3 Enzymes

Question 1

What is a protein molecule made up of?

Answer 1

long chains of small units called amino acids

Question 2

What functions do proteins carry out in your body?

Answer 2

• structural components such as muscles and tendons
• hormones such as insulin
• antibodies, which destroy pathogens
• catalysts in the form of enzymes

Question 3

What does a catalyst do?

Answer 3

speeds up a chemical reaction without being used up so it can be used repeatedly

Question 4

What biological catalyst does your body have?

Answer 4

enzymes control chemical reaction rates

Question 5

What are enzymes?

Answer 5

large protein molecules

• long chains of amino acids are folded to produce a molecule with a specific shape
• the special shape allows other molecules (substrates) to fit into the enzyme protein
• we call this the active site and the shape is vital for the way it works

Question 6

What are enzymes involved in? (give examples(3))

Answer 6

• building molecules from lots of smaller ones
  e. g.making glycogen from glucose or proteins from amino acids
• changing one molecule into another
  e. g.one sugar into another, such as glucose to fructose
• breaking down large molecules into smaller ones
  e. g.breaking down insoluble food molecules into small soluble molecules, such as glucose

Question 7

Are there different types of enzymes?

Answer 7

yes - different ones speed up specific types of reaction

Question 8

How do enzymes work?

Answer 8

• the substrate (reactant) of the reaction fits into the active site of the enzyme
• it is like a lock and key
• once in place the enzyme and substrate bind together
• the reaction then takes place rapidly and the products are released from the surface of the enzyme
• (remember enzymes can join small molecules together as well as break up larger ones)

Question 9

What factors affect enzymes activity?

Answer 9

• temperature

- pH

Question 10

What is the effect of temperature on enzyme action?

Answer 10

• reactions occurring in cells happen at fairly low temperatures
• the rate of enzyme-controlled reactions increases as the temperature increases…
• …this is only true up until around 40 degrees C because after this the protein structure of the enzyme is affected by high temperature and the long amino acid chains begin to unravel
• this changes the shape of the active site and the enzyme is denatured
• it can no longer work as a catalyst so the rate of reaction drops rapidly

Question 11

What is the optimum working temperature for enzymes?

Answer 11

37 degrees C

Question 12

What do we call enzymes when their active site has been changed and they are no longer useful?

Answer 12

denatured

Question 13

What is the effect of pH on enzyme action?

Answer 13

• a change in pH affects the forces holding the enzymes shape together
• this changes the shape of the molecule which causes the active site to be lost
• this means the enzyme no longer works as a catalyst

Question 14

Where does the shape of an enzyme come from?

Answer 14

the forces between the different parts of the protein molecule
these forces hold the folded chains in place

Question 15

Do all enzymes require the same pH to function properly?

Answer 15

no - different enzymes have different temperatures at which they work best and a change can stop them working completely

Question 16

What would happen if our body did not have enzymes?

Answer 16

none of the reactions in your body would happen fast enough to keep you alive

Question 17

Why is it dangerous if your temperature rises when you are ill?

Answer 17

once your body reaches 41 degrees C, your enzymes start to be denatured meaning that the reactions in your body aren’t happening quick enough so you’ll die

Question 18

Why does food need to be digested?

Answer 18

• food is made up of large, insoluble molecules which your body can’t absorb
• they need to be broken down into smaller, soluble molecules
• these can then be absorbed and used by your cells

Question 19

How are digestive enzymes different from most of the enzymes in your body?

Answer 19

• most of your enzymes work inside the cells of your body, controlling the rate of chemical reactions
• digestive enzymes work outside your cells because they must break down the food so that it can be absorbed and used in the cells

Question 20

Where are digestive enzymes produced?

Answer 20

in specialised cells in glands (like your salivary glands and pancreas) and in the lining of your gut

Question 21

What happens during digestion?

Answer 21

• the enzymes pass out of the cells into the gut itself
• your gut is a hollow, muscular tube that squeezes your food
• it helps to break down food into smaller pieces with a large surface area for your enzymes to work on
• it mixes your food with digestive juices so that enzymes come into contact with the food as much as possible
• the muscles of the gut move food along from one area to the next

Question 22

What are the enzymes which break down carbohydrates called?

Answer 22

carbohydrases

Question 23

What is one of the most common carbohydrates consumed and what is it broken down into?

Answer 23

starch

broken down into sugars in your mouth and small intestine

Question 24

Which enzymes catalyses the breaking down of starch into sugars? Where is it produced?

Answer 24

amylase
produced in your salivary glands (so digestion starts in the mouth) and in your pancreas and small intestine (no digestion takes place in the pancreas)

Question 25

Why does no digestion take place inside the pancreas?

Answer 25

all the enzymes made there flow into your small intestine where food such as starch is digested

Question 26

What enzymes breaks down proteins into amino acids?

Answer 26

proteases

Question 27

Where are proteases produced?

Answer 27

in your stomach, pancreas and small intestine

Question 28

Where does the breakdown of protein take place?

Answer 28

stomach and small intestine

Question 29

What is another name for fats and oils?

Answer 29

lipids

Question 30

What are lipids broken down into?

