Diffusion
What is diffusion?
The movement of particles from an area of high concentration to low concentration.
What is osmosis?
The movement of water through a partially permeable membrane from a dilute solution to a more concentrated one.
What is the job of an enzyme?
To speed up chemical reactions.
What is the main job of carbohydrates in our body?
To provide energy.
What part of the cell controls what goes in and out?
The cell membrane.
Which gas moves into cells by diffusion for respiration?
Oxygen.
What direction does water move during osmosis?
From high water concentration to low water concentration.
Are enzymes used up in chemical reactions?
No, they can be reused.
What are proteins made of?
Amino acids.
Is the cell membrane fully open or does it choose what passes through? What is the term for this?
It chooses; it is called selectively permeable.
Name two factors that affect the speed of diffusion.
Temperature and concentration gradient.
What kind of membrane does osmosis need?
A partially permeable membrane.
What happens to an enzyme if it gets too hot?
It becomes denatured – the shape changes and it stops working.
Name the 3 main types of biological molecules we learned about.
Carbohydrates, proteins, lipids.
What are two ways substances move through the membrane without energy?
Diffusion and osmosis.
Why do small particles diffuse faster than large ones?
They can move more easily and quickly through the membrane.
What happens to a plant cell in salty water? Name and describe the process.
It becomes plasmolysed; water leaves the cell by osmosis.
Why do enzymes only work with certain molecules?
Because their active site has a specific shape that fits only certain substrates.
Which molecule stores the most energy for the body: carbohydrates, proteins, or fats?
Fats (lipids).
What is the difference between diffusion and active transport across the membrane?
Diffusion needs no energy; active transport does.
Explain what happens if a cell is placed where there is a high concentration of oxygen outside and a low concentration inside. What direction will diffusion go?
Oxygen will move into the cell because diffusion goes from high to low concentration.
Compare what happens to a red blood cell and a plant cell when both are placed in pure water. Why do they react differently?
Red blood cells burst (no cell wall), but plant cells become turgid (have a strong cell wall).
Describe how temperature and pH affect enzyme activity.
Enzymes work best at an optimum temperature and pH. Too high or too low can denature them.
Match each molecule to its building block: Carbohydrates → ? Proteins → ? Lipids → ?
Carbohydrates → sugars, Proteins → amino acids, Lipids → fatty acids and glycerol.
Explain how the structure of the cell membrane helps diffusion and osmosis to happen.
It has tiny openings and is thin, allowing small molecules to pass through easily.