2.3 Transport Across Cell Membranes

Question 1

Define diffusion

Answer 1

Net movement of small uncharged particles down a concentration gradient (high to low)

Question 2

Define facilitated diffusion

Answer 2

Net movement of small charged particles down the concentration gradient using carrier or channel proteins

Question 3

Define Osmosis

Answer 3

Passage of water molecules from regions of high water potential to regions of low water potential across a semi permeable membrane

Question 4

Define active transport

Answer 4

Net movement of molecules up a concentration gradient using ATP (energy)

Question 5

Define exocytosis

Answer 5

Where molecules are wrapped in a vesicle that’ll fuse with cell surface membrane to allow contents to leave cell

Question 6

Define endocytosis

Answer 6

Where vesicle containing molecules will fuse with cell surface membrane to allow contents to enter cell

Question 7

What’s fluid mosaic model

Answer 7

Arrangement or cell surface membrane is related to its function

• As there’s water within cell surface membrane this allows free movent of molecules attached within membrane
• Membrane is referred to mosaic model due to random arrangement

Question 8

Describe Sodium/ Potassium Pump (Small Intestine)

Answer 8

• ileum is part of small Intestine that’s involved in absorption of molecules
• within ileum membrane, there are finger like projections called microvilli that increase SA for absorption
• initially, molecules will move from high conc. (ileum) to low conc. (bloodstream) allowing simple diffusion to occur
• eventually, conc. gradient between ileum and bloodstream will be = meaning that diffusion won’t occur

Question 9

What are channel proteins

Answer 9

Specific to one or few molecules

Interacts weakly with molecules

Question 10

What are carrier proteins

Answer 10

Induces conformation Al charge in shape of protein

Interacts weakly with molecules

Question 11

Explain process of Active transport

Answer 11

1. Molecule to be transported binds to a receptor on carrier proteins
2. Molecule/ ion is transported through carrier protein
3. At same time an ATP molecule binds to carrier proteins on inside of cell membrane
4. ATP molecules is hydrolysed to ADP and Pi
5. Hydrolysis reaction causes protein molecule to change shape and open