Answer 30

fatty acids and glycerol

Question 31

Which enzyme catalyses the breaking down of lipids?

Answer 31

lipases

Question 32

Where are lipase enzymes produced?

Answer 32

pancreas and small intestine (enzymes in the pancreas are passed into the small intestine)

Question 33

What happens once food molecules have been completely digested?

Answer 33

• the soluble molecules: glucose, amino acids, fatty acids and glycerol leave your small intestine
• they pass out into your bloodstream to be carried around the body to the cells which need them

Question 34

Why does your body make a variety of different chemicals? (digestion)

Answer 34

in order to help keep conditions ideal for your enzymes all the way through the gut
- protease enzymes in stomach works best in acidic conditions
- protease enzymes in pancreas need alkaline conditions to work at their best
keeping the pH levels in your gut is difficult

Question 35

How does the pH change through your gut in the process of digestion?

Answer 35

1) - stomach proteases function best in acidic conditions so the stomach produces a concentrated solution of hydrochloric acid from your glands (around 3 litres per day) the acid allows the enzymes to work effectively whilst also killing bacteria taken in with food
- your stomach also produces a thick layer of mucus which coats your stomach walls, protecting them from being digested by the acid and enzymes

2) - after a while the food travels to the small intestine which have enzymes working best in alkaline conditions (also pancreas)
- acidic liquid from stomach becomes an alkaline mix by squiring bile which neutralises and makes the mixture alkaline, providing the ideal conditions needed for enzymes
- bile is produced in your liver and stored in gall bladder until needed

Question 36

Why is it important for enzymes digesting food to have the largest possible surface area to work on?

Answer 36

• fats eaten don’t mix with water liquids in the gut so they stay as large globules that can make it hard for lipases to act
• not a problem with carbohydrates and proteins

Question 37

What are the 2 important functions of bile?

Answer 37

1) to turn the acidic liquid from stomach passing into the small intestine alkaline for enzymes to work optimally
2) to emulsify the fats in your food to allow lipases to act more efficiently

Question 38

How does bile help lipases to break down fats?

Answer 38

• emulsifies the large globules of fat which don’t break down in watery liquids in gut
• breaking down the fats into smaller droplets provides a larger surface area for the lipase enzymes to work on
• the larger surface area helps lipases chemically break down the fats much more quickly into fatty acids and glycerol

Question 39

How can enzymes be used in the home?

Answer 39

• people use biological detergents to remove stains
• they contain enzymes like proteases and lipases in order to break down proteins and fats in stains which gives a cleaner wash
• biological detergents work better than non-biological detergents because enzymes work best a lower temperatures so you can use cooler water and less electricity

Question 40

How can pure enzymes be used in industry?

Answer 40

• baby food) proteases are used to make baby food as they ‘predigest’ some of the proteins in the food to allow the baby’s digestive system to cope with it and make it easier to get the amino acids they need
• sugar syrup (+ ethanol) )carbohydrases are used to convert starch into sugar (glucose syrup) which is used in food production and plants like corn containing starch are very cheap (it is also an important for the process of making fuel from plants)
• slimming foods) glucose syrup can be passed though another process using a different set of enzymes - isomerase is used to change glucose syrup into fructose syrup (although containing the same amount of calories, fructose is sweeter so less can be used)

Question 41

What are the advantages and disadvantages of using enzymes?

Answer 41

A:
- enzyme-based processes are fairly cheap to run because they catalyse reactions at relatively low temperatures and normal pressures (solving problems in energy use and expensive equipment in industry)
- pure enzymes use substrate more efficiently
D:
- enzyme conditions must be carefully controlled so that they don’t become denatured which costs money e.g. temperature (below 45 degrees C) and no change in pH
- enzymes are expensive to produce because they must be supplied with food and oxygen, have waste products removed and use substrate to grow more micro-organisms
- pure enzymes are even more expensive to produce

Question 42

What are the pros and cons of biological detergents?

Answer 42

pros:
- break down biological stains such as sweat and are very effective at cleaning
- work at lower temperatures so therefore use less energy and electricity which is cheaper and environmentally friendly
cons:
- originally caused allergies (from enzyme dust in the air-proteins can cause allergies) but this was solved by putting the enzymes in tiny capsules
- the lower-temperature washes are less good at killing pathogens (but higher temperatures denature the enzymes)
- some worry about enzymes going into rivers and seas from sewage systems

Question 43

How can enzymes be used in medicine? (and examples (3))

Answer 43

• to diagnose a disease
  e. g.liver can be checked by testing blood for enzymes in your liver which leak if it is damaged
• to diagnose and control a disease
  e. g.can be used to test for diabetes as they have too much glucose in their blood so there will be excess in the urine and an enzyme can catalyse the breakdown of any found in the urine proving that glucose was present
• to cure disease
  e. g.if pancreas is damaged…more enzymes must be made which are transported in special capsules so they aren’t digested by stomach, if you have a heart attack…streptokinase enzyme will be injected into blood to dissolve clots etc, childhood blood cancer…enzyme speeds up breakdown of amino acid which cancer cells can’t produce (having taken it from bodily fluid) so the cancer cells can’t get any and die