Enymes

Question 1

Active site

def

Answer 1

The part of the enzyme to which a specific substrate can attach to or fit on to

Question 2

Catalyst

def

Answer 2

A substance that changes the rate of a chemical reaction without being changed or used up by the reaction itself

Question 3

Carbohydrate

def

Answer 3

Food belonging to the food group consisting of sugars, starch and cellulose. Carbohydrates are vital for energy in humans and are stored as fat if eaten in excess. in plants carbohydrates are important for photosynthesis

Question 4

Amino acid

def

Answer 4

The building blocks that makes up a protein molecule

Question 5

Iodine solution

Answer 5

A solution of iodine in potassium iodine solution, also referred to as potassium triiodide solution

Question 6

Benedict’s solution

Answer 6

A solution that can be used to test for the presence of a reducing sugar (or the presence of an aldehyde group)

Question 7

Biuret reagent

Answer 7

Chemical which turns purple or maybe in the presence of protein

Question 8

Calorimeter

def

Answer 8

A machine used to measure the energy involved in a chemical process

Question 9

calorimetry

def

Answer 9

Measuring the amount of heat given out or taken in by a process, such as the combustion of a fuel

Question 10

collagen

def

Answer 10

The most common protein found in connective tissue of animals

Question 11

Concentration

def

Answer 11

The concentration of a solution tells us how much of a substance is dissolved in water. The higher the concentration, the more particles of the substance are present.

Question 12

Emulsion

def

Answer 12

Cloudy mixture formed between a lipid and water

Question 13

Enzyme

def

Answer 13

Enzymes are proteins that function as biological catalysts. So, they are molecules that speed up a chemical reaction without being changed by the reaction.

Question 14

Fats

def

Answer 14

Naturally occurring compounds of carbon, hydrogen and oxygen. They are esters made from fatty acids and glycerol

Question 15

fructose

def

Answer 15

A monosaccharide which joins with glucose to make sucrose

Question 16

Glucose

def

Answer 16

A simple sugar used by cells for respiration

Question 17

Glycerol

def

Answer 17

A soluble carbohydrate which is coverted into glucose by the liver

Question 18

Glycogen

def

Answer 18

The storage form of glucose in animal cells

Question 19

Haemoglobin

def

Answer 19

The red protein found in red blood cells that transports oxygen round the body

Question 20

Joules

def

Answer 20

The unit of work or energy, written as J

Question 21

Keratin

def

Answer 21

A fibrous protein found in hair and fur

Question 22

Lipid

def

Answer 22

Fat or oils, composed of fatty acids and glycerol

Question 23

Lock and key hypothesis

def

Answer 23

Model which compares the specificity of enzymes with a key and its lock

Question 24

Metabolism

def

Answer 24

All the chemical reactions in the cells of an organism, including respiration

Question 25

Oils

def

Answer 25

Natural substances produced from the reaction of glycerol with fatty acids.

Question 26

Optimum

def

Answer 26

The best or most appropriate - for instance, the conditions under which an enzyme works best (eg temperature and pH)

Question 27

PH

def

Answer 27

Scale of acidity or alkalinity. A pH (power of hydrogen) value below 7 is acidic, a pH value above 7 is alkaline

Question 28

Substrate

def

Answer 28

A substance on which enzymes act

Question 29

Sucrose

def

Answer 29

A disaccharide made from glucose and fructose. It is used as table sugar

Question 30

Synthesise

def

Answer 30

To construct a larger biological molecule from smaller ones

Question 31

Lock and key hypothesis

Answer 31

Enzymes are folded into complex 3D shapes that allow smaller molecules to fit into them. The place where these molecules fit is called the active site.

In the lock and key hypothesis, the shape of the active site matches the shape of its substrate molecules. This makes enzymes highly specific. Each type of enzyme can usually catalyse only one type of reaction (some may catalyse a few types of reactions).

Question 32

Denaturing enzymes

Answer 32

If enzymes are exposed to extremes of pH or high temperatures the shape of their active site may change.

If this happens then the substrate will no longer fit into the enzymes. This means the key will no longer fit the lock. We say that the enzyme has been denatured.

It is important you use ‘denatured’ and not ‘killed’ as enzymes have never been alive.

Question 33

The rate of an enzyme-catalysed reaction is calculated by…

+Calculation

Answer 33

measuring the rate at which a substrate is used up or by the rate at which a product is formed.

rate of reaction = (amount of substrate used or amount of product formed) ÷ (time taken)

Question 34

How does temperature effect the reaction rate of an enzyme-catalysed reaction?

Answer 34

As with many chemical reactions, the rate of an enzyme-catalysed reaction increases as the temperature increases. However, at high temperatures the rate decreases again because the enzyme becomes denatured and can no longer function.

