Osmosis + Active transport

What is active transport? (2)

The movement of substances against the concentration gradient

Requires energy from respiration

How do molecules move with active transport (2)

Across the membrane via carrier proteins

Proteins are highly specific

What does active transport use?

Energy (ATP) released during respiration

What is ATP (2)

Adenosine triphosphate

Produced in respiration

What happens when ATP is hydrolysed? (3)

Forms ADP + P

Releases energy

ADP is adenosine diphosphate

Active transport: Stage 1 (2)

Molecules bind to carrier protein

ATP attaches to the membrane protein on the inside of the cell

Active transport: Stage 2 (2)

ATP splits into ADP and phosphate molecule

Releases energy

Active transport: Stage 3 (3)

Binding of phosphate molecule to protein causes the protein to change shape

Access for the molecules is open to the inside of the membrane

Closed to the outside

Active transport: Stage 4 (3)

Molecule/ion is released from cell

Protein reverts to original shape

ADP + P combine to form ATP again

Osmosis (2)

The net movement of water molecules from a region of higher water concentration to a region of lower water concentration

Across a selectively permeable membrane.

What is water potential (4)

Water potential is the pressure exerted by water molecules

Pure water has a water potential of zero

When a solute is added this lowers the water potential

When the water concentration is high, the water potential is high (closer to zero)

Why does water need to be faciliated by channel proteins? (2)

Water is polar

Repelled by the fatty acid tails inside the phospholipid bilayer