Chapter 5

Question 1

The proteins that are almost always present in the plasma membrane and permit water to pass freely through the membrane are called what?

Answer 1

Aquaporins

Question 2

Define Osmosis.

Answer 2

Net diffusion of water across a semipermeable membrane.

Question 3

In order for (net) osmosis to occur what conditions must be met?

Answer 3

1. Concentration of water must be different

2. Membrane permeable to water AND impermeable to a solute.

Question 4

What is the osmotic concentration blood plasma (ECF)?

Answer 4

~ (about) 300mOsM (million Osmolar)

Question 5

What would happen to the osmotic concentration of the blood if you ate many potato chips without drinking fluids?

Answer 5

Concentrations would increase

Question 6

Define isotonic.

Answer 6

no change in cell volume

Question 7

Define hypotonic.

Answer 7

cell volume increases; water enters the cell

“hippo-hypo”

Question 8

Define hypertonic.

Answer 8

sucks water from a cell; cell volume decreases

Question 9

Define simple diffusion. Make a list of the important molecules that move by simple diffusion.

Answer 9

Diffusion directly across the phospholipid bilayer of a membrane. (O2, CO2, lipid steroid testosterone)

Question 10

What about simple diffusion could be considered an advantage to a cell? Disadvantage?

Answer 10

Advantage - Molecules pass through quickly - fast

Disadvantage - Not good control

Question 11

Make a list of important molecules that cross cell membrane by diffusion through channel proteins.

Answer 11

Na+, K+, Cl-

Question 12

Explain how protein-carriers are different from channel proteins.

Answer 12

Channel proteins require a protein to open the channel whereas protein-carriers change the shape of the channel (protein) in order for it to open.

Question 13

What about facilitated diffusion (as a process) could be considered advantageous to a cell?

Answer 13

1. Uses no ATP

2. Provides cell with control

Question 14

Define active transport.

Answer 14

Requires cellular ATP to move molecules across the cell membrane against the concentration gradient.

Question 15

Where are somatic motor neurons located in the spinal cord?

Answer 15

in the ventral horn

Question 16

What is the name of the protein that generates and maintains the gradients for Na+ and K+ in a living cell?

Answer 16

Na+/K+ Pump

Question 17

Which structural type(s) of neurons may be sensory?

Answer 17

Bipolar, unipolar

Question 18

Which structural type(s) of neurons may be motor?

Answer 18

Multipolar

Question 19

Define (net) diffusion

Answer 19

Movement of molecules from high to low concentration.

Question 20

Provide a mechanistic explanation as to why diffusion occurs.

Answer 20

It occurs in order to make an even concentration throughout.

Question 21

Define passive transport.

Answer 21

Does not require ATP to move molecules across membrane - uses potential energy stored in concentration (Facilitated diffusion)

Question 22

List the factors that influence the rate at which molecules diffuse. Explain how changes in each will affect the rate of diffusion.

Answer 22

1. The higher the gradient, the faster the diffusion rate
2. Diffusion is faster over short distances
3. The higher the temperature, the faster the rate of diffusion
4. Smaller molecules diffuse more quickly

Question 23

What is the gradient?

Answer 23

the difference between concentrations.

Question 24

Briefly explain what protein-mediated transport is.

Answer 24

a protein “mediates” or makes it happen.

Question 25

What about channel proteins can be considered advantageous? disadvantage?

Answer 25

Advantages: 1. Does not need ATP, 2. Gives cell control Disadvantages:

Question 26

Define facilitated diffusion. List the important molecules that are moved by facilitated diffusion.

Answer 26

Transport that is passive and moves molecules down their concentration gradient stopping when concentrations are equal on both sides of the membrane. Glucose, sodium, chloride (GLUT4)

Question 27

Describe in detail the activity of calcium pumps found in the sarcoplasmic reticulum of skeletal muscle cells.

Answer 27

ATP is used to power the pump which moves Ca+ out of the cell.

Question 28

Describe in detail the activity of the Sodium/Potassium pump. In which body cells are these proteins found?

Answer 28

Found in all body cells. The Na+/K+ pump maintains the gradients for sodium and potassium in a living cell by pumping in K+ and pumping out Na+. The ECF is almost all Na+ and the ICF is almost all K+. 30-60% of BMR goes to powering this pump. It cost 1 ATP to move 3 Na+ ions out and 2 K+ in.

Question 29

Where is most of the sodium found in the body?

Answer 29

ECF

Question 30

Where is most of the potassium found in the body?