As the temperature increases so does the rate of enzyme activity. An optimum activity is reached at the enzyme’s optimum temperature. A continued increase in temperature results in a sharp decrease in activity as the enzyme’s active site changes shape. It is now denatured.

Question 35

How does pH effect the reaction rate of an enzyme-catalysed reaction?

Answer 35

Changes in pH also alter the shape of an enzyme’s active site. Each enzyme work bests at a specific pH value. The optimum pH for an enzyme depends on where it normally works. For example, enzymes in the small intestine have an optimum pH of about 7.5, but stomach enzymes have an optimum pH of about 2.

In the graph above, as the pH increases so does the rate of enzyme activity. An optimum activity is reached at the enzyme’s optimum pH, pH 8 in this example. A continued increase in pH results in a sharp decrease in activity as the enzyme’s active site changes shape. It is now denatured.

Question 36

How does substrate concentration effect the reaction rate of an enzyme-catalysed reaction?

Answer 36

Enzymes will work best if there is plenty of substrate. As the concentration of the substrate increases, so does the rate of enzyme activity. However, the rate of enzyme activity does not increase forever. This is because a point will be reached when the enzymes become saturated and no more substrates can fit at any one time even though there is plenty of substrate available.

As the substrate concentration increases so does the rate of enzyme activity. An optimum rate is reached at the enzyme’s optimum substrate concentration. A continued increase in substrate concentration results in the same activity as there are not enough enzyme molecules available to break down the excess substrate molecules.

Question 37

Investigating the effect of pH on enzyme
activity

Aim:
To determine the optimum pH at which an enzyme’s activity is greatest.

Method
Risks

Answer 37

Method:
1) Set up a Bunsen burner, heatproof mat, tripod and gauze.

2) Place a beaker of water on the gauze and adjust the flame to keep the water at about 35°C.
3) Now put two drops of iodine solution into each spot of a spotting tile.
4) Add 2 cm3 of amylase enzyme solution to a test tube.
5) Place 2 cm3 of starch solution into the same tube.
6) Finally add 1 cm3 of pH solution to the tube. This will keep the pH constant.
7) Mix the solution in the test tube and place it into the beaker of water on the Bunsen burner.
8) Use a pipette to remove a few drops of solution every 20 seconds from the test tube and put them into a different well of the spotting tile.
9) Repeat until the iodine solution stops turning black.
10) Record the time this takes.
11) Repeat with different pH solutions.

Risks:
-Iodine solution is an irritant. If it touches skin it should be washed off.

-Goggles should be worn at all times.

Question 38

Enzymes and food

Answer 38

Carbohydrates, proteins and lipids are large molecules that are needed by the body for growth, repair and metabolism. They are found in our food. These molecules are too large to pass from the intestine into the blood, so digestive enzymes break them down into smaller molecules. Once in the body, different enzymes use these raw materials to synthesise larger molecules.

Question 39

Carbohydrates

Answer 39

Carbohydrates include glycogen, starch, sucrose and glucose.

The basic building block of a carbohydrate is a monosaccharide. This is simple sugar, such as glucose and fructose. Enzymes join monosaccharides together to form disaccharides (two monosaccharides) and polysaccharides (long chains of monosaccharides).

Carbohydrase enzymes break disaccharides and polysaccharides into monosaccharides (simple sugars). Carbohydrase enzymes are produced in your mouth (in saliva), pancreas and small intestine.

Question 40

Proteins

Answer 40

Proteins are large molecules made from amino acids joined together to form chains. They include enzymes, haemoglobin, collagen and keratin. Each protein has hundreds, or even thousands, of amino acids joined together in a unique sequence and folded into the correct shape. This gives each protein its own individual properties.

Protease enzymes are responsible for breaking down proteins in our food into amino acids. Then different enzymes join amino acids together to form new proteins needed by the body for growth and repair. Protease enzymes are produced in your stomach, pancreas and small intestine.

Question 41

Lipids

Answer 41

Lipids are fats and oils. Lipids are large molecules made from smaller units of fatty acids and glycerol.

Digestive enzymes such as lipase break down lipids in the diet into fatty acids and glycerol. Lipase enzymes are produced in your pancreas and small intestine.

Question 42

Calorimetry

Answer 42

A calorimeter is a machine used in the process of calorimetry. Small samples of material are placed in the machine which burns them. The energy given off when the material burns is measured.

Calorimeters are often used in the food industry to measure the energy in food. This value is given in joules or calories in the nutritional information panel on the food packaging.

The simplest calorimeter can be made by arranging a beaker of water above a burning sample. The change in temperature of the water is a direct measure of the energy held within the sample.