membrane transport ✅

Question 1

In a phospholipid what is polar and non-polar

Answer 1

polar - phosphate head
non-polar - fatty acid tail

Question 2

what do phospjolipds consist of

Answer 2

a molecule of glycerol two fatty acid tail and a phosphate group

Question 3

What way do the hydrophobic tails face and head

Answer 3

inwards - tails
outwards - heads

Question 4

why can large molecules not pass through the bilayer

Answer 4

because the hydrophobic region is tightly packed and has low permeability to larger molecules

Question 5

why can polar molecules not pass through the lipid bilayer

Answer 5

polar molecules and ions through the hydrophobic tails because they have a hydrophilic nature which means they will not interact with hydrophobic fatty acids
tails

Question 6

What is the function of the phospholipid bilayer

Answer 6

provides a barrier to the movement of substances in and out of the cell

Question 7

3 factors of Integral proteins

Answer 7

• amphipathic
• embedded in phospholipids bilayer
• can be embedded across both /one layer of

Question 8

What type of membrane proteins

Answer 8

integral
peripheral

Question 9

3 factors of peripheral proteins

Answer 9

• hydrophilic
• attached either to surface of integral proteins
• inside or outside the cell

Question 10

What are the 4 functions of membrane proteins

Answer 10

Transport
Receptors
Immobilised enzymes
Cell adhesion

Question 11

What is the function of transport proteins

Answer 11

allow ions and polar molecules to travel across membrane

Question 12

What are the two types of transport proteins

Answer 12

Channel and carrier

Question 13

Explain channel proteins

Answer 13

these form holes/pores through which molecules can travel through

Question 14

Explain carrier proteins

Answer 14

undergo conformationa change to transport substances across a membrane

Question 15

Transport proteins

Answer 15

allow the cell to control which substances enter or leave

Question 16

What are the receptors used for

Answer 16

binding of peptide hormones
the binding generates a signal that triggers a series of reactions inside the cell

Question 17

What are immobilised enzymes

Answer 17

They are integral proteins with the active site exposed on the surface of the membrane

Question 18

What happens in cell adhesion

Answer 18

allows cells to attach to neighbouring cells within a tissue

Question 19

what is the purpose of glycoproteins in cell-to cell recognition

Answer 19

act as markers or antigens

Question 20

In simple diffusion what way do the molecules move

Answer 20

down the conc gradient (high to low)

Question 21

Example of simple diffusion in oxygen

Answer 21

oxygen diffuse into cells from capillaries

Question 22

Example of simple diffusion in c02

Answer 22

carbon dioxide diffuses out of cells and into capillaries

Question 23

What are the 3 factors that affect the way substances move across the membrane

Answer 23

• steepness of conc gradient
• temp
• surface area

Question 24

Explain how the steepness in conc gradient affects the rate at which substances move across membrane

Answer 24

• the greater the diff in conc across a membrane , the higher the rate of diffusion

Question 25

Explain how the temperature affects the rate at which substances move across membrane

Answer 25

the higher the temp the higher the rate of diffusion
(molecules have more kinetic energy move faster)

Question 26

Explain how the surface area affects the rate at which substances move across membrane

Answer 26

the greater the surface area the higher rate of diffusion

Question 27

What is the diffusion like in large molecules

Answer 27

they diffuse more slowly (require more energy to move )

Question 28

what is the diffusion like in uncharged molecules

Answer 28

diffuses faster as they move directly across the phospholipid bilayer

Question 29

explain the diffusion of non-polar

Answer 29

diffuse more quickly as they are soluble in non-polar phospholipid bilayer

Question 30

Define osmosis

Answer 30

the diffusion of water molecules from a dilute solution (high water potential) to a more concentrated solution (low water potential) across a partially permeable membrane (down conc gradient )

Question 31

what are aqua porins

Answer 31

channel proteins that allow water to pass through membranes more freely

Question 32

Facilitated diffusion is used for substances that cannot pass through the phospholipid bilayer

Answer 32

large molecules
polar molecules
ions

Question 33

what does facilitated diffusion involve

Answer 33

transport proteins
down a conc gradient
no energy required (passive )

Question 34

explain the process of a carrier proteins

Answer 34

the substance to be transported attaches to a binding site causing a conformational change in the carrier protein

Question 35

define active transport

Answer 35

the movement of molecules and ions across a cell membrane from a region of lower concentration to higher concentration (against )

Question 36

what are the factors do active a transport

Answer 36

• against conc gradient
• requires energy from respiration
• requires carrier proteins

Question 37

What is the role of ATP in action transport

Answer 37

ATp provides energy (produced during respiration) which allows carrier proteins to change shape
ATP hydrolysed to release energy

Question 38

define selective permeability

Answer 38

the ability of the membrane to differentiate between different types of molecules only allowing some molecules through by blocking others

Question 39

what is simple diffusion dependent on

Answer 39

size
hydrophilic/ hydrophobic nature of molecules

Question 40

what are glycoproteins

Answer 40

cell membrane proteins that have a carbohydrate chain attached on the extra cellular side

Question 41

What are glycolipids

Answer 41

lipids with carbohydrate chains attached

Question 42

What are the functions of glycoproteins/lipds

Answer 42

• The carb chain enables them to act as receptor molecules which allows them to bind with substances at the cell surface

Question 43

Why is the cell membrane described as “fluid”

Answer 43

the phospholipids and proteins can move around within their own layers

Question 44

why are cell membranes described as mosaics

Answer 44

because the scattered pattern produced by the proteins within the bilayer looks like a mosaic (from above )

Question 45

What does the fluid mosaic model involve

Answer 45

phospholipids
cholesterol
glycoproteins/lipds
integral and peripheral proteins