membranes

Question 1

3 types of diffusion

Answer 1

simple diffusion(no membrane or barrier), diffusion across membrane, facilitated diffusion

Question 2

What can affect rate of diffusion and why

Answer 2

temperature - increased ke particles

number of channel proteins -more sites for diffusion to occur

concentration gradient - larger difference in concentration gradient=faster rate

surface area of membrane = more area to diffusion to occur.

membrane thickness

Question 3

What is facilitated diffusion

Answer 3

Use Channel/carrier proteins to move larger polar substances across the membrane as polar molecules can’t diffuse across hydrophobic interior of membrane

Question 4

With what type of difusion do we describe the membrane as partially permeable

Answer 4

diffusion across membranes

Question 5

With what type of diffusion do we describe the membrane as selectively permeable

Answer 5

facilitated diffusion as the channel/ carrier proteins are specific to individual ions/molecules

Question 6

What is simple diffusion

Answer 6

The net movement of particles from down the concentration gradient- from a high concentration to a low concentration

Question 7

What happens when concentration equilibrium is reached in diffusion

Answer 7

The rate at which the forward and backward reaction occurs is the same (still happens- just hard to tell as occur at the same rate)

Question 8

With what type of diffusion do we describe the membrane as partially permeable

Answer 8

difusion across membrane

Question 9

What can and cannot difuse across a membrane

Answer 9

non polar molecules, partially polar molecules (h20)can diffuse but at low rates
polar molecules cannot pass through as ther charge repels hydrophobic interior

Question 10

why is rate of difusion faster over short distances than long distances

Answer 10

particles move at high speeds
they are constantly colliding which slows overall movement
short distances= less collisions
long distance= increased collisions

Question 11

What source of energy does diffusion rely on?

Answer 11

Energy from the natural random movement of particles

Question 12

what is active transport

Answer 12

movement of molecules or ions from region of low concentration to a region of high concentration

Question 13

why does active transport require atp

Answer 13

active process

requires atp as particles are moving against the concentration gradient

Question 14

what proteins are used during active transport

Answer 14

carrier proteins

Question 15

outline steps of active transport

Answer 15

• molecule binds on to carrier protein receptors on outside of cell
• ATP binds on the the carrier protein from the inside of the cell and is hydrolysed to from ADP+Pi
• The Pi attached to the carrier protein causes the carrier protein to change shape, moving the molecule into the cell
• As the Pi is released it reacts with an ADP to from ATP
• carrier protein reverts back to original shape

Question 16

What is the use of bulk transport and what are the different types

Answer 16

bulk transport is used to transport large molecules(enzymes, cells, hormones) through membrane as they are too large to fit through carrier + channel proteins.

• Endocytosis; phagocytosis, pinocytosis
• Exocytosis

Question 17

outline process of endocytosis

Answer 17

• cell membrane folds inwards to take in material that needs to be transported within the cell
• membrane enfold and fuses with the material to form a vesicle
• vesicle pinches off and travels into the cytoplasm to transfer material where they’re needed

Question 18

outline process of exocytosis

Answer 18

• vesicles formed by the Golgi body move and fuse with the cell membrane
• contents of the vesicle then released outside the cell

Question 19

what are the uses of atp in active transport

Answer 19

• move particles against concentration gradient
• movement of vesicles along cytoskeleton
• changing shape of cells to engulf materials
• fusion of membranes as vesicles form or meet the cell surface membrane

Question 20

name structures in the cell membrane

Answer 20

phospholipid bilayer - hydrophilic phosphate group and hydrophobic core(fatty acids tail)
intrinsic proteins- (channel protein, carrier proteins, glycoproteins),Extrinsic proteins, glycolipids, cholesterol

Question 21

Describe overall structure of intrinsic proteins

Answer 21

amino acids with hydrophobic R group that interacts with the hydrophobic core of membrane- keeping it in place

Question 22

Describe the overall structure of extrinsic proteins

Answer 22

amino acids with hydrophilic r group attached interacting with polar head of phospholipids

Question 23

function of cholesterol in plasma membrane

Answer 23

regulate fluidity of membrane

hydrophobic ends interact with tails of membrane and hydrophilic ends react with phosphate heads , pulling them together

Question 24

difference between channel and carrier proteins

Answer 24

channel proteins - provide an alternative pathway for polar molecules and ions to pass through.
carrier - “carries” larger molecules through- specific to certain molecules - involves shape of protein changing

Question 25

role of glycolipids

Answer 25

act as cell markers (antigens) to ensure immune system recognises it as a cell that belongs to the body.

Question 26

role of glycoproteins

Answer 26

used in cell signalling. Chemicals/hormones bind to receptors on the carbohydrate chain