Cell Surface Membrane

Question 1

How thick is the cell surface membrane

Answer 1

7-9Nm

Question 2

Phospholipid bilayer

Answer 2

Arrangement of phospholipids found in cell membrane, the hydrophilic phosphate heads form both the inner and outer surface of a membrane

Question 3

Hydrophilic head

Answer 3

Water loving, polar

Faces inwards and outwards from the cell

Question 4

Hydrophobic tail

Answer 4

Water hating
Faces the opposite way to the heads
2 fatty acids

Question 5

What does the cell surface membrane consist of

Answer 5

Lipids, proteins, and carbohydrates

Question 6

Function of the cell surface membrane

Answer 6

• Partially permeable barrier between the cell and its outside environment
• controls which substances enter + leaves the cell
• membranes allow recognition by other cells
• cell signalling
• site of chemical reactions

Question 7

What are intrinsic proteins

Answer 7

Proteins embedded within the membrane

Channel proteins, carrier proteins, glycoprotein

Question 8

Another name for Extrinsic protein

Answer 8

Peripheral proteins

Question 9

Channel protein

Answer 9

Provides a hydrophilic channel that allows passive movement of polar molecules down a concentration gradient.
Held in position by interactions between the hydrophobic core of the membrane and the hydrophobic R-groups on the outside of the proteins

Question 10

role of Carrier protein

Answer 10

intrinsic protein used in both passive and active transport

Used to transport large molecules

Question 11

Function on a glycolipid

Answer 11

lipids with attached carbohydrate chains

Act as cell markers or antigens, can be recognised by the immune system as ‘self’ or ‘non self’

Question 12

Extrinsic proteins

Answer 12

Extrinsic proteins serve in transport of molecules and as receptors
Are found outside the cell surface membrane involved in: cell signalling, cell recognition, act as receptors for other molecules

Question 13

Function of phospholipids

Answer 13

Controls which substances enter and leave the cell.
Site of communication with other cells
Separates cell from surroundings

Question 14

Function of cholesterol

Answer 14

Regulates the fluidity of membranes. Adds stability to membrane without making them too rigid.
Has a hydrophilic and a hydrophobic end allowing them to pull phospholipids together

Question 15

Function of receptor sites

Answer 15

Cape able of recognising and bonding to specific molecules

Question 16

Functions of enzymes and co-enzymes

Answer 16

Oxidation of fatty acids. Reactions take pax’s in membranes therefore enzymes are essential

Question 17

Name all the components of the cell surface membrane

Answer 17

Phospholipid bilayer, hydrophilic head, hydrophobic tail, intrinsic protein, extrinsic protein, channel proteins, carrier protein, receptor/glycoproteins

Question 18

What effect does high temp have on membranes

Answer 18

Phospholipids move/ vibrate more as they have more KE
increases gaps in membrane/ between the phospholipids
Bilayer becomes more fluid and melts
Proteins/ glycoproteins denature

Question 19

3 roles of membranes inside cells

Answer 19

Separate organelles from their outside environment
Attachment for enzymes
Creation of organelle gradients

Question 20

Functions of glycoproteins

Answer 20

are intrinsic proteins embedded in the cell surface membrane with attached carbohydrates of varying length
act as receptors for chemical signals which may cause a cascade of reactions inside the cell
e.g. neurotransmitters such as acetylcholine
receptors for peptide hormones

Question 21

Fluid mosaic model

Answer 21

Phospholipids are free to move within the layer relative to each other
Gives membrane flexibility
Membrane must be fluid as proteins that diffuse in vary in shape, size, and position

Question 22

Effect of solvents on membranes

Answer 22

Water is a polar solvent, hydrophilic/hydrophobic tails and heads face away and towards forming the bilayer
Other organic solvents are less polar than water, they dissolve the membranes

Question 23

Facilitated diffusion

Answer 23

Diffusion across a membrane through channel proteins is called facilitated diffusion.
Occurs with molecules that cannot pass through the phospholipid bilyaer e.g. large polar molecules and ions
Can also involve carrier proteins which change shape when a specific molecule binds to them

Question 24

Endocytosis

Answer 24

Bulk transport of material into cells
Phagocytosis for solids
Pinocytosis for liquids

Question 25

Exocytosis

Answer 25

Reverse of endocytosis Vesicles move towards and fuse with the cell surface membrane Contents of the vesicle are then released outside the cell

Question 26

Active transport

Answer 26

Molecules or ions from an area of lower concentration to a area of higher concentration Requires energy

Question 27

Process of active transport

Answer 27

- Molecule or ion to be transported binds to receptors in the channel of the carrier protein on the outside of the cell - On the inside, ATP binds to the carrier protein and is hydrolysed into ADP and phosphate - protein changes shape due to the binding of the phosphate molecule to the carrier protein - molecule or ion is released to the inside of the cell - phosphate is released and recombines with ADP To form ATP - Carrier protein resumes shape

Question 28

Advantages of active transport

Answer 28

Can work against the concentration gradient Can move large quantities Can carry specific molecules

Question 29

What are the properties of molecules that can freely diffuse through the cell membrane

Answer 29

Small, uncharged/non polar, lipid soluble

Question 30

the roles of membranes within cells and at the surface of cells

Answer 30

partially permeable barriers between the cell and its environment Barrier between organelles and the cytoplasm and within organelles • sites of chemical reactions • sites of cell communication (cell signalling)

Question 31

What is meant by the term cell signalling

Answer 31

Communication between cells to cooridnate action | E.g cytokines or hormonal response

Question 32

How can a glycoproteins act as a receptor

Answer 32

Complimentary shape of messenger molecule | Trigger a cascade of reactions inside the cell

Question 33

glycolipids

Answer 33

antigens | lipids with attach carbohydrate sugar chain