B2 3 Enzymes Flashcards Preview

AQA GCSE Science > B2 3 Enzymes > Flashcards

Flashcards in B2 3 Enzymes Deck (19):

What are protein molecules made up of?

They are made up of long chains of amino acids.


What do proteins act as?

Proteins act as:

• Structural components such as muscles or tendons.
• Hormones such as insulin.
• Antibodies, which destroy pathogens.
• Catalysts in the form of enzymes.


What do catalysts do?

Catalysts increase the rate of chemical reactions without changing themselves. Enzymes are biological catalysts.


What are enzymes involved in?

Enzymes are involved in:

• Building larger molecules from smaller ones. (anabolic reactions).
• Changing one molecule into another.
• Breaking down lager molecules into smaller ones (catabolic reactions).


What is a substrate?

The reactant of the reaction.


How do enzymes work?

The substrate fits into the active site of the enzyme, once it is in place- the enzyme and the substrate bind together. The reaction takes place rapidly and the products are released from the surface of the enzyme.


What is enzyme activity affected by?

Enzyme activity is affected by pH and temperature.


What do high temperatures do to enzymes?

High temperatures can denature the enzyme's active site, the long amino acid chains begin to unravel.


Digesting carbohydrates

Enzymes that break down carbohydrates are called carbohydrases. The break down of carbohydrates (in particular starch) occurs in the mouth where the salivary amylase breaks down the starch. Amylase is also made in the pancreas and the small intestine.


Digesting proteins

The breakdown of proteins is catalysed by protease enzymes. Protease enzymes are produced by the stomach, the pancreas and the small intestine. The breakdown of proteins into amino acids occurs in the stomach and small intestine.


Digesting fats

The lipids (fats and oils) are broken down into fatty acids and glycerol in the small intestine. The reaction is catalysed by lipase enzymes. These enzymes are made in the pancreas and the small intestine. The enzymes made in the pancreas are passed into the small intestine.

Once the food molecules have been completely digested, they leave your small intestine and they pass into your bloodstream to be carried around the body.


Does digestion occur in the pancreas?


The enzymes made in the pancreas flow to the places they are required.


Changing pH in the gut

After food leaves the stomach to go into the small intestine, alkaline conditions are required for digestion. The acidic liquid coming from the stomach needs to be neutralised. The liver makes a greenish-yellow substance called bile which is squirted onto the contents coming from the stomach. This neutralises the contents and makes them suitable for the ideal conditions needed in the small intestine.


Altering surface area

Another important function of bile is that bile emulsifies fats in food. The fats we eat do not mix with the watery liquids in the gut. Bile physically breaks down the large droplets of fat into smaller droplets. This provides a larger surface area for the lipase enzymes to act on. The large surface area helps the lipase enzymes chemically break down the fats more quickly into glycerol and fatty acids.


Enzymes at home

Biological detergents are used to remove stains such as grass, sweat and food from clothes. The powders contain proteases and lipases. These detergents work better at lower temperatures as they become denatured if used at high temperatures.


Enzymes in industry

Proteases are used to make baby foods. The proteases 'predigest' some of the protein in the food so the baby's digestive system can cope with the digestion of proteins. This makes it easier for the baby to get its amino acids.

Carbohydrases are used to convert starch into sugar (glucose) syrup. This is a cheap source of sweetness for manufacturers.

Slimming products, isomerase is used to convert glucose syrup into fructose syrup. Fructose contains fewer calories and is much sweeter than glucose so it is needed in smaller quantities for the same sweetness effect.


What do most enzyme names end in?



Advantages and disadvantages of using enzymes:

• Can be used at lower temperatures
• Speed up reactions
• Can be used again

• Expensive equipment is required
• Can only work at lower temperatures or they get denatured
• pH also needs to be monitored



Streptokinase is injected into the blood if you are having a heart attack. This dissolves the clots in the arteries of the heart wall and reduces the amount of damage done to the heart muscle.