Multiple choice. Choose the best answer (2 points each) 1. ___B_The bonds that are broken when water vaporizes are
A) ionic bonds.
B) hydrogen bonds between water molecules.
C) covalent bonds between H and O atoms within water molecules.
D) polar covalent bonds.
E) nonpolar covalent bonds
2.___B___The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?
A) a covalent bond B) a hydrogen bond C) an ionic bond D) a hydrophilic bond
E) a hydrophobic bond
3.__D___Which of the following is (are) not a result of the polar nature of water and the subsequent hydrogen bonding of water molecules to one another? A) the ability of a water strider to walk on the surface of water B) movement of water to the top of a tree C) sweating as a method of evaporative cooling D) the ability of buffers to resist pH change E) A and D
4. ____A_Which of the following solutions has the greatest concentration of hydrogen ions [H+]?
A) gastric juice at pH 2 B) vinegar at pH 3 C) tomato juice at pH 4 D) black coffee at pH 5
E) household bleach at pH 12
5. _A____ Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O ---> H2CO3. Carbonic acid (H2CO3) is a weak acid. Respiring cells release CO2. What prediction can we make about the pH of blood as that blood first comes in contact with respiring cells (before the buffering system kicks in)?
A) Blood pH will decrease slightly. B) Blood pH will increase slightly. C) Blood pH will remain unchanged. D) Blood pH will first increase, then decrease as CO2 combines with hemoglobin.
6. __C___Which of the following statements is (are) false? A) a buffer consists of a weak acid and a salt of that weak acid B) the major buffering system in the blood is the bicarbonate buffering system C) buffers always maintain a ph of 7.0 D) A and B e) none of the above statements are false (all are true)
7. __A___ Which action could produce a carbonyl group?
A) the replacement of the OH of a carboxyl group with hydrogen
B) the addition of a sulfhydryl to a hydroxyl
C) the addition of a hydroxyl to a phosphate
D) the replacement of the nitrogen of an amine with oxygen
E) the addition of a sulfhydryl to a carboxyl
8.__C OR D____Life is carbon based. All of the following properties of carbon contribute to this except: A) carbon has 4 electrons in its outermost shell B) carbon can form hydrocarbon chains when it reacts with hydrogen C) hydrogen has a valence of 4 D) carbon forms ionic bonds with hydrogen E) all of the above are properties of carbon that make it the element on which life is based.
Refer to the following diagrams of functional groups to answer questions # 9 and #10
9.__C___ Which is an acidic functional group that can dissociate and release H+ into a solution?
10. ___E__ Which functional group help to determine whether your hair is straight or curly because it forms covalent cross-links within or between protein molecules (keratin) that make up your hair?
11. __A____Hydrophobic substances such as vegetable oil are
A) nonpolar substances that repel water molecules. B) nonpolar substances that have an attraction for water molecules. C) polar substances that repel water molecules. D) polar substances that have an affinity for water. E) charged molecules that hydrogen-bond with water molecules
12.___C__ The molecular formula for glucose is C6H12O6. What would be the molecular formula for a polymer made by linking ten glucose molecules together by dehydration reactions?
A) C60H120O60
B) C6H12O6
C) C60H102O51
D) C60H100O50
E) C60H111O51
13.___E__ Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?
A) Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers.
B) Macromolecular synthesis occurs through the removal of water and digestion occurs through the addition of water.
C) Dehydration reactions can occur only after hydrolysis.
D) Hydrolysis creates monomers, and dehydration reactions break down polymers.
E) A and B are correct.
14.___D__ Which of the following is true of cellulose?
A) It is a polymer composed of sucrose monomers.
B) It is a storage polysaccharide for energy in plant cells.
C) It is a storage polysaccharide for energy in animal cells.
D) It is a major structural component of plant cell walls.
E) It is a major structural component of animal cell plasma membranes.
15.__B___Which of the following associations between monomers and the covalent bonds that join them is incorrect? A) monosaccharides/glycosidic bond B) nucleotides/peptide bonds
C) glycerol and fatty acids/ester bonds D) amino acids/peptide bonds E) B and C
16.__C___
The molecule illustrated above is: A) an amino acid B) a nucleotide C) saturated fatty acid
D) a fat E) RNA
17.___A__ Which bonds are created during the formation of the primary structure of a protein?
A) peptide bonds
B) hydrogen bonds
C) disulfide bonds
D) phosphodiester bonds
E) A, B, and C
18.__E___ The tertiary structure of a protein:
A) is bonding together of several polypeptide chains by weak bonds.
B) is the order in which amino acids are joined in a polypeptide chain.
C) is the unique three-dimensional shape of the fully folded polypeptide.
D) determines the function of the protein
E) C and D
19.__E___ The function of each protein is a consequence of its specific shape. What is the term used for a change in a protein's three-dimensional shape or conformation due to disruption of hydrogen bonds, disulfide bridges, or ionic bonds?
