Quiz 5

Question 1

What is most likely to happen to an animal’s target cells that lack receptors for local regulators?

a) They could develop normally in response to neurotransmitters instead.
b) They might not be able to multiply in response to growth factors from nearby cells.
c) They could divide but never reach full size.
d) Hormones would not be able to interact with target cells.
e) They might compensate by receiving nutrients via a factor.

Answer 1

b) They might not be able to multiply in response to growth factors from nearby cells.

Question 2

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

a) relay molecule
b) endocrine molecule
c) receptor
d) signal molecule
e) transducer

Answer 2

d) signal molecule

Question 3

GTPase activity is involved in the regulation of signal transduction because it..?

a) hydrolyzes GTP binding to G protein.
b) converts cGMP to GTP.
c) phosphorylates protein kinases.
d) decreases the amount of G protein in the membrane.
e) increases the available concentration of phosphate.

Answer 3

a) hydrolyzes GTP binding to G protein

Question 4

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following would provide evidence that this is related to cell signaling?

a) Enzymatic activity declines.
b) cAMP levels change very frequently.
c) Growth factor ligands do not bind as efficiently to receptors.
d) Their lower hormone concentrations elicit a lesser response.
e) ATP production decreases.

Answer 4

c) Growth factor ligands do not bind as efficiently to receptors.

Question 5

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

a) Estrogen is kept away from the surface of any cells not able to bind it at the surface.
b) Estrogen has specific receptors inside several cell types, but each cell responds in the same way to its binding.
c) Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding.
d) Estrogen is produced in very large concentration and therefore diffuses widely.
e) The subcomponents of estrogen, when metabolized, can influence cell response.

Answer 5

c) Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding.

Question 6

Which of the following most accurately describes a cyclin?

a) It is activated to phosphorylate by complexing with a Cdk.
b) It activates a Cdk molecule when it is in sufficient concentration.
c) It activates a Cdk when its concentration is decreased.
d) It decreases in concentration when MPF activity increases.
e) It is present in similar concentrations throughout the cell cycle.

Answer 6

b) It activates a Cdk molecule when it is in sufficient concentration.

Question 7

Why do chromosomes coil during mitosis?

Answer 7

to allow the chromosomes to move without becoming entangled and breaking

Question 8

Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called..?

Answer 8

cyclins

Question 9

Which of the following is (are) required for motor proteins to function in the movement of chromosomes toward the poles of the mitotic spindle?

a) ATP as an energy source
b) an MTOC (microtubule organizing center)
c) a kinetochore attached to the metaphase plate
d) intact centromeres
e)synthesis of cohesin

Answer 9

a) ATP as an energy source

Question 10

In which of the following ways do plant hormones differ from hormones in animals?

a) Plant hormones interact primarily with intracellular receptors.
b) Plant hormones may travel in air or through vascular systems.
c) Animal hormones are primarily for mating and embryonic development.
d) Animal hormones are found in much greater concentration

Answer 10

b) Plant hormones may travel in air or through vascular systems.

Question 11

Because most receptors are membrane proteins, which of the following is usually true?

a) They open and close in response to protein signals.
b) They are only attached to one membrane surface (interior or exterior).
c) They preferentially bind with lipid or glycolipid signal molecules.
d) They change their conformation after binding with signal polypeptides

Answer 11

d) They change their conformation after binding with signal polypeptides

Question 12

The function of phosphatases in signal transduction is best described as to

a) prevent a protein kinase from being reused when there is another extracellular signal.
b) inactivate protein kinases and turn off the signal transduction.
c) amplify the transduction signal so it affects multiple transducers.
d) amplify the second messengers such as cAMP.

Answer 12

b) inactivate protein kinases and turn off the signal transduction.

Question 13

Which of the following is the best explanation for the fact that most transduction pathways have multiple steps?

a) Most of the steps were already in place because they are steps in other pathways.
b) Multiple steps in a pathway require the least amount of ATP.
c) Multiple steps provide for greater possible amplification of a signal.
d) Each individual step can remove excess phosphate groups from the cytoplasm.

