active transport

Question 1

what is active transport

Answer 1

the movement of molecules or ions into or out of a cell from a region of low concentration to a region of high concentration. the process requires energy and carrier proteins

Question 2

why is energy needed in active transport

Answer 2

the particles are being moved up a concentration gradient

Question 3

where does the energy for active transport come from

Answer 3

the hydrolysis of ATP. cells may need to accumulate more of a particular ion than they could do by diffusion

Question 4

what are carrier proteins

Answer 4

they have specific regions that combine with certain solute molecules or ions. they have a region that binds to and allows the hydrolysis of ATP to release energy. this energy helps the carrier protein changes its shape and carry the ion from one side of the membrane to the other. they act as pumps.

Question 5

describe the process of active transport

Answer 5

1) the molecule or ion to be transported binds to receptors in the channel of the carrier protein on the outside of the cell.
2) on the inside of the cell, ATP binds to the carrier proteins and is hydrolysed into ADP and phosphate.
3) binding of the phosphate molecule to the carrier protein causes the protein to change shape - opening up to the cell inside of the cell
4) the molecule or ion is released to the inside of the cell
5) the phosphate molecule is released from the carrier protein and recombines with ADP to form ATP
6) the carrier protein returns back to its original shape

Question 6

simpler way of describing active transport

Answer 6

• molecule/ion binds to receptors on carrier protein on the outside of the cell
• inside the cell, ATP binds to carrier proteins and is hydrolysed to ADP and phosphate
• ADP is in the cell cytoplasm, phosphate binds to carrier protein
• phosphate causes molecule to change shape (opening flips over) so the molecule can be released inside cell
• phosphate released, binds with ADP to form ATP
• carrier protein reforms

Question 7

why is active transport selective

Answer 7

specific substances are transported by specific carrier proteins

Question 8

what is bulk transport

Answer 8

another form of active transport that requires energy from ATP/

Question 9

when does bulk transport occur

Answer 9

when large molecules such as enzymes, hormones and whole cells like bacteria are too large to move through channel or carrier proteins

Question 10

what is endocytosis

Answer 10

bulk transport of material into cells

Question 11

what happens in endocytosis

Answer 11

substances do not pass through the cell membrane. instead a segment of the plasma membrane surrounds and encloses the particle and brings it into the cell, enclosed in a vesicle.

Question 12

what are the two types of endocytosis and what is the difference between them

Answer 12

phagocytosis (solid matters) and pinocytosis (liquid matters)

Question 13

describe the process of endocytosis

Answer 13

the cell surface membrane first bends inwards when it comes into contact with the material to be transported. the membrane enfolds the material until eventually the membrane fuses forming a vesicle. the vescile pinches off and moves into the cytoplasm to transfer the material for further processing within the cell.

Question 14

why is ATP needed in endocytosis

Answer 14

to provide energy to form the vesicles and move them using molecular motor proteins.

Question 15

what is exocytosis

Answer 15

bulk transport of material outside of cells

Question 16

what happens in exocytosis

Answer 16

material doesnt pass through the plasma membrane. instead a vesicle containing them is moved towards and then fuses with the plasma membrane.

Question 17

describe the process of exocytosis

Answer 17

a membrane bound vesicle containing the substance to be secreted is moved towards the cell surface membrane.
the cell surface membrane and the membrane of the vesicle fuse together.
the fused site opens releasing the contents of the secretory vesicle

Question 18

why is ATP needed in exocytosis

Answer 18

energy in the form of ATP is required for movement of vesicles along the cytoskeleton changing the shape of cells to engulf materials and the fusion of cell membranes as vesicles form or as they meet the cells surface membrane.

Question 19

what is the difference between active transport and facilitated diffusion

Answer 19

both use carrier proteins but fd occurs down a concentration gradient and doesnt require energy