Cell Biology Exam 3

Which of the following can readily cross the cell plasma membrane without the aid of a transport protein?

a. K+ d.O2

b. Na+ e. amino acids

c. RNA

D. Oxygen

Transport of glucose by Na+/glucose symport is an example of

a. simple diffusion. d. indirect active transport.

b. facilitated diffusion. e. none of the above.

c. direct active transport.

D. Indirect active transport

A major difference between active transport and facilitated diffusion is that in facilitated diffusion

a. no proteins are involved.

b. solutes move from high concentration to low concentration.

c. solutes move from low concentration to high concentration.

d. the energy is provided by GTP instead of ATP.

e. none of the above.

B. Solutes move from high concentration to low concentration

The net outputs of ATP and NADH from fermentation of one molecule of glucose to two molecules of lactate are _____, and _____, respectively.

2; 0

The Na+/K+ pump located in the plasma membrane of animal cells actively moves

Na+ out of and K+ into a cell.

In the aerobic respiration, the position of each electron carrier in the electron transport system is determined by

Its standard reduction potential

During aerobic respiration, the TCA cycle occurs:

a. in the cytosol.

b. in the mitochondrial outer membrane.

c. in the mitochondrial matrix.

d. in the intermembrane space.

e. in the mitochondrial inner membrane.

C. In the mitochondrial matrix

Which of the following is a feature of the Fluid Mosaic Model of membrane structures?

a. Membranes consist of lipid bilayers that are coated on one side with a thin sheet of proteins

b. Membranes consist of lipid bilayers that are coated on both sides with thin sheets of proteins.

c. Membranes are in fluid state.

d. All of the above.

e. None of the above.

C. Membranes are in fluid state

Biological membrane asymmetry (the two monolayers are different) can be manifested by________.

a. the types of lipids present in each monolayer

b. the degree of unsaturation of the fatty acids in the phospholipid molecules

c. movement of each monolayer

d. a and b

e. a and c

D. A and B

Which of the following is NOT a product of the TCA cycle?

a. CO2

d.ATP

b. FADH2

e. pyruvate

c. NADH

Pyruvate

Protein X can be extracted from biological membranes only if the extract buffer contains detergent. Based on this result, it is highly likely that protein X is a(n)

integral membrane protein

Na+ may cross biological membranes via

a. active transport.

b. simple diffusion.

c. facilitated diffusion.

d. a and b.

e. a and c.

E. A and C

In the biological systems, hydrogenation reaction

a. is an oxidative reaction.

b. involves removal of electrons.

c. involves removal of protons.

d. all of the above

e. none of the above

e. None of the above

Aerobic respiration involves five stages, and the order of the five stages is

a. Glycolysis , pyruvate oxidation, electron transfer, TCA (tricarboxylic acid) cycle , ATP synthesis

b. Glycolysis, pyruvate oxidation, TCA (tricarboxylic acid) cycle, electron transfer, ATP synthesis

c. Glycolysis , TCA (tricarboxylic acid) cycle, pyruvate oxidation, electron transfer, ATP synthesis

d. Glycolysis, electron transfer, TCA (tricarboxylic acid) cycle, pyruvate oxidation, ATP synthesis

e. TCA (tricarboxylic acid) cycle, glycolysis, electron transfer, pyruvate oxidation, ATP synthesis

b. Glycolysis, pyruvate oxidation, TCA (tricarboxylic acid) cycle, electron transfer, ATP synthesis

Which of the following statements is correct for simple diffusion and facilitated diffusion?

a. Both processes have directionality.

b. Both processes can be inhibited by competitive inhibitors.

c. Both processes are membrane-protein mediated.

d. In both processes, solutes move from higher concentration to lower concentration.

e. In both processes, solutes move from low concentration to higher concentration

d. In both processes, solutes move from higher concentration to lower concentration.

The central function of the TCA (tricarboxylic acid) cycle is to

a. use the proton gradient to synthesize ATP.

b. transfer electrons from the reduced coenzymes to oxygen.

c. reduce pyruvate to lactate, and conserve free energy as reduced coenzymes and ATP.

d. oxidize acetyl CoA to CO2, and conserve free energy as reduced coenzymes and ATP

e. oxidize glucose to pyruvate, and conserve free energy as reduced coenzymes and ATP.

d. oxidize acetyl CoA to CO2, and conserve free energy as reduced coenzymes and ATP

Biosynthesis of starch occurs in the ___________

a. intermembrane space. d. mitochondria.

b. cytosol. e. nucleus.

c. chloroplast.

