Cell Membranes

Front 1

What is the membrane found around cells called?

Back 1

plasma membrane

Front 2

What is the plasma membrane made up of?

Back 2

Proteins and phospholipids bilayer

Front 3

true or false, the plasma membrane is a partially permeable barrier?

Back 3

true

Front 4

What could you see under an electron microscope (TEM)?

Back 4

Two dark bands the distance across the membrane would be about 7nm

Front 5

Who proposed the fluid mosaic model of membranes?

Back 5

Singer and Nicholson

Front 6

Why are membranes described as being arranged in a fluid mosaic way/

Back 6

Fluid: Phospholipids and proteins move around each other

Mosaic: describes the pattern of the arrangement of proteins within the phospholipid bilayer.

Front 7

What are the five main components of the plasma membrane?

Back 7

phospholipids

cholesterol

glycolipids

proteins

glycoproteins

Front 8

What is the role of phospholipids

Back 8

Act as a barrier to water soluble/polar molecules

allow lipid soluble, small non polar substnaces to diffuse across. Allow cells to maintain concentration gradients on either cells.

Front 9

How are phospholipids arranged?

Back 9

bilayer, hydrophobic tails face inwards, hydrophilic heads face outwards.

Front 10

Which type of cells is cholesterol found in?

Back 10

eukaryotic cells

Front 11

Why is cholesterol part of the plasma membrane?

Back 11

SAtbility and fluidity. It is a steroid molecule that fits between the fatty acid tails, completing the membrnae barrier to water and ions. It binds to the hydrophobic tails of phospholipids, causing them to pack more closely together.

Front 12

What is the structure of a glycolipid?

Back 12

phospholipids with carbohydrates attached.

Front 13

What are glycolipids there for?

Back 13

receptors for cell signalling and recognition

Front 14

What is the difference between intrinsic and extrinsic proteins?

Back 14

Extrinsic span half the bilayer and are there for cell signalling and recognition, to act as receptors as well as enzymes. Intrinsic proteins span across the whole bilayer and are channel or carrier proteins. They allowthe transport of polar molecules.

Front 15

True or false glucose is a polar molecule?

Back 15

true

Front 16

What are glycoproteins?

Back 16

Proteins with carbohydrate attached.

Front 17

What is the role of glycoproteins?

Back 17

Receptors for signalling molecules e.g. hormones. Cell signalling and recoginitions e.g. cell surface antigens. Binding cells together to the basemembrane making tissues, cell adhesion

Front 18

Why is it important for cell adhesion or binding to basement membrane (role of glycoproteins)?

Back 18

makes tissues

Front 19

Which enzyme in respiration is a extrinsic protein?

Back 19

atp synthase

Front 20

What does D show?

Back 20

Carbohydrate component of glycoprotein

Front 21

What is E?

Back 21

Phospholipid

Front 22

What is G?

Back 22

channel protein

Front 23

What is A?

Back 23

phospholipid

Front 24

What is the role of membrane within cells?

Back 24

Compartmentalisation- separate cell components from cytoplasm

Holding the compents of metabolic pathways e.g. mitochondria

regulating transport of material into and out of mitochondria.

Front 25

What is the role of membranes at the surface of cells?

Back 25

separate cell contents from outside environment

cell recognition and signalling

regulating transport materials into or out of cells.

Front 26

How do temperatures below 0C affect the plasma membrane?

Back 26

Increases permeability because although The phospholipids don't have much energy so they can't move very much and are packed close together. Proteins denature increasing the permeability of the membrane. Ice crystals may form and pierce the membrane making it highly permeable when it thaws.

Front 27

How does permeability change as temperature increases between 0-45C?

Back 27

As the temperature increases the phospholipids can move more because they have more kinetic energy, increasing the permeability of the membrane.

Front 28

What happens to the plasma membrane at temperatures above 45C?

Back 28

The phospholipid bilayer starts to break down (melt) and the membrane becomes more permeable. Water inside the cell expands putting pressure on the membrane. Channel and carrier proteins in the membrane denature so they can't control what enters or leaves the cell. Permeability increases

Front 29

What is diffusion?

Back 29

Movement of substances from an area of high concentration to an area of low concentration down a concentration gradient across the membrane via the phospholipid bilayer.

Front 30

What is required for diffusion to occur?

Back 30

concentration gradient, molecules must have kinetic energy.

Front 31

What molecules can diffuse through the bilayer?

Back 31

Lipid soluble e.g. steroid hormones

small e.g. CO2 O2

Small and polar e.g. H2O

Front 32

What factors affect rate of diffusion?

Back 32

Temperature

concentration gradient

thickness of exchange surface

surface area

Front 33

What is facilitated diffusion?

Back 33

The movement of substances from a high concentration to a low concentration, down a concentration gradient across the membrane via carrier or channel proteins.

Front 34

What is required for facilitated diffusion to occur?

Back 34

Concentration gradient, molecules have to have kinetic energy, carrier/channel proteins present.

Front 35

True or false ATP is required for facilitated diffusion and simple diffusion?

Back 35

false.

Front 36

What is facilitated diffusion limited by?

Back 36

temperature, concentration gradient, number of carrier/channel proteins in the membrane.

Front 37

What do channel proteins do?

Back 37

Act as pores allowing only specific ions through. They can be gated.

Front 38

What do carrier proteins do?

Back 38

Only allow specific large molecules to pass through. When a molecule e.g. glucose binds, it changes shape and transfers the molecule to the other side of the membrane.

Front 39

How do different cells allow exit and entry of different substances?

Back 39

Different membranes have different proteins in their bilayer

Front 40

What is osmosis?

Back 40

Movement of water from an area of high water potential to an area of low water potential down a water potential gradient across phospholipid bilayer or via aquaporins.

Front 41

What are aquaporins

Back 41

Protein channels which allow passage of water through plasma membrane.

Front 42

What is water potentials measured in?

Back 42

KPa

Front 43

What is the highest water potential possible?

Back 43

0kPa (pure water with no solutes) Solutes lower the water potential.

Front 44

What are hypertonic solutions?

Back 44

Have a lower water potential than cell causing water to move out of cell.

Front 45

What are isotonic solutions?

Back 45

Same water potential as the cell, there is no net movement of water molecules.

Front 46

What are hypotonic solutions?

Back 46

Has a higher water potential than that of cell, water moves into the cell.

Front 47

What happens to palnt cells in hypotonic solution?

Back 47

becomes turgid: call wall prevents from bursting. Cell membrane pushes against the cell wall, increase in oermanent vacuole.

Front 48

What happens to aniaml cells in hypotonic solutions?

Back 48

Burst open- haemolysed

Front 49

What happens to animal cells in hypertonic solutions?

Back 49

crenate (shrink)

Front 50

What happens to plant cells in hypertonic solutions?

Back 50

Phosmolysed as the plant cell membrane pulls away from cell wall.

Front 51

What is active transport?

Back 51

The movement of large or water soluble substances across the mebrane via carrier proteins. It does not require a concentration gradient, however ATP is required.

Front 52

Why do molecules require kinetic energy for active transport?

Back 52

to bind to carrier proteins.

Front 53

How do carrier proteins move substances?

Back 53

AT changes the shape of the cariier proteins. (this ensures one way flow)

Front 54

What molecules are actively transported?

Back 54

non-lipid soluble, large and polar

Front 55

How can the movement of molecules by active transport be stopped?

Back 55

Inhibiting ATp

Front 56

How are epithelial cells lining the ileum adapted for increased absorption?

Back 56

Microvilli-finger like projections that increase the surface area. Increased number of protein channels and carrier molecules in their membrane.