Diffusion, Osmosis, and Ctive transport

What is diffusion?

Diffusion is the movement of molecules from a region of its higher concentration to a region of its lower concentration down a concentration gradient

How can diffusion help organisms?

Gets rid of waste products, carries out gas exchange for respiration, and obtains nutrients

What factors affect diffusion?

Concentration gradient, temperature, distance, and surface area to volume ratio

What is osmosis?

Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane

What is a solution with high water potential?

Dilute solution, low solute concentration

What is low water potential?

Concentrated solution, high solute concentration

What happens when a plant cell is placed in a solution with higher water potential?

Water moves into the cells through osmosis, these water molecules push the cell membrane against the cell wall, increasing the turgor pressure in the cells which makes them turgid 

What happens when a plant cell is placed in a solution with lower water potential?

water molecules will move out of the plant cells by osmosis, making them flaccid and the plant cells becomes plasmolysed, meaning the cell membrane has pulled away from the cell wall

What happens when an animal cell is placed in a solution with higher water potential?

it will gain water by osmosis and, as it has no cell wall to create turgor pressure, will continue to do so until the cell membrane is stretched too far and it bursts

What happens when an animal cell is placed in a solution with a lower water potential?

it will lose water by osmosis and become crenated

What is active transport?

Active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration

Why is energy needed for active transport?

particles are being moved against a concentration gradient, in the opposite direction from which they would naturally move

How does active transport work?

Active transport works by using carrier proteins embedded in the cell membrane to pick up specific molecules and take them through the cell membrane against their concentration gradient

Describe the process of active transport

Substance combines with carrier protein molecule in cell membrane, carrier transports substances across membrane using energy from respiration to give them the kinetic energy needed to change shape and move the substance through the cell membrane, and the substance is released into cell

Describe the role of water as a solvent in regards to digestion

When we swallow food, some of it dissolves in water in the alimentary canal, where it is acted on by enzymes which also dissolve in water.

Describe the role of water as a solvent in regards to excretion

The kidneys excrete urea dissolved in water, to form urine

Describe the role of water in regards to transport

Substances are transported around the body dissolved in the water in blood plasma