Biological Membranes Flashcards
1
Q
Function of plasma membranes
A
- Barrier between cell and environment, controlling what enters and leaves the cell. Partially permeable so are selective about what enters/leaves
- Recognation by other cells e.g. immune cells
- Cell communication e.g. cell signalling
- Conatin enzymes involved in metabolic pathways
2
Q
Function of membrane within the cell
A
- Separate contents of organelles from the cytoplasm
- Can form vesicles for transport
- Can control what substances entre and leave organelles e.g. RNA leaving through nuclear pore
- Membranes that are sites of chemical reactions e.g. cisternae in mitochondrion
- Thylakoid membranes that have chlorophylll in chloroplasts
3
Q
Fluid mosaic model
A
- Describes the strucutre of all membranes
- Composed of lipids, proteins and carbohydrates
- Phospholipid molecules make bilayer
4
Q
Molecules present in bilayer
A
- Phospholipids that make up the bilayer
- Cholesteral molecules
- Glycoproteins
- Glycolipids
5
Q
Glycoproteins
A
-Proteins with polysaccaride chain attached to it
6
Q
Glycolipids
A
-Lipids with polysaccaride chain attached
7
Q
Structure of the phospholipid bilayer
A
- Molecules arrange themselves with hydrophilic heads facing outwards and hydrophobic tails facing inwards
- The centre of the bilayer is hydrophobic so membrane doesn’t allow water soluable substances e.g. ions to pass
- Fat soluable substances can dissolve through the bilayer
8
Q
Function of cholesteral in the bilayer
A
- Fit between the phospholipids and bind the hydrophobic tails to make them packed more closely together
- Makes the membrane less fluid and more rigid
- Regulate membrane fluidity
9
Q
Function of proteins in bilayer
A
- Control what entres and leaves the cell
- Some form channels which only let small or charged particles through
- Carrier proteins which transport molecules and ions by active transport or facilitated diffusion
- Receptors for molecules in cell signalling
10
Q
Function of glycolipids or glycoprotiens
A
- Act as receptors for messenger molecules
- Stabalise the membrane by forming hydrogen bonds with surrounding water molecules
- Sites where drugs, horomones and antibodies bind
- Antigens
11
Q
How does cell signalling work
A
- One releases a messenger molecule e.g. hormone
- Molecule travels to another cell e.g. in the blood
- Messenger molecule is detected by the cell because it binds to a receptor on its cell membrane
12
Q
Why do cells signal
A
-Need to communicate with each other to control processes inside the body and to respond to environmental changes
13
Q
Glucogen
A
- A hormone that’s released when there isn’t enough glucose in the blood
- It binds to receptors on the liver cells, causing the liver cells to break down stores of glycogen to glucose
14
Q
How does the temp at 0 affect membrane permeablilty?
A
- Phospholipids don’t have as much energy so can’t move much
- Packed closely together and membrane is rigid
- Channel and carrier proteins deform making it more permeable
15
Q
Permeability at 0-45 degrees
A
- Phospholipids can move around and aren’t packed as tightly together = partially permeable
- As temp increases. move more because of more kinetic energy, so permeablilty increases
