BIL 150 EXAM 1 TEST QUESTIONS

You have just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals. What is the significance of this finding? A) Cysteine residues are involved in disulfide bridges that help form tertiary structure. B) Cysteine causes bends, or angles, to occur in the tertiary structure of proteins. C) It will be important to include cysteine in the diet of the mice. D) Cysteine residues are required for the formation of α helices and β pleated sheets.

A) Cysteine residues are involved in disulfide bridges that help form tertiary structure.

Recall that in the experiment, caterpillars born in the spring looked like flowers, and caterpillars born in the summer looked like twigs. What is the most likely selective advantage for this difference in body shape? A) Looking like their food source lets the caterpillars blend into their surroundings, reducing predation. B) Looking like their food sources allows the caterpillars to move through their environment more efficiently. C) Looking like their food source will increase the caterpillars' feeding efficiency; this would increase their growth rate and survival rate. D) Development into the adult moth form is faster for caterpillars shaped like twigs than like flowers.

A) Looking like their food source lets the caterpillars blend into their surroundings, reducing predation.

Biological systems use free energy based on empirical data that all organisms require a constant energy input. The first law of thermodynamics states that energy can be neither created nor destroyed. For living organisms, which of the following statements is an important consequence of this first law? A) The organism must ultimately obtain all the necessary energy for life from its environment. B) Organisms are unable to transform energy from the different states in which it can exist. C) The entropy of an organism decreases with time as the organism grows in complexity. D) The energy content of an organism is constant except for when its cells are dividing.

A) The organism must ultimately obtain all the necessary energy for life from its environment.

The table represents the results of an experiment where the effects of pH buffers on an enzyme found in saliva (amylase) were studied. A spectrophotometer set at 500 nm was used to measure absorbance at the various pH levels every 20 seconds for 2 minutes. The higher absorbance values would indicate greater enzyme activity. All experiments were conducted at the same temperature. Which statement correctly identifies the result that the optimum pH for amylase function is 7? A) The pH with the highest absorbance values would indicate the optimum pH for amylase since this pH does not affect the structure or function of the protein. B) At pH 9, the enzyme is denatured and will lose its function, but not its structure. C) At pH 4, the structure of the enzyme will be altered, and the enzyme would not be able to catalyze the reaction. D) The pH with the lowest absorbance values would indicate the optimum pH for amylase since this pH does not affect the structure or function of the protein.

A) The pH with the highest absorbance values would indicate the optimum pH for amylase since this pH does not affect the structure or function of the protein.

How might a change of one amino acid at a site, distant from the active site of an enzyme, alter the substrate specificity of an enzyme? A) by changing the three-dimensional conformation of the enzyme B) by changing the binding site for a noncompetitive inhibitor C) by changing the stability of the enzyme D) by changing the optimum pH for the enzyme

A) by changing the three-dimensional conformation of the enzyme

The evolution of eukaryotic cells most likely involved A) endosymbiosis of an oxygen-using bacterium in a larger bacterial host cell-the endosymbiont evolved into mitochondria B) evolution of an endomembrane system and subsequent evolution of mitochondria from a portion of the smooth endoplasmic reticulum C) endosymbiosis of an oxygen-using bacterium in a larger bacterial host cell-the endosymbiont evolved into chloroplasts D) endosymbiosis of a photosynthetic archaeal cell in a larger bacterial host cell to escape toxic oxygen—the anaerobic archaea evolved into chloroplasts

A) endosymbiosis of an oxygen-using bacterium in a larger bacterial host cell-the endosymbiont evolved into mitochondria

Which of the following membrane activities requires energy from ATP hydrolysis? A) movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid B) movement of carbon dioxide out of a paramecium C) facilitated diffusion of chloride ions across the membrane through a chloride channel D) movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell

A) movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid

You disrupt all hydrogen bonds in a protein. What level of structure will be preserved? A) primary structure B) secondary structure C) tertiary structure D) quaternary structure

A) primary structure

The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and, therefore, abundant in liver cells? A) smooth endoplasmic reticulum B) rough endoplasmic reticulum C) Golgi apparatus D) nuclear envelope

A) smooth endoplasmic reticulum

A salamander relies on hydrogen bonding to stick to various surfaces. Therefore, a salamander would have the greatest difficulty clinging to a... A) surface of hydrocarbons B) surface of mostly carbon-nitrogen bonds C) surface of mostly carbon-oxygen bonds D) slightly damp surface

A) surface of hydrocarbons

Which of the following statements is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal? A) Sodium and glucose compete for the same binding site in the cotransporter. B) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose. C) Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell. D) Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient.

B) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.

