TRANSPORT IN CELLS

What is diffusion?

net movements of particles from a high concentration to a low concentration

What states of matter does diffusion occur in?

liquids or gases

How do particles move in diffusion?

down a concentration gradient

What kind of process is diffusion?

passive process

What is a passive process?

a process that doesn't require energy

What factors affect the rate of diffusion?

high temperature, steep concentration gradient and large surface area

Why does temperature affect rate of diffusion?

Particles gain more kinetic energy, so move quicker and diffuse faster

Why does concentration gradient affect the rate of diffusion?

The greater or steeper the concentration gradient, the faster the rate of diffusion

Why does surface area affect the rate of diffusion?

The bigger the surface area, the more area for particles to diffuse across, so faster diffusion

Why is diffusion important?

helps in getting raw materials and removing waste products

What are examples of raw materials?

• oxygen for respiration

• carbon dioxide for photosynthesis

• water in plant root hair cells

• food molecules diffused from small intestines into blood

What are examples of waste products?

• removing carbon dioxide from respiration

• oxygen from photosynthesis

• urea from cells into the blood

What are specialised surfaces for diffusion?

lungs, gills, roots, leaves

What do lungs use diffusion for?

gas exchange

How are lungs suited for diffusion?

• many alveoli

• alveoli only one cell thick

• the alveoli are surrounded by capillaries so have a good blood supply

• ventilation

• oxygen levels always being high in alveoli and low in blood

How do many alveoli suit the lungs for diffusion?

they provide a large surface area

How do 1 cell thick alveoli suit the lungs for diffusion?

there is a short diffusion distance

How do many capillaries and a good blood supply suit the lungs for diffusion?

it helps with a steep concentration gradient

How does ventilation suit the lungs for diffusion?

it helps with a steep concentration gradient

What do gills use diffusion for?

gas exchange

How are gills suited for diffusion?

• gills are made of stacks of gill filaments

• the gill filaments are thin

• the filaments are surrounded by many blood capillaries

• water constantly flows over the gills

How do stacks of gill filaments help with diffusion?

it gives them a large surface area

How do thin filaments help with diffusion?

there's a short diffusion distance

How do many blood capillaries help with diffusion?

it maintains a steep concentration gradient

What do the roots of plants use diffusion for?

absorbing water and mineral ions from the soil

How are roots suited for diffusion?

• root hairs cells have long projects

• thin

• water is continuously taken out of roots

How do long root hair cell projects help with diffusion?

to increase surface area

How do thin root hair cells help with diffusion?

for a short diffusion distance

How does water being taken out of the roots help with diffusion?

it maintains a high concentration gradient

What do leaves use diffusion for?

photosynthesis

How are leaves suited by diffusion?

• wide

• flat

• thin

How do wide and flat surfaces help with diffusion?

it increases surface area and absorbs more light and carbon dioxide

How do thin surfaces help with diffusion?

it has shorter diffusion distances for gases

What is osmosis?

diffusion of water from a dilute solution to a concentrated solution across a partially permeable membrane

What is a dilute solution?

a high concentration of water molecules/high water potential

What is a concentrated solution?

a low concentration of water molecules/low water potential

What is a partially permeable membrane?

it allows some molecules to pass through but not others

How to answer osmosis questions?

Water moves into/out of cells, by osmosis, from a dilute solution in/out of the cell to a more concentrated solution in/out of the cell, across/through a partially permeable membrane, so the cell will shrink/become plasmolysed/become turgid/burst/shrivel

How does osmosis in animal cells happen in dilute solutions?

they will burst (lysis)

Why do animal cells burst in dilute solutions?

As they don't have a cell wall

How does osmosis in animal cells happen in concentrated solutions?

they will shrivel

Why do animal cells shrivel in concentrated solutions?

water is moved out of the cell by osmosis

How does osmosis in plant cells happen in dilute solutions?

the cell will become turgid

What does turgid mean?

when a plant cell becomes swollen with water due to osmosis

Why do plant cells become turgid in dilute solutions?

the cell wall prevents the cell from bursting

How does osmosis in plant cells happen in concentrated solutions?

the cell will become plasmolysed

What does plasmolysed mean?

The cell membrane becomes detached from cell wall due to osmosis

Why do plant cells become plasmolysed in dilute solutions?

The vacuole and cytoplasm have shrunk which pulls away the cell membrane from the cell wall

How to find change in mass/length

new - old

How to find a percentage change in mass

change-original/original x 100

On a graph, what happens when the curve crosses the x- axis?

this is the concentration inside the cell (same concentration inside the cell and in the solution) so the change in mass is zero because the net movement of water is zero.

What is active transport?

Moves substances from a dilute solution to a more concentrated solution

How do particles move in active transport?

against the concentration gradient

What kind of process is active transport?

active process

What is an active process?

a process that requires energy

Examples of active transport?

• plant root hair cells absorbing mineral ions

• sugar molecules absorbed from lower concentrations from the gut into the blood which has a higher concentration

How do many mitochondria help with active transport?

it gives energy