Answer 13

c) Multiple steps provide for greater possible amplification of a signal.

Question 14

Which of the following describes the events of apoptosis?

a) The cell dies, it is lysed, its organelles are phagocytized, and its contents are recycled.
b) Its DNA and organelles become fragmented, it dies, and it is phagocytized.
c) Its nucleus and organelles are lysed, then the cell enlarges and bursts.
d) Its DNA and organelles are fragmented, the cell shrinks and forms blebs, and the cell self-digests.

Answer 14

d) Its DNA and organelles are fragmented, the cell shrinks and forms blebs, and the cell self-digests.

Question 15

Suppose a biologist can separate one of a dozen pieces of chromatin from a eukaryotic animal nucleus. It might consist of which of the following?

a) one-twelfth of the genes of the organism
b) two chromosomes, each with six chromatids
c) two long strands of DNA plus proteins
d) two chromatids attached together at a centromere

Answer 15

c) two long strands of DNA plus proteins

Question 16

If cells in the process of dividing are subjected to colchicine, a drug that interferes with the formation of the spindle apparatus, at which stage will mitosis be arrested?

a) prophase
b) anaphase
c) metaphase
d) telophase

Answer 16

c) metaphase

Question 17

All cell cycle checkpoints are similar in which way?

a) They respond to the same cyclins.
b) They give the go-ahead signal to progress to the next checkpoint.
c) They each have only one cyclin/Cdk complex.
d) They activate or inactivate other proteins.

Answer 17

d) They activate or inactivate other proteins.

Question 18

Since steroid receptors are located intracellularly, which of the following is true?

a) The receptor molecules are free to move in and out of most organelles.
b) The unbound steroid receptors are quickly recycled by lysosomes.
c) The concentration of steroid receptors must be relatively high in most cells.
d) The receptor molecules are themselves lipids or glycolipids.
e) The steroid/receptor complex can cross the nuclear membrane.

Answer 18

e) The steroid/receptor complex can cross the nuclear membrane.

Question 19

Testosterone functions inside a cell by

a) binding with a receptor protein that enters the nucleus and activates specific genes.
b) acting as a signal receptor that activates tyrosine kinases.
c) acting as a steroid signal receptor that activates ion channel proteins.
d) coordinating a phosphorylation cascade that increases spermatogenesis.

Answer 19

a) binding with a receptor protein that enters the nucleus and activates specific genes.

Question 20

Where do apoptotic signals come from?

a) mitochondrial protein leakage only
b) the nucleus only
c) the ER only
d) ligand binding only
e) all of the above

Answer 20

e) all of the above

Question 21

What is a cleavage furrow?

a) the space that is created between two chromatids during anaphase
b) a ring of vesicles forming a cell plate
c) the separation of divided prokaryotes
d) the metaphase plate where chromosomes attach to the spindle
e) a groove in the plasma membrane between daughter nuclei

Answer 21

e) a groove in the plasma membrane between daughter nuclei

Question 22

A student is looking through his light microscope (~450 X) at a squashed and stained onion root tip. Some, but not all, of the cells have clearly visible chromosome strands.

When the cell has just completed telophase, which of the following does the student see?

a) chromosomes clustered at the poles
b) a clear area in the centre of the cell
c) individual chromatids separating
d) formation of vesicles at the midline
e) two small cells with chromatin

Answer 22

e) two small cells with chromatin

Question 23

For anaphase to begin, which of the following must occur?

a) Kinetochores must attach to the metaphase plate.
b) Cohesin must be cleaved enzymatically.
c) Spindle microtubules must begin to depolymerize.
d) Chromatids must lose their kinetochores.
e) Cohesin must attach the sister chromatids to each other.

Answer 23

b) Cohesin must be cleaved enzymatically.