A) hydrolysis
B) stabilization
C) destabilization
D) renaturation
E) denaturation
20.__D___According to the Central Dogma: A) DNA is translated into protein
B) monosaccharides are joined by glycosidic bonds C) buffers resist pH changes D) RNA is translated into protein E) all organisms are made of one or more cells
21.__E___ Which structure-function pair is mismatched?
A) nucleolus; production of ribosomal subunits
B) lysosome; intracellular digestion
C) ribosome; protein synthesis
D) Golgi; protein trafficking
E) microtubule; muscle contraction
22._D____ Which structure is common to plant and animal cells?
A) chloroplast
B) wall made of cellulose
C) central vacuole
D) mitochondrion
E) all of the above
23.__C___Which of the following is not a limitation of the transmission electron microscope (TEM) for use to study cells? A) The TEM requires that specimens be viewed in a vacuum
B) Tissue has to be fixed in preservatives and sliced very thinly to be viewed C) The TEM gives you images with very high degrees of resolution D) all of the above are limitations of using the TEM to study cells
24.___D__ Which of the following is a major cause of the size limits for certain types of cells?
A) the evolution of larger cells after the evolution of smaller cells
B) the difference in plasma membranes between prokaryotes and eukaryotes
C) the evolution of eukaryotes after the evolution of prokaryotes
D) the need for a surface area of sufficient area to allow the cell's function
E) the observation that longer cells usually have greater cell volume
25.__C___ Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
A) lipids
B) starches
C) proteins
D) steroids
26.___C__ Tay-Sachs disease is a human genetic abnormality that results in cells accumulating and becoming clogged with very large and complex lipids. Which cellular organelle must be involved in this condition?
A) the endoplasmic reticulum
B) the Golgi apparatus
C) the lysosome
D) mitochondria
E) membrane-bound ribosomes
27.___B__ Which of the following is a compartment that often takes up much of the volume of a plant cell?
A) lysosome
B) vacuole
C) mitochondrion
D) Golgi apparatus
E) peroxisome
28.__D___The terms inner membrane which is highly folded, intermembrane space, matrix, and two compartments separated by a membrane best describe the organization of this cell structure: A) the endoplasmic reticulum
B) the Golgi apparatus
C) the lysosome
D) mitochondria
E) the cytosleletal system
29.__A___ Which of the following are capable of converting light energy to chemical energy?
A) chloroplasts
B) mitochondria
C) vacuoles
D) ER
E) Golgi bodies
30.___C__ If an individual has abnormal microtubules, due to a hereditary condition, in which organs or tissues would you most expect dysfunction? A) heart B) skin C) sperm D) blood
E) GI tract (intestines)
31.___D__ Which of the following statements about the cytoskeleton is false?
A) The dynamic aspect of cytoskeletal function is made possible by the assembly and disassembly of cytoskeletal elements including microtubules
B) Movement of cilia and flagella is the result of motor proteins (dyneine arms) causing microtubules to move (slide) relative to one another.
C) Chemicals that block the assembly of the cytoskeleton would have a little effect on the cell's ability to produce ATP
D) Chemicals that block the assembly of the cytoskeleton would have a little effect on the cell's ability to divide
32.__E___ Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through
A) plasmodesmata.
B) intermediate filaments.
C) tight junctions.
D) desmosomes.
E) gap junctions.
33. ( 4 points each) Agree or disagree with the following statements. If you agree, explain why. If you disagree, explain why. Fully justify your position.
A. The definition of pH provides an explanation for why a solution of pure water has a pH value of 7.0
Agree- ph= -log [H+]
At equilibrium, the [H+] = 1 X 10 -7
pH=-log of 1 X 10 -7 = 7.0
B. The phosphorylation and dephosphorylation of protein molecules plays a crucial role in the operation of cilia and flagella.
Agree-Phosphorylation (adding a phosphate to a protein) and dephosphorylation (removing a phosphate from a protein) both cause conformational changes in protein molecules (allowing them to change back and forth between two conformations). Cilia and flagellar motion both are the result of microtubules sliding past one another bending the flagella/cilia side to side. This sliding is due to the alternate phosphorylation (triggered by ATP hydrolysis) and dephosphorylation of the dyneine arms which interact with the microtubules causing them to bend.
C. If two organic molecules contain the exact same kinds of monomer units (i.e.., amino acids), then those two organic molecules must have the same biological function.
Disagree-If 2 polypeptide chains are made of the exact same kind and number of amino acids but they are in a different order, they will have different primary structures. Since primary structure determines tertiary structure, and tertiary structure determines function, these two polypeptide chains will have different functions.
34. (8 points) Using hemoglobin as an example, describe why it is necessary for the human body to have mechanisms that maintain the homeostatic pH levels of blood at a certain value. Describe how the blood’s bicarbonate buffering system helps the blood to maintain its normal pH when acid is added to the blood.
