B3- Cell Membranes And Transport

Front 1

What is the structure of the phospholipids?

Back 1

The phospholipids form a bilayer

Front 2

Is the polar head hydrophilic or hydrophobic?

Back 2

The polar heads are hydrophilic so interact with tissue fluid/ plasma

Front 3

Are the non- polar tails hydrophilic or hydrophobic?

Back 3

The tails are hydrophobic so face inwards

Front 4

What is the structure of all the proteins found in the cell membrane)

Back 4

All the proteins are globular

Front 5

What is the function of extrinsic proteins?

Back 5

Extrinsic proteins act as receptors for hormones

Front 6

What is the function of intrinsic proteins?

Back 6

Intrinsic proteins act as carriers or channels

Front 7

What is the name of the carbohydrates when they are attached to proteins? And to phospholipids?

Back 7

Attached to proteins: glycoproteins, attached to phospholipids: glycoproteins

Front 8

What is the function of glycoproteins and glycolipids?

Back 8

They are used for cell recognition, signalling and adhesion

Front 9

Where is the cholesterol found in the cell membrane?

Back 9

Cholesterol is found between the phospholipids

Front 10

Why is the structure of the cell membrane called the fluid mosaic model?

Back 10

Fluid: because the proteins and lipids are able to move around within the membrane, Mosaic: because of the mosaic like make up of the components

Front 11

What is the function of the cell membrane?

Back 11

The cell membrane aids the transport of substances in and out of the cell

Front 12

What is the function of the phospholipids?

Back 12

The phospholipids form a selective bilayer that allows non polar charged molecules through

Front 13

What is the function of the cholesterol is the cell membrane?

Back 13

The cholesterol controls cell membrane fluidity

Front 14

How do lipid soluble and non- polar substances pass through the membrane?

Back 14

Small uncharged molecules can dissolve and diffuse across the cell membrane

Front 15

How do water soluble and polar substances (such as glucose and amino acids) pass through the membrane?

Back 15

Charge molecules pass through intrinsic protein molecules, e.g. channel/ carrier proteins

Front 16

How is the permeability of the membrane affected by high temperatures?

Back 16

In high temperatures the fluidity of the lipids increases so the membrane become more fragile and an increase in temperature debated the intrinsic and extrinsic proteins causing the substances to leak out.

Front 17

How is the cell membrane affected by organic solvents?

Back 17

Organic solvents can dissolve lipids so they’re capable of dissolving the membrane forming holes and increasing the permeability. Ethanol could also denature the proteins as it can destroy hydrogen bonds.

Front 18

Definition of Diffusion.

Back 18

Diffusion can be defined as the passive movement of molecules down the concentration gradient from a region of high concentration to low.

Front 19

How does temperature affect the rate of diffusion?

Back 19

The hotter it is the more energy the particles have so the quicker diffusion is

Front 20

How does the concentration gradient affect the rate of diffusion?

Back 20

The greater the concentration gradient the quicker diffusion is

Front 21

How does the thickness of the surface affect the rate of diffusion?

Back 21

The thinner the surface the quicker the rate of diffusion

Front 22

How does the size of the molecule affect the rate of diffusion?

Back 22

The smaller molecules have more kinetic energy so diffusion is quicker

Front 23

How does the nature of the molecule affect the rate of diffusion?

Back 23

Phospholipid soluble (non-polar) molecules are quicker than polar molecules are quicker at getting through the membrane

Front 24

How do you calculate the rate of diffusion? (Ficks law)

Back 24

Rate of diffusion = (surface area x concentration difference) / length of diffusion

Front 25

Why can ions pass through channel proteins?

Back 25

Ions can pass through channel proteins are the pores are hydrophilic

Front 26

Why are there lots of different channel proteins?

Back 26

As each channel is specific to one type of ion

Front 27

How can channel proteins alter depending on the needs of the cell?

Back 27

They can open and close

Front 28

What molecules go through the cell membrane using carrier proteins?

Back 28

Carrier proteins allow the diffusion god larger polar molecules such as glucose and amino acids

Front 29

How do molecules travel through carrier proteins?

Back 29

They attach to the binding site, it changes shape and the molecule is released on the other side.

Front 30

Definition of facilitated diffusion.

