SPEC POINT 2.4

Question 1

What is diffusion?

Answer 1

1. The net movement of a substance from a region of its higher concentration to a region of its lower concentration (down a concentration gradient)
2. no proteins involved
3. passive

Question 2

When does diffusion occur, and when does it stop?

Answer 2

Wherever there is a concentration gradient, and it stops when the particles of the substance are evenly spread throughout the whole volume

Question 3

What are the properties of molecules that move by simple diffusion?

Answer 3

Small (can fit between phospholipids)

Non-polar (can interact with hydrophobic non polar tails)

Question 4

What is facilitated diffusion?

Answer 4

1. Facilitated diffusion is the process of molecules or ions diffusing across a biological membrane via specific transmembrane integral proteins.
2. passive

Question 5

What molecules require facilitated diffusion, and why?

Answer 5

Large, polar, charged molecules (cannot fit through phospholipid bilayer and cannot pass through hydrophobic tails)

Question 6

What is a carrier protein?

Answer 6

A transmembrane protein that switches shapes when the ion or molecule binds onto a specific site on the protein, which then changes shape and as a result the ion or molecules crosses the membrane (direction dependent on concentration gradient)
requires ATP

Question 7

What is a channel protein?

Answer 7

Hydrophilic pores that extend from one side of the membrane to the other, allowing charged substances to diffuse through. Has a FIXED SHAPE

Question 8

What is active transport?

Answer 8

The movement of a substance against a concentration gradient, requiring ATP and a CARRIER protein

Question 9

What are the properties of molecules that move by active transport?

Answer 9

Large, polar, charged molecules

Question 10

What is passive transport?

Answer 10

No metabolic energy required for the transport, driven by concentration gradient.

Question 11

What is exocytosis?

Answer 11

Exocytosis is the release of substances, usually proteins or polysaccharides, from the cell

Question 12

How does exocytosis occur, and what is an example of this?

Answer 12

Vesicles containing substance pinch off from sacs of Golgi apparatus, move towards and fuse with the cell surface membrane to be released outside of the cell. ACTIVE PROCESS
Example - insulin released into blood by exocytosis

Question 13

What is endocytosis?

Answer 13

Endocytosis is taking in substances from outside the cell

Question 14

How does endocytosis occur, and what is an example of this?

Answer 14

Cell surrounds a substance with a section of cell surface membrane, the membrane engulfs the substance and pinches off inside the cell to form a temporary vacuole. ACTIVE PROCESS
Example - white blood cells ingesting bacteria (phagocytosis)