Question 24

Apoptosis protects healthy “neighbours” from a dying cell by preventing..?

a) release of cellular energy that would interfere with the neighbours’ energy budget.
b) bits of membrane from the dying cell merging with neighbours and bringing in foreign receptors.
c) cell death spreading from one cell to the next via paracrine signals.
d) neighbouring cells activating immunological responses.
e) lysosomal enzymes exiting the dying cell that would damage surrounding cells.

Answer 24

e) lysosomal enzymes exiting the dying cell that would damage surrounding cells.

Question 25

Which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding?

a) autocrine signalling
b) endocrine signalling
c) hormonal signalling
d) paracrine signalling
e) synaptic signalling

Answer 25

d) paracrine signalling

Question 26

Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?

a) centromere
b) kinetochore
c) chromatid
d) centriole
e) centrosome

Answer 26

e) centrosome

Question 27

If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?

a) 20
b) 10
c) 80
d) 40
e) 30

Answer 27

b) 10

TIP:
remember, cell already copied DNA it wouldn’t be double. the cell needs to split to create daughter cells so each gets half of centromeres.

Question 28

Why do neurons and some other specialized cells divide infrequently?

a) They show a drop in MPF concentration.
b) They no longer have active nuclei.
c) They can no longer bind Cdk to cyclin.
d) They no longer carry receptors for signal molecules.
e) They have been shunted into G0

Answer 28

e) They have been shunted into G0

Question 29

The extracellular matrix is thought to participate in the regulation of animal cell behaviour by communicating information from the outside to the inside of the cell via which of the following?

a) plasmodesmata
b) gap junctions
c) the nucleus
d) DNA and RNA
e) integrins

Answer 29

e) integrins

Question 30

Only once all kinetochores are attached to spindle microtubules can ________ proceed.

a) synthesis
b) G0
c) anaphase
d) metaphase
e) MPF

Answer 30

c) anaphase

Question 31

The centromere is a region in which

a) chromosomes are grouped during telophase.
b) the nucleus is located prior to mitosis.
c) new spindle microtubules form at either end.
d) chromatids remain attached to one another until anaphase.
e) metaphase chromosomes become aligned at the metaphase plate

Answer 31

d) chromatids remain attached to one another until anaphase.

Question 32

Which of the following describe(s) cyclin-dependent kinase (Cdk)?

a) Cdk is inactive, or “turned off,” in the presence of cyclin.
b) Cdk is present throughout the cell cycle
c) Cdk is inactive, or “turned off,” in the presence of cyclin and it is present throughout the cell cycle.
d) Cdk is an enzyme that attaches phosphate groups to other proteins.
e) Cdk is present throughout the cell cycle and is an enzyme that attaches phosphate groups to other proteins.

Answer 32

e) Cdk is present throughout the cell cycle and is an enzyme that attaches phosphate groups to other proteins.

Question 33

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?

a) G0
b) G1
c) M
d) S
e) G2

Answer 33

e) G2

Question 34

A molecule that specifically binds to another molecule (often a larger one) is known as a(n)

a) transcription factor.
b) receptor
c) scaffolding protein
d) activator.
e) ligand.

Answer 34

e) ligand.

Question 35

How do hydrophobic (H2O fearing) molecules get across cell membranes?

Answer 35

Diffuse easily across the membrane

Question 36

When a glucose molecule binds to a glucose carrier protein, what happens to the protein?

Answer 36

protein changes shape & function

Question 37

How do polar molecules like ions (K+, Na+) cross cell membranes?

Answer 37

by using carrier or channel proteins

Question 38

In this simplified model of taste cell (recall: apical end has lots of microvilli, and basal end is bottom edge), how many different types of transport proteins are involved (directly or indirectly) in the transport of glucose through this intestinal epithelial cell?

Hint: there are roughly 3 green proteins on the diagram, only 2 are directly involved

Answer 38

there are 3 types