2.5 Biological membranes Flashcards
What is compartmentalisation?
-Formation of sperate membrane-bound areas in a cell
What is the plasma membrane and it’s role?
- plasma membrane is the cell surface membrane that separates the cell from the external environment.
-It is partially permeable, an attachment for the cytoskeleton, a site of chemical reactions and cell communication
What is cholesterol and how do they make the membrane more or less permeable?
-A type of lipid
-Present in all cell membranes
-Fit between phospholipids making them more rigid as it causes them to pack more closely
What are the two types of membrane proteins?
-Intrinsic: proteins that are inside the bilayer
-Extrinsic: proteins that are partially embedded or on the surface
What are Intrinsic proteins?
-Membrane proteins that span the width of the membrane
-Transport water and soluble charged particles
-Channel proteins= a hydrophilic passage for water and charged substances to passively diffuse accross
-Carrier proteins= change shape to move substances from one side to another this can be against or with the concentration gradient
What are glycoproteins?
-Intrinsic protein with a carbohydrate branching off the protein
-Involved in cell adhesion (cells joining together), can act as receptors for chemical signals, drugs can bind to these receptors setting off either a direct response or a cascade
What are glycolipids?
-Lipids on the phospholipid bilayer with attached carbohydrate chains
-They are also called antigens and can be recognised by an immune system as foreign or non-foreign
-They also stabilize the membrane by forming hydrogen bonds with surrounding water.
How do different substances have different levels of permeability through the phospholipid bilayer?
-Small, non polar molecules like oxygen and carbon dioxide diffuse rapidly across a membrane
-Small polar molecules diffuse slowly but really require proteins
-Charged particles won’t diffuse across unless there is a protein
How does temperature affect membrane permeability?
-As temperature increases particles have more kinetic energy, the membrane breaks and becomes more fluid, and carrier and channel proteins denature so substances can freely pass through
-At very low temperatures, low kinetic energy and phospholipids vibrate less so pack closely together and carrier proteins don’t have any ATP (less respiration at low temps) to carry out active transport so permeability decreases.
How does the proportion of saturated and unsaturated fatty acid tails affect membrane permeability?
-Unsaturated fatty acids have kinks so can’t pack as close as saturated fatty acids and will therefore increase membrane permeability
What are the factors that affect diffusion across a membrane and simple diffusion?
-Diffusion across a membrane: temperature, thickness, surface area, concentration gradient
-Simple diffusion: temperature and concentration gradient
What solvents will and won’t affect the plasma membrane?
-Polar solvents like water won’t affect the plasma membrane as hydrophilic heads won’t dissolve
-Less polar and non-polar solvents however can dissolve the membrane
What are the alveoli’s key adaptations?
-Massive S/A
-One cell thick lining (short diffusion)
-Good blood supply (high concentration gradient)
What are villi and key features?
-tiny structures that increase the s/a of the intestine
-one cell thick
-they have a network of blood capillaries
-lacteals (villi in the small intestine that help with nutrient absorption)
What are the key adaptations of the Gills?
-Lamellae (tiny structures that increase s/a)
-Have a counter current flow (water flows in opposite direction to blood)
