Enzymes

Question 1

Enzyme

Answer 1

Biological catalysts that control reactions in the body. Each enzyme is specific to its substrate and the activity is affected by temperature, substrate concentration and pH

Question 2

Effect of temperature on enzyme activity

Answer 2

At lower temperatures, molecules move more slowly so reaction speeds are slower

At optimum temperatures, the enzyme is working at the fastest rate

High temperatures cause the active site to change shape so the reaction slows down

At very high temperatures, the active site becomes de-natured

Question 3

Effect of substrate concentration

Answer 3

Lower concentration = lower rate of reaction

Question 4

Effect of pH on enzyme activity

Answer 4

The enzyme works the fastest at the optimum pH

As you go further from the optimum, the reaction is slower

Question 5

Digestion and enzymes

Answer 5

Carbohydrates are broken into sugars (by amylase)
Proteins are broken into amino acids (by lipase)
Lipids are broken into fatty acids and glycerol (by protease)

Question 6

Testing for starch

Answer 6

Add a few drops of iodine solution onto solid food or mix with a solution of the food

Turns blue/black if starch is present

Question 7

Testing for reducing sugars

Answer 7

Add an equal volume of benedict’s solution to a food solution and mix. Heat the mixture in a 95C water bath for a few minutes

Turns green/orange/red depending on how much sugar is present

Question 8

Testing for proteins

Answer 8

Add an equal volume of potassium hydroxide solution to the food solution and mix. Add a few drops of copper sulfate solution and mix

pale purple if proteins are present

Question 9

Testing for fats

Answer 9

Add an equal volume of ethanol to the food solution, and shake. Add water to the mixture.

turns cloudy if fats are present

Question 10

Using calorie try

Answer 10

Temperature of the water at the start is measured
Mass of the food is measured
food is set alight then placed under the tube
The temperature of the water at the end is measured and change of temperature is calculated

Question 11

Diffusion

Answer 11

The movement of particles from an area of high concentration to an area of low concentration across a partially-permeable membrane.

Question 12

Active transport

Answer 12

Movement of particles against the concentration gradient.

Question 13

Osmosis

Answer 13

The movement of water particles from an area of high water potential to an area of low water potential, across a partially permeable membrane.