Transport in Cells Flashcards
What is meant by 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?
- Temperature - which gives particles more energy
- The bigger the concentration gradient (difference)
- Surface Area
What is the Cell Membrane?
It controls the movement of substances in and out of the cell.
What molecules CAN diffuse through the cell membrane?
- Oxygen
- Glucose
- Amino Acids
- Water
What molecules CANNOT diffuse through the cell membrane?
Big molecules:
- Starch
- Protien
How does diffusion take place in the membrane?
The particles flow through the cell membrane where there is an area of higher concentration to where there is an area of lower concentration.
They move Randomly and go both ways, but there will be an overall net movement to the one side.
What is meant by Osmosis?
The movement of water molecules across a partially permeable membrane, from an area of higher water concentration to an area of lower water concentration
What happens to the water molecules during osmosis?
They actually pass through both ways of the membrane during Osmosis, however, there is an overall net movement of water particles.
What is the process of Active Transport?
The absorption of substances against a concentration gradient (lower to a higher concentration).
What is required for Active Transport to work?
Energy and Respiration
What does Active Transport allow plants to do?
Allows them to absorb minerals from a very dilute solution, against a concentration gradient.
Where is active transport used in the human body?
Used in the gut where there is a lower concentration of nutrients in the gut, but a higher concentration of nutrients in the blood.
What is Surface Area to Volume Ratio?
A ratio that shows that the larger the organism, the smaller its surface area is compared to volume.
How are exchange surfaces adapted to maximise effectiveness?
- They have a thin membrane, so substances only have a short distance to diffuse
- They have a large surface area so lots of a substance can diffuse at once
- Gas exchange surfaces in animals are often ventilated too.
How does gaseous exchange occur in the lungs?
- The alveoli transfer the oxygen into the blood and remove the carbon dioxide through diffusion.
