Biology: Diffusion, Active Transport and Osmosis

Question 1

What is Simple Diffusion?

Answer 1

• No cell membrane needed for simple diffusion.
• Molecules can pass across the cell membrane
• High to low concentration
• No energy required

Question 2

What is Facilitated Diffusion?

Answer 2

• Facilitated Diffusion can only occur is Carrier proteins have a complementary binder site.
• The molecule binds to the binding site of the carrier protein cause a change in the orientation of the protein by changing its tertiary structure leading to the transportation of the molecule across the cell membrane.
• The rate of facilitated diffusion is proportional to the number of specific proteins in the cell membrane.

Question 3

What is Active Transport?

Answer 3

• Molecules move against the concentration gradient
• Active Transport requires ATP synthesised synthesised from Mitochondria in aerobic respiration.
• Active Transport requires specific complementary shaped binder sites in carrier proteins in the cell membrane.
  -The cause of the change in the orientation of the carrier protein is the hydrolysis of ATP and Pi.
• The rate of active transport is proportional to the number of specific proteins in the cell membrane.

Question 4

What is Osmosis?

Answer 4

Osmosis is the net movement of water molecules from an area of higher water potential to an area of lower water potential across a semi-permeable membrane.

Question 5

What is a Hypotonic solution?

Answer 5

Hypotonic is a higher concentration of solutes inside the cell membrane than outside the semi-permeable membrane. The net movement of water molecules moves from a higher water potential to a lower water potential resulting in the expansion of the egg.

Question 6

What is a Hypertonic?

Answer 6

Hypertonic is a lower concentration of solutes inside the cell membrane than outside the semi-permeable membrane. The net movement of water molecules moves from a higher water potential to a lower water potential resulting in the shrinking of the egg.

Question 7

Hydrolysis of ATP

Answer 7

Hydrolysis of ATP to adenosine diphosphate (ADP) and an inorganic phosphate group (Pi) is catalyses by the enzyme ATP hydrolase. The hydrolysis of ATP can be coupled to energy-requiring reactions within cells.

Question 8

How are cells adapted for transportation?

Answer 8

Cells may be adapted for rapid transport across their internal or external membranes by an increase in surface area of, or by an increase in the number of protein channels and carrier molecules in, their membranes.