Dissolved substances Flashcards
How do dissolved substances move into and out of cells?
By diffusion and active transport.
How does water move across boundaries?
By osmosis.
Define osmosis.
The movement of water from a dilute to a more concentrated solution through a partially permeable membrane that allows the passage of water molecules.
What causes water to move into or out of a cell by osmosis?
Differences in the concentrations of the solutions inside and outside a cell.
What substances do most soft drinks contain?
Water, sugar and ions.
Why do sports drinks contain sugar?
To replace the sugar used in respiration during the activity.
Why do sports drinks contain water and ions?
To replace the water and ions lost during sweating.
What happens if water / ions are not replaced?
The water / ion balance of the body is disturbed and the cells do not work as efficiently.
What is active transport?
Active transport is a process that enables cells to absorb ions from very dilute solutions. It is when substances are absorbed against a concentration gradient. It requires energy from respiration.
What is the effectiveness of an exchange surface increased by?
- Having a large surface area.
- Being thin, to provide a short diffusion path.
- (in animals) Having an efficient blood supply.
- (in animals, for gaseous exchange) being ventilated.
Why are gaseous and solute exchange surfaces in humans and other organisms adapted?
To maximise effectiveness.
What increases the difficulty of exchanging materials?
The size and complexity of an organism.
How is the surface area of the lungs increased?
By the alveoli.
How is the surface area of the small intestine increased?
By the villi.
How do the villi increase surface area?
They have an extensive network of capillaries to absorb the products of digestion by diffusion and active transport.