A researcher discovered a species of moth that lays its eggs on oak trees. Eggs are laid at two distinct times of the year: early in spring when the oak trees are flowering and in midsummer when flowering is past. Caterpillars from eggs that hatch in spring feed on oak flowers and look like oak flowers, but caterpillars that hatch in summer feed on oak leaves and look like oak twigs. How does the same population of moths produce such different-looking caterpillars on the same trees? To answer this question, the biologist caught many female moths from the same population and collected their eggs. He put at least one egg from each female into eight identical cups. The eggs hatched, and at least two larvae from each female were maintained in one of the four temperature and light conditions listed below. A) The longer day lengths of summer trigger the development of twig-like caterpillars. B) Differences in air pressure, due to differences in elevation, trigger the development of different types of caterpillars. C) Differences in diet trigger the development of different types of caterpillars. D) The cooler temperatures of spring trigger the development of flowerlike caterpillars.

B) Differences in air pressure, due to differences in elevation, trigger the development of different types of caterpillars.

In every case, caterpillars that feed on oak flowers look like oak flowers. In every case, caterpillars that were raised on oak leaves looked like twigs. These results support which of the following hypotheses? A) The longer day lengths of summer trigger the development of twig-like caterpillars. B) Differences in diet trigger the development of different types of caterpillars. C) Differences in air pressure, due to elevation, trigger the development of different types of caterpillars.D) The differences are genetic. A female will either produce all flowerlike caterpillars or all twig-like caterpillars.

B) Differences in diet trigger the development of different types of caterpillars.

A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose? A) Permeability will decrease initially then increase as the bilayer fills with glucose. B) Permeability to glucose will increase. C) Permeability to glucose will stay the same. D) Permeability to glucose will decrease.

B) Permeability to glucose will increase.

Why are hydrocarbons insoluble in water? A) They exhibit considerable molecular complexity and diversity. B) The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages. C) The majority of their bonds are polar covalent carbon-to-hydrogen linkages. D) They are less dense than water.

B) The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.

Saturated fats... A) have multiple double bonds in the carbon chains of their fatty acids B) contain more hydrogen than unsaturated fats that consist of the same number of carbon atoms C) are generally liquid at room temperature D) are more common in plants than in animals

B) contain more hydrogen than unsaturated fats that consist of the same number of carbon atoms

Suppose a young boy is always tired and fatigued, suffering from a metabolic disease. Which of the following organelles is most likely malfunctioning in this disease? A) smooth endoplasmic reticulum B) mitochondria C) lysosomes D) Golgi apparatus

B) mitochondria

A research team is working on the design of a new drug for the treatment of lung cancer. To be most effective, this drug must specifically enter the cytoplasm of lung cells while not entering the cells of other tissues. Which of the following characteristics would likely enhance the specificity of this drug? A) phospholipid composition of lung cell plasma membranes B) similarity of the drug molecule to other molecules normally transported lung cells C) specificity of the drug molecule for binding to the extracellular matrix of lung cells D) the relative hydrophobicity of the drug molecule

B) similarity of the drug molecule to other molecules normally transported lung cells

One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that, when placed in an aqueous solution, dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+). H2CO3 ↔ HCO3 + H+ If the pH of blood drops, one would expect A) a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3- B) the HCO3- to act as a base and remove excess H+ by the formation of H2CO3 C) the concentration of bicarbonate ions (HCO3-) to increase D) the HCO3- to act as an acid and remove excess H+ by the formation of H2CO3

B) the HCO3- to act as a base and remove excess H+ by the formation of H2CO3

When an ionic compound such as sodium chloride (NaCl) is placed in water, the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of solute particles (molecules or ions)? A) 1 liter of 1.0 M glucose B) 1 liter of 0.5 M NaCl C) 1 liter of 1.0 M NaCl D) 1 liter of 1.0 M NaCl and 1 liter of 1.0 M glucose will contain equal numbers of solute particles.

C) 1 liter of 1.0 M NaCl

Which of the following molecules act as building blocks (monomers) of polypeptides? A) 11,12, and 13 B) 1,4, and 6 C) 2,7, and 8 D) 7,8, and 13

C) 2,7, and 8

If one strand of a DNA molecule has the sequence of bases 5′-ATTGCA-3′, the mRNA synthesized following the template will be... A) 5′-TGCAAT-3′ B) 5′-TAACGT-3′ C) 3′-UAACGU-5′ D) 5′-UGCAAU-3′

C) 3′-UAACGU-5′

Which of the following statements describes a central role that ATP plays in cellular metabolism? A) Its terminal phosphate bond is stronger than most covalent bonds in other biological macromolecules. B) Hydrolysis of the terminal phosphate group stores free energy that is used for cellular work. C) ATP provides energy coupling between exergonic and endergonic reactions. D) Hydrolysis of ATP provides an input of free energy for exergonic reactions.

