Movement in and out of cells Flashcards
What is Diffusion?
The net movement of molecules and ions from a region of their higher concentration to a region of their lower concentration, down a concentration gradient, as a result of their random movement.
Give examples of Diffusion in living things.
Diffusion of carbon-dioxide from the atmosphere into the leaf of plants for photosynthesis.
The absorption of nutrients from food by the ileum in large intestine.
The deception by orchid flower to attract male wasps for pollination.
What are the factors affecting Diffusion?
●Surface area - As the surface area increases, the rate of diffusion increases. This is because there is more space available for the substances to diffuse through.
● Temperature - As temperature increases, the rate of diffusion increases. This is because the molecules gain kinetic energy and thus move faster.
● Concentration gradient - As the concentration gradient increases, the rate of diffusion increases.
● Diffusion distance - A greater diffusion distance slows the rate of diffusion as molecules must travel further.
Define osmosis.
Osmosis is the net movement of water molecules from an area of higher water potential to an area of lower water potential through a partially permeable membrane.
Define turgid, turgor pressure, flaccid and plasmolysis.
Turgid - cells are described as turgid when they are swollen due to a high-water content.
Turgor pressure - The pressure on the cell wall from the cell membrane pushing upon it. This is a result of the cell becoming turgid as water moves into the cell via osmosis.
Flaccid - Occurs when water moves out of the cell via osmosis. The cell shrinks but the cell membrane does not peel away from the cell wall. If more water leaves the cell, it becomes plasmolysed.
Plasmolysis - Occurs when there is too little water in cells. In plant cells, the cell membrane peels away from the cell wall.
What do you mean by active transport?
The movement of molecules and ions in and out of a cell through the cell membrane against a concentration gradient, using energy from respiration.
What are carrier proteins?
Carrier proteins facilitate active transport. They are embedded in the cell membrane and allow passage through it.
Molecules from the side with lower concentration bind to the carrier protein.
The carrier protein then changes shape using energy from respiration.
This forces the molecules to move through the membrane to the side with high concentration, where it is released.
Give 2 examples of active transport.
Uptake of ions by root hair cells - plants take up ions such as nitrates and magnesium from the soil via root hair cells. The concentration of ions in the root hair cell is greater than the concentration of ions in the soil. Energy from respiration is therefore used to transport ions into the cell against the concentration gradient.
Uptake of glucose - glucose is taken up in the small intestine and kidney tubules. Glucose moves against the concentration gradient through carrier proteins.