Chloroplast

Which of the following statements accurately describes the function of the Calvin cycle?

a. In this process, carbon dioxide is reduced to organic sugars.

b. In this process, NADP+, ADP and Pi are regenerated for the Light reactions

c. In this process, electrons are transferred through electron transfer system

d. a and b

e. a, b and c

d. a and b

_______ and _______ molecules usually can pass through the lipid bilayer via simple diffusion.

Hydrophobic; small

Which of the following sugar molecules can exit from the Calvin cycle and are used for carbohydrate synthesis?

a. ribulose1,5-bisphosphate (containing 5 carbons) d. all of the above

b. triose phosphate (containing 3 carbons)

e. none of the above

c. riulose-5-phosphate (containing 5 carbons)

b. triose phosphate (containing 3 carbons)

Which of the following microorganisms would have the highest levels of unsaturated fatty acids comprising its cell membranes?

a. bacteria growing in the North or South Pole

b. bacteria growing in the gut of the human body

c. bacteria found in a hot spring

d. bacteria growing near the rim of an active volcano

e. c and d

a. bacteria growing in the North or South Pole

Which of the following processes in the aerobic respiration generate(s) carbon dioxide?

a. glycolysis

b. the reaction by which pyruvate is converted into acetyl CoA

c. TCA or Krebs cycle

d. a and b

e. b and c

e. b and c

When cells decrease the relative concentration of short chain fatty acids in cell membrane

a. the transition temperature of the membrane decreases

b. the transition temperature of the membrane increases

c. the transition temperature of the membrane is unaffected

d. the cell membrane malfunctioning

e. none of the above

b. the transition temperature of the membrane increases

In the late stage of lactate fermentation, pyruvate is reduced to lactate. This process is required because:

a. lactate is important for the physiology of bacteria

b. pyruvate is toxic to cells so it has to be converted to lactate

c. the reaction produces more ATP for cells

d. NADH produced during glycolysis has to be converted back to NAD+ for maintaining the continuous

operation of glycolysis.

e. all of the above

NADH produced during glycolysis has to be converted back to NAD+ for maintaining the continuous

operation of glycolysis

The electron transport components in the mitochondria are linked to ATP synthesis by:

c. transporting protons across the inner mitochondrial membrane

A transport protein that moves one solute into the cell and simultaneously move another solute out of the cell. This transport protein is called a(n) _____.

antiporter

Antenna chlorophyll absorbs photons and passes the energy to neighboring chlorophyll or accessory pigment by:

a. electron transfer system. d. all of the above.

b. fluorescence energy transfer.

e. none of the above.

c. resonance energy transfer.

c. resonance energy transfer.

Which of the following is one of the immediate substrates of the TCA cycle?

a. lactate d. ethanol

b. acetyl CoA e. NADPH

c. O2

acetyl CoA

If you use radioactive 14CO2 to feed plants under sunlight, the first detectable photosynthetic product contains ___carbons.

a.6

d. 3

b. 5

e. 2

c. 4

d. 3

Each electron that passes from water to NADP+ is photoexcited _____.

a. once by photosystem I

b. twice, first by photosystem I and then by photosystem II

c. twice, first by photosystem II and then by photosystem I

d. three times, first by photosystem I followed by photosystem II and photosystem III e. none of the above

c. twice, first by photosystem II and then by photosystem I

Which of the following molecules would require input of energy for passing through a lipid bilayer membrane?

a. CO2 d. Na+

b. ethanol e. H2O

c. O2

d. Na+

Which of the following molecules is the ultimate electron acceptor in aerobic respiration?

a. H2O d. pyruvate

b. ethanol e. ATP

c. O2

c. O2

Which of the following types of proteins penetrate into the lipid bilayers?

a. integral membrane proteins

d. a and b

b. lipid-anchored proteins

e. a and c

c. peripheralproteins

d. A and B

Considering alcoholic (ethanol) fermentation and aerobic respiration, which of the following is common to both?

a. NADH and FADH2 are produced

d. CO2 is produced

b. The energy source is completely oxidized

e. lactate is produced

c. The energy source is partially oxidized.

