Cell Transport Flashcards
State Fick’s law [1 mark]
Rate of reaction = (surface area x difference in concentration) / diffusion distance
Difference in concentration = concentration gradient
What’s the difference between carrier and channel proteins? [2 marks]
Carrier proteins…
change tertiary structure in order to transport substances.
Channel proteins…
do not change tertiary structure in order to transport substances.
What are the similarities between carrier and channel proteins? [3 marks]
> Transports SPECIFIC substances across membrane.
Made of polypeptides.
Found in cell membrane.
Can be used for facilitated diffusion.
Can allow transport down the concentration gradient - high to low.
Name and explain 3 factors that affect membrane permeability?
> Temperature =
high temperature denatures membrane proteins - phospholipid molecules have more kinetic energy & move further apart.
> pH =
changes tertiary structure of membrane proteins.
> Use of a solvent =
may dissolve membrane.
What are intrinsic proteins? Give examples.
Connects/spans from 1 side of phospholipid bilayer to the other.
E.G.
Channel proteins
Carrier proteins
What are extrinsic proteins? Give examples.
Occur/embedded in the surface of phospholipid bilayer.
E.G.
Receptors
Are small molecules polar or non-polar in terms of cell transport?
Non-polar
(think about it - a small molecule will barely have any charge)
Are large molecules polar or non-polar in terms of cell transport?
Polar
(think about it - a large molecule will have a large difference in charge)
State how small non-polar molecules and large polar molecules are transported [2 marks]
Small and non-polar —> via simple diffusion
Large and polar —> via facilitated diffusion
What is meant by simple diffusion?
The NET movement of small/non-polar molecules through a membrane from a high to low concentration down the concentration gradient, until evenly distributed.
What are examples of small, non-polar molecules?
Oxygen
Carbon dioxide
What are examples of large, polar molecules?
Water
Ammonia
What is meant by osmosis?
The movement of water through an area of high water potential to an area of low water potential down the concentration gradient through a partially permeable membrane.
What is active transport?
The movement of substances across a membrane via a CARRIER PROTEIN from an area of low concentration to a high concentration against the concentration gradient.
Uses ENERGY from RESPIRATION / Hydrolysis of ATP.
What is co-transport?
Movement of a substance against its concentration gradient coupled with the movement of another substance down its concentration gradient, across a cell membrane via a CARRIER PROTEIN
What kind of process is simple diffusion?
A passive process
meaning it does not require energy from ATP hydrolysis
What is facilitated diffusion?
The NET movement of large/polar substances through specific CHANNEL or CARRIER down the concentration gradient.
What kind of process is facilitated diffusion?
A passive process
meaning it does not require energy from ATP hydrolysis
Explain how channel proteins and carrier proteins work
Channel =
Hydrophilic channels bind to specific ions - 1 side of the protein closes & the other opens.
Carrier =
Binds to the complementary molecule - releases the molecule on the other side of membrane.
What kind of process is active transport?
Active process
ATP hydrolysis releases phosphate group that binds to carrier protein, causing it to change shape.
Compare and contrast active transport and facilitated diffusion.
BOTH =
> May involve carrier proteins.’
Active transport =
> Active process - requires energy from ATP hydrolysis
> Against conc gradient
Facilitated diffusion =
> Passive process
> May also involve channel proteins.
> Down conc gradient
Explain how co-transport is involved in the absorption of glucose/ amino acids in the small intestine.
Ileum / Lumen (inside of intestine) —– Epithelial cells (villi) —— capillary (bloodstream)
1) Na+ actively transported out of epithelial cells & into bloodstream.
2) Na+ concentration lower in epithelial cells than lumen of gut.
3) Transport of glucose/ amino acids from lumen to epithelial cells is ‘coupled’ to facilitated diffusion of Na+ down concentration gradient.
Explain how co-transport is involved in the absorption of glucose/ amino acids in the small intestine. (long answer)
https://www.youtube.com/watch?v=zn9ypKnhQZA
Ileum / Lumen (inside of intestine) —– Epithelial cells (villi) —— capillary (bloodstream)
Na+ actively transported out of epithelial cells into bloodstream.
This reduces Na+ concentration in epithelial cells.
Na+ ions can facilitated diffuse from lumen down conc. gradient into epithelial cells.
Na+ diffuses through a co-transported protein, so glucose/amino acids attach and are transported to the epithelial cells against their conc. gradient.
Glucose/amino acids then move by facilitated diffusion from the epithelial cell to the blood.
What does the sodium-potassium pump do in active transport?
A carrier protein that transports sodium out of and potassium into the cell as it repeatedly changes shape