B3 - Diffusion & Active Transport Flashcards
What is osmosis?
The movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration
What is a partially permeable membrane?
A membrane with very small holes in it so that only small molecules like water can pass through
Why do some of the water molecules involved in osmosis go towards the high concentration region?
The water molecules move about randomly and sometimes deflect off another water molecules at the right angle so that it passes into the high concentration region
However, the net movement of the water molecules is towards the low concentration region
How is osmosis used in the human body?
So that water or solutions can travel into and out of cells
What decides if osmosis causes the water to go into or out of the cell?
If the cell is short of water, the concentration of water outside the cell will be higher so osmosis will bring water into the cell
If the cell has too much water, the opposite will occur
What are the 3 ways in which substances move around living organisms?
Osmosis
Diffusion
Active transport
What is diffusion?
Where substances move from an area of high concentration to an area of low concentration without the input of energy
What is active transport?
Where substances move from an area of low concentration to an area of high concentration because another substance is carrying it
Active transport requires energy
What is an exchange surface?
What the substances need to pass through
What are the 2 ways that diffusion is used in plants?
Carbon dioxide diffuses through the stomata into the plant
Oxygen diffuses out of the plant through the stomata
What are guard cells?
Cells that control the size of the stomata
They control the amount of water lost and make it equal to the amount of water coming into the plant through the roots
In terms of diffusion, why are leaves flat?
To increase the area of the exchange surface making diffusion more effective
Describe the process of gas exchange
Oxygen in the alveoli diffuses into the capillary network to get into the bloodstream
Carbon dioxide in the blood passes the alveoli and diffuses into them so that it can escape
What are villi and how do they work?
Tiny hair-like projections on the inside of the small intestine that increase the surface area of the small intestine massively
The digested food is absorbed by the villi and it passes into the capillary network inside the villi
What do alveoli and villi have in common?
They are both exchange surfaces