U1 Lecture 4

Question 1

Two types of transport across the membrane

Answer 1

1. Passive Transport

2. Active Transport

Question 2

Define passive transport

Answer 2

Substances move down their concentration gradient (high to low concentration) without energy input from the cell

Question 3

Define active transport

Answer 3

Substances move against their concentration gradient (low to high concentration) using energy from the cell (ATP)
- NEEDS ENERGY

Question 4

Define Diffusion

Answer 4

• Type of passive transport
• The rate of diffusion is proportional to the concentration gradient
• Diffusion occurs rapidly over short (cellular) distances; but slowly over long (organismic) distances

Question 5

Diffusion across a membrane (barrier)

Answer 5

• To diffuse in or out of cell, solutes must enter the lipid bilayer
• Hydrophillic (polar) solutes can’t
• Hydrophobic (non-polar) solutes can ‘partition’ through the membrane

Question 6

Types of passive transport

Answer 6

1. Simple diffusion
2. Osmosis
3. Channel mediated facilitated diffusion
4. Carrier mediated facilitated diffusion

Question 7

Osmosis

Answer 7

Passive flow of water across a semipermeable membrane in response to a gradient in the chemical activity of water
*water follows solute

Question 8

Channel-Mediated Facilitated Diffusion

Answer 8

The passive transport of molecules or ions across a selective and saturable membrane made of integral proteins
- Has a plug on protein

Question 9

Carrier-Mediated Facilitated Diffusion

Answer 9

Protein consumes a molecule on one end and spits it out on the other side of the membrane

Question 10

Types of active transport

Answer 10

1. Primary active transport - uses ATP
2. Secondary active transport - uses ion gradient
3. Bulk transport - transport in vesicles

Question 11

Define primary active transport

Answer 11

Energy derived from hydrolysis of ATP changes the shape of the carrier protein and “pumps” the substance across the membrane against the concentration gradient (Na+/K+ pump is a good example)

Question 12

Na+ / K+ Pump and ATP as its energy source

Answer 12

3 Na+ ions removed from inside the cell as 2 K+ ions are brought into the cell
- 1 ATP hydrolyzed (compound broken down with water)

Question 13

Define secondary active transport

Answer 13

Energy stored in the Na+ of H+ gradient is used to move other substances against their concentration gradients

Question 14

Define bulk (vesicular) transport

Answer 14

The movement of macro-molecules like proteins or polysaccharides in or out of the cell using ATP

Question 15

Types of bulk transport

Answer 15

1. Endocytosis = transport into cell (ex: phagocytosis/ cellular eating consumes food particles into cell)
2. Exocytosis = transport outside of cell (ex: Golgi complex sends macromolecules out through transport vesicles)
3. Transcytosis = transport through the cell from one external side to e other (ex: transport of insulin)