d. CO2 is produced

To which of the following amino acid residues in a protein are oligosaccharide chains attached?

a. threonine

d. all of the above

b. asparagine

e. none of the above

c. serine

d. all of the above

Which of the following determines the transition temperature of a biological membrane?

a. whether the fatty acids of the lipids are saturated or unsaturated

b. the extent of glycosylation of the membrane

c. the length of the fatty acid chains

d. a and b

e. a and c

e. A and C

In which of the following parts of a cell usually you can find more glycosylated proteins?

a. the nucleus

d. inner surface of cell membrane

b. mitochondria

e. none of the above

c. outside surface of cell membrane

c. outside surface of cell membrane

Which of the following protein is NOT involved in unwinding DNA at the replication fork during DNA replication?

A) DNA helicase.

B) topoisomerase.

C) single-strand DNA binding proteins.

D) DNA polymerase I.

E) All of the above.

D. DNA polymerase I.

*The ________ is a complex network of interconnected filaments and tubules that extends throughout the cytosol, from the nucleus to the inner surface of the plasma membrane.

cytoskeleton

*Which of the following is NOT a function of the cytoskeleton?

A) movement of ions across membrane.

B) movement of organelles.

C) movement of chromosomes during cell division.

D) muscle contraction.

E) cell movement.

A. Movement of ions across membrane

*Intermediate filaments

A) are solely responsible for animal cell shape.

B) provide structural support for cells.

C) are composed of alpha and beta tubulins.

D) have polarity.

E) are important for cellular motility.

B. provide structural support for cells

The period in the cell cycle between the end of DNA replication and the beginning of mitosis is called the _____ phase.

A) G1

B) S

C) G2

D) M

E) G0

C. G2

The microtubule-organizing center (MTOC)

A) serves as a site for microtubule and microfilament assembly.

B) is positioned near the cell membrane.

C) serves as a site at which microtubule assembly is initiated.

D) acts as an anchor for both ends of the microtubule.

E) is composed of microfilaments and intermediate filaments.

C) serves as a site at which microtubule assembly is initiated.

*Which stage of mitosis starts as sister chromatids split apart and begin to move toward opposite poles?

A) prophase

B) metaphase

C) prometaphase

D) anaphase

E) telophase

D. anaphase

When motor protein kinesin "walks" along microtubules, the light chain of the kinesin attaches to ______ , and the "feet" (the globular heads) of the kinesin "walk" on the _____

an organelles; tubulins in a microtubule

You wish to inhibit the contraction of muscle in vitro as a control for an experiment you are conducting. To do this, which of the following would you use?

A) ATPase inhibitors.

B) contractionase.

C) serotonin.

D) dyneinase.

E) mysoinase II.

A. ATPase inhibitors

DNA fragment A and fragment B have similar length. Fragment A's melting temperature (™) is 60 degrees C, and its G-C content is 55%. Fragment B's melting temperature is 40 degrees C so fragment B's G-C content.

should be lower than 55%

*Which of the following is the correct order of the levels of DNA packaging in a dividing eukaryotic cell?

nucleosome -> 30 nm chromatin fiber -> looped domains -> heterochromatin

*The phase of the cell cycle associated with the replication of DNA is

interphase

In a eukaryotic cell, the large and small ribosomal subunits are assembled

in the nucleolus

*DNA replication is

A. non-conservative.

B. irregular.

C. conservative.

D. semi-conservative.

E. none of the above.

D. semi-conservative

*Older people often find that their joints are less flexible, and their skin becomes wrinkled. These changes are caused by

A) increasingly cross-linked collagens and loss of elastins in the tissues.

B) increasingly cross-linked elastins and loss of collagens in the tissues.

C) increasingly cross-linked proteoglycan and loss of fibronectins in the tissues.

D) increasingly cross-linked fibronectins and loss of proteoglycan in the tissues.

E) None of the above.

A) increasingly cross-linked collagens and loss of elastins in the tissues.

A plant cell has

A) one genomes: a nuclear genome.

B) two genomes: a nuclear genome and a mitochondrial genome.

C) three genomes: a nuclear genome, a mitochondrial genome and a chloroplast genome.

D) four genome: a nuclear genome, a mitochondrial genome, a chloroplast genome and an ER genome.

E) many genomes.

C) three genomes: a nuclear genome, a mitochondrial genome and a chloroplast genome.

