Biology - Movement of substances into and out of cells (2.15-17)

Diffusion

The net movement of particles from an area of high concentration to an area of low concentration

Diffusion example in plants and humans

• Plants: O2 and CO2 diffuse into and out of leaves through the stomata

• Humans: movement of O2 from the air in the alveoli to the blood in the lungs

Osmosis

The net movement of water particles from an area of high concentration to an area of low concentration across a partially permeable membrane.

Osmosis example in plants and animals

• Plants: Water moves from soil into root hair cells

• Animals: Water moves from cell cytoplasm into salt solution

What is a hypotonic solution

• Cell has lower water potential than solution

• Water moves into cell

• Plants: cell becomes turgid

• Animals: cell becomes turgid or burst/ lyse

What is an isotonic solution

• Water potential equal between cell and solution

• No net movement of water molecules

What is a hypertonic solution

• Cell has higher water potential than solution

• Water moves out of the cell

• Plants: cell becomes flaccid or plasmolyzed (cytoplasm pulls away from the cell wall)

• Animals: cell shrivels/ becomes crenated

Active transport

The movement of particles from an area of low concentration to an area of high concentration against a concentration gradient using a specific carrier protein and energy in the form of ATP.

Example of active transport in plants and animals

• Plants: mineral ions move from the soil (low concentration) to root hair cells (high concentration)

• Animals: used in the digestive system when the there is a low concentration of nutrients in the gut and a high concentration of nutrients in the blood (to not starve)

Adaptations of cells carrying out active transport (2)

• Many mitochondria (energy)

• Many specific carrier proteins

Factors affecting rate of movement of substances

• Surface area to volume ration

• Concentration gradient

• Distance

• Temperature

Affect of SA:V ratio

The larger the SA:V ratio, the faster the rate of diffusion

Affect of concentration gradient

The steeper the concentration gradient, the faster the rate of movement (but doesn’t affect active transport)

Affect of distance

The smaller the distance, the faster the rate of movement

Affect of temperature

The higher the temperature, the faster the rate of movement (increased kinetic energy, particles move faster)