Transport Flashcards
Can you describe the fluid-mosaic model of membrane structure?
Enzymes/Peripheral proteins/receptors
Glycoproteins
Integral proteins
Channel Proteins
Carrier proteins
Why are phospholipids present in cell membranes?
Forms a bilayer that allows lipid soluble substances in by simple diffusion.
Prevents passage of polar molecules like ions.
Why is cholesterol present in cell membranes?
High cholesterol reduces permeability and increases stability by reducing the fluidity and lateral movement of phospholipids.
Why are glycoproteins present in cell membranes?
Cell recognition act as an antigen
Can attach together and form tissues
Why are proteins present in cell membranes?
Carrier: transport of large molecules by FD/AT
Channel: small polar molecules by FD
Receptors to specific hormones
Enzymes
Why are glycolipids present in cell membranes?
Can act as a receptor and recognition site and can also form tissues.
Explain the permeability of the cell-surface membrane:
Lipid soluble due to phospholipid bilayer. Non-polar cannot enter by simple diffusion
What is diffusion?
Passive process, net movement of particles from a high to low concentration across a partially permeable membrane.
Why does simple diffusion happen?
Difference in concentration across a permeable membrane,
Random kinetic motion of particles
Reach an equilibrium in conc.
What is facilitated diffusion?
Net movement of molecules from high to low concentration down a concentration gradient through a channel/carrier protein.
Proteins are a specific shape only transports specific molecules complementary to binding site.
Rate of FD limited by number of carrier/channel proteins.
What affects the rate of diffusion?
Temperature, surface area, concentration gradient, diffusion distance, kinetic energy.
What is osmosis?
Net movement of water molecules from a high to low water potential through a partially permeable membrane.
Explain what is meant by the terms solute, water potential and solution:
Solute: water soluble molecules.
WP: Pressure entered by free moving water molecules
Solution: solute dissolved in solvent.
Why does osmosis happen?
More water causes more collisions so higher pressure and WP, random net movement/diffusion reached equilibrium.
How does osmosis affect animal cells?
Bursting, crenation, stays the same.
How does osmosis affect plant cells?
Cell wall Prevents bursting, or plasmolysis (shrivelling)
What is active transport?
Transport against concentration gradient from low to high concentration with carrier proteins/ ATP.
How could cells be adapted for rapid transport across their internal or external membranes?
More mitochondria, ATP, Transport proteins, Carrer/co transport/pumps
What is co-transport?
2 potassium in 3 sodium out,
Conc grad est.
Sodium and glucose in through co transport protein
Glucose FD out to blood
Sodium AT out.
How does oral rehydration therapy work?
Contains water potassium ions glucose and other electrolytes
To maintain electrolyte balance, stimulate appetite and precent metabolic acidosis.
What are the roles of diffusion and active transport in absorption?
Carrier proteins (glucose, AA)
Co transport (sodium potassium)
Diffusion of micelles In absorption of lipids.
Can you explain specific adaptations of specialised cells in relation to the rate of transport across their membranes? E.g. Epithelial cells
Low diffusion distance due to thin membrane
Lots of transport proteins
Many mitochondria