Smaller molecules (less than 20,000 Daltons) go into the nucleus by

A) active transport through the nuclear pores.

B) passive diffusion through the nuclear pores.

C) active transport through specialized transporters.

D) passive diffusion without aid of any transport proteins.

E) none of the above.

B) passive diffusion through the nuclear pores.

*In paracrine signaling, the signaling molecule

A) acts on cells in close proximity to the secreting cell.

B) acts on target cells far away from the secreting cell.

C) acts on the same cells that secreted the signaling molecule.

D) is carried to the target cells by the blood.

E) None of the above.

A) acts on cells in close proximity to the secreting cell.

*Which of the following statement about a G protein-coupled receptor is true?

A) It contains seven transmembrane domains.

B) When activated, its extracellular domains activate the G-proteins.

C) When activated, its cytoplasmic domains activate the G-proteins.

D) A) and B).

E) A) and C).

E. A and C

*In the activation of epidermal growth factor receptors (receptor tyrosine kinases), the activation process proceeds in the order of

A) ligand binding -> transphosphorylation -> dimerization.

B) ligand binding -> dimerization -> transphosphorylation.

C) dimerization -> ligand binding -> transphosphorylation.

D) transphosphorylation -> ligand binding -> dimerization .

E) none of the above

B. ligand binding -> dimerization -> transphosphorylation

*Which of the following statement about Ras protein is correct?

A. Ras protein acts as a molecular switch changes between the active

B) GDP-Ras complex is inactive

C) GTP-Ras complex is active

D) all of the above.

E) none of the above.

D. All of the above

*In cells, cAMP mediated pathways are turned on by ________, and turned off by ________________.

Adenylyl cyclase;

phosphodiesterase

*In the microtubule-based movements, microtubules

A) directly binds to organelles and transport them to different locations.

B) directly binds to vesicles and transport them to different locations.

C) functions as a set of tracks for the transport.

D) All of the above

E) None of the above.

C. Function as a set of tracks for the transport

During muscle contractions, the cross-bridges are formed between ______ and _________.

A) the beta-tubulin in microtubules and the motor protein kinesin.

B) the myosin head of the thick filament and the F-actin of the thin filament.

C) the F-actin of the thin filament and tropomyosin of the thick filament.

D) the F-actin of the thin filament and troponin of the thick filament.

E) the tropomyosin of the thick filament and troponin of the thin filament.

B) the myosin head of the thick filament and the F-actin of the thin filament.

*Nucleosome core particle consists of ______, and ________.

about 146 base pairs of DNA;

8 molecules of histone proteins

Euchromatin is:

A. transcriptionally active

B. transcriptionally inactive

C. the tightly packed chromatin

A. transcriptionally active

Mitochondria and chloroplast

A. are dependent on the near genome to encode all of their proteins

B. are able to code for all of their proteins

C. are semiautonomous: are able to code for most of their proteins, but dependent on the nuclear genome to encode a small portion of them.

D. are semiautonomous: are able to code for some of their proteins, but dependent on the nuclear genome to encode most of them.

E) none of the above.

D. are semiautonomous: are able to code for some of their proteins, but dependent on the nuclear genome to encode most of them.

The latest estimate of the number of genes in human genome is

A) approximately 35,000.

B) less than 10,000.

C) more than 100,000.

D) approximately 25,000.

E) approximately 50,000.

D. approximately 25,000

Nuclear export is used mainly for _________, whereas nuclear import is devoted largely to __________.

exporting RNA molecules;

importing proteins

In some animal tissue, epithelial cells secret growth factor PDGFs, which in turn stimulate the nearby fibroblast cells. This type of signaling belongs to

A) endocrine signaling.

B) paracrine signaling.

C) autocrine signaling.

D) signaling by plasma membrane-attached proteins.

E) non of the above.

B. paracrine signaling

Which of the following molecules usually CANNOT pass the gap junctions from one cell to another cell?

A) ions

B) amino acids

C) glucose molecules

D) nucleotides

E) proteins

E. proteins

The type A bacteria were isolated from a hot spring where the temperature is around 95C, and the type B bacteria were isolated from soil where the temperature is in the range of 10C-30C. The G-C content in the genome of

the type A bacteria should be ________________ that in the genome of the type B bacteria.

higher than

What is chromatin that remains compacted during interphase called?

