Cell Physiology

Question 1

Which of the following enzymes may be directly activated by ligand binding to G protein-coupled receptors?

Protein kinase A
All answers are correct
Protein kinase C
Phospholipase C

Answer 1

Phospholipase C

Question 2

Which of the following situations does not represent a homeostatic mechanism?

During a hot summer day, a person sweats a lot and keeps body temperature the same.
As age increases, the skin loses its elasticity and becomes wrinkled.
In a cold day, a person shivers to increase production of body heat.
Eating a large serving of salty food increases salt content in the urine.

Answer 2

As age increases, the skin loses its elasticity and becomes wrinkled

Question 3

The property of adaptability allows organisms to:

maintain a state of equilibrium
replace regulatory systems.
modify their responses.
rank multiple control systems

Answer 3

Modify their responses

Question 4

The Na+/Ca2+ exchanger couples the efflux of calcium out of the cell to the influx of sodium into the cell. If inhibition of the Na+/K+-ATPase stops the Na+/Ca2+ exchanger, one can state that Na+/Ca2+ exchange is by:

passive diffusion.
facilitated diffusion.
primary active transport.
secondary active transport

Answer 4

secondary active transport

Question 5

Which of the following 1 L solutions has the highest water concentration?

50 mM glucose, 150 mM NaCl, 10 mM CaCl2
130 mM sucrose, 50 mM KCl, 50 mM CaCl2
300 mM glucose, 25 mM NaCl, 10 mM CaCl2
40 mM sucrose, 50 mM NaCl, 100 mM KCl, 1 mM CaCl2

Answer 5

40 mM sucrose, 50 mM NaCl, 100 mM KCl, 1 mM CaCl2

Question 6

Which of the following is a correct statement?

The % of total body water is always 60% of body weight.
Water does not move between compartments.
Total body water is proportional to lean body mass.
Increased body fat content increases water content as well.

Answer 6

Total body water is proportional to lean body mass

Question 7

Which of the following is more likely to act via G protein-coupled receptors?

Thyroid hormone
Peptide hormones
Progesterone
Cortisol

Answer 7

Peptide hormones

Question 8

Consider the possible relationships between the rate of flux of a molecule and the concentration gradient across the cell membrane shown in the graph below:

Which of the lines represents the function of the Na+/K+ pump) and which the movement of glucose via glucose transporters (e.g., GLUT2), respectively?

Answer 8

Parabolic increase

Question 9

Which of the following cells do not have a nucleus?

Smooth muscle cells
Intestinal epithelial cells
Neurons
Red blood cells

Answer 9

Red blood cells

Question 10

Pores and channels are:

peripheral membrane proteins.
gated.
binding sites for hormones.
integral membrane proteins.

Answer 10

integral membrane proteins

Question 11

Which of the following best describes the role of endocytosis on water and solute movement?

It allows the entry of large macromolecules.
It serves to import lipid-soluble compounds.
It serves to release neurotransmitters.
It couples facilitated diffusion to receptors.

Answer 11

It allows the entry of large macromolecules

Question 12

Which of the following statements about extracellular signals is true?

All signals are small and lipophilic.
Signals can be peptides and proteins.
Signals bind to cellular DNA.
All signals act on intracellular receptors.

Answer 12

Signals can be peptides and proteins

Question 13

Hydrocortisone (a steroid hormone) is used topically to treat poison ivy because it decreases the synthesis of prostaglandins and leukotrienes. Based on its chemistry, hydrocortisone is prepared in:

injectable form.
an oil-based cream.
pills and capsules.
a water-based lotion.

Answer 13

an oil-based cream

Question 14

A female subject continuously recorded her temperature for 30 days. She found that her body temperature fluctuated between 37.5C during the day and 36.9C at night. Which of the following is most likely true?

Warmer daytime temperatures slightly increase her body temperature.
She may have an infection because she has a slight fever during the day.
Her body temperature drops at night because sleep blunts neuronal reflexes.
Her body temperature set point changes during the day and night.

Answer 14

Her body temperature set point changes during the day and night

Question 15

A UK laboratory has discovered a new hormone. The investigators determined that the new hormone is a small lipophilic molecule that is transported in the blood bound to proteins. Based on this information, you predict that the new hormone:

binds to intracellular receptors.
activates phospholipase C.
binds to G protein-coupled receptors.
inhibits gene transcription.

Answer 15

Binds to intracellular receptors

Question 16

The processes of facilitated diffusion and active transport share the following characteristic:

they depend on the Na+/K+-ATPase activity.
both use membrane antiporter molecules.
they need specialized membrane transport molecules.
both use ATP to move molecules against their gradients.

Answer 16

They need specialized membrane transport molecules

Question 17

Dr. Chemist developed a hydrophilic non-ionic, non-dissociable fluorescent dye “X”. In a separate experiment, Dr. Chemist concluded that “X” does not diffuse into human cells. If human red blood cells are placed in a solution of 50 mM NaCl, 40 mM CaCl2, and 100 mM “X”, what would happen?

The cells will shrink first, and then swell.
The cells will shrink.
The cells will not change.
The cells will burst.