Answer 30

ICF

Question 31

Define the term "Resting Membrane Potential" (RMP)

Answer 31

difference in charge across the cell membrane when the cell is at rest (measured in mV)

Question 32

Which ion is the most important in determining the resting membrane potential (RMP)?

Answer 32

K+ (potassium)

Question 33

what is osmolarity?

Answer 33

the expression of concentration for biological solutions; the number of osmotically active particles per liter of solution. Expressed in osmoles per liter (OsM)

Question 34

What is the equation for converting between molarity and osmolarity?

Answer 34

molarity (mol/L) x particles/molecule (osmol/mol) = osmolarity (OsM)

Question 35

Define isosmotic

Answer 35

two solutions containing the same number of solute particles per unit volume.

Question 36

Define hyperosmotic

Answer 36

If solution with higher osmolarity than another solution

Question 37

Define hyposmotic

Answer 37

A solution that has fewer osmoles per unit volume than another solution.

Question 38

Define tonicity

Answer 38

a measure of the effective osmotic pressure gradient (as defined by the water potential of the two solutions) of two solutions separated by a semipermeable membrane

Question 39

Which structural type(s) of neurons may be sensory?

Answer 39

Unipolar, sometimes bipolar

Question 40

Which structural type(s) of neurons may be motor?

Answer 40

multipolar

Question 41

Which structural type(s) of neurons may be association?

Answer 41

multipolar

Question 42

The cell bodies of somatic motor neurons in the spinal cord are typically found in the what?

Answer 42

gray matter of the ventral horn of the spinal cord

Question 43

The cell bodies of somatic sensory neurons are typically found where in the body?

Answer 43

in the ganglia throughout the spine

Question 44

What happens to the RMP as the extracellular K+ is increased? Use on of the following pairs of terms to describe this: (more/less, negative/positive)

Answer 44

More negative (repolarization)

Question 45

What generates the gradients for Na+ and K+ in a living cell.

Answer 45

Sodium Potassium pump

Question 46

What could happen to the membrane potential of a person's cells if his ECF concentration of K+ was elevated?

Answer 46

becomes more negative - possible Hyperpolarization?

Question 47

If Na+ channels were suddenly opened in a resting neuron what would happen to the MP?

Answer 47

it would become more positive (depolarization)

Question 48

What was the threshold voltage to generate an action potential (AP)?

Answer 48

-55mV

Question 49

State the law that describes the action potential threshold property.

Answer 49

All or none

Question 50

Explain the mechanism of the action of lidocaine. Explain how it is a useful compound in medicine.

Answer 50

Lidocaine is a voltage-gated Na+ channel blocker. Without Na+ flowing in, the AP stops and won't send the pain sensation to your brain. It is useful in surgeries and other invasive procedures.

Question 51

What is the effect of increasing stimulus intensity on AP frequency?

Answer 51

There would be no effect to the AP as it will always be the same - The intensity would be encoded in the signal.

Question 52

What 2 factors influence conduction velocity?

Answer 52

1. the presence of schwann cells with knodes of Ranvier | 2. Neuron size - the larger the neuron, the more energy can flow

Question 53

What is the resting membrane potential of a typical neuron?

Answer 53

-70mV

Question 54

What is the threshold of a typical neuron?

Answer 54

-55mV

Question 55

What is the action potential of a typical neuron?

Answer 55

+30mV

Question 56

What is the depolarization phase of an action potential? What is happening during this phase?

Answer 56

The phase in which membrane potential becomes more positive (-70mV - +30mV) Na+ is entering the cell

Question 57

What is the repolarization phase of an action potential? What is happening during this phase?

Answer 57

The phase in which membrane potential become more negative; membrane potential moves back toward the resting membrane potential (+30mV - -70mV)

Question 58

What is hyperpolarization? What is happening during this phase?

Answer 58

The membrane potential becomes lower than resting potential (more negative than -70mV). It is due to the slow closing of the K+ channel.

Question 59

When drawing an Action Potential what is the y axis labeled? What is the x axis labeled?

Answer 59

Y-axis - Membrane Potential (mV) (bottom -90mV up to +30mV) | X-axis - Time (msec) (left 0 to right, about 4

Question 60

What is the absolute refractory period?

Answer 60

the delay that happens after the first action potential has begun, before the second can be triggered (the period of time which no new AP can be formed - the time required for the Na+ channel gates to reset to their resting positions - about 1-2msec)

Question 61

What is the relative refractory period?

Answer 61

follows the absolute refractory period. During this time some, but not all, Na+ channel gates have reset to their original positions and some K+ channels are still open.