transport across membranes

Question 1

factors that effect the rate of diffusion

Answer 1

• temperature
• concentration gradient
• lipid solubility
• size of the molecule
• diffusion distance
• surface area

Question 2

what are 2 types of transport across membranes

Answer 2

1. passive transport
2. active transport

Question 3

does passive transport require energy or not

Answer 3

no it does not require any external energy

Question 4

does active transport require energy or not

Answer 4

yes- requires energy in the form of the energy molecule ATP)

Question 5

what is diffusion

Answer 5

the net movement of particles from a high concentration to a region of lower concentration DOWN a concentration gradient.
it is passive (does not require energy)

Question 6

what are the 2 types of diffusion

Answer 6

1. simple diffusion
2. facilitated diffusion

Question 7

what is simple diffusion

Answer 7

particles can simply diffuse across the phospholipid

Question 8

what is required for facilitated diffusion

Answer 8

channel proteins (small water soluble molecules) and carrier proteins (larger, water soluble ions)

Question 9

what are carrier proteins

Answer 9

• they allow larger polar molecules to pass through the membrane e.g. glucose
• when a molecule that is specific enough to the carrier present, it binds to the protein
• this causes a shape change and releases to the other side.

Question 10

what is active transport

Answer 10

• the movement of particles into or out of a cell from a region of lower concentration to a region of higher concentration.
• (AGAINST its concentration gradient)
• using ATP and carrier proteins

Question 12

describe the steps of active transport

Answer 12

1. the molecule/ion being transported across the membrane binds to specific carrier proteins at the binding site
2. inside the membrane, ATP binds to the carrier protein, causing it to split (hydrolise) releasing ADP
3. this causes carrier protein to change shape and open opposite side of membrane
4. the inorganic phosphate is released so carrier protein goes back to its orgininal shape