[lecture 6] diffusion and trafficking

Question 1

passive transport

Answer 1

doesnt require energy

Question 2

active transport

Answer 2

requires energy, against concentration gradient

Question 3

what is diffusion

Answer 3

movement of molecules from areas of high concentration to areas of low concentration
* some molecules can diffuse freely across membranes and others need channels

Question 4

what are channels used for

Answer 4

transport of specific molecules (regulates transport)

Question 5

factors affecting diffusion

Answer 5

1. surface area
2. temperature
3. distance across membranes
4. size and nature of molecules

Question 6

what is osmosis

Answer 6

diffusion of water from an area with high concentration of water to an area of low concentration of water

Question 7

osmoregulation: 3 types

Answer 7

hypertonic: water just leaves, cells become flaccid
isotonic: water leaves and enters, optimum condition for cells
hypotonic: too much water enters cells, cells become turgid

Question 8

examples of active transport

Answer 8

1. ion pumps
2. motor proteins
3. exocytosis, endocytosis, macropinocytosis, phagocytosis

Question 9

Na+ K- ATPase- how does it work

Answer 9

for each ATP molecule, 3 sodium ions are pumped out and 2 potassium ions are pumped in

Question 10

how do motor proteins transport things

Answer 10

• they use the cytoskeleton as highways – actin fibers and microtubules
• most common motor proteins are the Myosin family (move along actin fibres) and Dynein and Kinesin (move along microtubules)

Question 11

how is cargo carried by motor proteins

Answer 11

in form of vesicles (liposomes)

Question 12

what is endocytosis

Answer 12

the cell surrounds material with plasma membrane and brings in a
small vesicle

Question 13

types of endocytosis

Answer 13

1. phagocytosis: fuse with lysosome for digestion
2. pinocytosis: non specific process
3. receptor mediated endocytosis: triggered by molecular signalling

Question 14

what is exocytosis

Answer 14

materials are released from cells when a vesicle fuses with the plasma membrane

Question 15

types of exocytosis

Answer 15

1. constitutive secretion: plasma membrane lipids and plasma membrane proteins secrete through unregulated membrane fusion.
2. regulated secretion: secretory vesicle containing secretory proteins wait for a signal such as hormone or neurotransmitter and then fuse with the cell membrane and let their contents out.