Topic 3 Enzymes Flashcards
Enzyme Structure
- globular proteins
- spherical/ ball shaped
- mostly tertairy structure (some quaternary)
- 3D structure due to interactions between R groups
- Soluble
Enzyme feature
- biological catalysts (spead up chemical reactions)
- doesn’t get used up
- can break down or synthesise substances
- used to control metabolic reactions
- increase rate of reaction (through lowering activation energy)
- has specific active site
- effective in small amounts
How to substrate bind to enzymes (lock and key mechanism & Induced fit mechanism)
Lock and Key mechanism
- active site doesn’t change shape
- shape of active site is fully complementory to the shape of substrate
= substrate expected to fit in exactly
Induced fit mechanism
- active site is flexible and mould around substrate
- shape of active site is partially complementory to the shape of substrate
= bettwe fit & stronger binding of substrate
Mode of action (enzyme & substrate)
- enzyme and substrates move and collide randomly
(only collisions in the right orientation with enought energy result in successful reaction) - formation of Enzyme-substrate complex (ESC)
- product formation
(interaction between active site and substrate=lowers activation energy)
Enzymatic reaction (catalase + amylose)
catalase- breaks down hydorgen peroxide (H2O2) to Oxygen (O2) and water (H2O)
Amylose- breaks down starch to maltose
how to measure rate of reaction
rate= speed/ time
(measured my rate of product formation/substrate disappearance)
What is a Colorimeter
- measures light absorbance in arbitory units (a.u)
- measure relative absorbance to a control (distilled water)
Factors that affect enzyme reaction
- Substrate concentration
- Enzyme concentration
- Temperature
- pH
- Inhiitors
How does substrate concentration affect enzyme action
(when substrate concetration is high)
- all active site is saturated
- enzyme is the limiting factor
- increase in substrate doesn’t increase rate
(when substrate concentration is low)
- enzyme in excess
- active sites available for binding
- few collisions between enzymes and substrate
How does enzyme concentration affect enzyme action
(when enzyme concetration is high)
- More number of ESC formed (enzyme substrate complex)
- substrate is the limiting factor
- increase in enzyme doesn’t increase rate
(when enzyme concentration is low)
- substrate in excess
- few collisions between enzymes and substrate
How does temperature affect enzyme action
Low temperature:
- low kinetic energy for frequent collisions
- Less ESCs formed
High temperature:
- maximum rate of enzyme reaction
- different enzymes have different optimum temp.
- (most human enzymes ~40 degrees celcius)
How does pH affect enzyme action
High/low pH:
- changed shape of active site
Opitmum pH:
- max. number of ESC formed
- different enzymes have different optimum pH
What are two types of inhibitors and how does inhibitors affect enzyme action
competitive: inhibitor binds to active site and has similar shape to substrate
incompetitive: inhibitor binds to allosteric site and changes shape of active site
Low concentration:
- reduced rate of reaction
- enzyme’s function inhibited
High concentration:
- Less affected by inhibitors
- more ESCs formed
what are immobilised enzymes?
Capsulated enzymes
Why use immobilised enzymes?
- can easily reuse enzymes
- less purification/ downstream process needed
- reduces end product inhibtion
- enzymes are more tolerant to pH, temperature changes
Why is Immobilised enzymes more tolerant to pH and temperature changes?
- alginate protects enzyme
- enzyme less exposed to solution: shape of active site is less disrupted
- 3D structure of enzyme is stabilised
- less likely to be denatured
Induced fit mechanism
- active site changes shape once substrate enters
- active site is partially permeable to substrate
- active site is more flexible
- binds stronger
