Chapter 8 - Enzymes Flashcards
Define an enzyme
A globular protein molecule which acts as a biological catalyst to speed up chemical reactions without itself being changed during the reaction
Explain that every metabolic reaction is catalysed by enzymes
- Enzymes are responsible for every metabolic reaction
- Metabolism is the name given to all chemical reactions in living organisms
- Anabolism is larger molecules built up from smaller ones
- Catabolism is larger molecules broken down into smaller ones
- Anabolism + Catabolism = Metabolism
- Thousands of different enzymes, they catalyse only one reaction
- Cells can control the synthesis and activity of enzymes
Name 9 properties of enzymes
- Made of proteins
- Biological catalysts
- Remain unchanged during reactions
- Very specific
- Can be used over and over
- In small quantities
- Affected by temperature
- Affected by pH
- Lower activation energy
Name four factors on which the rates of activity in enzymes depend
- pH
- Temperature
- Concentration of enzyme
- Concentration of substrate
Describe the structure of an enzyme
Enzymes are globular protein molecules consisting of long chains of amino acids in specific order and number
Describe the primary structure of proteins
Long chain of amino acids held together by peptide bonds
Describe the secondary structure of proteins
Different amino acids affect the folding of the chain into an alpha helix or beta pleated sheet, which is stabilised by hydrogen bonds
Describe the tertiary structure of proteins
The secondary structure folds into a specific 3D shape, stabilised by disulphide, ionic and hydrogen bonds
Describe the quaternary structure of proteins
Combination of more than one polypeptide or protein chain
Explain enzyme activity in terms of the active site
Enzymes are very specific. The active site has a specific shape, in which only one type of substrate will fit. When the correct substrate enters the active site, it will fit and a reaction will occur. When an incorrect substrate enters the active site, it will not fit and no reaction will take place
Define a substrate
A molecule or substance on which an enzyme acts
Define an active site
A dent in an enzyme molecule which has exactly the correct shape for a certain substance to fit into
Define a product
New molecules which leave the active site after the enzyme had acted on the substrate
How to enzymes speed up reactions?
- Enzymes has active sites which make them specific
- A substrate collides with the active site
- The active site has a complimentary shape
- An induced fit occurs between the enzyme and the substrate
- An enzyme substrate complex forms
- The enzyme acts on the substrate and new molecules are released from the active site
- The enzyme remains unchanged and ready to form new enzyme-substrate complexes
- Enzymes increase the rate of reactions by lowering activation energy
Name the enzyme and the product associated with starch
- amylase
- maltose
Name the substrate and the product associated with maltase
- multose
- glucose
Name the enzyme and the substrate associated with fatty acids and glycerol
- lipase
- lipids (fats & oils)
Name the substrate and the product associated with sucrase
- sucrose
- fructose and glucose
Name te enzyme and the product associated with proteins
- pepsin
- polypeptides
name the product and substrate associated with trypsin
- polypeptides
- amino acids
Explain what is meant by ‘optimum temperature’
The temperature at which the rate of reaction is the highest
Explain why humans have less energy when it is cold
The rate of enzyme activity is slow, because the lack of kinetic energy means that there are less collisions between enzymes and substrates and less ESC’s form.
Explain why it is dangerous to be exposed to extremely high temperatures
When enzymes gain too much kinetic energy, the molecules vibrate too violently and break the bonds which holds the structure together. This causes the active site to change shape, and the substrate will not be able to fit into the active site. The enzyme is then said to be denatured
Describe the role of enzymes in the germination of seeds
- Seeds contain enzymes, an embrio plant and stored nutrients
- Protein, starch and lipid molecules are insoluble and cannot be used by the embrio plant unless changed by enzymes
- Enzymes become active by absorbing water during germination
- Gibberellic acid is formed in the embrio and activates the enzymes to digest insoluble nutrients into soluble nutrients
- Amylase (starch to maltose), protease (proteins to polypeptides) and lipase (lipids to fatty acids & glycerol)
- Soluble nutrients are used by the embrio for growth and respiration
