bonds can only be formed between to cysteine residues because it is the only amino acid that contains a sulfur atom.

27. What is the location of the C-terminus of the protein in the figure?A. nucleusB. golgiC. embedded within the membraneD. extracellularE. none of the above

(E) The C-terminus is located in the cytoplasm (intracellular).

28. Refer to the figure. Which level of structure is being maintained by the disulfide bond?

A. tertiaryB. secondaryC. primaryD. quaternaryE. both A and D

(A) Disulfide bonds are important for maintaining tertiary structure.

29. Which of the following would be an example of a cofactor?A. an enzyme active site that contains an α-helixB. the non-protein heme group in a hemoglobin moleculeC. a β-pleated sheet hidden on the inside of a protein’s tertiary structureD. the disulfide bridge that forms between cysteine residuesE. all of the above

(B) Cofactors are not part of an enzyme, but are non-protein molecules that are required for the enzyme to function.

30. According to the central dogma of molecular biology: A. DNA is translated into RNA; RNA is transcribed into protein.B. RNA is transcribed into DNA; DNA is translated into protein.C. DNA is transcribed into RNA; RNA is translated into protein.D. RNA is translated into DNA; RNA is transcribed into protein.E. None Of The Above.

(C) Definition.

31. In the above cartoon of a nucleotide, where is the sugar? What does “A” represent? What is attached at “E” in RNA?

A. B; Nitrogenous base; -OHB. C; Phosphate group; -OHC. B; Nitrogenous base; -HD. C; Phosphate group; -HE. None Of The Above.

(A) Definition

32. When two nucleotides polymerize, the hydroxyl group attached to the ___ carbon attacks the phosphate group attached to the ___ carbon in a ____ reaction.

A. 2’; 3’; condensationB. 3’; 5’; hydrolysis C. 3’; 5’; condensationD. 2’; 5’; hydrolysisE. None Of The Above.

(C) 3’ -OH attacks 5’ P in a condensation reaction

33. For the following mRNA sequenceAUGGGGGUUAAG

What percent of the template DNA strand contains purine bases? What percent of the template DNA contains uracil?

A. 75%; 25%B. 50%; 50%;C. 25%; 25%D. 25%; 0%;E. None Of The Above.

(D) AUGGGGGUUAAG’s DNA template is TACCCCCAATTC. Purines are A and G; 3 As, 0 Gs; 3/12 = 25%. There is no uracil in DNA.

34. In terms of structure and function how do DNA, RNA, and proteins compare?A. RNA is intermediate between the complexity of DNA and the simplicity of proteins.B. Proteins are intermediate between the complexity of RNA and the simplicity of DNA.C. DNA is intermediate between the complexity of proteins and the simplicity of RNA.D. RNA is intermediate between the complexity of proteins and the simplicity of DNA.E. None Of The Above.

(D) DNA can only really form secondary structures (double helix). RNA can adopt more complex structures due to stacking of bases and helices. Proteins can adopt a wide variety of tertiary structures.

35. What is/are the variable structure(s) of a nucleotide?A. the phosphate groupB. the baseC. the sugar and the baseD. the sugarE. None Of The Above.

(C) Nucleotides can vary at the 2’ carbon (-OH for RNA; -H for DNA); there are 5 different nitrogenous bases (ATCG for DNA; AUCG for RNA)

36. Gel electrophoresis is a technique to separate nucleotides by size using an electrical current. DNA moves towards the ____ because it has a ____ charge.

A. positive electrode; positiveB. positive electrode; negativeC. negative electrode; positiveD. negative electrode; negativeE. None Of The Above.

(B) DNA is negatively charged due to the phosphate groups in its backbone. Thus DNA moves toward the positive electrode in the gel electrophoresis apparatus.

37. Information is propagated from RNA to protein using the ______ and is catalyzed by _______.A. genetic code; RNA polymeraseB. DNA polymerase; ribosomesC. genetic code; ribosomesD. RNA polymerase; genetic codeE. None Of The Above.

(C). The genetic code dictates the amino acid coded by a particular codon through the process of translation. Translation is catalyzed by the ribosome.

38. _____ catalyzes the chemistry of translation; _____ catalyzes the chemistry of transcription. This provides evidence that ____ may be the first molecule of life.

A. Protein enzymes; ribozymes; RNAB. Ribozymes; protein enzymes; RNAC. Protein enzymes; protein enzymes; DNAD. Ribozymes; protein enzymes; proteinE. None Of The Above.

(B) The ribosome’s catalytic core is made up of an RNA enzyme (ribozyme) while polymerases are made up of proteins. Because translation, the process of making protein, is entirely dependent on RNA, this provides evidence that RNA existed before proteins. DNA, while a nucleotide, cannot catalyze chemical reactions.

