MCB 181 Exam 2 Practice

In plants and algae, which of the following is a by-product of photosynthesis?

A) O2
B) CO2
C) H2O
D) C6H12O6
E) H+

Epithelial tissue is found:

A) on the outer surface of the body.
B) lining the gastrointestinal tract.
C) lining the lungs.
D) lining the blood vessels.
E) All of these choices are correct.

A cellular response to a signal can be terminated by:

A) depletion of the signal that activates the receptor.
B) inactivation of intracellular signal-transduction proteins.
C) automatic inactivation of proteins in the signal pathway over time.
D) depletion of a second messenger.
E) All of these choices are correct.

Defects in cell signaling can lead to a cancerous cell due to:

A) overproduction of signals that trigger cell division.
B) overproduction of a receptor that triggers cell division.
C) a defective receptor that stays in the activated state and triggers cell division continuously.
D) a defective signal-transduction protein that stays in the activated state and triggers cell division continuously.
E) All of these choices are correct.

The reducing agent during the Calvin cycle is:

A) NADPH.
B) ATP.
C) oxygen.
D) water.
E) FADH2

Which of the following statements about cadherins and integrins are true?

A) They are found on the surfaces of most animal cells.
B) They are transmembrane proteins that attach to cytoskeletal elements inside the cell.
C) They are highly diverse, and highly specific for what their extracellular domain will attach to.
D) They are found in embryonic cells.
E) All of the above are correct.

Which of the following is the most precise description of the role of enzymes in catalyzing biochemical reactions?

A) Enzymes provide the necessary activation energy to overcome the transition state.
B) Enzymes stabilize the transition state and decrease its free energy.
C) Enzymes cut hard-to-break bonds allowing the reaction to proceed.
D) Enzymes increase the ΔG of the reactions making them proceed rapidly.
E) Enzymes decrease the ΔG of the reactions making them proceed rapidly.

Cellular respiration is a series of _____ reactions.

A) catabolic
B) anabolic
C) glycolytic
D) phosphorylation
E) carboxylation

Which of the following would you predict for an allosteric enzyme?

A) An increase in the concentration of substrate molecules could activate the enzyme.
B) A downstream product later in the pathway could inactivate the enzyme.
C) An allosteric inhibitor could cause a conformational change in the enzyme decreasing its activity.
D) All of the above

Three critical amino acids in the active site of an enzyme are leucine, tryptophan, and alanine. Which of the following characteristics would you predict the substrate to possess in order to bind the active site of this enzyme? (You may use the figure on page 1 to answer this question.)

A) relatively hydrophobic
B) hydrophilic, with a negative charge
C) hydrophilic, with a positive charge
D) hydrophilic, but without a charge

Which of the following types of cellular activities can be a response to cell signaling?

A) Cell division is triggered.
B) Gene expression patterns are changed.
C) Enzyme activity patterns are changed.
D) Cell signals are released to communicate with other cells.
E) All of these choices are correct.

Which of the following processes is NOT part of the communication at a neuromuscular junction?

A) The neuron releases a neurotransmitter to signal contraction by the muscle cell.
B) A cell-surface receptor on the muscle cell is activated by acetylcholine binding.
C) Upon activation, the acetylcholine receptor on the neuron undergoes a conformational change to activate an ion channel in the muscle cell.
D) An opened ligand-gated ion channel allows sodium ions to rush across the plasma membrane to the inside of the muscle cell.
E) A sudden influx of sodium ions across the plasma membrane drastically reduces the membrane potential and activates the contractile machinery of the muscle cell.

Cilia:

A) are used by epithelial cells to move substances along cell surfaces.
B) move through coordinated activity of cytoskeletal structures.
C) are used by sperm cells for motion.
D) A and B
E) B and C

Autotrophs typically obtain their carbon from:
A) C6H12O6.
B) ATP.
C) CO2.
D) CH4.
E) CH3OH

During photosynthesis, _____________ is reduced to _____________.

A) water; carbon dioxide
B) carbon dioxide; glucose
C) oxygen; water
D) glucose; oxygen
E) carbon dioxide; oxygen

The hydrogen ion gradient across the thylakoid membrane is required to ________________.

