Cellular Interactions and Cell Membrane Transport

Question 1

define the extracellular matrix (ECM)

Answer 1

cells that make up tissues/organs are embedded in extracellular material

Question 2

what is the ECM made of

Answer 2

protein fibres, ground substance, and integrins

Question 3

how are cells able to communicate with each other

Answer 3

by secreting chemical regulators into the extracellular environment

Question 4

how can it be said that cells have a give-and-take relationship with their extracellular environment

Answer 4

cells receive nourishment from it, and they release wastes to it

Question 5

what are fluid-filled compartments separated by

Answer 5

epithelial membranes

Question 6

where is transport occurring between intracellular and extracellular environments

Answer 6

across the plasma membrane

Question 7

why are membranes important for transport

Answer 7

acts as a regulator for the passage of fluid b/w compartments (most made up of water)

Question 8

why is water an important solvent?

Answer 8

it can interact with large (proteins) and small (inorganic ions, sugars, amino acids), molecules

Question 9

draw a flowchart of the body fluid compartments

Answer 9

total body water splits into intracellular (67%) and extracellular fluids; extracellular fluid splits into interstitial fluid (80%) and blood plasma

Question 10

compare intracellular and extracellular fluids

Answer 10

intra: fluid inside cells; protein and K+ rich

extra: fluid outside cells; few proteins and Na+ rich

Question 11

compare interstitial fluid and blood plasma

Answer 11

ISF: fluid that surrounds cells except blood cells in circulatory system; few proteins

blood plasma: fluid that surrounds blood cells in circulatory system; protein rich

Question 12

why is compartmentalization important

Answer 12

each cell can make exchanges b/w internal and external cellular environments; body systems can transfer material which helps with maintaining homeostasis

Question 13

what is total body water

Answer 13

total volume of fluid in all compartments

Question 14

what type of permeability does the plasma membrane have

Answer 14

selective

Question 15

Why is the plasma membrane permeable to small, uncharged polar molecules even though the interior of the membrane is hydrophobic?

Answer 15

• they move between gaps that perform between fatty acid tails of membrane (dynamic structure with constant ‘moving’)
• kinetic barrier is not great enough to prevent diffusion from occurring on a time scale relevant to that of living systems

Question 16

Is the plasma membrane permeable to nucleic acids, proteins and structural molecules?

Answer 16

• no
• large in size
• DNA has - charge

Question 17

moving substances across the plasma membrane can be categorized in different ways. list them

Answer 17

carrier-protein requiring: carrier-meditated transport, non-carrier-meditated transport

energy requiring: active, passive, bulk transport

Question 18

describe passive transport

Answer 18

spontaneous, no cell energy needed, “downhill” transport along conc gradient

Question 19

what are the types of passive transport

Answer 19

osmosis, simple diffusion, facilitated diffusion (channel or carrier mediated)

Question 20

explain the process of simple diffusion; what is the net movement

Answer 20

random ‘mixing’ of particles from one location to another (physical separation not necessarily needed); net movement is from higher solute concentration to lower solute concentration

Question 21

define mean diffusion time

Answer 21

the average time it takes for a solute to diffuse

Question 22

what can transport through simple diffusion through the plasma membrane. provide some examples

Answer 22

• small, uncharged (non-polar) lipid soluble molecules pass easily like O2, CO2, steroid hormones, ethanol, urea
• charged ions can pass through using ion channels

Question 23

explain gas exchange in simple diffusion

Answer 23

net diffusion of O2 into cells and CO2 out of cells due to concentration gradients

Question 24

what are the factors affecting rates of diffusion

Answer 24

magnitude of driving force, membrane surface area, membrane permeability, temperature

Question 25

what do we mean by the magnitude of driving force

Answer 25

how large the concentration gradient is

Question 26

what is one way membrane surface area can be increased

Answer 26

thru microvilli

Question 27

explain the process of osmosis

Answer 27

passage of water through plasma membrane by aquaporins from low to high solute concentration

Question 28

what are aquaporins and where are they found

Answer 28

water membrane channels; found in kidneys, eyes, lungs, salivary glands, brain

Question 29

what are the requirements for osmosis

Answer 29

- solute concentration difference on either side of a membrane permeable to water - membrane must be impermeable to solute, otherwise concentration difference won't be maintained

Question 30

what are osmotically active solutes

Answer 30

those that cannot cross the membrane but can permit osmosis

Question 31

describe the net movement of water for osmosis

Answer 31

from more dilute (low solute) to less dilute (high solute)