Back 30

Facilitated diffusion is the passive transfer of polar molecules or changed ions down a concentration gradient through carrier or channel proteins.

Front 31

Make two factors that affect the rate of diffusion through carrier and channel proteins.

Back 31

The rate of facilitated diffusion is affected but the number of channel/ carrier proteins and the concentration gradient

Front 32

Name two benefits of facilitated diffusion.

Back 32

Facilitated diffusion allows ions and polar molecules to be transported across the membrane and it is faster than diffusion.

Front 33

Definition of co-transport.

Back 33

Co-transport is a type of facilitated diffusion that brings molecules and ions into cells together on the same protein transport molecule

Front 34

Definition of active transport.

Back 34

Active transport is the transport of ions and molecules against the concentration gradient using carrier proteins and energy from the hydrolysis of ATP

Front 35

How is active transport used to transport molecules across the cell membrane?

Back 35

The molecule bond to the carrier protein, ATP transfers a phosphate group to the carrier protein, the carrier protein changed shape and the molecule is released before the protein returns to its original shape.

Front 36

How is active transport affected by inhibitors?

Back 36

Active transport requires ATP so if respiration is inhibited active transport stops.

Front 37

How does the increasing the concentration difference affect active transport?

Back 37

As the concentration gradient increases so does the rate of until the carrier proteins become saturated then the rate plateaus.

Front 38

How does the increasing the concentration difference affect diffusion?

Back 38

As the concentration difference increases so does the rate of uptake ad the rate is proportional

Front 39

How does a respiratory inhibitor affect the rate of diffusion?

Back 39

It has no effect as diffusion is a passive process.

Front 40

How does the increasing the concentration difference affect facilitated diffusion?

Back 40

As the concentration difference increases so does the rate of uptake until the carrier/channel proteins become saturated (when the number of channel proteins becomes the limiting factor)

Front 41

How does a respiratory inhibitor affect facilitated diffusion?

Back 41

The respiratory inhibitor has no affect as facilitated diffusion is passive .

Front 42

Describe the process of exocytosis

Back 42

A vesicle is produced in the cytoplasm (budding of the Golgi body), the vesicle migrated to the cell membrane where it fuses with it, the contents secrete to the outside of the cell.

Front 43

Describe the process of endocytosis.

Back 43

The cell membrane folds around the particle, the folding closes off so the particle is fully trapped inside the cell

Front 44

Definition of osmosis.

Back 44

Osmosis is the diffusion if water from an area of higher water potential to lower across as selectively permeable membrane.

Front 45

Definition of water potential.

Back 45

Water potential is the tendency for water to leave a cell by osmosis

Front 46

Definition of osmotic strength of a solution

Back 46

The osmotic stench is the reduction is water potential due to the presence of a solute.

Front 47

Definition of pressure.

Back 47

The pressure exerted by the cells contents on the cell walls increase the tendency of water to move out.

Front 48

What is the equation for water potential?

Back 48

Water potential = osmotic strength + pressure

Front 49

Definition of hypertonic.

Back 49

A hypertonic solution has a low water potential and a high concentration of solute therefore water moves out.

Front 50

What happens to an animal cell when in a hypertonic solution? And in a plant cell?

Back 50

An animal cell shrivels when in a hypertonic solution and a plant cell becomes plasmolysed.

Front 51

Definition of an isotonic solution?

Back 51

An isotonic solution has the same water potential as a cell so there is no net movement of water.

Front 52

What happens to an animal cell and a plant cell when in an isotonic solution?

Back 52

An animal cell will be normal and a plant cell will be flaccid.

Front 53

Definition of a hypertonic solution.

Back 53

A hypertonic solution has a high water potential and a low concentration of solute so water moves in.

Front 54

What happens to an animal and a plant cell when in a hypertonic solution?

Back 54

An animal cell will become lysed (burst) and a plant cell would become turgid

Front 55

What is the theoretical definition of incipient plasmolysis?

Back 55

The point where the cell membrane is just about to come away from the cell wall.

Front 56

What is the experimental definition of incipient plasmolysis?

Back 56

Where 50% of the cells are plasmolysed.

Front 57

What is the equation for incipient plasmolysis?

Back 57

Water potential = osmotic strength