C) ATP provides energy coupling between exergonic and endergonic reactions.

Cotton-topped tamarins are small primates with tufts of long white hair on their heads. While studying these creatures, you notice that males with longer hair get more opportunities to mate and father more offspring. To test the hypothesis that having longer hair is adaptive in these males you should.... a) test whether males with shaved heads are still able to mate b) test whether other traits in these males are also adaptive c) determine if hair length is heritable d) look for evidence of hair in ancestors of tamarins

C) Determine if hair length is heritable

A mutation that disrupts the ability of an animal cell to add polysaccharide modifications to proteins would most likely cause defects in which of the following organelles or structures? A) mitochondria and Golgi apparatus B) nuclear matrix and extracellular matrix C) Golgi apparatus and extracellular matrix D) nuclear pores and secretory vesicles

C) Golgi apparatus and extracellular matrix

In the figure, why does the reaction rate plateau at higher reactant concentrations? GRAPH Rate of an enzyme-catalyzed reaction as a function of varying reactant concentration, with the concentration of enzyme constant. A) The reaction nears equilibrium at high reactant concentrations. B) The rate of the reverse reaction increases at high reactant concentrations. C) Most enzyme molecules are occupied by substrate at high reactant concentrations. D) Feedback inhibition by product occurs at high reactant concentrations.

C) Most enzyme molecules are occupied by substrate at high reactant concentrations.

Why is a scientific topic best discussed by people of varying points of view, from different subdisciplines, and representing diverse cultures? A) People need to exchange their ideas with other disciplines and cultures because everyone has a right to an opinion in science. B) Scientists can coordinate with others to conduct experiments in similar ways. C) Robust and critical discussion between diverse groups improves scientific thinking. D) This is a way of ensuring that everyone gets the same results.

C) Robust and critical discussion between diverse groups improves scientific thinking.

Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics? A) Living organisms do not obey the second law of thermodynamics, which states that the entropy of an organism increases with each energy transformation. B) Living organisms are able to transform chemical energy into entropy. C) The decrease in entropy is associated with growth of an organism. As a consequence of growth, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their increased complexity. D) As a consequence of growth, the decrease in entropy of the organism is associated with a corresponding decrease in the entropy of the universe.

C) The decrease in entropy is associated with growth of an organism. As a consequence of growth, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their increased complexity.

Gaucher disease is the most common of lipid storage diseases in humans. It is caused by a deficiency of an enzyme necessary for the breakdown of lipids. This leads to the accumulation of fatty material in organs of the body including the spleen, liver, kidneys, lungs, brain, and bone marrow. Using your knowledge of the structure of eukaryotic cells, identify the statement below that best explains how internal membranes and the organelles of cells may be involved in Gaucher disease. A) The rough endoplasmic reticulum contains too many ribosomes, which results in an overproduction of the enzyme involved in lipid breakdown. B) The mitochondria are most likely defective and do not produce adequate amounts of ATP needed for cellular energy. C) The lysosomes lack sufficient amounts of enzymes necessary for the metabolism of lipids. D) The Golgi apparatus produces vesicles with faulty membranes, which fail to be transported to the plasma membrane for secretion.

C) The lysosomes lack sufficient amounts of enzymes necessary for the metabolism of lipids.

How does a noncompetitive inhibitor decrease the rate of an enzyme-catalyzed reaction? A) by binding to the active site of the enzyme, thus preventing binding of the normal substrate B) by decreasing the free-energy change of the reaction catalyzed by the enzyme C) by binding to an allosteric site, thus changing the shape of the active site of the enzyme D) by binding to the substrate, thus changing its shape so that it no longer binds to the active site of the enzyme

C) by binding to an allosteric site, thus changing the shape of the active site of the enzyme

If the cytoplasm of a cell is at pH 7, and the mitochondrial matrix is at pH 8, then the concentration of H+ ions A) in the cytoplasm is 8/7 the concentration in the mitochondrial matrix B) in the cytoplasm is 7/8 the concentration in the mitochondrial matrix C) is 10 times higher in the cytoplasm than in the mitochondrial matrix D) is 10 times higher in the mitochondrial matrix than in the cytoplasm

C) is 10 times higher in the cytoplasm than in the mitochondrial matrix

Sulfur is in the same column of the periodic table as oxygen, but has electronegativity similar to carbon. Compared to water molecules, molecules of H2S will... A) have greater cohesion to other molecules of H2S B) have a greater tendency to form hydrogen bonds with each other C) not form hydrogen bonds with each other D) have a higher capacity to absorb heat for the same change in temperature

