GCSE Biology B1
Key Concepts in Biology
cell structures
Eukaryotes are cells that have a nucleus and other organelles surrounded by membranes.
both animal and plant cells are eukaryote cells
Prokaryotes are cells that have random strands of DNA that are surrounded by a membrane. These cells can only been seen
This is often bacteria, protists and fungi
enzymes
They are proteins that act as biological catalysts. They speed up the rate of reaction of breaking down food in the digestive system
the 'lock and key' hypothesis is how an enzyme would break its substrate. The substrate connects to the active site of the enzyme and breaks it down
rate of reaction = amount of product formed/time taken
If the pH or temperature is too high, then the enzyme will denature.
the effects of denaturing is that the active site changes shape
substrate concentration, pH and temperature can change the activity of an enzyme and how fast it reacts.
enzyme tests
the benedict test is used to test enzymes for reducing sugars. the positive results is cloudy orange or red
the biuret test is used to test enzymes for proteins. the positive results is mauve or purple .
the emulsion test is used to test enzymes lipids. the positive results is cloudy.
Transport in
cells
Diffusion is when a liquid or gas moves from high or low concentration. It is a passive transport as energy is not required to move this.
A calorimeter is used to test how much energy food can give you.
In a leaf, gas exchange is caused by diffusion as oxygen leaves the leaf and carbon dioxide enters the leaf.
In the alveoli in the lungs, carbon dioxide in the blood stream moves into the alveoli and oxygen concentration in the alveoli moves into the blood stream in the red blood cell