2.1 | Biological Membranes Flashcards
What is cholesterol?
Extrinsic protein
Has a hydrophobic and hydrophilic end
What do Cholesterol do?
Interacts with phospholipid, pulling them together
Adds to stability
Stops grouping, so prevents crystallisation
What is a glycoprotein?
Extrinsic protein
Carbohydrate chains vary in length
Embedded in membrane
What does a glycoprotein do?
Receptor for neurotransmitters on nerve cells at synapses (neurotransmitter binding triggers/prevents an impulse in the next neuron)
Receptor for peptide hormones-affect uptake and storage of glucose
Some drugs work by binding to receptors e.g. blocking so preventing from working
Have specific shapes
What is a glycolipid?
Lipid with a carbohydrate chain
Are cell markers (antigens)-recognised by cells of the immune system
What does a glycolipid do?
Helps to body react to pathogens
What is a channel protein and what does it do?
Intrinsic
Hydrophilic
Allows passive movement of polar molecules and ions
Held in place by hydrophobic core and R group interactions
What is a carrier protein and what does it do?
Intrinsic
Important in active transport and facilitated diffusion
Shape of protein changes
What is the role of a membrane?
Compartmentalisation-holding organelles in place helps speed up metabolic reactions
Separate cell contents from outside
Cell recognition and signalling
Regulating transport in and out
What is the structure of a membrane?
Phospholipid bilayer
Hydrophilic heads, hydrophobic tails
What type of channel proteins do kidney cells contain?
Aquaporins-fast diffusion of water molecules
What did the fluid mosaic model propose?
That proteins occupy various positions in the membrane, and phospholipids were free to move within the layer, so are flexible
Why do proteins have to be in particular positions to work?
For chemical reactions to occur e.g. in mitochondria cristae
How does temperature affect membrane structure?
Phospholipids are constantly moving. If temp increases, have more kinetic energy so move more. Becomes more fluid and looses its structure creating gaps. Will eventually completely break down, this increases permeability. Channel and carrier proteins will denature (affects permeability)
How do solvents affect membrane structure?
Water: Charged heads interact, so help keep membrane intact.
Organic Solvents: Less polar than water. Dissolve membranes. Pure alcohol are toxic. They enter the membrane disrupting the structure=more fluid and permeable.
Can alter function e.g. receptors don’t work as efficiently, so impulses aren’t transmitted as normal e.g. after drinking (signal don’t reach brain)
