Lecture notes
Membranes
- Module
- Biology of disease
- Institution
- University Of Wolverhampton
Membranes introduction
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MEMBRANES:PLASMA MEMBRANE
Lipid molecules are highly mobile and constantly moving past membrane proteins.
- Forms a bilayer which is extremely tough and FLEXIBLE.
- It is permeable (allows material in and out the cell.)
- Selective control via selective diffusion
INTEGRAL MEMBRANE PROTEINS
- Protein carriers
- Protein channels
Both are highly selective
Peripheral membrane proteins can send messages from the
channel/carrier proteins to cytoskeletal filaments or communicate with
other cells…
GLYCOPROTEINS – protein with a carbohydrate attached
Phospholipid bilayer: phosphate heads (hydrophilic) and lipid tails (hydrophobic)
IMPORTANCE OF MEMBRANES:
- Provide a surface for chemical reactions to occur
- They separate areas inside a cell separate different reactions within a cell
Lipids are really important: found in plasma, adipose tissue and biological membranes
- Phospholipid bilayer is an example of this.
- Glycolipid carbohydrate + lipid
MEMBRANE LIPIDS:
Membrane lipids are AMPHIPHILLIC meaning they have both hydrophilic and
hydrophobic and lipophilic properties.
Hydrophillic and hydrophobic parts.
Membranes fold up into a ball shape as if it were straight it would be exposed
to water.
MEMBRANE FORMATION:
Lipid bilayer is formed by hydrophobic interactions due to van der Waals
- Strong hydrogen bonding due to polarity of the water and polar heads
GLYCOLIPIDS:
USES:
, 1. BLOOD TYPES: Blood type is determined by the four main types A, B, AB, O. It is
determined by the oligosaccharide attached to a specific glycolipid on the surface of
a red blood cell which acts as an antigen
2. IMMUNE RESPONSE: Selectins found on white blood cells (Leukocytes) bind to the
carbohydrates attached to the glycolipid. This initiates an immune response.
- This causes leukocytes to migrate to site of inflammation.
- Recognition of host cells by viruses
3. CELL TO CELL INTERACTION: Glycolipids serve as recognition sites. initiates cell
responses, contributing to cell regulation, cell growth and apoptosis
CHOLESTEROL:
Regulator in membrane FLUIDITY
- Cholesterol has a different shape to phospholipids so disrupts to regular interactions
between fatty acids.
Drop in temperature = more membrane fluidity
Increase in temperature = less fluidity
MEMBRANE FLUIDITY:
Transportation or signalling depend on the fluidity.
When a membrane warms up cholesterol becomes more solid.
Lipid Rafts:
Lipid rich areas which contain cholesterol. They form between lipids and cholesterol
- Spontaneously come together
- They play a role in concentrating proteins so Play an important role in signal
communication and neurotransmission
CHOLESTEROL:
Important for cell structure and function.
Cholesterol produces important compounds like:
- Sex hormones progesterone, testosterone, oestrogen (Testes/Ovaries)
- Steroids Cortisol, Aldosterone (formed in Adrenal glands)
- Vitamin D (skin)
- Bile fats (gall bladder & liver)
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