Transport Across Membranes

Question 1

Simple diffusion

Answer 1

Net movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium reached
Doesn’t require atp -passive

Molecules to diffuse across membrane. Must be lipid soluble and small

Question 2

Facilitated diffusion

Answer 2

Proteins are used to transport molecules .
Movement of ions and polar molecules which can’t simply diffused can be transported by facilitated using protein channels and carrier protiens ms

Protein channels - form tubes filled with water enables water soluble ions to pas through the membrane .

Question 3

Osmosis

Answer 3

The movement of water from an area of higher water potentials to an area of lower water potentiell across partially permeable membrane .

Water potential is the pressure created by water molecules
Measured in kPA
Pure water has 0kpa
More negative the water potential the more solute must be dissolved in iy

Question 4

Osmosis - isotonic hypotonic hypertonic

Answer 4

Isotonic - the water potential is the same in the solution and the cell within the solution.
Animal cells -no gain or loss of water

Hypotonic - water potential of a solution is more positive closer to zero then the cell
Animal cell- more water moving out of cells by osmosis cell will shrink

Hypertonic - the water potential of a solution is more negative then the cell

Animal cells - water move in the cell by osmosis cell will burst

Question 5

Active transport

Answer 5

The movement of a substance from a low concentration to a high concentration using metabolic energy and a carrier protein

1. Molecule bind to a receptor complementary in shape on the protein
2. Atp binds forget the carrier protein from the inside of the cell and is hydrolysed into ADP +Pi
   3.causes the carrier protein change shape and release the molecule to the other side
3. Phosphate ion is then release and the protein returns to its original Shape

Question 6

Why we use co-transport and active transport

Answer 6

Absorb glucose form the lumen to the gut there must be high conc of glucose in the the lumen then epitheal
Usually more glucose in the epithelial cells
This is why active transport and co transport used

Question 7

Co-transport of glucose and sodium ions in the linen

Answer 7

1. Sodium ions are actively transported out of the epithelial cell into the blood
   2.this reduces the sodium ion concentration in the epithelial cells
2. Sodium ions can then diffuse from the lumen down their concentration gradient into the epithelial cells
3. The protien the the sodium ions diffuse is a co transport protein either glucose or amino acids attach and are transported to into the epithelial against concentration gradient .
4. Glucose then moves by facilitated diffusion from epithelial to blood

Question 8

Adaptations for rapid transport

Answer 8

Increase surface area
Increase number of protein channels and carrier molecules in membrane