Transport across cell membranes

Question 1

Define Diffusion

Answer 1

The movement of molecules from a higher concentration to an area of lower concentration. It is a passive process

Question 2

what are the functions of cell surface membranes

Answer 2

1. controls what enters & leaves cells
2. partially permeable
3. substances move across by diffusion, osmosis and active transport
4. allows cell communication

Question 3

explain the function of phospholipids

Answer 3

phospholipids make up the phospholipid bi layer

Question 4

explain the function of glycoproteins

Answer 4

glycoproteins are made up of extrinsic proteins and a carbohydrate branch, used for signalling

Question 5

explain the function of glycolipids

Answer 5

made up of a phospholipid and a carbohydrate branch

Question 6

explain the function of cholesterol

Answer 6

cholesterol gives the membrane stability/ keeps it rigid, despite the other components moving around

Question 7

explain the function of protein channels

Answer 7

protein channels allow large, charged, polar molecules into the cell

Question 8

Learn-
The basic structure of all cell membranes, including cell-surface membranes and the membranes around the cell organelles of eukaryotes, is the same.

Answer 8

The basic structure of all cell membranes, including cell-surface membranes and the membranes around the cell organelles of eukaryotes, is the same.

Question 9

explain simple diffusion

Answer 9

Simple diffusion is a type of passive transport which is simply the unassisted movement from an area of high concentration to an area of low concentration

Question 10

explain facilitated diffusion

Answer 10

Facilitated diffusion is a type of passive transport. Facilitated diffusion is like normal diffusion, except that it happens through special protein channels and carrier proteins.

Question 11

explain active transport

Answer 11

the movement of molecules from a low concentration to a high concentration using energy from ATP & carrier molecules

Question 12

What is Fick’s law

Answer 12

surface area x steepness
rate of diffusion= —————————————–
thickness of membrane

Question 13

explain co-transport

Answer 13

the coupled transport of chemical substances across a cell membrane in which the energy required to move a substance against a concentration gradient

Question 14

what factors affect rate of transfer across membrane

Answer 14

1. surface area
2. temperature
3. diffusion distance
4. number of channel proteins
5. steepness of gradient

Question 15

is -5kPa more or less concentrated than -70kPa

Answer 15

-5kPa is a dilute solution, but -70kPa is a highly concentrated solution

Question 16

what happens when diffusion reaches equilibrium

Answer 16

the substances move back and forth across the membrane keeping the concentrations equal

Question 17

why can’t water soluble molecules move through the phospholipid bi layer

Answer 17

the hydrophobic fatty acid tails

Question 18

what’s the formula for surface area

Answer 18

L x H x faces

Question 19

Is sodium in high or low concentration in the lumen

Answer 19

high concentration

Question 20

is sodium in high or low concentration in the epithelial cell

Answer 20

low concentration

Question 21

is sodium in high or low concentration in the bloodstream

Answer 21

low concentration

Question 22

is glucose in high or low concentration in the epithelial cell

Answer 22

high glucose concentration

Question 23

is glucose in high or low concentration in the bloodstream

Answer 23

low concentration

Question 24

explain the movement of sodium from the lumen to the bloodstream

Answer 24

A low concentration of sodium is maintained in the epith

Question 25

explain the movement of sodium from the lumen to the bloodstream

Answer 25

A low concentration of sodium is maintained in the epithelial cell by actively transporting it out of the cell and into the blood stream through a sodium potassium pump. This means that sodium can move with the concentration gradient into the epithelial cell, co-transporting glucose with it

Question 26

explain the movement of glucose from the lumen to the bloodstream

Answer 26

Glucose is in low concentration in the lumen. Glucose moves into the epithelial cell, where it is in high concentration, through co-transportation with sodium. It leaves the cell through facilitated diffusion

Question 27

how do ice crystals affect membrane permeability

Answer 27

ice crystals pierce the membrane and when they melt leave gaps for molecules to enter the cell

Question 28

how do high temperatures affect membrane permeability

Answer 28

high temperatures cause the proteins to denature and

Question 29

Define dynamic Equilibrium

Answer 29

Diffusion never completely stops but when it reaches equilibrium the molecules move back and forth, as there is no concentration gradient

Question 30

Describe the relationship between size and surface area to volume ratio

Answer 30

As an object gets smaller the surface area to volume ratio gets bigger.

Question 31

How does surface area to volume ratio affect diffusion

Answer 31

The larger the surface area to volume ration the greater the diffusion levels