Answer 17

The cells will shrink

Question 18

When a chemical messenger functions in an endocrine fashion, it:

binds to intracellular receptors that activate adenylate cyclase.
binds to membrane receptors in neighboring cells only.
reaches target cells after being transported in the blood.
activates receptors that stimulate gene transcription.

Answer 18

reaches target cells after being transported in the blood

Question 19

Emily is a senior living in a dormitory without air conditioning. On a hot summer day, Emily finds herself hot and sweating profusely. Yet, when she checks her temperature with a thermometer, it shows 98.5F (normal for healthy subjects). Which of the following represents an effector in this scenario?

Spinal cord
Temperature-sensitive sensory neuron
Hypothalamus
Sweat gland

Answer 19

Sweat gland

Question 20

Interferon is a cytokine (chemical signal) produced by cells infected with viruses. When
secreted, it acts on neighboring cells of the same tissue. That means that interferon
behaves as:

a. an endocrine signal.
b. a paracrine signal.
c. an autocrine signal.
d. an exocrine signal.

Answer 20

a paracrine signal

Question 21

In contrast to a steady state, in a state of equilibrium:

a. energy is used to hold a parameter at a certain value.
b. the parameter must be held at a fixed value.
c. two open systems interact with each other.
d. the parameter does not need to be regulated.

Answer 21

the parameter does not need to be regulated

Question 22

Which of the following statements about steady states is correct?

a. Inputs must equal outputs.
b. Parameters cannot change.
c. Positive balances are common.
d. They are always regulated by positive feedback.

Answer 22

inputs must equal outputs

Question 23

Compared to the plasma, the interstitial fluid has:

a. less sodium, more proteins.
b. more calcium, same chloride
c. less proteins, same potassium
d. only potassium, no sodium

Answer 23

less proteins, same potassium

Question 24

An athlete passed out after running sprints on an extremely hot day. A quick check of his
vital signs showed his body temperature was 102F. A short while later, body temperature
rose to 103F and then to 105F. The athlete was submerged in an iced water bath; that
brought his body temperature to 97F. However, body temperature then increased to 98.6F.
Which of the following statements is most likely TRUE?

a. The rising body temperature is likely due to positive feedback.
b. The body’s temperature set point changed to 105F temporarily to help the athlete run
faster.
c. The athlete lacks the normal homeostatic set point for body temperature.
d. The athlete’s body temperature would have eventually cooled to 98.6F without the ice
bath.

Answer 24

the rising body temperature is likely due to positive feedback

Question 25

The diffusion coefficient (D) from Fick’s first law of diffusion accounts for:

a. the area available for diffusion.
b. the charge of the molecule.
c. the thickness of the membrane.
d. how lipid soluble the molecule is.

Answer 25

how lipid soluble the molecule is

Question 26

Compared to a typical eukaryotic cell (300 mOsm/L), a solution consisting of 50 mM CaCl2
+ 50 mM NaHCO3 + 50 mM urea will be:

a. isosmotic.
b. hyperosmotic.
c. it cannot be determined.
d. hyposmotic.

Answer 26

isosmotic

Question 27

When the transport rate of a membrane transport protein reaches a maximal velocity that
does not change even when the concentration gradient of its substrate increases, we can
say that the transport protein is a:

a. gated channel
b. solute carrier
c. pore
d. sodium channel

Answer 27

solute carrier

Question 28

Digitalis is a drug that inhibits the Na+ /K+ -ATPase in the cardiac muscle cells. Digitalis
likely_________ Na+ concentration inside cardiac muscle cells. The change in Na+
concentration likely ___________ the secondary active transport of glucose through the
Na+ /glucose symporter.

a. increases — decreases
b. increases — increases
c. decreases — decreases
d. decreases — increases

Answer 28

increases – decreases

Question 29

Testosterone is a small lipid-soluble steroid hormone; therefore, it is likely to enter cells via:

a. endocytosis.
b. facilitated diffusion.
c. passive diffusion.
d. pinocytosis.

Answer 29

passive diffusion

Question 30

Which of the following is not a step in a typical cell signaling pathway?

a. Ligand binding induces an intracellular signal.
b. Nuclear receptors have guanylyl cyclase activity.
c. The outcomes include functional changes.
d. Receptors transduce the extracellular signals.

Answer 30

nuclear receptors have guanylyl cyclase activity

Question 31

In contrast to nuclear receptors, membrane receptors may also induce:

a. changes in protein synthesis.
b. a response to steroid hormones.
c. changes in gene expression.
d. the production of second messengers.

Answer 31

the production of second messengers

Question 32

Which of the following statements about G protein-coupled receptors is true?

a. The G protein subunits dissociate after ligand binding.
b. All lipid-soluble hormones act via G protein-coupled receptors.
c. Their tyrosine kinase activity starts after autophosphorylation.
d. The receptors contain two enzymatic domains.

Answer 32

the G protein subunits dissociate after ligand binding

Question 33

The stimulation of adenylyl cyclase activity may result in:

a. increased intracellular levels of cGMP.
b. inhibition of cAMP phosphodiesterase.
c. increased protein kinase A activity.
d. increased diacylglycerol content.

Answer 33

increased protein kinase A activity