1.15: transport of subtances

What methods do substances use to move in and out of cells?

Diffusion, osmosis, active transport

What is diffusion?

The random movement of particles from an area of high concentration to an area of low concentration until an equilibrium is reached

What is an equilibrium?

When both areas have the same concentration - they are equal

Is diffusion active or passive?

Passive

What is a passive process?

One which doesn’t require energy to work

What is an active process?

One which does require energy to work

What factors is diffusion affected by?

The concentration gradient, temperature, surface area and distance

To increase the rate of diffusion, what temperature do you want?

High

To increase the rate of diffusion, what concentration gradient do you want?

Steep - there are lots of particles in one area and very few in the other

To increase the rate of diffusion, what surface area do you want?

A large one

To increase the rate of diffusion, what distance do you want?

A short one

What state can diffusion happen in?

Liquids and gases

What is osmosis?

The movement of water from an area of high water concentration to an area of low water concentration through a partially permeable membrane

Where does diffusion take place?

Into and out of cells, the alveoli in the lungs, plant leaves, and the blood stream

What is another way of describing osmosis?

The movement of water from a dilute solution to a more concentrated solution (lots of water molecules to few water molecules) through a partially permeable membrane

Is osmosis active or passive?

Passive

What is the purpose of the partially permeable membrane?

It allows small molecules through, such as water, but prevents larger molecules from going through, such as sugar molecules

What is active transport?

The movement of substances from an area of low concentration to an area of high concentration against a concentration gradient through a partially permeable membrane

Is active transport active or passive?

Active

What substances does osmosis transport?

Water only

How does active transport gain energy?

From respiration

Where does active transport take place?

In the gut - glucose molecules are carried from the gut into blood

In the kidney - active transport is used to transport glucose from the kidney into the bloodstream

In plants - mineral ions are transferred from the soil into root hair cells

What is significant about transport in the gut?

Sometimes it uses active transport if there are lots of glucose molecules in the gut (such as after drinking a sugary drink) but sometimes it uses diffusion as there are not many glucose molecules in the gut

What is significant about transport in the kidneys?

Multiple substances are being transported into and out of the kidneys - diffusion is used to transport urea, glucose and excess salts from the bloodstream. Later, active transport is used to transport glucose back into the bloodstream when it is needed