transport across membranes Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

explain why a cell surface membrane is often called as a fluid mosaic model?

A
  • bilayer membrane
  • position of molecules within membrane is fluid = are able to move around in the membrane
  • membrane made up of many different molecules arranged in a mosaic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

explain the arrangement of the phospholipids in the cell surface membrane

A

bilayer
- hydrophobic fatty acid tails face away from water and hydrophilic heads attract water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the function of the phospholipids in the cell surface membrane

A
  • hydrophobic tails repel water and hydrophilic head attracts water, forming a bilayer
  • allows LIPID SOLUBLE (NON-POLAR) molecules to pass
  • via SIMPLE DIFFUSION
  • prevents small POLAR molecules like ions to pass
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is the function of cholesterol in the cell surface membrane?

A
  • decreases permeability AND
  • increases stability of the membrane
    (more cholesterol = less fluidity of the membrane)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the function of the channel proteins in the cell surface membrane?

A
  • have specific 3 structure only transporting specifically complementary molecules
  • only allow SPECIFIC IONS/POLAR or SMALL molecules to move across membrane
  • via FACILIATED DIFFUSION
  • can be open or closed or intrinsic (allow ions to move straight through)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the function of the carrier proteins in the cell surface membrane?

A
  • transport ions and LARGE molecules (eg: glucose, amino acids)
  • via faciliated diffusion AND active transport
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the function of the receptor proteins in the cell surface membrane?

A
  • specific cells have specific receptors, only specific molecules can bind to specific receptors
  • protein molecules act as specific receptiors for complementary molecules (ie: hormones like insulin, which cell responds by increasing the cell permeability to glucose).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the function of the glycoproteins in the cell surface membrane?

A

glycoprotein = carb + protein
- used in cell recognition, act as antigens
- on outer surface membrane
- produced in golgi body
- immune cells detect shape of glycoproteins to detect if SELF or NON SELF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the function of aquaporins in the cell surface membrane?

A
  • specific type of channel proteins specific to water
    more aquaporins = more permeable to water = easier osmosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

diffusion

A
  • passive process = no ATP from respiration
  • net movement of non-polar, small molecules (eg: 02, CO2 and oestrogen) from an area of highER concentration to an area of lowER concentration
  • across a partially permeable membrane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

ficks law

A

rate of diffusion = (SA x CG) divided by diffusion distance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

factors affecting rate of diffusion

A
  1. temperature = increased kinetic energy, faster rate of diffusion of molecules
  2. Surface Area = larger surface area allows more space for molecules to move through, alows more proteins to be present (eg: microvilli)
  3. concentration gradient = as concentration difference increases, rate of diffusion increases
  4. diffusion distance = shorter distance/ fewer membranes to cross means faster diffusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

faciliated diffusion

A
  • channel and carrier proteins have a specific shape that are compkementry to a specific ions
  • passive, no ATP
  • proteins have binding sites
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

faciliated diffusion graph

A
  • levels off when carrier proteins are saturated/ binding sites are full
  • B plateaues at a lower rate because less specific carrier proteins
  • number of proteins is a limiting factor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

many different substances enter and leave the cell by crossing its cell surface membrane. describe how substances can cross via a CSM

A
  • diffusion from a higher concentration to a lower concentration
  • small, non-polar molecules pass via phospholipid bilayer
  • water moves by osmosis from a high water potential to a lower water potential
  • active transport is movement of substances from low concentration to a higher concentration, against a concentration gradient
  • active transport requires energy
  • glucose cotransported
  • active transport and faciliated diffusion involves proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

osmosis

A
  • net movement of water molecule from a higher water potential to a lower water potential
  • via a selectively permeable membrane
17
Q

the movement of substances across cell membranes is affected by membrane structure. describe how.

A
  • phospholipid bilayer allows movement of non polar substances
  • phospholipid bilayer prevents diffusion of polar substances across bilayer
  • carrier proteins allow active transport
  • channel and carrier proteins allow faciliated diffusion
  • shape determines which substances move
  • number of channels determines how much movement
  • membrane surface area determines how much diffusion
  • cholesterol affects permeability
18
Q

water potential

A

pressure water exerts on membrane in kPa
- highest water potential = 0kPa
- adding solute makes it negative

FOR AO2 Questions
- identify and state where water potential is highest
- state where water potential is more negative
- water moves down the water potential gradient via osmosis
- consequence, eg: lysis, shrivelling, stops metabolic reactions

19
Q

when water potential higher outside than inside organelle

A

swelling/lysis
cell bursts
water moves in by osmosis

20
Q

higher water potential inside cell

A

shrivelling
plant membrane shrivels from cell wall
water moves out by osmosis, mass lost

21
Q

isotonic

A

no net movement of water in or out of cells
- no water potential gradient

22
Q

active transport

A

used to transport molecules across membrane against the concentration gradient
- only uses carrier proteins; speciifc shape with a complementary binding site
- requires ATP energy; hydrolysis phosphorylates the carrier protein and changes its shape so it can transport the molecule

23
Q

bulk transport

A

endocytosis
exocytosis

24
Q

exocytosis

A
  • uses vesicles to transport large quanitiies of molecules (eg: enzymes, insulin) from inside a cel to outside cell
  • also moves enzymes and glycoproteins from golgi body to csm to secrete proteins, atp required to transport vesicles
  • vesicles fuse with csm
25
Q

endocytosis

A

membrane pulled inwards to create a vesicle
- requires breakdown of atp
- movement of vesicle also requires breakdown of ATP

26
Q

AO2: ACTIVE TRANSPORT
what happens if aerobic respiration is inhibited

A
  • no ATP
  • active transport cant occur
  • all other types of transport can still continue
27
Q

what happens if the tertiary structure of the carrier protein changes

A
  • FD ans active transport cant occur
  • binding sites have changed shapes so no longer specifically complementary to molecule, therefore will not bind