Cell Biology Exam #1

The cytoskeleton provides support, structure, motility, and organization and it forms tracks to direct organelle and vesicle transport. Which of the cytoskeletal elements listed below is the thickest? (a) microtubules (b) actin filaments (c) None of these (all have the same thickness) (d) intermediate filaments

(a) microtubules

mitochondria perform cellular respiration, a process that uses oxygen, generates carbon dioxide, and produces chemical energy for the cell. Which answer below indicated a correct pairing of the material "burned" and the form of energy produced during cellular respiration? (a) sugar, ATP (b) fat, protein (c) fat, ADP (d) sugar, fat

(a) sugar, ATP

If the isotope 32S has 16 protons and 16 neutrons, how many protons, neutrons, and electrons will the isotope 35S have, respectively? (a) 16;19;17 (b) 16;19;16 (c) 16;20;15 (d) 16;19;15

(b) 16;19;16

_____ are fairly small organelles that provide a safe place within the cell to carry out certain biochemical reactions that generate harmful, highly reactive oxygen species. These chemicals are both generated and broken down in the same location. (a) Nucleosomes (b) peroxisomes (c) Lysosomes (d) Endosomes

(b) Peroxisomes

Despite the differences between eukaryotic and prokaryotic cells, prokaryotes have proteins that are distantly related to eukaryotic actin filaments and microtubules. What is likely to be the most ancient function of the cytoskeleton? (a) vesicle transport (b) cell division (c) membrane support (d) cell motility

(b) cell division

NADH and NADPH are activated carrier molecules that function in completely different metabolic reactions. Both carry two additional ________ and one additional _____________. This combination can also be referred to as a hydride ion. (a) electrons; phosphate (b) electrons; proton (c) protons; electron (d) hydrogens; electron

(b) electrons; proton

Although covalent bonds are 10-100 times stronger than non-covalent interactions, many biological processes depend upon the number and type of non covalent interactions below will contribute most to the strong and specific binding of two molecules, such as a pair of proteins? (a) hydrogen bonds (b) electrostatic attractions (c) hydrophobic interactions (d) van der Waals attractions

(b) electrostatic attractions

What unit of length would you generally use to measure a typical plant or animal cell? (a) millimeters (b) micrometers (c) nanometers (d) centimeters

(b) micrometers

Seed oils are often dehydrogenated and added back into processed foods as partly unsaturated fatty acids. In comparison with the original oil, the new fatty acids have additional double carbon-carbon bonds, replacing what were once single bonds. This process could also be described as _____________. (a) isomerization. (b) oxidation. (c) reduction. (d) protonation.

(b) oxidation

Your body extracts energy from the food you ingest by catalyzing reactions that essentially "burn" the food molecules in a stepwise fashion. What is another way to describe this process? (a) reduction (b) oxidation (c) solvation (d) dehydration

(b) oxidation

The graph in the figure illustrates the relationship between reaction rates and substrate concentration for an enzyme-catalyzed reaction. What does the Km value indicate with respect to enzyme-substrate interactions? (a) the number of enzyme active sites (b) the enzyme-substrate binding affinity (c) the equilibrium rate of catalysis (d) the maximum rate of catalysis

(b) the enzyme-substrate binding affinity

Which of the following factors DO NOT influence the length of a covalent bond? (a) the minimization of repulsive forces between the two nuclei by the cloud of shared electrons (b) the tendency of atoms to fill the outer electron shells (c) the repulsive forces between the positively charged nuclei (d) the attractive forces between negatively charged electrons and positively charged nuclei

(b) the tendency of atoms to fill the outer electron shells

The first task you are assigned in you summer lab job is to prepare a concentrated naOH stock solution. The molecular weight of NaOH is 40. How many grams of solid NaOH will you need to weigh out to obtain a 500 mL solution that has a concentration of 10 M? (a) 800g (b) 400g (c) 200g (d) 160g

(c) 200g

Sulfur has a molecular weight of 32. Therefore, 32 g of sulfur = 1 mole of sulfur = 6x10^23 sulfur atoms. How many moles and atoms, respectively, are there in 120 grams of sulfur? (a) 3.75; 6x10^23 (b) 1.75; 1.05x10^-24 (c) 3.75; 2.25x10^24 (d) 32; 6x10^23

(c) 3.75; 2.25x10^24

Larger molecules have hydrogen bonding networks that contribute to specific, high-affinity binding. Smaller molecules such as urea can also form these networks. How many hydrogen bonds can urea form if dissolved in water? (a) 3 (b) 4 (c) 6 (d) 5

(c) 6

The graph in figure below illustrates the change in the rate of an enzyme-catalyzed reaction as the concentration of substrate is increased. Which of the values listed below is used to calculate the enzyme turnover number? (a) 1/2 Vmax (b) Vmax - Km (c) V max (d) Km

(c) Vmax

When there is an excess of nutrients available in the human body, insulin is released to stimulate the synthesis of glycogen from glucose. This is a specific example of a/an _____ process, a general process in which larger molecules are made from smaller molecules. (a) catabolic (b) biosynthetic (c) anabolic (d) metabolic

(c) anabolic

Zebrafish (Danio rerio) are especially useful in the study of early development because their embryos ______________. (a) are exceptionally large. (b) develop slowly. (c) are transparent. (d) are pigmented.

