B3.1 Movement of molecules in and out of cells Flashcards
What is osmosis?
Osmosis is diffusion of water molecules from a region of high water concentration (a dilute) to a region on low water concentration (more concentrated solution) through a PARTIALLY PERMEABLE MEMBRANE
What is a partially permeable membrane?
a membrane with very small holes in it so that only small molecules (such as water) can pass through it
What causes water to move to move into and out of cells by osmosis?
difference in the concentrations of the solutions inside and outside a cell
What do most soft drinks contain?
water, sugar, ions
Why do sports drinks contain sugars?
to replace the sugar used in energy release during the activity
What do sports drinks contain ions and water?
to replace the water and ions lost during sweating
What happens if the water and irons are not replaced after having done exercise?
the iron/ water balance of the body is disturbed and the cells do not work as efficiently.
Describe what happens if a cell is short of water
the solution inside the cell will become more concentrated. This means that the solution outside the cell is more dilute.
therefore water will move into the cell by OSMOSIS
Describe what happens if a cell has lots of water
the solution inside it will be more dilute. water will be drawn out of the cell by OSMOSIS
What is active transport?
the process where substances are absorbed against a concentration gradient.
they move from a region of low concentration to a region of high concentration
this requires the use of energy from respiration
What does active transport enable?
enables cells to absorb ions from very dilute solutions
What does active transport require?
energy from respiration
Many organisms are …….. for exchanging materials
specialised
The effectiveness of an exchange surface is increased by:
4 factors
1) having a large surface area - so lots of a substance can diffuse at once
2) being thin, to provide a short diffusion path
3) (in animals) having an efficient blood supply- lots of blood vessels to get substances into and out of the blood quickly
4) (in animals, for gaseous exchange- eg alveoli) being ventilated - so air can move in and out
Gas and solute exchange surfaces in humans and other organisms are ….. to maximise effectiveness
adapted
Why does exchanging substances get more difficult in bigger, more complex organisms?
as the place where the substance is needed is further away from the exchange surfaces
In humans, how is the surface area of the lungs increased by?
increased by the alveoli
In humans, how is the surface area of the small intestine increased by?
by villi
How do the villi in the small intestine allow substances to diffuse through more easily?
- provide a large surface area - so digested food is absorbed faster into the blood
- have an extensive network of capillaries- to absorb products of digestion by diffusion and active transport
- have a single layer of surface cells- short diffusion and active transport path
How are the alveoli in the lugs specialised to maximise the diffusion of oxygen and carbon dioxide?
- large surface area
- a moist lining for absorbing gases
- thin walls
- good blood supply
What is the upper part of the body called?
the thorax
What are lungs protected by?
the ribcage
What is the lower part of the body called?
the abdomen
How are the lungs separated from the lower part of the body (the abdomen)?
separated by the diaphragm
Describe the function of the breathing system
takes air into and out of the body so that oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air