C) not form hydrogen bonds with each other

People who are lactose intolerant cannot extract energy from milk because A) they are missing the bacteria that can digest lactoseB) milk is fermented to a by-product, which cannot be digestedC) they are missing an enzyme D) lactose is too big to be digested by the enzymes

C) they are missing an enzyme

Which of the following combinations of molecules illustrated could be linked to form a nucleotide? A) 3,7, and 8 B) 1,2, and 11 C) 5,9, and 10 D) 11,12, and 13

D) 11,12, and 13

Which molecule is a saturated fatty acid? A) 5 B) 1 C) 8 D) 9

D) 9

Misfolding of polypeptides is a serious problem in cells. Which of the following diseases are associated with an accumulation of misfolded polypeptides? A) Type I Diabetes B) Alzheimer's C) Parkinson's D) Alzheimer's and Parkinson's

D) Alzheimer's and Parkinson's

Human immunodeficiency virus (HIV) infects cells that have both CD4 and CCR5 cell surface molecules. The viral nucleic acid molecules are enclosed in a protein capsid, and the protein capsid is itself contained inside an envelope consisting of a lipid bilayer membrane and viral glycoproteins. One hypothesis for viral entry into cells is that binding of HIV membrane glycoproteins to CD4 and CCR5 initiates fusion of the HIV membrane with the plasma membrane, releasing the viral capsid into the cytoplasm. An alternative hypothesis is that HIV gains entry into the cell via receptor-mediated endocytosis, and membrane fusion occurs in the endocytotic vesicle. To test these alternative hypotheses for HIV entry, researchers labeled the lipids on the HIV membrane with a red fluorescent dye. What would be observed by live-cell fluorescence microscopy immediately after HIV entry if HIV is endocytosed first, and then later fuses with the endocytotic vesicle membrane? A) A spot of red fluorescence will diffuse in the infected cell's cytoplasm. B) A spot of red fluorescence will be visible on the infected cell's plasma membrane, marking the site of membrane fusion and HIV entry. C) A spot of red fluorescence will remain outside the cell after delivering the viral capsid. D) The red fluorescent dye-labeled lipids will appear in the infected cell's interior.

D) The red fluorescent dye-labeled lipids will appear in the infected cell's interior.

Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature? A) Since the cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium, the membrane must be asymmetrical. B) Since cell membranes communicate signals from one organism to another, the cell membranes must be asymmetrical. C) Proteins only function on the cytoplasmic side of the cell membrane, which results in the membrane's asymmetrical nature. D) The two sides of a cell membrane face different environments and carry out different functions.

D) The two sides of a cell membrane face different environments and carry out different functions.

Why are lipids and proteins free to move laterally in membranes? A) Hydrophilic portions of the lipids are in the interior of the membrane. B) The interior of the membrane is filled with liquid water. C) Lipids and proteins repulse each other in the membrane. D) There are only weak hydrophobic interactions in the interior of the membrane.

D) There are only weak hydrophobic interactions in the interior of the membrane.

The force driving simple diffusion is ________, while the energy source for active transport is... A) a concentration gradient; ADP B) transmembrane pumps; an electrochemical gradient C) phosphorylated carrier proteins; ATP D) a concentration gradient; ATP hydrolysis

D) a concentration gradient; ATP hydrolysis

The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane— more acidic outside the cell than inside the cell. In this bacterial cell, phosphate transport is an example of... A) facilitated diffusion B) passive diffusion C) cotransport D) active transport

D) active transport

In sickle-cell disease, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. Based on this information alone, we can conclude that sickle-cell hemoglobin exhibits... A) only altered tertiary structure B) only altered primary structure C) only altered quaternary structure D) altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered

D) altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered

Testosterone and estradiol are male and female sex hormones, respectively, in many vertebrates. In what way(s) do these molecules differ from each other? Testosterone and estradiol A) are cis-trans isomers but have the same molecular formula B) are enantiomers of the same organic molecule C) are structural isomers but have the same molecular formula D) have different functional groups attached to the same carbon skeleton

D) have different functional groups attached to the same carbon skeleton

Humans can digest starch but not cellulose because... A) the monomer of starch is glucose, while the monomer of cellulose is galactose B) Starch is softer than cellulose C) starch monomers are joined by covalent bonds, and cellulose monomers are joined by ionic bonds D) humans have enzymes that can hydrolyze the α-glycosidic linkages of starch but not the β-glycosidic linkages of cellulose

D) humans have enzymes that can hydrolyze the α-glycosidic linkages of starch but not the β-glycosidic linkages of cellulose

The chemical reaction... A) links two polymers to form a monomer B) joins two fatty acids together C) is a hydrolysis reaction D) results in a peptide bond

D) results in a peptide bond