(c) are transparent

Which of the following choices BEST describes the role of the lysosome? (a) sorting of transport vesicles (b) the storage of excess macromolecules (c) clean-up, recycling, and disposal of macromolecules (d) transport of material to the Golgi apparatus

(c) clean-up, recycling, and disposal of macromolecules

Enzymes facilitate reactions in living systems. Figure below represents an energy diagram for the reaction X---> Y. The solid line in the energy diagram represents changes in energy as the reactant is converted to product under standard conditions. The dashed line shows changes observed when the same reaction takes place in the presence of a dedicated enzyme. Which equation below indicated how the presence of an enzyme affects the activation energy of the reaction 9catalyzed versus uncatalyzed)? (a) d-c versus b-c (b) d-c versus b-a (c) d-a versus b-a (d) a+d versus a+b

(c) d-a versus b-a

Which of the following are examples of isomers? (a) glycogen and cellulose (b) alanine and gylcine (c) glucose and galactose (d) adenine and guanine

(c) glucose and galactose

Which combination of answers best completes the following statement: When atoms are held together by ____ _____, they are typically referred to as _____. (a) double bonds; nonpolar (b) hydrogen bonds; molecules (c) ionic interactions; salts (d) ionic interactions; molecules

(c) ionic interactions: salts

The central dogma provides a framework for thinking about how genetic information is copied and used to produce structural and catalytic components of the cell. From the choices below, select the order of biochemical processes that best correlates with the tenets of the central dogma. (a) translation, replication, transcription (b) translation, transcription, replication (c) replication, transcription, translation (d) replication, translation, transcription

(c) replication, transcription, translation

Select the option that BEST finishes the following statement: Evolution is a process (a) by which all present-day cells arose from 4-5 different ancestral cells. (b) that required hundreds of thousands of years (c) that can be understood based on the principles of mutation and selection (d) that results from repeated cycles of adaptation over billions of years

(c) that can be understood based on the principles of mutation and selection

Scientists learned that cell death is a normal and even important part of life by studying the development of the nematode worm C. elegans. What was the most important feature of C. elegans for the study of programmed cell death? (a) 70% of c. elegans genes have homologs in humans (b) the nematode is smaller and simpler than the fruit fly (c) the developmental pathway of each cell in the adult worm was known (d) Its genome was partially sequenced.

(c) the developmental pathway of each cell in the adult worm was known

If proteins A and B have complementary surfaces, they may interact to form the dimeric complex AB. Which of the following is the correct way to calculate the equilibrium constant for the association between A and B? (a) kon/koff = K (b) K = [A][B]/[AB] (c) K = [AB]/[A][B] (d) (a) and (c)

(d) (a) and (c)

Because there are four different monomer building blocks that can be used to assemble DNA/RNA polymers, the number of possible sequence combinations that can be created for DNA/RNA molecule made of 100 nucleotides is (a) 100^4 (b) 100/4 (c) 4x100 (d) 4^100

(d) 4^100

Cells contain buffers that help maintain a neutral pH. Which of the following statements is not relevant to how buffers work? (a) buffers can donate protons to bases (b) Buffers are mixtures of weak acids and bases (c) Buffers can accept protons from acids (d) Buffers catalyze oxidation-reduction reactions.

(d) Buffers catalyze oxidation -reduction reactions

Which species was the key model organism for the advancement of molecular biology (understanding DNA replication, decoding the DNA to make proteins, etc?) (a) C. elegans (b) D. melanogaster (c) S. pombe (d) E. coli

(d) E. coli

Choose the phrase that best completes this sentence: Microtubules __________ and are required to pull duplicated chromosomes to opposite poles of dividing cells. (a) are intermediate in thickness (b) generate contractile forces (c) are found in especially large numbers in muscle cells (d) can rapidly reorganize

(d) can rapidly reorganize

Chemical reactions carried out by living systems depend on the ability of some organisms to capture and use atoms from nonliving sources in the environment. The specific subset of these reactions that break down nutrients in food can be described as (a) biosynthetic (b) anabolic (c) metabolic (d) catabolic

(d) catabolic

Living systems are incredibly diverse in size, shape, environment, and behavior. It is estimated that there are between 10 million and 100 million different species. Despite tis wide variety of organisms, it remains difficult to define what it means to say something is alive. Which of the following can be describes as the smallest living unit? (a) organelle (b) protein (c) DNA (d) cell

(d) cell

The energy used by the cell to generate specific biological molecules and highly ordered structures is stored in the form of _____________. (a) light waves (b) Brownian motion (c) heat (d) chemical bonds

