Biological molecules Flashcards
What are the three main biological molecules?
- Carbohydrates
- Proteins
- Lipids
What are carbohydrates?
Molecules made up of simple sugars
What elements do carbohydrates contain?
Carbon, hydrogen and oxygen.
What are starch and glycogen?
Large complex carbohydrates made up of smaller units (glucose and maltose molecules) joined together in a long chain.
What are proteins?
A long chain of amino acids
What elements do proteins contain?
Carbon, hydrogen, oxygen and nitrogen.
What are lipids?
Molecules made up of fatty acids and glycerol
What elements do lipids contain?
Carbon, hydrogen and oxygen.
How do you test for glucose?
Benedict’s reagent
What colour is benedicts reagent?
Blue
What happens if glucose is present?
A coloured precipitate is formed. The colour of the precipitate changes from: blue-green-yellow-orange-brick red
The higher the concentration of glucose…
… The further the colour change goes!
How do you test for starch?
Iodine test
If starch is present?
Sample changes colour to a dark blue-black one
If theres no starch?
Sample stays browny-orange
What are enzymes?
Biological catalysts in metabolic reactions
What is a catalyst?
A substance which increases the speed of a reaction without being changed or used in the reaction.
What are enzymes made of?
Proteins - long chain of amino acids folded into unique shapes to help the enzymes do their job
What is a substrate?
A molecule that is changed in a reaction
What is the active site?
The part where the substrate joins onto the enzyme.
What has to be correct to fit the active site?
The shape of the substrate otherwise the enzyme wont work
What is the model called when the substrate fits the active site perfectly?
The “lock and key” model
The higher the temperature…
The quicker the rate of the reaction (up to a certain point) as the enzymes and substrate particles have more energy, so more about more - higher collision rate
The lower the temperature…
The slower the reaction, so lower collision rate
What happens if the enzyme gets too hot?
The bonds holding the enzymes together break.
If the enzyme loses its shape…
The active site doesn’t fit the substrate anymore. This means it cant catalyse the reaction and its stops - the enzyme is said to be denatured
What is the optimum temperature?
Where the enzyme works the quickest, which in this case is 37 degrees - same as humans
How else can enzymes be affected?
By the pH
If the pH is too high or low…
It interferes with the bonds holding the enzymes together changing the shape of the active site and denaturing the enzyme
What is the optimum pH of an enzyme?
pH 7 (neutral)
What enzyme is an exception for the optimum pH?
Pepsin - This enzyme is used to break down proteins in the stomach and works best at pH 2 (acidic conditions)
What two enzymes can you use to show how temperature effects its activity?
Catalase and amylase
What equipment is needed in the catalase experiment?
- Water bath
- Beaker
- Boiling tube (containing source of catalase)
- Measuring cylinder
- Delivery tube
How can you use catalase in an experiment?
- Breaks down hydrogen peroxide into water and hydrogen
- Can collect oxygen produced and measure how much is given off in a certain amount of time (measuring cylinder)
- Can change the temperature in water bath and see how they affect the activity of the catalase
What variables in the catalase experiment need to be controlled in order to make it a fair test?
- Enzyme concentration
- pH
- Volume of solution
What equipment is needed in the amylase experiment?
- Spotting tile
- Pipette
- Beaker
- Boiling tube
- Iodine solution
How can you use amylase in an experiment?
- Catalyses the breakdown of starch into maltose
- Use iodine to detect starch (the substrate)
- Time how long it takes for starch to disappear by regularly sampling starch solution
- Adjust water bath temperature to see the affect of amylase activity
How can the functioning of enzymes be affected?
By changing the temperature (changes the active site) as it changes the rate of the enzyme catalysed reaction