A) granular chromatin

B) euchromatin

C) anabolic chromatin

D) heterochromatin

E) homochromatin

D. heterochromatin

Which of the following statements is (or are) correct about the nucleolus?

A. There may be more than one nucleoli in the nucleus.

B. The nucleolus is the site where the ribosome subunits are assembled.

C. The nucleolus is wrapped by one membrane.

D. Both A) and B).

E. Both B) and C).

D. Both A and B

Which of the following activities is not normally supported by the nuclear pores in a eukaryotic cell?

A. Export the ribosome subunits out of the nucleus.

B. Export the tRNAs out of the nucleus.

C. Export the mRNAs out of the nucleus.

D. Export the proteins required for transcription out of the nucleus.

E. All of the above.

D. Export the proteins required for transcription out of the nucleus

Which of the following statement is NOT correct concerning DNA replication?

A. Synthesis at each replication fork is continuous in the direction of fork movement for the leading strand, but discontinuous in the opposite direction for the lagging strand.

B. The discontinuous synthesis of DNA involves short intermediates called Okazaki fragments.

C. The Okazaki fragments in DNA replication are synthesized in the 3' -> 5' .

D. The matured Okazaki fragments are joined together by DNA ligase

E. None of the above.

C. The Okazaki fragments in DNA replication are synthesized in the 3' -> 5'

During mitosis, the chromosomes are separated by mitotic spindle, which is largely composed of

A) microtubules

B) microfilaments.

C) intermediate filaments.

D) DNAs

E) RNAs.

A. microtubules

Cytokinesis divides

A. cellular proteins .

B. cellular DNAs.

C. cellular RNAs.

D. the cytoplasm.

E. cellular DNA, RNA and proteins.

D. the cytoplasm

Approximately what percentage of the human genome sequence represents protein coding sequence.

A) around 2%

B) around 50%

C) around 60%

D) around 70%

E) virtually 100%

A. around 2%

How do cells receive and transduce signals?

(3 things)

-G-protein coupled receptor-mediated signaling

-Protein kinase receptor-mediated signaling

-Steroid hormone receptor-mediated signaling

The ability of a cell to translate a receptor-ligand interaction to changes in its behavior or gene expression.

Signal transduction

A signaling molecule (e.g., hormone, pheromone, ion, neurotransmitter, drug).

Ligand

A protein molecule, embedded in either the plasma membrane or cytoplasm of a cell, to which a mobile signaling (or "signal") molecule may attach.

Receptor

In animals, signaling by extracellular

molecules can be classified into 4 types

What are those 4 types?

-Endocrine

― Paracrine

― Autocrine

― Signaling by plasma membrane-attached proteins

Hormone released by endocrine cell and carried in bloodstream to distal target cells

Endocrine signaling

signaling molecules only affect target cells in close proximity to secreting cells

Paracrine signaling

cells respond to substances that they themselves release, affect target sites on same cell

Autocrine signaling

Membrane-bound proteins can interact to signal; what type of signaling is this?

Signaling by plasma membrane-attatched proteins

a small signal produces many cell responses.

Signal amplification

What are the 6 steps of signal transduction?

1. Protein kinase 1

2. Protein kinase 2

3. Protein kinase 3

4. Transcription factor

5. DNA

6. mRNA

receptors embedded in the plasma membrane.

Plasma membrane receptors

What are the 2 common classes of Plasma membrane receptors?

G-protein-coupled receptors and protein kinase receptors.

receptors located inside the cell rather than on its cell membrane.

Intracellular receptors

Ex: estrogen, and other hormone receptors are inside the cell

What does G-proteins stand for?

Guanine nucleotide-binding proteins.

______ act like molecular switches, changing

between "on" and "off" states.

G-proteins

There are more than ____ G-protein-coupled receptors (GPCRs), that account for 5% of human total genes

1000 GPCRs

GPCRs contain ____ transmembrane domains

7

A ligand binds to the extracellular portion of the receptor, causing an intracellular portion of the receptor to bind and activate a ______

G protein

What are the 6 classes of intermediate filaments used for?

for diagnostic medicine.

ALL receptors are ___

Proteins

Type of signaling for "long distances"

-Like sending a letter

Endocrine

Type of signaling for "Localized" substances

Paracrine

"Self signaling"

Autocrine