Exchange Across Cell Membrane - ACTIVE TRANSP Flashcards
What is active transport?
Move molecules/ions across membrane against concentration gradient
What type of transport protein is involved in active transport?
Carrier proteins
Two differences between active transport and facilitated diffusion:
- AT: Move solutes from a low to a high concentration
- FD: High to low
- AT: Requires ATP
- FD :’Passive’
What are co-transports?
Type of carrier proteins
What are co-transporters?
- Bind two molecules at a time
- Concentration gradient of one molecule is used to move other molecule againt its concentration gradient
- e.g sodium ions and glucose
Factors affecting active transport
- Speed of invidiual carrier proteins - faster , increase rate
- Number of carrier proteins : More , increase rate
- Rate of respiration in cell and availity of ATP : Respiration inhibited , no active transport can be conducted
Where is glucose absorbed into the bloodstream by?
Small intestine
When does glucose have to be co-transport to be absorbed from lumen of ileum?
Ileum the concentration of glucose is too low to diffuse out into the blood
Instructions of glucose entering the ileum epithelium with sodium ions
- Sodium ions actively transport out of the ileum epithelial cells into the blood by sodium-potassium pump
- Cause sodium ions to diffuse from the lumen of the ileum into the epithelial cell down the concentration gradient - transporter protein
- Carries glucose into the cell with sodium, increase glucose inside cell
- Glucose diffuses out of cell into blood by faciliated diffusion
Contrast the processes of facilitated diffusion and active transport.
- Facilitated diffusion involves channel or carrier proteins whereas active transport only involves carrier proteins;
- Facilitated diffusion does not use ATP / is passive whereas active transport
- uses ATP;
- Facilitated diffusion takes place down a concentration gradient whereas active
- transport can occur against a concentration gradient.
Some substances can cross the cell-surface membrane of a cell by simple diffusion through the
phospholipid bilayer. Describe other ways by which substances cross this membrane
By osmosis (no mark)
No mark awarded for naming terms e.g. osmosis, facilitated
diffusion, active transport, co-transport etc.
- From a high water potential to a low water potential / down a water potential gradient;
- Through aquaporins / water channels
In this investigation, the scientists cut the strawberries into slices (step 1).
Explain the advantage of this
Increases (surface) area / inside surface exposed / more
cells exposed / shorter distance for water to move;
- Producing water loss
In the second column of the table, the percentage loss in mass for one of the values has
been recorded as not applicable. Explain why
This is initial mass / the time is too short for water to have left / the time is too short
for osmosis / have not been treated;
You could use the data in the table to predict the time that strawberries should be left in
sucrose solution to dehydrate them fully. Describe how you could use a graph to do this.
Plot graph of percentage loss in mass against time;
- Draw curve (of best fit);
Although curve is the technical term accept references to line etc
- Extrapolate / record when no further change in mass / record when curve
flattens out;
Instructions of single molecule or ion active transport
- The carrier porteins span on plasma membrane and bind to be transported on side of it
- They bind to the receptor sites on the carrier proteins
- ATP binds to the protein , causing it to spilt to ADP and Pi. As a result protein changes shape and opens to opposite site
- Molecule/ion released to other side
- Phosphate released from protein which causes protein to revert ot shape and ready for process to be repeated. Phosphate molecule then recombines with ADP to form ATP during respiration
