B4d: Diffusion and osmosis

Question 1

Describe diffusion

Answer 1

the net movement of particles from an area of higher concentration to an area of lower concentration, down a concentration gradient until an equilibrium is reached

Question 2

What is diffusion the result of?

Answer 2

the constant random movement of individual particles; far more move from high to low concentration than vice versa

Question 3

How do substances move in and out of cells?

Answer 3

by diffusion through the cell membrane

Question 4

Factors increasing the rate of diffusion (3)

Answer 4

shorter distance for particles to travel

greater concentration difference/gradient - greater net movement

greater surface area - particles have more area to diffuse across

Question 5

Describe osmosis

Answer 5

the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of
lower water concentration until an equilibrium is reached

Question 6

Osmosis is a type of _

Answer 6

diffusion

Question 7

What is a partially-permeable membrane

Answer 7

membrane that has small pores through which small molecules such as water can pass, but not larger molecules such as proteins

Question 8

What is osmosis a result of?

Answer 8

the constant random movement of individual water particles; far more move from high to low concentration than vice versa

Question 9

How are plants supported

Answer 9

the entry of water into plant cells increases the pressure pushing on the cell wall, which is rigid and not elastic
-this turgor pressure supports the cell, stopping it, and the whole plant from collapsing

Question 10

What is wilting

Answer 10

When too much water leaves a cell causing it to lose its turgor pressure

Question 11

What is lysis

Answer 11

Animal cells absorb too much water through osmosis and swell up and burst

Question 12

What is crenation

Answer 12

too much water leaves an animal cell through osmosis and it shrinks

Question 13

What is turgid

Answer 13

a plant cell fully inflated with water, where turgor pressure helps keep cell firm

Question 14

What is flaccid

Answer 14

a plant cell becoming limp due to a reduction a pressure inside the cell when too much water leaves the cell through osmosis

Question 15

What is plasmolysed

Answer 15

cell membrane pulled away from the inside of the cell wall due to a loss of water through osmosis

Question 16

Adaptations of the leaf for diffusion (5)

Answer 16

broad = large SA for gases to diffuse

thin = short diffusion distance for CO2 to diffuse to the mesophyll and palisade cells

air spaces in spongy mesophyll = allow CO2 to diffuse from stomata to palisade cells

air spaces = large internal SA:V ratio = maximum absorption of gases

stomata for gases to diffuse into leaf

Question 17

Why do plant cells not burst when it is fully inflated with water

Answer 17

its inelatic cell wall stops the cell from bursting