Cell Membrane

Question 1

Plasma membranes

Answer 1

Barrier between cell and environment
Control what leaves and enters the cell
Recognition from immune system
Cell signalling

Question 2

Membranes within cells

Answer 2

Divide organelles from cytoplasm
Form vesicles for transportation
Control movement in and out organelles
Sites of chemical reactions

Question 3

Fluid mosaic model

Answer 3

Phospholipid molecules constantly moving
Cholesterol and proteins scattered
Mosaic look

Question 4

Phospholipid bilayer

Answer 4

Head is hydrophillic
Tail is hydrophobic
Arrange into bilayer with heads on outside
Centre doesn’t allow water soluble polar substances through

Question 5

Cholesterol

Answer 5

Fits between phospholipids binding to hydrophobic tails
Cause them to pack closer together so less fluid more rigid
Low temperatures cholesterol prevents them packing too close togethrr

Question 6

Proteins

Answer 6

Form channels to allow small or charged particles through
Carrier proteins transport large or ion molecules
Receptors used in c3ll signalling

Question 7

Glycolipids/proteins

Answer 7

Glycolipids
Glycoproteins
Stabilise membrane by forming hydrogen bonds with membrane
Drugs hormone and antibody binding sites
Receptors for cell signalling
Antigens

Question 8

Temperature

Answer 8

Below 0- phospholipids lack kinetic energy and pack very closely together. Ice crystals can pierce making it permeable
0-45- phospholipids able to move, partially permeable, as temperature increases the lipids move more increasing permeability
Above 45- phospholipid bilayer starts to melt, more permeable. Water inside expands, membrane proteins deform

Question 9

Solvent

Answer 9

Ethanol increases permeability
Solvent dissolves lipids. Losing structure

Question 10

Simple diffusion

Answer 10

Net movement from high concentration to low concentrations
Passive process requiring concentration gradient
Small, non polar molecules
Depends on gradient, diffusion distance, surface area, temperature

Question 11

Facilitated diffusion

Answer 11

Larger charged molecules cannot pass easily
Require protein channel or carrier

Question 12

Active transport

Answer 12

Active process
Goes against concentration gradient
Requires atp for carrier to change shape

Question 13

Endocytosis

Answer 13

Cell surrounds substance with cell membrane
Pinches off to form vesicle
Cell takes in larger substances
Requires atp

Question 14

Exocytosis

Answer 14

Large substances produced by cell re,eased
Vesicles pinch off golgi apparatus and fuse with plasma membrane
Released outside cell

Question 15

Osmosis

Answer 15

Diffusion of water across partially permeable membrane down water potential gradient
Pure water has highest water potential

Question 16

Water potential effects on animals

Answer 16

Hypotonic- net movement in cell, cell bursts
Isotonic- cell stays same
Hypertonic- net movement out, cell shrivels

Question 17

Water potential affects on plant cells

Answer 17

Hypotonic- vacuole swells, cell is turgid
Isotonic- cell stays same
Hypertonic- cell becomes flaccid, membrane pulls away from cell wall (plasmolysis)