Practice Final

A cell can crawl through a tissue because of the transmembrane __________ proteins that can bind to collagen (indirectly through fibronectin) outside of the cell. A. integrin B. glycosaminoglycans C. gap junction D. actin

A

Adherens junctions A. can be used to bend epithelial sheets into tubes. B. are most often found at the basal surface of cells. C. are found only in adult tissues. D. involve fibronectin and integrin interactions.

A

Proteoglycans in the extracellular matrix of animal tissues A. chiefly provide tensile strength. B. allow cartilage to resist compression. C. are linked to microtubules through the plasma membrane. D. are solely composed of polysaccharides.

B

Cadherins A. are used to transfer proteins from one cell to another. B. mediate cell-cell attachments through homophilic interactions. C. are abundant in the plant cell wall. D. bind to collagen fibrils.

B

NADH contains a high-energy bond that, when cleaved, donates a pair of electrons to the electron-transport chain. What are the immediate products of this bond cleavage? A. NAD+ + OH− B. NAD+ + H − C. NAD− + H + D. NAD + H

B

Osmosis describes the movement of water across a biological membrane and down its concentration gradient. In chemiosmosis, useful energy is harnessed by the cell from the movement of __________ across the inner mitochondrial membrane into the matrix __________ a concentration gradient. A. ATP, against B. protons, down C. electrons, down D. ADP, against

B

The figure above shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine? A. a smooth muscle cell that has a defect in guanylyl cyclase such that it cannot bind NO B. a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP C. a muscle cell that has cyclic GMP phosphodiesterase constitutively active D. a drug that blocks an enzyme involved in the metabolic pathway from arginine to NO

B

The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine kinase called RGFR. Which of the following types of alteration would be most likely to prevent receptor dimerization? A. a mutation that increases the affinity of RGFR for RGF B. a mutation that prevents RGFR from binding to RGF C. changing the tyrosines that are normally phosphorylated on RGFR dimerization to alanines D. changing the tyrosines that are normally phosphorylated on RGFR dimerization to glutamic acid

B

1. Which of the following statements about mitochondrial division is TRUE? A. Mitochondria divide in synchrony with the cell. B. The rate of mitochondrial division is the same in all cell types. C. Mitochondrial division is mechanistically like prokaryotic cell division. D. Mitochondria cannot divide and produce energy for the cell at the same time.

C

The lab you work in has discovered a previously unidentified extracellular signal molecule called QGF, a 75,000 -dalton protein. You add purified QGF to different types of cells to determine its effect on these cells. When you add QGF to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival. Given these observations, which of the following statements is most likely to be TRUE? A. Because it acts on so many diverse cell types, QGF probably diffuses across the plasma membrane into the cytoplasm of these cells. B. Glial cells do not have a receptor for QGF. C. QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed. D. Heart muscle cells, fibroblasts, and nerve cells must all have the same receptor for QGF.

C

Which situation described below will lead to an increase in Brainy transcription? A. a mutation in the Nerd gene that produces a protein that cannot be phosphorylated by PKA B. a mutation in the nuclear import receptor protein that prevents binding to PKA C. a mutation in cAMP phosphodiesterase (degrades cAMP) that makes the enzyme inactive D. a mutation in the gene that encodes adenylyl cyclase that renders the enzyme unable to interact with the α subunit of the G protein

C

. Which component of the electron-transport chain is required to combine the pair of electrons with molecular oxygen? A. cytochrome c B. cytochrome b-c1 complex C. ubiquinone D. cytochrome c oxidase

D

During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in __________ signaling. A. endocrine B. paracrine C. neuronal D. contact-dependent

D

Hemidesmosomes are important for A. tubulation of epithelial sheets. B. linkages to glycosaminoglycans. C. forming the basal lamina. D. attaching epithelial cells to the extracellular matrix.

D

Stage 2 of photosynthesis, sometimes referred to as the dark reactions, involves the reduction of CO2 to produce organic compounds such as sucrose. What cofactor is the electron donor for carbon fixation? A. H2O B. NADH C. FADH2 D. NADPH

D

Which of the following statements about animal connective tissues is TRUE? A. Enzymes embedded in the plasma membrane synthesize the collagen in the extracellular matrix extracellularly. B. In connective tissue, the intermediate filaments within the cells are important for tissue tensile strength. C. Cells can attach to a collagen matrix by using cadherin, an integral membrane protein. D. Proteoglycans can resist compression in the extracellular matrix.

D

Which of the following statements about the possible fates of glyceraldehyde 3-phosphate is FALSE? A. It can be exported from the chloroplast to the cytosol for conversion into sucrose. B. It can be used to make starch, which is stored inside the stroma of the chloroplast. C. It can be used as a precursor for fatty acid synthesis and stored as fat droplets in the stroma. D. It can be transported into the thylakoid space for use as a secondary electron acceptor downstream of the electron-transport chain.

