B03 Movement into and out of cells - no osmosis

Name two ways substances can move in and out of cells

Diffusion, active transport

Name the process that allows molecules or ions to move from an area of high concentration to an area of low concentration

Diffusion

What does concentration gradient mean?

The difference between the concentration of two locations e.g. inside a cell and outside a cell

Name the process that allows molecules or ions to move down a concentration gradient

Diffusion

Define diffusion

The net movement of molecules or ions from an area of high concentration to an area of lower concentration across a partially permeable membrane until equilibrium is reached

What does net movement mean?

The overall / most common direction of movement

Name 1 substance that diffuses into cells for respiration to occur in the mitochondria

oxygen

Name 1 substance that diffuses out of cells after aerobic respiration occurs

carbon dioxide

Describe an example of diffusion in the lungs

There is a high concentration of oxygen in the alveoli of the lungs, which diffuses into the red blood cells in the bloodstream and can be transported around the body to respiring cells OR There is a high concentration of carbon dioxide in the bloodstream, which diffuses into the alveoli and can be exhaled as a waste product.

Describe an example of diffusion in plants

Oxygen and carbon dioxide diffuse down their concentration gradient between the atmosphere and the mesophyll of a plant through the stomata

The xylem in plants is made up of dead cells, yet diffusion still occurs. Why?

Diffusion is a passive process, so does not need energy from respiration of living cells to occur

In diffusion, what do the particles move through?

partially permeable membrane

Why do substances passively move between cells?

Because there is a concentration gradient

Name 4 factors that affect the speed of diffusion

Temperature, size of molecules, distance over which to diffuse, steepness of the concentration gradient

Name 4 factors that speed up the rate of diffusion

A. Steep concentration gradient B. Short distance C. Large surface area D. Higher temperature

What can diffuse?

Fluids (a fluid includes liquids and gases, because they can flow!)

What is a solute?

A substance in which is dissolved in another substance

What is a solvent?

A liquid in which the solute dissolves

What is a solution?

A solute dissolved in a solvent

What does soluble mean?

A substance that will dissolve in a solvent

What does "concentrated solution" mean?

A large mass of solute dissolved in a volume of solvent

What does "dilute solution" mean?

A small mass of solute dissolved in a volume of solvent

Describe a solution that has a high water potential

A small mass / no mass of solute dissolved in a large volume of water when compared with another location

Describe a solution that has a low water potential

A larger mass of solute dissolved in a large volume of water when compared with another location

What happens to plant cells when they are put into a concentrated solution / hypertonic solution?

There is a higher water potential inside the the cell, so water moves out of the cell. The vacuole shrinks, so the cell membrane pulls away from the cell wall and the cell is plasmolysed / flaccid

Why do animal cells but not plant cells burst when they take up water?

Plant cells have a cell wall. Animal cells do not

Define active transport

The movement of molecules or ions from an area of low concentration to an area of higher concentration (i.e. against the concentration gradient) across a partially permeable membrane

Name the process that is the movement of molecules or ions against the concentration gradient

Active transport

How is active transport different to diffusion?

Active transport requires carrier proteins, energy from respiration and transports molecules against the concentration gradient

What are the three features of active transport that makes it different from other methods?

Against a concentration gradient (from low to high), requires a carrier protein to pass through the membrane, Requires energy from respiration.

Why are there lots of mitochondria in root hair cells?

To do aerobic respiration to produce energy for active transport of mineral ions (because there is a higher concentration of mineral ions in the root hair cells than in the soil)

Give examples of where active transport may occur

Mineral ions across plant roots. Absorption of glucose by the epithelial cells of the villi in the small intestine

If too much water is in the soil around a plant, why can't it uptake mineral ions/nutrients?

Soil waterlogged, which means that there is no oxygen, so aerobic respiration cannot occur to produce energy for active transport

Cyanide inhibits respiration, how would this effect the roots of plants

There would be no active transport of mineral ions into the root hair cells. This is because respiration cannot occur, so there is no energy for active transport

What is a partially permeable membrane?

A membrane with small holes that allows some substances (like small water molecules) to pass through but will not allow larger molecules through.