Hemoglobin is a protein whose function (oxygen transportation) depends on its structure. If the pH of the blood changes, the charges on the R groups of the amino acids may change and the protein will denature, losing its function. The bicarbonate buffering system consists of carbonic acid (a weak acid) and bicarbonate ( usually the salt form of that weak acid). This equation describes how the buffering system works
CO2 + H2O à H2CO3 à HCO3- + H +
ß ß
35. (8 points) What is the major function of nucleic acids in cells? What is the relationship between proteins and a cell‘s phenotype (characteristics)? What is a gene? Describe the relationship between a gene and a protein.
Nucleic acids (DNA and RNA) make up the cell’s genetic information system. A gene is a segment of DNA that encodes the information for a polypeptide chain. Polypeptide chains, especially enzymes, determine the phenotype of a cell. Therefore, genes determine a cell’s characteristics. Genes are transcribed into RNA. RNA is the translated into proteins on the cell’s ribosomes.
36. (8 points)What roles do white blood cells play in your body? Describe 3 cellular structures (organelles or systems) that are involved in white blood cell function and explain how the organelle/system you are describing contribute to these white blood cell functions.
White blood cells play a protective role in your body by destroying invading bacteria and virus as well as cancer cells. They do this by 1) phagocytosis (engulfing) and 2) producing antibodies.
Any three of the following cellular structures would be acceptable.
The following cell organelles play a role in phagocytosis:
a) cytoskeletal system which allows the cell to move by crawling (amoeboid movement)
b) mitochondria which produce ATP necessary for amoeboid movement
c) Vacuoles which contain the engulfed material and are produced by endocytosis
d) lysosomes, which fuse with the engulfed vacuoles and release digestive enzymes that break down the engulfed material
The following cell organelles play a role in antibody production:
a) the nucleus contains the antibody genes
b) RER produces the antibody and may slightly modify it
c) vesicles transport the antibody to the Golgi
d) the Golgi modifies the antibody by glycosylating it.
e) the mitochondria makes ATP necessary for synthesizing the antibody (translation).
Bonus (not optional points)-Each question is worth 1 point. The total bonus points are determined by subtracting the number of questions answered incorrectly (X 0.5) from the number of correct answers (an unanswered question is not counted as being incorrect). Therefore, there is a penalty for guessing when your bonus points are determined. However, the lowest grade you can get on the bonus section is 0 (so it can’t hurt your final score) Any bonus you receive on this exercise will be added to your final grade..
Synaptic transmission of a nerve impulse between 2 neurons begins when Na+ moves into the cell, causing depolarization of the axon-terminal membrane. Membrane depolarization in turn causes the voltage-regulated Ca2+ channel proteins to change from the closed to the open
conformation. The opened channels allow Ca2+ to enter the axon terminal passively, following the existing Ca2+ gradient (Figure 1). Membrane hyperpolarization caused by the outward flux of K+ ions, closes the Ca2+ channel.
The neurotransmitter is synthesized and packaged into vesicles by the neuron's endoplasmic reticulum and Golgi apparatus. Vesicles containing neurotransmitter molecules are located near the cytoplasmic side of the presynaptic membrane of the axon. The protein synapsin is thought to hold the vesicles near the presynaptic membrane by attaching them to microtubules and microfilaments (Figure 1). Elevated Ca2+ levels in the cytoplasm cause release of the vesicles from the cytoskeleton. The vesicles then undergo exocytosis; that is, they fuse with the presynaptic membrane, burst open, and release their contents into the synaptic cleft.
__D___1.All of the following are required for neurotransmitter release EXCEPT:
a. microtubules and microfilaments; b. synapsin; c. elevated Ca2+ levels; d. closed
Ca2+ channels.
__C___2.A neuron that is exposed to a Ca2+ channel blocker will be: a. unable to hyperpolarize; b. unable to depolarize; c. able to hyperpolarize, but no Ca2+ will enter the presynaptic membrane; d. able to depolarize, and Ca2+ will enter the presynaptic membrane.
__A___3.Synaptic transmission of a nerve impulse is important because it allows the impulse to be transmitted: a. in 1 direction only; b. in many directions at once; c. more rapidly than by electrical transmission; d. whether or not electrical transmission is occurring.
__D__4. Which of the following experimental observations would provide the best evidence that synapsin is necessary for exocytosis? a. synapsin is found only in neurons; b. synapsin is found in other cell types known to export material by exocytosis; c. the rate of exocytosis is directly correlated with the amount of synapsin present per cell; d. a mutant cell line of neurons lacks only synapsin and is incapable of exocytosis.
_B___5. The exocytosis of a neurotransmitter vesicle involves all of the following processes EXCEPT: a. initial packaging of the neurotransmitter into vesicles at the Golgi apparatus; b. fusion of the microtubules with the presynaptic membrane; c. opening of the Ca2+ channel; d. attachment of the neurotransmitter vesicles to the cytoskeleton.
___A_6. What is the most likely function of synapsin in the process of neurotransmitter release?
a. to prevent premature exocytosis by binding secretion vesicles to cytoplasmic structures; b. to make the secretion process independent of diffusion; c. to decrease the dependency of the synaptic process on Ca2+; d. to initiate the synthesis of vesicles containing neurotransmitter.
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