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Plasma Membranes - Coggle Diagram
Plasma Membranes
Structure and Function
Extrinsic Protein:
Present on one side of the bilayer but can move between them. Normally hydrophilic R-groups which interact w/ polar heads of phospholipids / Intrinsic proteins.
Intrinsic Proteins:
Transmembrane proteins (embedded through both layers) that have hydrophobic R-groups on external surface which interact w/ hydrophobic core of membrane, keeping them in place.
Includes:
- Channel proteins ~ Provide hydrophilic channel for passive movement of polar molecules + ions through membrane.
- Carrier proteins ~ Role in passive + active transport into cells. Often the shape of the protein changes.
- Glycoproteins ~ Embedded in cell-surface membrane w/ carbohydrate chains. Role in cell adhesion + act as receptors
Cholesterol:
A lipid w/ both a hydrophobic (interacts w/ phospholipid tail) + hydrophilic (interacts w/ phospholipid head) end. Regulates membrane fluidity. Positioned between phospholipids to add stability by pulling them together + prevent phospholipids grouping too closely + crystalising.
Glycolipids:
Lipids w/ carbohydrate chains. Are antigens for the immune system to recognise as self or none-self / foreign organisms.
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Diffusion
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Rate of diffusion can be affected by:
- Surface area
- Thickness of membrane
- Temperature
- Concentration difference
- Num. of channel + carrier proteins
Facilitated diffusion ~ Channel proteins allow molecules and ions to pass through membrane (Hydrophobic interior repels them). Carrier proteins change shape when specific molecules bind to them, allowing them through.
Active Transport
Active transport ~ The overall movement of particles from an area of low to high concentration, against the concentration gradient, requiring energy.
Through Carrier Proteins:
- Molecule/ion binds to receptors inside carrier protein from outside the cell.
- ATP binds to carrier protein + hydrolyses into Phosphate + ADP
- Binding of phosphate changes shape of carrier protein so molecules/ions released into cell
- Phosphate recombines w/ ADP to for ATP so carrier protein returns to original shape.
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Osmosis
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Effects of Osmosis
In Animal cells:
- When placed in a solution w/ a higher water potential, water enters by osmosis, hydrostatic pressure ↑, leading to Cytolysis.
- When placed in a solution w/ a lower water potential, water leaves by osmosis, causing Crenation.
In Plant cells:
- When placed in a solution w/ a higher water potential, water enters by osmosis, hydrostatic pressure pushes the membrane against the cellulose cell wall, causing Turgor.
- When placed in a solution w/ a lower water potential, water leaves by osmosis, reducing the volume of the cytoplasm, causing the cell to become Plasmolysed.