Biological Molecules Pg.6,7,13-16 Flashcards
What is a catalyst
A catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction
What is an enzyme
an enzyme is a protein made up of amino acids and a biological catalyst which speeds up useful chemical reactions in the body (metabolic reaction)
What is a substrate
A substrate is a molecule that is changed in a reaction
What does every enzyme have
They all have an active site
What is the active site
the active site of an enzyme is where a substrate joins on to the enzyme.
What model is used to represent enzyme activity with a substrate
The ‘lock and key’ model. Shows how the substrate fits into the enzyme just like a key fits into a lock.
Name 2 factors that affect enzyme function
Temperature and pH
How does temperature affect enzyme function
At the start, a higher temperature increases the rate of reaction at first. This is because the enzymes and substrate have more energy, so they move about more and collide and form enzyme-substrate complexes. All enzymes have an optimum temperature.
However if it gets too hot, the bonds that hold the enzymes together can break. This changes the enzyme’s shape of the active site which means the substrate will no longer fit with its specific enzyme.
ENZYME IS DENATURED
How does pH affect enzyme activity/function
If pH is too high or too low it will also affect the rate of reaction. The pH interferes with the bonds holding the enzymes together. Which means the shape of the active site can change and the substrate no longer fits with its specific enzyme and this denatures the enzyme.
All enzymes have an optimum pH that they work best at. This is usually pH 7 (neutral)
How do you investigate the affect of temperature in enzyme activity using a potato
- Catalase (an enzyme) catalyses the breakdown of hydrogen peroxide into water and oxygen
- You can collect this oxygen and measure how much is produced in a set time
- Use a pipette to add a set amount of hydrogen peroxide to a boiling tube, put the tube in a water bath at 10 degrees C
- Add a source of catalase (1cm3 of potato) to the hydrogen peroxide and attach the bung immediately
- Record how much oxygen is produced in the first minute. Repeat 3 times and find the mean average
- Repeat at different temperatures e.g. 20, 30, 40
- Control variables e.g. pH, the potato used, size of potato in order to make it a fair test
How do you measure the affect of temperature on enzyme activity with a substrate disappearing.
- Amylase catalyses the breakdown of starch into maltose
- use iodine solution to test if starch is present, if present the solution will go from browny-orange to blue-black.
- Mix the amylase and starch into a solution in water bath at a set temperature
- Put a drop of iodine solution in every well in a spotting tile
- Every 10 seconds add a sample of the mixture of amylase and starch into a well.
- When iodine remains browny-orange it indicates that starch is no longer present.
- Record time taken
- Repeat with different temperature in water bath and see how temperature affects how quickly starch is broken down
How do you investigate pH to see if it affects enzyme activity
Adapt the catalase (potato) and the amylase and starch experiment so that you add a buffer solution with a different pH level and see how it affects rate of reaction
What are carbohydrates made of
carbohydrates are made of simple sugars. Carbohydrates molecules contain the elements carbon, hydrogen and oxygen
what are proteins made of
proteins are made of long chains of amino acids. They all contain the elements carbon, nitrogen, hydrogen and oxygen
what are lipids made of
lipids are made of fatty acids and glycerol. They contain the elements carbon, hydrogen and oxygen.
How do you make a food sample
- break up the piece of food using a pestle and mortar
- Transfer the ground up food to a beaker and add distilled water.
- stir the mixture with a glass rod to dissolve some of the food.
- Filter the solution using a funnel lined with filter paper to get rid of the solid bits of the food.
How do you test for glucose
- prepare a food sample and transfer 5cm3 to a test tube
- Prepare a water bath that is set to 75 degrees C
- Add about 10 drops of benedict solution to the test tube using a pipette
- If food sample contains glucose then it will turn from blue to green/yellow in low conc. or brick-red in high conc. of glucose
how do you test for starch
Make a food sample and transfer 5cm3 to a test tube. Add a few drops of iodine solution and gently shake to mix up the content. If sample contains starch then it will turn from browny-orange to blue-black.
How do you test for proteins
Prepare sample of your food and transfer 2cm3 to a test tube. Add 2cm3 of biuret solution and mix content my gently shaking. If sample contains protein then it will turn from blue to pink/purple. No proteins = colour stays the same
How do you test for lipids
Prepare unfiltered sample of food you‘re testing and transfer 5cm3 to a test tube. Add 3 drops of Sudan III (3) stain solution to the test tube using a Pipette and gently shake. Sudan III stains the lipid, so if lipids are present then mixture will separate into 2 layers. The top layer being bright-red. If no lipids are present, no separate red layer will form.
state the sources and function of carbohydrates
Found in pasta, rice and sugar
Provides energy for the body
state the sources and function of lipids
Found in butter, oily fish
provides energy, acts as an energy store and provides insulation for the body
state the sources and function of proteins
found in meat, fish
needed for growth and repair of tissue, also provides energy in emergencies
state the sources and function of Vitamin A
found in Liver
Helps to improve vision and keeps you skin and hair healthy
