2.5- Biological membranes

Question 1

What is the role of membranes? (name 3)

Answer 1

• To act as a partially a partially and sometimes selectively permeable membrane between cells and their environments
• Site of Chemical reactions
• Sites of cell communication and signalling

Question 2

What is the function of phospholipids in a cell membrane

Answer 2

Phospholipids form the bilayer and are the main component of the surface area

Question 3

What Is the function of Cholesterol in a cell mambrane?

Answer 3

It regulates membrane fluidity and flexibility

Question 4

What is the function of proteins in cell membranes?

Answer 4

carrying out chemical reactions or regulating cross membrane transport

Question 5

What are the 2 types of proteins in cell membranes?

Answer 5

Integral- span the entire membrane

Peripheral- embedded in half of a membrane

Question 6

What is the function of glycoproteins and glycolipids in cell membranes?

Answer 6

can be antigens or receptor molecules

can bind with extracellular signalling molecules such as hormones

Question 7

An increased temperature leads to the membrane increasing its……………..

Answer 7

Fluidity and permeability

Question 8

Why does an increased temperature increase fluidity and permeability? (Phospholipids)

Answer 8

Phospholipids aquire more energy so they move around more

Question 9

Why does an increased temperature increase fluidity and permeability? (Fatty acids)

Answer 9

fatty acids become less compressed

Question 10

Why does an increased temperature increase fluidity and permeability? (Proteins)

Answer 10

proteins can denature at high temperatures reducing their ability to control transport across membranes

Question 11

Which 3 factors can affect membrane permebility?

Answer 11

Increased temperature
Changes in PH - affect the function of proteins in the membrane
Organic solvents such as ethanol can damage a membrane by dissolving lipids held through it

Question 12

Can you draw the fluid Mosic model?

Answer 12

Hmmmmmmmmm

Question 13

What is the definition of diffusion?

Answer 13

The movement of molecules from a region of high concentration to a region of low concentration until the concentrations of the 2 regions are equal.

Question 14

What 3 factors does the rate of diffusion depend on?

Answer 14

Surface area of cell
thickness of membrane
Temperature

Question 15

i am a small non polar molecule. can i diffuse through a membrane?

Answer 15

yes, i can diffuse quickly

Question 16

I am a small polar molecule. can i diffuse across a membrane?

Answer 16

yes, although it will be slower

Question 17

I am an ion. Can i diffuse across a cell membrane?

Answer 17

Noooo, i have to be transported by other methods

Question 18

I am a large polar molecule. Can i diffuse across a cell membrane??

Answer 18

nope, i have to be transported by other methods

Question 19

Give 3 examples of molecules which can diffuse through a membrane.

Answer 19

Oxygen
CO2
Steroids
Fat soluble vitamins

Question 20

What is the definition of osmosis?

Answer 20

the diffusion of water molecules from a region of high concentration to low concentration across a partially permeable membrane

Question 21

Is osmosis a form of active transport

Answer 21

No, osmosis is a specialised form of diffusion.

Question 22

What molecules can facilitated diffusion transport that normal diffusion cant?

Answer 22

large and polar molecuses

Question 23

Give 4 examples of molecules that are transported by facilitated diffusion.

Answer 23

glucose
fructose
ions
urea

Question 24

is facilitated diffusion an active process?

Answer 24

No, it is passive

Question 25

What is needed for facilitated diffusion to occur?

Answer 25

Carrier proteins or Channel proteins

Question 26

What are the 3 steps for facilitated diffusion through a carrier protein?

Answer 26

- Molecule binds with carrier proteins molecules on cell surface - Protein changes shape and transports molecule through - Molecule detaches and protein reverts to its original shape

Question 27

What does the rate of facilitated diffusion depend on?

Answer 27

- Concentration gradient | - Number of channels or transporter proteins that are available

Question 28

What are 3 passive processes which move molecules across membranes?

Answer 28

Diffusion Facilitated diffusion Osmosis

Question 29

What are 3 active processes that are used to transport molecules across membranes?

Answer 29

Active transport Endocytosis Exocytosis

Question 30

Why do active processes require energy?

Answer 30

They move molecules against their concentration gradient

Question 31

What is endocytosis?

Answer 31

the bulk transport of substances into a cell

Question 32

What is exocytosis?

Answer 32

The bulk transport of substances out of a cell

Question 33

What to carrier proteins use to transport molecules across membranes?

Answer 33

ATP

Question 34

What is endocytosis of liquids called?

Answer 34

pinocytosis

Question 35

How does endocytosis work?

Answer 35

a vesicle forms around the molecules that have entered the cell, containing them

Question 36

How does exocytosis work?

Answer 36

a membrane bound vesicle moves towards the membrane and then fuses together to release the contents of the vesicle into the extracellular environment

Question 37

What is a hypotonic soloution?

Answer 37

A soloution where water potential outside the cell is higher than inside

Question 38

What is an isotonic soloution?

Answer 38

a soloution where water potential is equal inside and outside the cell

Question 39

What is a hypertonic soloution?

Answer 39

a soloution where water potential is higher on the inside of the cell than outside

Question 40

Can plant cells burst?

Answer 40

no, they have a cell wall

Question 41

What solution are animal cells put in to burst?

Answer 41

a hypotonic one

Question 42

jimmy says that "in an isotonic soloution and a cucumber, no water is moving" Explain why jimmy is stupid

Answer 42

Water will flow in and out at an equal rate | there is no net change in concentrations but water is still moving

Question 43

When an animal cell shrinks, what is it called?

Answer 43

crenation

Question 44

When a plant cell shrinks, it becomes.................

Answer 44

plasmolysed

Question 45

Why doesn't a plant cell collapse when placed in a hyper tonic solution?

Answer 45

The cell wall keeps it rigid

Question 46

I am a turgid cell that hasnt burst. What am i?

Answer 46

A plant cell in a hypotonic solution

Question 47

How do membranes change when temperature is increased?

Answer 47

- The phospholipids require more energy and move around more so fluidity and permeability increase - The way protiens are positioned may differ which can alter rates of reaction

Question 48

How does a temperature decrease affect membrane permeability?

Answer 48

- Saturated fatty acids become compressed | - But unsaturated fatty acids become compressed and push adjacent phospholipid molecules away which maintains fluidity

Question 49

What is the effect of solvents on cell membranes?

Answer 49

they damage cell membranes and dissolve lipids

Question 50

What are the units of water potential?

Answer 50

kPa

Question 51

What is the highest water potential?

Answer 51

0 kPa

Question 52

What is a very low water potential example?

Answer 52

-100 kPa