Diffusion

Question 1

Describe the movement of molecules in diffusion

Answer 1

molecules (gas or dissolved)move around randomly because they have kinetic energy

when there is an equal concentration of molecules there is no net movement

(heat energy converts into kinetic energy)

Question 2

Describe the movement of molecules in terms of concentration

Answer 2

at high concentration molecules bump into one another and spread out

molecules move from areas of high concentraion to areas of low concentration until an equilibrium is reached

Question 3

Define diffusion

Answer 3

the movement of gases or dissolved molecules from an area of high concentration to an area of low concentration

the movement of molecules down a concentration gradient

Question 4

Describe diffusion across membranes

(fill in blanks)

Answer 4

cell membranes are selectively permeable

Question 5

Describe concentration gradient and diffusion

Answer 5

the higher the concentration of the gradient the greater the rate of diffusion

Question 6

Describe diffusion distance and diffusion

Answer 6

the larger the diffusion distance the lower the rate of diffusion

Question 7

Describe surface area with diffusion

Answer 7

the larger the surface area the greater the rate of diffusion

Question 8

Describe temprature with diffusion

Answer 8

the higher the temprature the greater the rate of diffusion as the molecules have more kinetic energy

Question 9

Calculate the surface area, volume and surface area/volume ratio for this shape

Answer 9

SA= 6cm²

V= 1cm³

SA/V= 6cm (6:1)

Question 10

Calculate the surface area, volume and surface area/volume ratio for this shape

Answer 10

S= 24cm²

V= 8cm³

SA/V= 3cm (3:1)

Question 11

Calculate the surface area, volume and surface area/volume ratio for this shape

Answer 11

S= 54cm²

V= 27cm³

SA/V=2cm (2:1)

Question 12

What happens as an organism gets bigger in terms of SA/V and diffusion

Answer 12

the amount of surface area it has per unit of volume gets smaller

diffusion into the organism takes longer

Question 13

Why do big organims have a disadvantage?

Answer 13

their surface area is too small for their volume: their ‘middle’ is too far away from their surface

Question 14

What is surface area to volume ratio?

Answer 14

the amount of surface area per unit of volume

Question 15

What are the advantages of a large SA/V?

Answer 15

lose heat (hot climate)

gets rid of waste products (carbon dioxide etc…)

take up of useful molecules (nutrients, oxygen etc…)

Question 16

What are the advantages of a small SA/V?

Answer 16

retains heat (cold climate)

Question 17

How can an organism increase its SA/V?

Answer 17

increase surface area

decrease volume

Question 18

Faciliated Diffusion

Answer 18

movement of a molecule from an area of high concentration to an area of low concentration with the help of channel or carrier protein (this controls the speed of entry)

e.g. glucose, amino acids, ions

Question 19

Passive Transport

Answer 19

movement of molecules through cell membranes down a concentration gradient without the use of energy (diffusion, faciliated diffusion, osmosis)

Question 20

Active Transport Across Membrane

Answer 20

movement of molecules through cell membranes against a concentration gradient. This requires energy and a carrier protein

e.g. glucose, amino acids, ions

[energy (ATP)]

Question 21

what is a movement of substances that does need energy

Answer 21

active transport

Question 22

membranes that allow some substances to pass through but not others are called ….?

Answer 22

selectively permeable

Question 23

name a requirement of faciliated transport

Answer 23

the help of channel and carrier proteins

Question 24

what does a channel or carrier protiens do?

Answer 24

control the speed of entry