A) power ATP synthase.
B) provide a source of hydrogen ions needed for carbohydrate in the Calvin cycle.
C) provide a source of hydrogen ions to combine with molecular oxygen to make water.
D) reduce NADP to NADPH.
E) None of the above

In human cells such as muscle tissue, the product of anaerobic respiration is:

A) acetic acid.
B) pyruvate.
C) lactic acid.
D) FADH2.
E) ethanol

Cancer can be characterized by:

A) a mass of rapidly dividing cells called a tumor.
B) metastasized tumor cells that leave the tumor and invade distant parts of the body.
C) cells that express a type of intermediate filament that is inappropriate for that area of the body.
D) cells with an enhanced ability to adhere to proteins in the basal lamina.
E) All of these choices are correct.

Most of the ATP produced during cellular respiration is generated through:

A) substrate-level phosphorylation.
B) oxidative phosphorylation.
C) reduction of NAD+.
D) reduction of FAD.
E) oxidation of pyruvate.

In a thylakoid membrane, absorbed light energy is passed from one chlorophyll molecule to another until:

A) it is dissipated as heat.
B) it is released as fluorescence.
C) it is passed to a reaction center.
D) it is converted to ATP.
E) it is converted to triose phosphate.

Mammalian steroid hormones are signaling molecules that function in which of the following types of cell signaling?

A) juxtacrine
B) paracrine
C) autocrine
D) endocrine
E) All of these choices are correct

The extracellular matrix in animals:

A) is located exclusively in connective tissue.
B) is formed by many types of cells, primarily fibroblasts, on their cell surfaces.
C) is a meshwork of insoluble fibrous proteins, primarily collagens, that assemble in a double helix.
D) differs from one tissue to the next, essential for maintaining the integrity of the tissue it surrounds.
E) is attached to cells by Gap junctions.

Which one of the following is a characteristic of integrins in metastatic cells?

A) These integrins give the cells a stronger attachment to the extracellular matrix, especially that of the basal lamina.
B) These integrins allow the cells to cross the capillary basal lamina.
C) These integrins allow the cells to cross the layer of capillary endothelial cells.
D) These integrins can be targeted by an anticancer therapy that specifically targets the metastatic cells.
E) All of these choices are correct.

The phosphorylation of glucose during glycolysis serves to:

A) destabilize the molecule, making it easier to cleave.
B) trap imported glucose inside the cell.
C) reduce a biological cofactor, storing energy for later.
D) A and B
E) B and C

Which one of the following statements about integrins is correct?

A) Integrins indirectly connect microfilaments with the extracellular matrix.
B) The integrins in animal cells are identical to the integrins in plant cells.
C) There is a single type of integrin, capable of binding to multiple types of extracellular matrix proteins.
D) Integrins are the primary cell adhesion molecule in a desmosome.
E) Adjacent integrins create channels referred to as gap junctions.

Electrons farthest from the nucleus have the ____________.

A) least potential energy
B) most kinetic energy
C) least kinetic energy
D) most potential energy
E) same amount of energy as electrons closest to the nucleus

Which product(s) of the Calvin cycle is(are) exported from the chloroplast for use by the plant cell?

A) triose phosphates
B) sucrose and glucose
C) RuBP
D) NADPH
E) Rubisco

The majority of energy generated in the citric acid cycle is in the form of:

A) ATP via substrate level phosphorylation.
B) GTP via substrate level phosphorylation.
C) energy electrons donated to NAD+ and FADH.
D) ATP via oxidative phosphorylation.
E) GTP via oxidative phosphorylation.

Signal amplification relies on:

A) increasing amounts of ligand as signal transduction proceeds.
B) a sequential increase in the different components of the signal transduction pathway.
C) increasing numbers of cell-surface receptors as the signal is transduced.
D) increased activity of protein phosphatases.

DNP (2,4-dinitrophenol) is an effective weight-loss agent that was used in diet pills in the 1930s. It has since been removed from the market (though it is available online) because of serious side effects such as fever, cataracts, rashes, and sometimes death. DNP inserts into the inner mitochondrial membrane and shuttles protons between the intermembrane space and the matrix. Based on this information, which of the following might you predict?

