What is endocytosis?
Way of absorbing nutrients into cell
What are characteristics of cells?
- Endocytosis
- Asexual reproduction
- Active (carries out specific function)
- Excrete (waste products)
- React (to irritation or stimulation)
What are 4 compartments of cell?
- Cell membrane
- Cytoplasm
- Nucleus
- Nucleoplasm
How thick is cell membrane?
7.5-10nm
What is cell membrane made from?
Double layer of self-sealing phosophlipids with protein molecules dispersed throughout.
Hydrophobic fatty acid tails form inside of membrane
Hydrophilic polar heads form outside
What is the fluid mosaic model?
The phosopholipids form a ‘liquid’ structure and the proteins give structural support
What are some of the proteins in the cell membrane and what do they do?
Integral plasma membrane proteins (PMPs)
- some for transport of materials in and out of cell
- some are receptor sites
Peripheral PMPs
- bind loosely to cell surface and easily separated
- used in cell signalling
- some used as enzymes to catalyse cellular reactions
What are functions of the cell membrane?
- Anchors cytoskeleton
- Allows cells to attach together forming the cellular matrix (tissues)
- Responsible for transport of molecules/substances into the cell
What are functions of proteins found in cell membrane?
- Structural support
- Enzymes
- Regulates water soluble substances going through membrane
- Receptors for hormones/neurotransmitters
- Glycoproteins (for cell-cell recognition)
What is passive transport?
Molecules entering/leaving the cell by moving down a concentration gradient. No cellular energy is required.
What are 4 types of passive transport?
- Simple diffusion
- Facilitated diffusion
- Osmosis
- Filtration
What is simple diffusion?
Net passive movement of molecules or ions due to the heir kinetic energy from an area of higher to one of lower concentration until equilibrium reached
What does rate of simple diffusion depend on?
- The substance - gasses diffuse moree rapidly than liquids
- Temperature - higher temp = faster diffusion
- Size of molecules - Smaller diffuse faster
- Surface area of cell membrane
- Solubility of molecules
- Concentration gradient
What is facilitated diffusion?
Larger molecules that can’t do simple diffusion hitch a ride with other proteins.
e.g. glucose - picked up by carrier molecule insulin - becomes soluble and can pass through membrane.
What is osmosis?
Net movement of water molecules from high to low concentration through a selectively permeable membrane.
What causes haemolysis of cells?
High osmotic pressure - if cell in low contracted solute. too much water goes into cell to balance and under high pressure the cell gets damaged.
What is filtration (type of passive transport)?
movement of solvents and solutes across semipermeable membrane as a result of gravity or hydrostatic pressure until there is no pressure difference.
Occurs in kidneys where BP forces water and small molecules through blood vessels into tubules.
What are 3 types of active transport?
- Using ATP
- Endocytosis
- Exocytosis
What is active transport?
Movement in the cell that uses cellular energy
What is ATP?
adenosine triphosphate
How does ATP active transport work?
Energy comes from ATP being split into ADP and a phosphate.
Typically a cell uses 40% of ATP for active transport
What are 2 advantages of ATP active transport over facilitated diffusion?
- Allows desirable solutes to accumulate within cells and undesirable to be removed
- Much of energy used is conserved so can be used as way of storing energy.
What are 4 main active transport systems?
- sodium-potassium pump
- calcium pump (actively pumps Ca2+ into cells of muscles
- sodium-glucose linked co-transporter - found in intestinal musosa of s.intestine and proximal tubule of nephron
- high-affinity hydrogen glucose cotransporter
What is endocytosis (active transport)
Absorbing of molecules by engulfing them.
Membrane pinched off to form vesicle.