39. In transcription, DNA is read in the ___ to ___ direction; in translation, RNA is read in the ___ to ___ direction.

A. 5’ to 3’; 5’ to 3’B. 3’ to 5’; 3’ to 5’C. 5’ to 3’; 3’ to 5’D. 3’ to 5’; 5’ to 3’E. None Of The Above.

(D). DNA and RNA are synthesized in the 5’ to 3’ direction so DNA must be read in the 3’ to 5’ direction. Codons are read 5’ to 3’ during translation.

40. The redundancy of the genetic code is a consequence of _____.A. having more codons than amino acidsB. having fewer codons than there are amino acidsC. having three-letter-long genetic words (codons)D. having an equal number of codons and amino acidsE. None Of The Above.

(A) There are 64 codons and 20 amino acids. Three codons code for stop.

41. _____ tRNAs are essential for translation by base pairing its ____ to mRNA using ____ bonds in order to determine the appropriate amino acid which is attached to the tRNA by a ____ bond.

A. Charged; anticodon; hydrogen; covalentB. Charged; codon; covalent; hydrogenC. Aminoacyl; anticodon; covalent; covalentD. Aminoacyl; codon; hydrogen; hydrogenE. None Of The Above.

(A) Charged tRNA and aminoacyl tRNA are synonymous. The tRNA’s anticodon pairs to mRNA using hydrogen bonds. The amino acid is covalently attached to an aminoacyl tRNA.

42. A _____ mutation results in an early stop codon while a ____ mutation does not change the animo acid specified by a codon.

A. missense; frameshiftB. frameshift; nonsenseC. nonsense; missenseD. silent; misssenseE. None Of The Above.

(E) Definition. frameshift; silent

43 . The proteome is all the proteins produced by an organism. The genome is the totality of all genes of an organism. If the proteome is much larger than the genome, which of the following statements would be accurate?

A. This finding lends support to the one-gene, one-enzyme hypothesis.B. Noncoding DNA is important in determining the proteome.C. The number of monomeric subunits found in proteins is fewer than the number of

monomeric subunits found in genes.D. At least in some cases, a single gene must code for more than one protein.E. None Of The Above.

(D) Most, but not all, genes encode proteins. If there are more proteins than genes, some protein coding genes must encode more than one protein.

44. Which of the following molecules must move across the membrane after being synthesized from a DNA sequence before being translated by a ribosome in eukaryotic cells?

A. rRNAB. tRNAC. mRNAD. DNAE. None Of The Above.

(C) Transcription and translation are not couple in eukaryotic cells.

45. Which of the following classes of macromolecules always contains a carbohydrate portion?

A. nucleic acidsB. waterC. proteinsD. all of the aboveE. none of the above

(A) Nucleic acids contain a pentose (ribose).

46. Which of the following can vary among monosaccharides?A. the presence of a carbonyl groupB. the presence of hydroxyl groupsC. the number of carbon atomsD. both A and BE. both B and C

(C) The number of carbon atoms varies but all monosaccharides contain a carbonyl and hydroxyl groups.

47. How do the α and β forms of glucose differ?A. Their linear structures differ in the location of a hydroxyl group.B. The α form can be involved in 1,4 and 1,6 glycosidic linkages; the β form can

participate only in 1,4 linkages.C. The oxygen atom inside the ring is located in a different position.D. Their ring structures differ in the location of a hydroxyl group.E. all of the above

(D) In an α glucose molecule, the hydroxyl group is below the plane of the ring. In a β glucose molecule, the hydroxyl group is above the plane of the ring.

48. Enzymes that readily break starch apart cannot hydrolyze the glycosidic linkages found in cellulose. Why is this logical?

A. Starch is held together by peptide bonds, not glycosidic linkages.B. Cellulose molecules are highly branched, and enzymes are too bulky to fit.C. The geometry of the bonds is different, and the shapes of the enzyme active sites are

highly specific.D. Starch is held together by hydrogen bonding, not covalent bonding.E. none of the above

(C) Enzymes for glucose catalysis are highly specific.

49. A carbohydrate has the formula (CH2O)8 has a single carbonyl group (-C=O) in its linear form. Based on the number of oxygen atoms in glucose, how many hydroxyl groups (-OH) would you expect glucose to have?

A. 3B. 1C. 5D. 8E. none of the above

(E) There are eight oxygen atoms in the carbohydrate. One has a double bond to carbon (the carbonyl), leaving seven that are attached to H.

50. Different types of glycosidic linkage cause glucose polymers to form a helix (e.g., in glycogen) versus a straight chain (e.g., in cellulose). Which statement best explains why?

A. Glycosidic linkages resulting from condensation reactions produce helical polymers; glycosidic linkages resulting from hydrolysis reactions produce straight chains.

B. The geometry of the β-1,4-glycosidic linkage results in a flipped orientation of adjacent glucose monomers; the α-1,4-glycosidic linkage does not.