A) reduced ATP production B) dissipation of the proton gradient
C) decreased difference in pH between matrix and intermembrane space
D) All of the above
E) None of the above

The potential energy in a molecule of ATP is held in the:

A) carbon-carbon bonds of the sugar.
B) repulsion of the phosphate groups from each other.
C) the carbon-nitrogen bonds of the base.
D) the carbon-oxygen bonds of the sugar.
E) repulsion of the sugar and the base.

Which of the following is NOT true about how communities of cells interact within tissues?

A) All cells in a tissue carry out the same function independently.
B) Cells communicate with neighboring cells and their environment.
C) Cells stick together to function together in a tissue.
D) Cells carry out specialized functions within a multicellular organism.
E) All cells require energy to function.

Inactivation of a cell-surface receptor depends on:

A) the binding affinity of the receptor.
B) the activity of phosphatases in the cytosol.
C) the concentration of ligand surrounding the cell.
D) both the binding affinity of the receptor and concentration of ligand surrounding the cell.

Which of the following statements about communication among bacteria is correct?

A) At lower population density, a higher concentration of signaling molecules is typically observed.

B) Unlike eukaryotes, in bacterial communication no receptor molecule is required.

C) Cellular communication in bacteria is based on the same principles as communication within multicellular organisms.

D) Like eukaryotes, MAP kinases pathways end in the nucleus.

E) All of these choices are correct.

In plants and algae, __________ is the source of the electrons needed for photosynthesis.
A) O2
B) CO2
C) H2O
D) NADPH
E) H+

Which of the following would NOT be considered a cell-surface receptor?

A) a receptor that binds a nonpolar steroid hormone and activates transcription
B) a receptor that allows ions to enter the cell when a ligand binds
C) a receptor that causes GDP to be exchanged for GTP in a G protein
D) a receptor that must form a dimer after binding the ligand to transmit a

When fats are used as an energy source, the fatty acids are broken down to acetyl-CoA. That means that fats bypass the reactions of ___ and enter the respiratory pathway at ________.

A) glycolysis; the citric acid cycle
B) fermentation; glycolysis
C) the citric acid cycle; oxidative phosphorylation
D) the citric acid cycle; glycolysis
E) oxidative phosphorylation; fermentation

Which one of the following statements best represents the relationship between cellular respiration and photosynthesis?

A) Photosynthesis stores energy in organic molecules, while respiration releases it.
B) Photosynthesis occurs only during the day and respiration occurs only at night.
C) Respiration occurs only in animals and photosynthesis occurs only in plants.
D) Respiration stores energy in organic molecules, while photosynthesis releases it.
E) Photosynthesis reverses the biochemical pathways of respiration.

Phosphatases are a family of enzymes that specifically remove phosphate groups from proteins that were added by protein kinases. Vanadate is an inhibitor of phosphatases in eukaryotic cells. What effect would vanadate have on the response of cells to signals received by receptor kinases?

A) The response of the cell would last longer than it normally would.
B) The response of the cell would be shorter than it normally would.
C) The signal would still bind the receptor, so there would be no effect.
D) The response of the cell would not change as bound receptor would still be activated.

What is the end result of activating the MAP kinase pathway?

A) a change in gene expression
B) phosphorylation of multiple cytosolic proteins
C) synthesis of second messenger molecules
D) ion flow

The approximate yield of ATP from the full oxidation of a molecule of glucose is:

A) 2
B) 6
C) 12
D) 32
E) 64

Leaves absorb the least amount of light in the ________ range of the visible spectrum.
A) orange
B) green
C) blue
D) yellow
E) violet

In eukaryotic cells, glycolysis occurs in:

A) the cytoplasm.
B) the nucleus.
C) the matrix of the mitochondria.
D) the endoplasmic reticulum.
E) vacuoles

Metastatic cancer cells:

A) are able to leave the tumor where they originated and travel to distant locations to set up new tumors at distant sites.
B) become malignant when they cross the capillary basal lamina.
C) only need to cross a single layer of capillary endothelial cells to form tumors at distant sites.
D) All of these choices are correct.

The energy of activation of a reaction is:

A) the net change in free energy.
B) the difference in energy between substrate and product.
C) the energy input needed to reach the transition state.
D) the difference in energy between the transition state and the product.
E) equivalent to the ΔG of ATP hydrolysis.

Which one of the following is an example of potential energy?

