Exam 1 HW Questions

You wake up and grab your phone from the bedside table. The weather app tells you it will get very hot this afternoon. As a result, you decide to wear shorts. This is an example of

feedforward regulation

A sensor detects an increase in the amount of a certain substance; this causes an effector to produce more of that substance. This is

positive feedback

When your stomach is empty, you get hungry, so you eat. When your stomach is full, you stop being hungry and so you stop eating (at least we hope it works this way). This would be an example of

negative feedback

Suppose that your body temperature goes up and you start to feel hot, so you take off your sweatshirt. Then your body temperature goes down and you start to feel cold, so you put your sweatshirt back on. This is an example of

negative feedback

If the amount of a substance is controlled by negative feedback, a decrease in the amount of the substance leads to

an increase in production of the substance

Which organism is likely to have the highest mass-specific metabolic rate?

a. Elephant (3000 kg)

b. Shrew (7 g)

c. Blue whale (175,0000 kg)

Shrew (7g)

Which organism is likely to have the highest absolute metabolic rate?

a. Elephant (3000 kg)

b. Shrew (7 g)

c. Blue whale (175,0000 kg)

Blue whale (175,000 kg)

Na⁺ (a sodium ion) binds to a protein in a cell membrane at one binding site and an amino acid binds to the same protein at another binding site. When the protein changes shape, both the Na⁺ and the amino acid move from the outside to the inside of the cell. This is an example of

secondary active transport

The sodium-potassium (Na⁺/K⁺) pump

uses adenosine triphosphate (ATP)

If molecules are crossing a lipid bilayer that contains no proteins, the molecules could be moving across via which one of these?

simple diffusion

Which of the following is true of every voltage-gated ion channel?

a. it is a protein

b. it only allows certain kinds of ion to pass through it

c. it can change shape if the membrane potential changes

all of the above

Osmosis involves

diffusion of water molecules

The equilibrium potential for potassium (E_K) is typically about

-90 mV

The resting membrane potential of a cell would be more negative than normal if

all sodium (Na⁺) channels were removed from the cell membrane

Which of the following normally contributes to cells having a negative resting potential?

sodium-potassium (Na⁺/K⁺) pumps

Which of the following would make the resting potential of a cell more negative?

increasing the membrane permeability to potassium (K⁺)

Which of the following would make the resting potential of a cell less negative?

a. increasing the membrane permeability to sodium (Na+)

b. increasing the extracellular sodium (Na+) concentration

c. decreasing the membrane permeability to potassium (K+)

all of the above

Na⁺/K⁺ pumps

a. move Na+ into the cell and move K+ out of the cell

b. have the net effect of making a cell’s membrane potential less negative

c. move Na+ and K+ down their concentration gradients and so do not use energy

none of the above

Substances only move down their concentration gradient, from higher to lower concentration, in

facilitated diffusion

A protein in a cell’s membrane binds both a sodium ion (Na⁺) and a molecule of substance Q at the same time. The protein changes shape and both Na⁺ and Q move across the membrane. Na⁺ moves from the side where it is more concentrated to the side where it is less concentrated. Q moves from the side where it is less concentrated to the side where it is more concentrated. No ATP is used. This is an example of

secondary active transport

During secondary active transport, a molecule or ion

 

moves against its concentration gradient

A neuron's resting potential is typically nearest the equilibrium potential for

 

potassium ions (K⁺)

Which of the following would make the sodium equilibrium potential (E_Na) of a cell less positive?

a. decreasing the membrane permeability to potassium (K+)

b. increasing the extracellular sodium (Na+) concentration

c. increasing the membrane permeability to sodium (Na+)

none of the above

If we could add open Na⁺ (sodium) channels to the cell membrane of a typical neuron at rest, this would

depolarize the neuron

For a cell at a typical resting potential, which of the following types of ions typically would have a net movement against its electrical gradient (assuming the membrane is permeable to this ion)?

 

potassium (K⁺)

Which of the following is typically more concentrated inside a cell?

 

potassium (K+) 

Each time a sodium/potassium (Na⁺/K⁺) pump functions

 

the inside of the cell becomes more negative

Which of the following normally involves the breakdown of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and phosphate?

 

operation of sodium-potassium pumps

Which of the following contributes to making a typical cell more negative on the inside than the outside?

a. a higher concentration of potassium ions (K+) inside the cell than outside it

b. sodium/potassium (Na/K) pumps

c. impermeant anions inside

all of the above

If a cell changes its membrane potential from -70 mV to -50 mV, it has been

depolarized

If we magically increase the concentration of potassium ions (K⁺) in the interstitial fluid that surrounds a typical neuron at rest, this will

depolarize the neuron

In your cells, an equilibrium potential of +60 mV is typical for

sodium (Na+)

During a neuronal action potential, membrane depolarization triggers

a. opening of sodium (Na+) channels

b. opening of potassium (K+) channels

c. inactivation of sodium (Na+) channels

all of the above

During a neuronal action potential, there is a net flux out of the cell of which of the following?

potassium

Repolarization follows the peak of an action potential partly because

Na+ (sodium) channels inactivate

Myelinated axons conduct action potentials faster than unmyelinated axons of the same diameter because

 

the flow of Na⁺ and K⁺ ions is concentrated in the unmyelinated spaces

In a neuron, opening 100 times more Cl- channels than either Na+ or K+ channels would

make an action potential less likely to occur

As an action potential propagates along an axon from the axon hillock to the axon terminals, the action potential

stays the same size

In general, how is intensity of a neural signal communicated via a neuron?

 

By increasing the frequency of successive action potentials.

Which of these happens last during an action potential?

closing of potassium (K+) channels

A neurotransmitter is released from an axon terminal and diffuses across a synapse to inhibit a chemically-gated K+ channel. With these channels inhibited, the membrane permeability of K+ decreases by a factor of 10. What effect will this have on the membrane potential?

membrane potential will become more positive

An inhibitory postsynaptic potential (IPSP) is produced at a particular chemical synapse. If the extracellular calcium (Ca²⁺) concentration outside the presynaptic axon terminal is decreased, the postsynaptic potential will

become a smaller IPSP