Question 32

describe the movement of water if aquaporins were not present

Answer 32

extremely slow

Question 33

describe channel-mediated transport

Answer 33

- needs transmembrane protein that functions like a passageway or pore - substance-specific - some channels always open, some are gated - most membrane channels are ion channels

Question 34

what does a transmembrane protein refer to

Answer 34

protein embedded into membrane and spans it

Question 35

describe gated ion channels

Answer 35

can open based on conformational shape change due to physiological stimuli (e.g. chemical regulator binding), otherwise remains closed

Question 36

compare aquaporins and ion channels

Answer 36

aq: highly selective (water only), gated, have different classes ion chan: have leak channels and gated channels

Question 37

what are ion leak channels

Answer 37

channels that are open all the time (non-gated)

Question 38

explain the process of carrier mediated transport

Answer 38

- passive transport (no ATP) - high to low conc - needs specific carrier-mediated proteins for each transported material - conformational shape change with binding to "swing" material to low conc. side

Question 39

what is the name(s) of the specific glucose carriers in central nervous system

Answer 39

GLUT1 and 3

Question 40

where is carrier GLUT 2 typically found

Answer 40

pancreatic beta cells, hepatocytes (liver cells)

Question 41

where is carrier GLUT 4 typically found

Answer 41

fat tissue, skeletal muscle

Question 42

what are the properties of carrier-mediated transport

Answer 42

specificity, competition, saturation

Question 43

what do we mean by competition in carrier-mediated transport

Answer 43

some molecules with compete with each other for the binding sites on a carrier since they are so similar (EX amino acids)

Question 44

what do we mean by saturation in carrier-mediated transport

Answer 44

a limit to the rate of transport (to a point)

Question 45

describe the transport maximum

Answer 45

the plateau region of saturation effects on carrier mediated transport, in which any factors above this will not make any difference to the rate of transportation

Question 46

explain the process of active transport

Answer 46

- movement of ions and molecules against their concentration gradient - nonspontaneous (needs energy) - movement is uphill and needs a "pump"

Question 47

what are the types of active transport

Answer 47

primary and secondary

Question 48

explain the primary active transport process using the Ca +2 pump example

Answer 48

- Ca+2 inside cells binds to carrier protein site facing inside cell - ATP hydrolyzed into ADP + P which bind to pump - release of ADP causes conformational shape change releasing Ca+2 to extracellular side - P releases from pump to trigger carrier to change back into original shape and let Ca+2 bind again - this continues as long as there is ATP

Question 49

how many Na+ and K+ are moving into and out of the cell in 1 primary active transport cycle; what enzyme does this

Answer 49

ATPase enzyme pumps 3 Na+ out of the cell and 2 K+ into the cell

Question 50

What are the 3 functions of the sodium/potassium pump

Answer 50

1) Provides energy for coupled transport of other molecules 2) Produces electrochemical impulses in neurons and muscle cells 3) Maintains osmolality of cells

Question 51

explain the process of secondary active transport

Answer 51

- uses energy from an electrochemical gradient or concentration gradient previously created by primary active transport - Involves two molecules or ions

Question 52

describe cotransport

Answer 52

both substances move in same direction

Question 53

describe countertransport

Answer 53

both molecules move in opposite directions

Question 54

how is the SGLT pump able to transport glucose against its concentration gradient

Answer 54

via energy from sodium movement along its concentration gradient

Question 55

the small intestine has what type of sodium coupled glucose transporter; the ratio of sodium:glucose

Answer 55

SGLT 1; 2:1

Question 56

the kidneys have what type of sodium coupled glucose transporter; the ratio of sodium:glucose

Answer 56

SGLT 2; 1:1

Question 57

ICF/ECF composition differs, but ICF composition remains relatively steady. Why don't intracellular concentrations change?

Answer 57

due to leak channels allowing for passive transport of materials back in to their originating spots (e.g. K passively diffuses back out despite normally being pumped in)

Question 58

define exocytosis; what is it used for; energy?

Answer 58

- fusion of a vesicle with the plasma membrane, needs ATP - used for large molecule secretion, like proteins, hormones, and neurotransmitters

Question 59

define endocytosis; what is it used for

Answer 59

cells engulf large substances like cholesterol into a vesicle (usually triggered by plasma membrane protein and transport protein interacting) and bring it inwards

Question 60

explain how a molecule moves in facilitated diffusion

Answer 60

down (along) its concentration gradient with the assistance of a protein carrier molecule, and no energy is required