Chapter 6: Cell Interactions

Question 1

Facilitated Diffusion

Answer 1

Passive, carrier-mediated

Question 2

Active Transport

Answer 2

Requires energy (ATP), carrier-mediated
- move from low to high concentration

Question 3

Simple Diffusion

Answer 3

Through the PM or nonspecific channels
Non-carrier-mediated

Question 4

Mean Diffusion Time

Answer 4

Average time it takes for a solute to diffuse

Question 5

Rate of Diffusion depends on: (5)

Answer 5

1. Concentration gradient
2. Membrane permeability
3. Temperature
4. Surface area of membrane
5. Distance solute must travel

Question 6

Osmotic Pressure

Answer 6

force required to stop osmosis, describes the osmotic pull of a solution (how strongly it draws water by osmosis)
- More [solute] = higher osmotic pressure
- pure H2O = 0 osmotic pressure

Question 7

Molarity

Answer 7

= moles solute/Kg solute

Question 8

Osmolarity

Answer 8

= total molarity of solution (all solutes added together)

Question 9

Tonicity

Answer 9

effect of a [solute] on the osmosis of water
- takes into account membrane permeability

Question 10

Hypotonic

Answer 10

More [solute] in cell than outside
H2O moves INTO the cell
- Cell will burst (hemolysis)

Question 11

Hypertonic

Answer 11

More [solute] outside cell than in
H2O moves OUT of the cell
- Cell will shrivel (crenate)

Question 12

Osmoreceptors

Answer 12

in hypothalamus
detect increases in osmolarity (dehydration)
- triggers ADH release = lowers excretion of H2O

Question 13

Tm

Answer 13

Transport Maximum
All carriers are in use, no greater rate of transport can occur

Question 14

Glucose transport carriers:

Answer 14

GLUT
GLUT1: CNS
GLUT2: pancreatic beta cells + hepatocytes
GLUT3: neurons
GLUT4: adipose tissue + skeletal muscles

Question 15

Primary Active Transport

Answer 15

hydrolysis of ATP is directly responsible for carrier protein function
transport protein = ATPase (hydrolyze ATP)

Question 16

ATPase pumps ___ Na+ in/out of the cells and ___ K+ in/out of the cell (via Na+/K+ pumps)

Answer 16

3 Na+ and 2 K+

Question 17

Secondary Active Transport

Answer 17

“coupled transport”
symport or antiport

Question 18

Synport

Answer 18

molecules move together in same direction

Question 19

Antiport

Answer 19

molecules move in opposite directions

Question 20

Concentrations of Na+, K+, and Ca+ in and out of the cell

Answer 20

IN/OUT:
Na+ = 12mM/145mM
K+ = 150mM/5mM
Ca+ = 0.0001mM/2.5mM

Question 21

Potential difference

Answer 21

Measured in voltage (V) using Nernst equation

Question 22

Potential difference for Na and K

Answer 22

+66 mV and -90 mV

Question 23

Nernst Equation

Answer 23

Ex = 61 * log [Xo]/[Xi]

Question 24

Resting Membrane Potential

Answer 24

potential of a cell not producing impulses
- most cells between -65 mV to -85 mV
- Neurons = -70 mV

Question 25

Autocrine

Answer 25

regulatory molecules act on the same cell that releases the chemical

Question 26

Paracrine

Answer 26

Cells within an organ secrete molecules that diffuse across extracellular space to nearby target cells
- “local signalling”

Question 27

Synaptic

Answer 27

involves neurons secreting neurotransmitters across a synapse to target cells

Question 28

Endocrine

Answer 28

involves glands secreting hormones into the blood-stream
- can reach multiple target cells

Question 29

Second Messengers

Answer 29

Steps:
1. signaling molecule binds to a receptor
2. activates an enzyme to produce messenger from ATP
3. messenger activates other enzymes in cytoplasm
4. cell activates change in response

ie. cAMP

Question 30

G-Proteins

Answer 30

Shuttle between receptor proteins and enzyme proteins, 3 subunits
- one subunit dissociates when a signal molecule binds to the receptor + travels to the enzyme/ion channel