D

Which of the following statements is FALSE? A. A constitutively active mutant form of PKA in skeletal muscle cells would lead to a decrease in the amount of unphosphorylated phosphorylase kinase. B. A constitutively active mutant form of PKA in skeletal muscle cells would not increase the affinity of adrenaline for the adrenergic receptor. C. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glucose available. D. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.

D

Which of the following statements is FALSE? A. In the presence of a survival signal, Akt is phosphorylated. B. In the absence of a survival signal, Bad inhibits the cell-death inhibitor protein Bcl2. C. In the presence of a survival signal, the cell-death inhibitory protein Bcl2 is active. D. In the absence of a survival signal, Bad is phosphorylated.

D

Based upon what you know about metabolism, explain how electrons are stripped from food molecules and used to drive the electron-transport chain.

Food molecules are ultimately converted into an acetyl group. Electrons removed during the generation of acetyl are added to the cofactors NAD+ and FAD to generate the reduced cofactors NADH and FADH2, respectively. The two carbon atoms in the acetyl group are then fed into the citric acid cycle, where they are oxidized to two molecules of CO2. The electrons removed during this oxidation are also captured by the activated carriers NADH and FADH2. The high-energy electrons in all these activated carriers, which derived from carbons that were formerly part of food molecules are now transferred to the protein complexes in the electron-transport chain.

The citric acid cycle generates NADH and FADH2, which are then used in the process of oxidative phosphorylation to make ATP. The reactions in the citric acid cycle do not utilize oxygen. Yet the citric acid cycle stops almost immediately when O2 is removed. Explain this observation.

The citric acid cycle stops almost immediately when oxygen is removed because several steps in the cycle require the oxidized forms of NAD+ and FAD. In the absence of oxygen, these electron carriers can be reduced by the reactions of the citric acid cycle but cannot be reoxidized by the electrontransport chain that participates in oxidative phosphorylation.

When adrenaline binds to adrenergic receptors on the surface of a muscle cell, it activates a G protein, initiating an intracellular signaling pathway in which the activated α subunit activates adenylyl cyclase, thereby increasing cAMP levels in the cell. The cAMP molecules then activate a cAMP-dependent kinase (PKA) that, in turn, activates enzymes that result in the breakdown of muscle glycogen, thus lowering glycogen levels. You obtain muscle cells that are defective in various components of the signaling pathway. Indicate how glycogen levels would be affected in the presence of adrenaline in the following cells. Would they be higher or lower than in normal cells treated with adrenaline? A. cells that lack adenylyl cyclase

higher

When adrenaline binds to adrenergic receptors on the surface of a muscle cell, it activates a G protein, initiating an intracellular signaling pathway in which the activated α subunit activates adenylyl cyclase, thereby increasing cAMP levels in the cell. The cAMP molecules then activate a cAMP-dependent kinase (PKA) that, in turn, activates enzymes that result in the breakdown of muscle glycogen, thus lowering glycogen levels. You obtain muscle cells that are defective in various components of the signaling pathway. Indicate how glycogen levels would be affected in the presence of adrenaline in the following cells. Would they be higher or lower than in normal cells treated with adrenaline? B. cells that lack the GPCR

higher

Name the three main classes of cell-surface receptor.

ion-channel-coupled receptors; G-protein-coupled receptors; enzyme-coupled receptors

When adrenaline binds to adrenergic receptors on the surface of a muscle cell, it activates a G protein, initiating an intracellular signaling pathway in which the activated α subunit activates adenylyl cyclase, thereby increasing cAMP levels in the cell. The cAMP molecules then activate a cAMP-dependent kinase (PKA) that, in turn, activates enzymes that result in the breakdown of muscle glycogen, thus lowering glycogen levels. You obtain muscle cells that are defective in various components of the signaling pathway. Indicate how glycogen levels would be affected in the presence of adrenaline in the following cells. Would they be higher or lower than in normal cells treated with adrenaline? C. cells that lack cAMP phosphodiesterase

lower

When adrenaline binds to adrenergic receptors on the surface of a muscle cell, it activates a G protein, initiating an intracellular signaling pathway in which the activated α subunit activates adenylyl cyclase, thereby increasing cAMP levels in the cell. The cAMP molecules then activate a cAMP-dependent kinase (PKA) that, in turn, activates enzymes that result in the breakdown of muscle glycogen, thus lowering glycogen levels. You obtain muscle cells that are defective in various components of the signaling pathway. Indicate how glycogen levels would be affected in the presence of adrenaline in the following cells. Would they be higher or lower than in normal cells treated with adrenaline? D. cells that have an α subunit that cannot hydrolyze GTP

lower