Lecture 12

Question 1

Bulk transport

Answer 1

occurs by exo or endocytosis

small moelcuiels and water enter or leave the cell through the lipid bilayer or by transport proteins

large molecules cross the membrane in bulk via proteins

bulk transport requires energy

Question 2

Exocytosis

Answer 2

in exocytosis, transport vesicles migrate to the membrane fuse with it and release their contents

many secretory cells use exocytosis to export their products

Question 3

Endocytosis

Answer 3

in endocytosis, the cell takes in macromolecules by forming vesicles from the plasma membrane

endocytosis is a reversal of exocytosis, involving different proteins

Question 4

Three types of endocytosis

Answer 4

phagocytosis (cellular eating)
pinocytosis (cellular drinking)
receptor-mediated endocytosis

Question 5

Phagocytosis

Answer 5

a cell engulfs a particle in a vacuole

the vacuole fuses with a lysosome to digest the particle

Question 6

Pinocytosis

Answer 6

molecules are taken up when extracellular fluid is gulped into tiny vesicles

Question 7

Receptor-mediated endocytosis

Answer 7

in a receptor mediated endocytosis, binding of ligands to receptors triggers vesicle formation

a ligand is any molecule that binds specifically to a receptor site of another molecule

Question 8

Clathrin

Answer 8

is a main component for receptor mediated endocytosis

Clathrin coated vesicles code the membrane

Question 9

Endocytic recycling-combining

Answer 9

where endocytosis and exocytosis are combined in a meta-process

Question 10

Exocytosis functions

Answer 10

• to secrete digestive enzymes
• to deposit cell wall material (for protection)

Question 11

Endocytosis functions

Answer 11

to recycle membrane lipids and proteins

to avoid congestion