C. The geometry of the α-1,4-glycosidic linkage results in a flipped orientation of adjacent glucose monomers; the β-1,4-glycosidic linkage does not.

D. The geometry of the α-1,6-glycosidic linkage produces helical polymers; the β-1,4-glycosidic linkage does not.

E. none of the above(B) The monomers of cellulose are flipped in orientation, removing the possibility of hydrogen bonding that would be necessary to form the helix.

51. Peptidoglycan forms sheets that stiffen the cell walls of bacteria. How is the formation of sheets possible?

A. The glycosidic linkages between monosaccharides in peptidoglycan are extraordinarily strong.B. The polysaccharides in peptidoglycan are highly branched and form a network.C. Individual strands are joined by peptide bonds–a type of covalent bond.D. The polysaccharides in peptidoglycan form helical structures, as in cellulose.E. both A and C

(C) Adjacent strands form peptide bonds between the amino acids attached to the monosaccharide.

52. Which of the following molecules would you expect to have the most free energy per gram?

A. one with hydrogen and oxygen atoms onlyB. one with carbon and hydrogen atoms onlyC. one with a variety of atoms that are found in cellsD. one with carbon, hydrogen, and oxygen atoms onlyE. they would all have an equal amount of free energy

(B) Carbon–Hydrogen bonds are higher energy because they are electronegatively similar atoms and share their electrons nearly equally (no polarity).

53. In what way do carbohydrates contain and/or display information for cells?A. Carbohydrates are attached to proteins known as glycoproteins.B. Carbohydrates display information in order to bond to substrates and catalyze

reactions.C. Carbohydrates contain and display information at the cell surface.D. both A and BE. both A and C

(E) Glycoproteins have oligosaccharides and are imbedded in the cell membrane.

54. What do phospholipids and triglycerides have in common?A. They both contain serine or some other organic compound.B. They both have a phosphate.C. They both have a glycerol backbone.D. both A and BE. both A and C

(C) Definition.

55. Which statement most accurately describes how the structures of fats, steroids, and phospholipids compare?

A. Fats and phospholipids contain isoprene, steroids do not.B. Fats and phospholipids both contain three ester bonds, steroids do not.C. Fats and steroids contain ring structures, phospholipids do not.D. Fats and phospholipids contain a phosphate group, steroids do not.E. none of the above

(E) Defintion.

56. You make a phospholipid bilayer with short, saturated hydrocarbon tails. You measure the permeability of this membrane to H2O. You then double the length of the hydrocarbon tails, and remeasure membrane permeability. You then double the length of the hydrocarbon tails again, and make a third measurement of membrane permeability. You graph membrane permeability as a function of hydrocarbon tail length. Which of the graphs below best represents the data you expect?

A B

C D

(A) The longer the tails, which are hydrophobic, the more difficult for a polar water molecule to pass through the membrane.

57. Which of the following is true of osmosis?A. Water moves from areas of low water concentration to areas of high water

concentration.B. It is an energy-demanding or "active" process.C. Water moves from areas of low solute concentration to areas of high solute

concentration.D. It only takes place in red blood cells.E. none of the above

(C) Definition.

58. In cells, membrane proteins are responsible for the passage of substances that can't cross the membrane on their own. Channels and transporters are involved in facilitated diffusion. Pumps are involved in active transport. In terms of their properties or functions, which statement most accurately describes how these three types of membrane proteins compare?

A. Channels and transporters are integral membrane proteins; pumps are peripheral membrane proteins.

B. Pumps are selective; channels and transporters are not selective.C. Among the three types, only pumps can concentrate substances on one side of the

membrane.D. Among the three types, only pumps are thought to undergo a shape change as part

of their function.E. all of the above

(C) Only a pump can move molecules against their electrochemical gradient.

59. Which statement most accurately describes the relationship between the permeability and fluidity properties of phospholipid bilayers and their structure?

A. Bilayers are more permeable as well as more fluid when they consist of shorter, unsaturated hydrocarbon tails.

B. Bilayers are more permeable but less fluid when they consist of shorter, unsaturated hydrocarbon tails.

C. Bilayers are more permeable as well as more fluid when they consist of longer, unsaturated hydrocarbon tails.

D. Bilayers are more permeable as well as more fluid when they consist of longer, saturated hydrocarbon tails.

E. none of the above are accurately describe the relationship between permeability and fluidity properties.

(A) Permeability is affected by hydrocarbon tail length and saturation.

60. How is carbohydrate use similar or different between plants and animals? Select the true statement below.

A. Carbohydrates catalyze reactions in both animals and plants.B. In animals, carbohydrates have mainly a structural role, while in plants,

carbohydrates are mainly used to store energy.C. Carbohydrates play a structural role in some types of animals and in all plants.D. both A and BE. both A and C

(C) In insects and crustaceans, chitin is important for forming the exoskeleton, and is structural. In plants carbohydrates are used to build the cell wall that defines a plant cell.