L2.2 Membrane Transport- Passive & Active Transport

Question 1

define transport proteins

Answer 1

molecules that can’t diffuse across the plasma membrane can travel through transport proteins. they span the plasma membrane and have either channel proteins or carrier proteins.

Question 2

transport of molecules across the plasma membrane can be: ____ or ____

Answer 2

transport of molecules across the plasma membrane can be: PASSIVE or ACTIVE

• Passive: does not require cellular energy, move down the concentration gradient
• Active: requires cellular gradient, against the concentration gradient

Question 3

what is facilitated diffusion? and types?

Answer 3

down the concentration gradient, doesn’t require ATP

types: channels or carriers

Question 4

explain the difference between channels and carriers

Answer 4

channels: don’t interact w/ molecules; hydrophilic tunnel through the plasma membrane; transport small molecules; some channels are gated (open or close in response to a stimulus)
carriers: interact w/ molecules; carrier proteins change shape to transport solutes across the membrane (see notes for process)

Question 5

what is active transport? and types?

Answer 5

transport through a carrier (NOT A CHANNEL) against the concentration gradient; requires ATP
types: primary active transport, secondary active transport

Question 6

what is the difference between primary and secondary active transport?

Answer 6

primary active transport: directly uses ATP; the terminal phosphate group in ATP is transferred to the carrier; called phosphorylation; causes the carrier to change shape (see notes for sodium-potassium pump example)

secondary active transport: ATP isn’t directly used; the movement of a solute down it’s concentration gradient provides a ‘driving force’ (energy) for the movement of a second solute against the concentration gradient; two solutes transported together in the same (symport) or opposite (antiport) direction (see notes for example)

Question 7

what is vesicular transport? and types?

Answer 7

transfer of materials between the ECF and ICF within vesicles membrane; requires energy from ATP
types: endocytosis (vesicular transport into the cell); exocytosis (vesicular transport out of the cell)

Question 8

what are the 3 types of endocytosis?

Answer 8

1. receptor mediated endocytosis (uptake triggered when target molecule binds to receptors on the plasma membrane)
2. pinocytosis (cell drinking- uptake of ECF)
3. phagocytosis (cell eating- uptake of solid objects such as bacteria and cellular debris)

Question 9

explain receptor mediated endocytosis

Answer 9

target module binds to cell surface receptor, which triggers the invagination of the cell membrane

Question 10

explain pinocytosis

Answer 10

1. solute molecules and water molecules are outside the plasma membrane
2. membrane pockets inward, enclosing solute molecules and water molecules
3. pocket pinches off as endocytic vesicle containing sample of ECF

non selective uptake of fluid (water, ions, glucose etc.)
a way to recover ‘extra’ plasma membrane added to the cell surface during exocytosis

Question 11

explain phagocytosis

Answer 11

cell engulfs large solid particle (e.g. bacterium), the cell extends pseudopods (cytoplasmic extension) around the object

Question 12

what is exocytosis?

Answer 12

reverse of endocytosis
secretory vesicles are released from the golgi complex, they bind to the cell membrane, releasing their contents
secretory vesicles may release produces continuously (unregulated) or may remain in the cell until release is triggered (regulated)