Chapter 04 - Enzymes Flashcards
Define enzymes
Enzymes are proteins that function as biological catalysts. They catalyse/speed up the rate of chemical reactions while remaining chemically unchanged at the end of the reaction
What is a catalyst?
A substance that speeds up a chemical reaction without chemically changing at the end of the reaction
What is activation energy?
The minimum amount of energy required to initiate a chemical reaction
What is the relationship between activation energy and the rate of a chemical reaction?
The lower the activation energy, the faster the reaction
What do enzymes do to activation energy?
Enzymes lower activation energy - allows chemical reactions to occur more effeciently
What do enzymes break down?
Enzymes break down complex substances into simpler and smaller substances. In digestion, substances are broken down to become soluble in water and small enough to diffuse through cell membranes (Catabolic)
What do enzymes build up?
Enzymes build up/synthesises complex substances from simpler ones (Anabolic)
Name 2 examples of digestive enzymes
1) Starch —-> (amylase) —-> Maltose
2) Maltose —-> (maltase) —-> Glucose
3) Protein —-> (protease) —-> Polypeptides —-> (protease) —-> Amino Acids
4) Fats —-> (lipase) —-> glycerol and 3 fatty acids
Describe an example of enzymes building up/synthesising complex substances from simpler substances
1) Amino acids are taken into cells to build up proteins. Cells contains special enzymes to catalyse the reactions
2) Enzymes synthesise glucose from carbon dioxide and water during photosynthesis
Describe an example enzymes breaking down complex substances into simpler substances
1) Catalase breaks down hydrogen peroxide a toxic substance in water and oxygen cells. Protects cell from harmful effects which can damage cell parts. Catalase is found in many cells to detoxify harmful substances
2) In cellular respiration, enzymes are involved in chemical reactions to break down glucose in order to release energy
3) In digestion, enzymes catalase the process of breaking down large insoluble food molecules into small and soluble substances to pass through the cell membrane
Enzymes ____ all reactions and are only ____ when needed
Enzymes catalyse all reactions and are only produced when needed (e.g digestive enzymes produced when food needs to be digested)
Enzymes are ____ in their action
Enzymes are specific in their action (e.g amylase only breaks down starch)
Why are enzymes specific in their action?
1) Enzymes only work on a specific type of substrate molecule due to the enzymes specific shape at the active site
2) Only a substrate with complementary shape will fit into the active site
3) Only one type of substrate will bind to the active site
Describe the process of an enzyme catalysing a reaction
1) The enzyme has a 3D shape with an active site complementary and specific to the substrate
2) Substrate molecules bind to the active site of an enzyme to form an enzyme-substrate complex’. Reactions occur at the active site and substrate molecules are converted into products
3) The product is released from the active site. The enzyme is chemically unchanged at the end of the reaction and can repeat the reaction many times.
What are the 5 characteristics of enzymes?
1) Speed up chemical reactions
2) Specific in action
3) Able to be used over and over again
4) Affected by temperature
5) Affected by pH
How do enzymes speed up chemical reactions?
Enzymes speed up chemical reactions by lowering the activation energy required to start the reaction
How are enzymes specific in their action?
Enzymes are specific in their action as only substrates with a complementary shape to the active site of the enzyme can bind.
Why can enzymes be re used over and over again?
Enzymes remain chemically unchanged a the end of a reaction
Describe what happens to enzymes at a low temperature
Enzymes are less active at a low temperature
- Less thermal energy converted to kinetic energy
- Enzymes and substrate molecules move slowly
- Rate of effective collision between substrate molecules and enzyme is very low
Describe what happens to enzymes at increasing temperature
Enzymes are increasingly active at an increasing temperature
- More thermal energy converted to kinetic energy
- Enzymes and substrate molecules move faster and faster
- Rate of effective collision between substrate molecules and enzyme increases
Describe what happens to enzymes at optimum temperature
Enzymes are most active at optimum temperature
- Most thermal energy converted to kinetic energy
- Enzymes and substrate molecules move fastest
- Rate of effective collision between substrate molecules and enzyme is highest
What is the optimum temperature for humans?
37 degrees celcius
Describe what happens to enzymes at above optimum temperature
Enzyme reaction rapidly decreases
- High heat causes the breaking of chemical bonds
- Active site of the enzyme molecule loses its original 3D shape
- The active site is no longer complementary to the shape of the substrate molecule
- Enzymes denature
How are enzymes affected by pH?
1) If enzymes are placed in pH conditions that vary from optimum, enzymes will denature
2) Extreme changes in acidity/alkalinity causes enzymes to denature
What is denaturation?
The change in 3D structure of an enzyme or any other soluble protein caused by heat/chemicals/acids/alkali
