2.1.5 biologocial membranes Flashcards
1
Q
describe the structure of the plasma membrane
A
- a phospholipid bilayer
- with hydrophilic region facing outwards
- and hydrophobic region facing inwards
- and glycoproteins, glycolipids, and cholesterol embedded in the bilayer
2
Q
what is simple diffusion?
A
- the net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient.
3
Q
is diffusion an active or passive process?
A
passive
4
Q
what molecules move by simple diffusion?
A
- lipid soluble molecules
- non polar molecules
- non charged molecules
- smaller molecules
5
Q
what is facilitated diffusion?
A
- the net movement of particles from an area of high concentration to an area of low concentration via a channel or carrier protein
6
Q
what molecules move by facilitated diffusion?
A
- polar molecules
- non charged molecules
- large molecules
- non lipid soluble molecules
7
Q
what factors affect the rate of of simple diffusion? (6)
A
- temperature
- diffusion distance
- thickness of a membrane
- surface area
- size of the diffusing molecules
- concentration gradient
8
Q
what is osmosis
A
- the net movement of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane
9
Q
what is active transport ?
A
- the movement of molecules from an area of low concentration to an area of high concentration using a carrier protein, and requires ATP
10
Q
what is endocytosis?
A
- the bulk form of transport INTO a cell, which requires ATP
11
Q
what is exocytosis?
A
the bulk movement of particles out of a cell, which requires ATP
12
Q
what is the role of membranes within cells, around organelles (6)
A
- compartmentalisation : separating organelles from cytoplasm
- allow concentration gradients to form
- provide attachment sites for proteins and enzymes
- site of chemical reactions
- site of cell communication (cell to cell signalling)
- form vesicles for transport
13
Q
why is the plasma membrane described as the fluid mosaic model?
A
- it is fluid because it can move side to side
- mosaic because it has proteins randomly scattered and embedded in the fluid bilayer like a mosaic
14
Q
what factors affect the permeability of a membrane?
A
- temperature
-pH - protein concentration in the bilayer
15
Q
what is the role of phospholipids ?
A
16
Q
what is the role of cholesterol ?
A
