Session 1 ILOs - General Introduction (membranes etc.) Flashcards
List the categories of Endocrine Paracrine signalling molecules
Endogenous - made in the body
Exogenous 1 - Natural (plant based e.g. morphine, antibiotics)
Exogenous 2 - Synthetic (Man Made - thousands!)
Describe the main features of the 4 major groups of Endocrine Hormones
Main features:
- Secreted into the blood stream
- Highly potent
- Act over long distances
- Slow transmission (sec/months)
Major groups:
- Amine - e.g. Noradrenaline
- Peptide - e.g. Oxytocin
- Protein - e.g. Human Growth Hormone
- Steroid - e.g. Testosterone, Progesterone
Describe the main features of the 3 major groups of Paracrine Neurotransmitters
Main features:
- One way transmission
- Either excitatory or inhibitory
- Act over a very short distance
- Very quick transmission (msec)
Major groups:
- Acetylcholine
- Monoamines
- Amino acids
Recall the main classes of therapeutic drug targets
R - Receptors
I - Ion Channels
T - Transporters
E - Enzymes
K - Kinase Linked Receptors
I - Ligand Gated ION Channels
N - Nuclear/Intracellular
G - G-protein Coupled Receptors
What are the functions of biological membranes?
- Continous, highly selective barrier
- Control the enclosed environment
- Communication
- Recognition
- Signal generation in response to stimuli
Describe the composition of a biological membrane in %
60% = Protein 40% = Lipid 1-10% = Carbohydrate
What three types of lipids are involved in the bilayer?
Phospholipids
Glycolipids
Cholesterol
What is meant by a fluid membrane?
The molecules are able to move and gives the membrane stability, flexibility and durability
How does cholesterol contribute to membrane fluidity?
Cholesterol increases the range of temperatures over which the membrane can maintain fluidity. At high temperatures, it stabilises the membrane and raises its melting point, whereas at low temperatures it intercalates between the phospholipids and prevents them from clustering together and stiffening.
What is the evidence that membrane proteins exist?
2 forms of evidence
- SDS Page - where a cell is digested and the organelles were centrifuged out which left behind a range of proteins which must be membrane proteins
- Freeze fracture - Take a crystal with a cell within it and press until the crystal fractures and you get half of the membrane proteins going to the E fracture face and half going to the P fracture face
How may membrane proteins move?
Membrane proteins can move in 3 ways: 1. Conformational change 2. Rotation 3. Lateral diffusion = NO FLIP FLOP
How do membrane proteins associate with the lipid bilayer?
2 main ways:
- Intergral proteins - are held onto the membrane by ionic forces and hydrogen bonds (so can be removed)
- Peripheral proteins - one or more of the membranes pass through the membrane and interact with the hydrophobic core (so are not easily removed)
How can membrane proteins contribute to the cytoskeleton?
Intergral membrane proteins can attach the cytoskeleton and act as ‘gluing proteins’
How are membrane proteins inserted into membranes?
Ribosome is brought down to the endoplasmic reticulum where the signal is released from the SRP and passed onto the signal sequence receptor where the synthesis continue until the hydrophobic region (of ~20-22 amino acids) is reached and forms an interaction with the membrane which acts as a STOP sequence
Complicated - so see notes!
How is correct orientation of membrane proteins maintained?
N-terminal is unable to go straight into the ER lumen due to positive charges so these charges bind to the signal sequence receptor on the cytoplasmic side forming a hairpin bend and this is cut by the signal peptidase and the N-terminal goes into the ER lumen and the C terminal is on the cytoplasmic side
