enzymes Flashcards
What is the function of an enzyme?
To speed up the rate of reaction by lowering the activation energy
What are enzymes? [2]
Biological catalysts
Proteins
What is a substrate?
The substance that the enzyme acts on
What is an active site?
The area of an enzyme where the complimentary substrate fits
What is wrong with the Lock and Key model?
It is old and outdated
Describe the Lock and Key model [3]
- The active site is a fixed shape
- complementary to one substrate only
- after a successful collision an enzyme-substrate complex is formed
Describe the Induced Fit Model [4]
- Before reaction, active site NOT completely COMPLIMENTARY to substrate
- Active site alters structurally as substrate binds
- enzyme-substrate complex forms
- This stresses / distorts the bonds in a substrate leading to a reaction
What structural level are enzymes?
tertiary
What is a metabolic reaction?
reaction that occurs inside a living organism
What is Anabolism? [3]
- Simple molecules become more complex
- Uses energy
e.g. photosynthesis
What is Catabolism?
- Complex molecules become simpler
- Release energy
e.g. respiration
How does enzyme / substrate concentration affect the rate of reaction? [4]
- As concentration increases rate of reaction increases
- more successful collisions and enzyme-substrate complexes
- At a certain point it plateaus
- The enzyme / substrate concentration becomes the limiting factor
How does a decreased temperature affect rate of reaction? [4]
- Reactant molecules have a low kinetic energy
- For enzyme-substrate complexes to form reactants must collide with a particular amount of force
- Low kinetic energy results in fewer successful collisions
- Decreasing rate of reaction
How does an increased temperature affect rate of reaction? [9]
- Kinetic energy increases
- More successful collisions and enzyme-substrate complexes
- Increased rate of reaction
- Once the temperature increases above the optimum
- Bonds within the enzyme begin to break
- 3D structure of the enzyme including active site alters
- substrate no longer complimentary to active site
- enzyme denatured
- rate of reaction decreases
How does altered pH affect the rate of reaction? [4]
- bonds break
- tertiary structure of enzyme including active site structurally alters
- fewer successful collisions and enzyme-substrate complexes as enzymes denatured
- decreased rate of reaction
What are inhibitors?
Prevents enzymes from working
What are Competitive Inhibitors? [4]
- Similar in shape to the substrate
- competes for the active site
- usually reversible
e.g. methanol poisoning
What are Non-Competitive Inhibitors? [5]
- Bind to an area of the enzyme other than the active site (allosteric)
- Causing the 3D structure of the enzyme, including active site, to alter
- Enzyme-substrate complex can’t form
- Often irreversible
e.g. heavy metals : Mercury, lead, arsenic
What are End-Product Inhibitors? [2]
- As levels of end product increase the enzyme is inhibited
- When levels of the end product decrease again the inhibition stops
How is Starch digested? [2]
- Starch hydrolysed to Maltose by amylase
- Maltose hydrolysed to glucose by maltase
How is Protein digested?
- Intrinsic bonds within the Protein are broken and Proteins are hydrolysed into polypeptides by endopeptidases
- terminal bonds within polypeptides are then broken and polypeptide hydrolysed into dipeptides by exopeptidase
- peptide bonds between amino acids are broken and dipeptides are hydrolysed into amino acids by didpeptidase
How are Lipids digested?
- Lipids are emulsified by bile salts into emulsified Lipids
- Emulsified Lipids are hydrolysed by lipase into fatty acids and glycerol
