Membranes Flashcards
What are the components of a membrane?
Basic unit has 2 aliphatic tails attached to a polar head. These membranes associate together as a bilayer with polar heads facing aqueous environment and non polar tails associate in centre. Attached to the lipids are carbohydrates side chains and proteins at the surface or embedded or spanning the membrane.
What is the movement of membranes?
They are fluid and asymmetrical. They are selectively permeable and fluid. Individual phospholipids drift in a lateral movement.
What affects the membranes fluidity?
Degree of saturation and presence of cholesterol affect membrane fluidity.
How do molecules pass through membranes?
They pass through hydrophobic region, often proteins span the membrane with hydrophobic R groups that allow the molecules to pass through them
Why is transport in cells important?
Cells must receive and export metabolites and remove waste products
What are the 3 types of transport?
Passive (diffusion or osmosis), Facilitated diffusion (protein pores, carrier pores and ion pores) and active transport
How does diffusion work?
Movement of substance from high concentration to low concentration, down own concentration gradient and creates energy
How does osmosis work?
Movement of water molecules from a dilute to less dilute solution (diffusion of water)
How does facilitated diffusion work?
Passive transport aided by proteins. Channel proteins (provide corridors for selective molecules to pass), Ion channels (process ions, can be gated), Carrier proteins (binds molecules) and goes down concentration gradient
How does active transport work?
Movement from low concentration to high concentration (against concentration gradient), uses energy, coupled to other transport and has ion pumps
What is hypertonic?
Water leaving cell via osmosis and cells become crenated. Becomes shrivelled and plasmolyzed
What is isotonic?
Outside and inside concentration is the same. Cell is normal and flacced
What is hypotonic?
More watery to less watery-net movement inside the cell- haemolysis. Cell is lysed and turgid
What must be provided for net movement of solutes across a membrane which required energy?
Concentration Gradient, Electrochemical gradient and coupled to the use of ATP
