Cell Transport (Unit 1)

Question 1

What is diffusion in the context of passive transport?

Answer 1

Diffusion is the process in which molecules move from a region of higher concentration to a region of lower concentration until equilibrium is reached, known as net diffusion.

Question 2

What factors affect the rate of simple diffusion across a membrane?

Answer 2

The size and charge of a molecule significantly affect its rate of diffusion across a membrane.

Question 3

What is facilitated diffusion?

Answer 3

Facilitated diffusion is a type of passive transport where molecules are transported across a membrane with the help of membrane proteins such as channeling proteins.

Question 4

How do carrier proteins function in facilitated diffusion?

Answer 4

1. Carrier protein binds solute molecule when the binding site faces region of higher concentration.
2. Binding induces a change in the protein’s conformation, exposing the binding site towards the region of lower concentration.
3. Solute is released, and carrier protein returns to its original conformation

Question 5

Describe the process of osmosis.

Answer 5

Osmosis is the diffusion of water through a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Question 6

What is active transport and how does it function?

Answer 6

Active transport involves the movement of substances against their concentration gradient, using energy from ATP. Transport proteins bind ATP, undergo a conformational change to bind ions or molecules, then release them on the other side of the membrane after hydrolyzing ATP.

Question 7

What is secondary active transport?

Answer 7

Secondary active transport uses the energy from the ion gradient created by primary active transport. It includes symport (solute and ion move in the same direction) and antiport (solute and ion move in opposite directions).

Question 8

What is exocytosis

Answer 8

Export of materials, primarily carries secretory proteins and some waste materials from cytosol to the exterior of cell

Question 9

Key steps of exocytosis?

Answer 9

1. Secretory vesicles move through cytosol and contact plasma membrane
2. Vesicle membrane fuses with plasma membrane, releasing contents to exterior of cell

Question 10

What is endocytosis?

Answer 10

Import may carry proteins, larger aggregates of molecules, or whole cells from the exterior of the cell into the cytosol

Question 11

Keys steps of endocytosis?

Answer 11

1. Proteins/other substances trapped in pit-like depression, bulging inward from plasma membrane
2. Pinches off as an endocytic vesicle

Question 12

What is receptor-mediated endocytosis

Answer 12

Molecules to be taken in are bound to the outer cell surface by receptor proteins, which then collect into a pit coated with a network of proteins (clathrin)

Question 13

Key steps of receptor-mediated endocytosis?

Answer 13

Binding of molecules to receptor proteins on cell surface
Formation of coated pit with clathrin
Coated pit breaks free of membrane, forming a vesicle
Vesicle loses clathrin coating and may fuse with a lysosome
Enzymes within lysosome digest cargo, breaking it down into smaller molecules useful to the cell