Biological Molecules Pg.6,7,13-16

Question 1

What is a catalyst

Answer 1

A catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction

Question 2

What is an enzyme

Answer 2

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)

Question 3

What is a substrate

Answer 3

A substrate is a molecule that is changed in a reaction

Question 4

What does every enzyme have

Answer 4

They all have an active site

Question 5

What is the active site

Answer 5

the active site of an enzyme is where a substrate joins on to the enzyme.

Question 6

What model is used to represent enzyme activity with a substrate

Answer 6

The ‘lock and key’ model. Shows how the substrate fits into the enzyme just like a key fits into a lock.

Question 7

Name 2 factors that affect enzyme function

Answer 7

Temperature and pH

Question 8

How does temperature affect enzyme function

Answer 8

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

Question 9

How does pH affect enzyme activity/function

Answer 9

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)

Question 10

How do you investigate the affect of temperature in enzyme activity using a potato

Answer 10

1. Catalase (an enzyme) catalyses the breakdown of hydrogen peroxide into water and oxygen
2. You can collect this oxygen and measure how much is produced in a set time
3. 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
4. Add a source of catalase (1cm3 of potato) to the hydrogen peroxide and attach the bung immediately
5. Record how much oxygen is produced in the first minute. Repeat 3 times and find the mean average
6. Repeat at different temperatures e.g. 20, 30, 40
7. Control variables e.g. pH, the potato used, size of potato in order to make it a fair test

Question 11

How do you measure the affect of temperature on enzyme activity with a substrate disappearing.

Answer 11

1. Amylase catalyses the breakdown of starch into maltose
2. use iodine solution to test if starch is present, if present the solution will go from browny-orange to blue-black.
3. Mix the amylase and starch into a solution in water bath at a set temperature
4. Put a drop of iodine solution in every well in a spotting tile
5. Every 10 seconds add a sample of the mixture of amylase and starch into a well.
6. When iodine remains browny-orange it indicates that starch is no longer present.
7. Record time taken
8. Repeat with different temperature in water bath and see how temperature affects how quickly starch is broken down

Question 12

How do you investigate pH to see if it affects enzyme activity

Answer 12

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

Question 13

What are carbohydrates made of

Answer 13

carbohydrates are made of simple sugars. Carbohydrates molecules contain the elements carbon, hydrogen and oxygen

Question 14

what are proteins made of

Answer 14

proteins are made of long chains of amino acids. They all contain the elements carbon, nitrogen, hydrogen and oxygen

Question 15

what are lipids made of

Answer 15

lipids are made of fatty acids and glycerol. They contain the elements carbon, hydrogen and oxygen.

Question 16

How do you make a food sample

Answer 16

1. break up the piece of food using a pestle and mortar
2. Transfer the ground up food to a beaker and add distilled water.
3. stir the mixture with a glass rod to dissolve some of the food.
4. Filter the solution using a funnel lined with filter paper to get rid of the solid bits of the food.

Question 17

How do you test for glucose

Answer 17

1. prepare a food sample and transfer 5cm3 to a test tube
2. Prepare a water bath that is set to 75 degrees C
3. Add about 10 drops of benedict solution to the test tube using a pipette
4. 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

Question 18

how do you test for starch

Answer 18

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.

Question 19

How do you test for proteins

Answer 19

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

Question 20

How do you test for lipids

Answer 20

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.

Question 21

state the sources and function of carbohydrates

Answer 21

Found in pasta, rice and sugar
Provides energy for the body

Question 22

state the sources and function of lipids

Answer 22

Found in butter, oily fish
provides energy, acts as an energy store and provides insulation for the body

Question 23

state the sources and function of proteins

Answer 23

found in meat, fish
needed for growth and repair of tissue, also provides energy in emergencies

Question 24

state the sources and function of Vitamin A

Answer 24

found in Liver
Helps to improve vision and keeps you skin and hair healthy

Question 25

state the sources and function of Vitamin C

Answer 25

Found in oranges (fruits)
prevents scrurvy

Question 26

state the sources and function of Vitamin D

Answer 26

found in eggs and can be made by your body when exposed to sunlight
Needed for calcium absorption

Question 27

state the sources and function of calcium (mineral ions)

Answer 27

Found in milk and cheese
needed to make bones and teeth

Question 28

state the sources and function of Iron (mineral ions)

Answer 28

found in red meat
needed to make haemoglobin for healthy blood

Question 29

state the sources and function of Water

Answer 29

Found in foods and drinks
Needed for pretty much all bodily function, we need constant supply of water to replace the water lost through urinating, breathing, sweating.

Question 30

state the sources and function of Dietary fibre

Answer 30

Found in Wholemeal bread and fruit
Aids the movement of food through the gut

Question 31

What is a balanced diet

Answer 31

balanced diet is a diet that gives you all the essential nutrients you need in the right proportions.

Question 32

What is the 7 essential nutrients

Answer 32

carbohydrates, proteins, lipids, vitamins, minerals, water and fibre

Question 33

State 3 factors that affect energy requirement

Answer 33

Activity level, Age, Pregnancy

Question 34

How does activity level affect energy requirements

Answer 34

More active people need more energy as they burn more calories and energy daily

Question 35

How does pregnancy affect energy requirements

Answer 35

Pregnant women need more energy that other women as they have to provide energy for their babies to develop aswell.

Question 36

How do you test for the energy in a food sample

Answer 36

1. Get a food that will burn easily, preferably dry
2. Weigh the food and skewer it on a mountain needle
3. add set volume of water to a boiling tube that is heal with a clamp
4. measure the temperature of the water, set fire to the food using a bunsen burner
5. Quickly hold the burning food under the boiling tube until it stops burning. Relight the food and keep repeating until food won’t burn again
6. Measure the temperature of the water again and then do the calculation

Question 37

How do you calculate the amount of energy in the food

Answer 37

Energy in food (J) = Mass of water (g) * Temperature change in water (C) * 4.2 (amount of energy (J) needed to raise the temperature of water by 1 degrees C)

Question 38

How do you calculate the amount of energy in J per gram

Answer 38

Energy per gram of food (in J/g) = Energy in food (J) / Mass of food (g)

Question 39

How do you increase the accuracy of the energy in food practical

Answer 39

Insulate the boiling tube with foil, minimises heat loss to surroundings.