Osmosis, Diffusion, Active Transport Flashcards
What is diffusion?
Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration.
What factors affect the rate of diffusion?
Concentration gradient-(bigger concentration gradient faster diffusion rate)
Temperature- The higher the temperature the faster the diffusion rate, particles have more energy so move faster.
Surface area- The larger the surface area, the faster diffusion rate.
Why does diffusion happen?
Dissolved substances can move in and out of cells by diffusion. (only small molecules-Oxygen, glucose, amino acids and water,) not starch or proteins.
What is osmosis?
Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
What is a partially permeable membrane?
Membrane with very small holes in it. only tiny molecules like water can pass through, sucrose cannot because its too big.
Net flow?
Particles on each side but more on one side so there is a net flow of water on the region with fewer water molecules.
What is active transport?
Substances sometimes need to be absorbed against the concentration gradient from a lower to a higher concentration, This is called active transport.
Active transport on root hairs
each root is covered in hairs that give the plant a large surface area for absorbing water and mineral ions from the soil. The concentration of minerals is normally higher in the root hair cells than in the soil around them so they can’t use diffusion and result to active transport.
What does active transport do?
Active transport allows the plant to absorb minerals from a very dilute solution against a concentration gradient, this is essential for growth. Active transport requires ENERGY from respiration to make it work. It also happens in humans, e.g. taking glucose from the gut and kidney tubules.
Active transport in humans?
Used in the gut when there is a lower concentration of nutrients in gut but higher concentration of nutrients in the blood.
high concentration of glucose and amino acids in gut they will diffuse naturally in blood but
low concentration of glucose and amino acids in gut means concentration gradient is the wrong way.
Active transport is used to take the nutrients to the blood despite the wrong concentration gradient.
Glucose can be taken into the bloodstream when its concentration in the blood is already higher than in the gut and can then be transported to cells for respiration.