(d) chemical bonds

The pH of an aqueous solution is an indication of the concentration of available protons. however, you should not expect to find lone protons in a solution; rather, the proton is added to a water molecule to form a/an ____ ion. (a) ammonia (b) chloride (c) hydroxide (d) hydronium

(d) hydronium

The amino acids glutamine and glutamic acid are shown in a figure. They differ only in the structure of part of their side chains. At pH7, what type of interactions are possible for glutamic acid but not for glutamine? (a) covalent bonds (b) van der Waals interactions (c) hydrogen bonds (d) ionic bonds

(d) ionic bonds

Which of the following organelles has both an outer and an inner membrane? (a) ER (b) peroxisome (c) lysosome (d) mitochondrion

(d) mitochondrion

There are 20^100 different possible sequence combinations for a protein chain with 100 amino acids. In addition to the amino acid sequence of the protein, what other factors INCREASE the potential for diversity in these macromolecules? (a) free rotation around single bonds during synthesis (b) the planar nature of the peptide bond (c) the directionality of amino acids being added (d) non-covalent interactions sampled as protein folds

(d) non-covalent interactions sampled as protein folds

Macromolecules in the cell can often interact transiently as a result of non covalent interactions. These weak interactions also produce stable, highly specific interactions between molecules. Which of the factors below is the most significant in determining whether the interaction will be transient or stable? (a) the rate of synthesis (b) the size of each molecule (c) the concentration of each molecule (d) surface complementarity between molecules

(d) surface complementarity between molecules

Double covalent bonds are both shorter and stronger than single covalent bonds, but they also limit the geometry of the molecule because they... (a) limit the rotation of the bonded atoms (b) prevent additional bonds from being formed with the bonded atoms (c) create a new arrangement of electron shells (d) change the reactivity of the bonded atoms

(a) limit the rotation of the bonded atoms

Which pair of values best fills in the blanks in this statement: On average, eukaryotic cells are _____ times longer and have______times more volume than prokaryotic cells. (a) 10;1000 (b) 10;200 (c) 5;100 (d) 10;100

(a) 10;1000

Activated carriers are small molecules that can diffuse rapidly and be used to drive biosynthetic reactions in the cell. Their energy is stored in a readily transferable form such as high energy electrons or chemical groups. Which of the molecules below donates a chemical group rather than electrons? (a) ATP (b) FADH2 (c) NADPH (d) NADH

(a) ATP

Oxidation is a favorable process in an aerobic environment, which is the reason cells are able to drive energy from the oxidation of macromolecules. Once carbon has been oxidized to ____, its most stable form, it can only cycle back into the organic portion of the carbon cycle through_________. (a) CO2; photosynthesis (b) CH3; combustion (c) CO2; respiration (d) CO; reduction

(a) CO2; photosynthesis

Biologists cannot possibly study all living species. Instead, they try to understand cell behavior by studying a select subset of them. Which of the following characteristics are useful in an organism chosen for use as a model in laboratory studies? (a) all of these (b) ability to grow under controlled conditions (c) rapid rate of reproduction (d) amenability to genetic manipulation

(a) all of these

Choose the answer that best fits the following statement: Cholesterol is an essential component of biological membranes. Although it is much smaller than the typical phospholipids and gycolipids in the membrane, it is a/an _____ molecule, having both hydrophilic and hydrophobic regions. (a) amphipathic (b) oxygen-containing (c) polar (d) hydrophobic

(a) amphipathic

Select the answer that BEST completes the following statement: Chemical reactions in living systems occur in an_______ environment, within a narrow range of temperatures. (a) aqueous (b) organic (c) extracellular (d) optimal

(a) aqueous

Brewer's yeast, apart from being an irreplaceable asset in the brewery and in the bakery, is an experimental organism used to study eukaryotic cells. However, it does have some limitations. Which of the processes below cannot be studied in yeast? (a) differentiation (b) cell division (c) exocytosis (d) motility

(a) differentiation

The cell constantly exchanges materials by bringing nutrients in from the external environment and shuttling unwanted by-products back out. Which term describes the process by which external materials are captured inside transport vesicles and brought into the cell? (a) endocytosis (b) exocytosis (c) phagocytosis (d) degradation

(a) endocytosis

Mitochondria contain their own genome, are able to duplicate, an actually divide on a different time line from the rest of the cell. Nevertheless, mitochondria cannon function for long when isolated from the cell because they are (a) endosymbionts (b) viruses (c) parasites (d) anaerobes

(a) endosymbionts

Cells that are specialized for the secretion of proteins are likely to have which of the following features? (a) enlarged endoplasmic reticulum (b) small volume of cytoplasm (c) large population of mitochondria (d) long bundles of actin/myosin proteins

(a) enlarged endoplasmic reticulum

Which three characteristics best support the rapid evolution of prokaryotic populations? (a) large population, rapid growth, can exchange DNA (b) no organelles, cell wall, can exchange DNA (c) aerobic, motile, rapid growth (d) microscopic, motile, anaerobic

(a) large population, rapid growth, can exchange DNA