A) a moving muscle
B) light
C) heat
D) an electrochemical gradient
E) wind

Dynamic instability of microtubules:

A) is caused by the large size of this type of cytoskeletal element.
B) results from a deficiency of free tubulin subunits.
C) allows microtubules to perform their functions.
D) is shared by all other cytoskeletal elements.
E) All of these choices are correct.

Which of the following is NOT found in the extracellular matrix of animal cells?
A) cellulose fibers
B) elastin fibers
C) collagen fibers
D) laminin fibers
E) polysaccharide matrix

Which of the following reactions would you predict could be coupled to ATP hydrolysis to ADP + Pi to make it energetically favorable, or spontaneous?

A) creatine phosphate + H2O → creatine + Pi, ΔG -10.3 kcal/mol
B) phosphoenolpyruvate + H2O → pyruvate + Pi, ΔG -14.8 kcal/mol
C) glucose 6-phosphate + H2O → glucose + Pi, ΔG -3.3 kcal/mol
D) glucose 1-phosphate + H2O → glucose + Pi, ΔG -5.0 kcal/mol
E) glutamic acid + NH3 → glutamine, ΔG +3.4 kcal/mol

The basal lamina:

A) is a specialized extracellular matrix found beneath epithelial tissues.
B) surrounds endothelial cells found in blood vessels.
C) is a collagen-rich extracellular matrix
D) links to epithelial cells through hemidesmosomes, which attach to intermediate filaments.
E) All of these choices are correct

A new experimental pesticide is being tested by a large agricultural chemical company. An unfortunate side effect in plants treated with this new product is a decrease in ATP production in the chloroplasts. (Interestingly, production of ATP in the mitochondria is unaffected.) Given this observation, which of the following would you expect to be DIRECTLY affected by the new pesticide?

A) the synthesis of triose phosphates from 3-phosphoglycerate
B) the transport of electrons along the photosynthetic electron transport chain
C) the carboxylation of RuBP by rubisco
D) the oxidation of RuBP by rubisco

Which of the following reactions is most likely to be exergonic?

A) the synthesis of a phospholipid from glycerol and fatty acids
B) the replication of DNA from free nucleotides
C) the formation of cellulose from individual glucose molecules
D) the digestion of protein from food into amino acids
E) None of the above

Which of these summarizes the overall reactions of cellular respiration?

A) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy
B) 6 CO2 + 6 H2O + energy → C6H12O6 + 6 O2
C) C6H12O6 + 6 O2 + energy → 6 CO2 + 12 H2O
D) 6 CO2 + 6 O2 → C6H12O6 + 6 H2O
E) H2O → 2 H+ + 1/2 O2 + 2e-

Which of the following types of molecules is(are) likely to bind to the active site of an enzyme?

A) a substrate
B) a competitive inhibitor
C) a non-competitive inhibitor
D) A and B
E) A and C

Glucose is stored in plants as _________ and in animals as _________. A

A) glycogen; starch
B) cellulose; glycogen
C) starch; cellulose
D) starch; glycogen
E) cellulose; starch

Anabolic pathways of metabolism are pathways that ________________________.

A) build complex molecules from simple ones
B) release stored chemical energy
C) take place primarily in skeletal muscle
D) make large quantities of ATP
E) All of the above

Cell shapes are largely determined by:

A) cytoskeletal protein networks in the cytoplasm.
B) adhesion proteins that assemble at cell surfaces.
C) a mesh of proteins and polysaccharides in the extracellular matrix.
D) cytosolic proteins that assemble into structures called cellular junctions.
E) All of these choices are correct.

A G protein:

A) is a component of a signal-transduction pathway that is coupled to a G protein-coupled receptor.
B) is composed of three subunits and is inactive when bound to GDP.
C) releases GDP and binds to GTP when associated with an activated receptor.
D) becomes deactivated when bound GTP is dephosphorylated to GDP.
E) All of these choices are correct.

In most living cells, which one of the following is not a product of cellular respiration?

A) carbon dioxide
B) water
C) oxygen
D) ATP
E) All of these choices are products of cellular respiration in most living cells.

A cell that responds to an environmental condition by the release of a chemical is an example of which of the following elements of cellular communication?

A) a signaling cell
B) a signaling molecule
C) a receptor molecule
D) a responding cell
E) None of these choices is correct.