Enzymes & catalysis Flashcards
(27 cards)
1
Q
Enzymes
A
- Biological catalysts speed up specific enzyme reactions
- In all organisms and regulates all chemical reactions
- Catalytic activity determined by the folding and conformation of protien
2
Q
Properties of enzyme
A
- Specific to substrate
- Catalytic power which is fast
- Efficient can be reused and not used up in reactions (active at low concentrations)
- Can be regulated
3
Q
Lock and key model
A
- Substrate binds to specifc region of the active site
- Forms enzyme substrate complex perfectly complementory
- Static model and ridgid
4
Q
Induced fit model
A
- Substrate is not exactly complementory
- After binding there is a conformational change allows better fit between active site and substrate
- Dynamic model
5
Q
Active site
Substrate binding site
A
- Maintain shape small 3D grove located in a small region of the enzyme
- Amino acid chaim interact withs substrate
- interaction orentates active site to the substrate
6
Q
Active site
Catalytic site
A
- Few amino acid that performs a catalytic reaction
- Binding alters structure promotes formation of transition state
7
Q
Catalytic power
A
- The ability to increase rate of chemical reaction
- Minimum amount of energy activtation energy
- Lower activation energy faster the reaction occours to go from transtion state to products
8
Q
Temperatures effect on enzymes
A
- Archea are extreamophiles higher optimum temperature
- enzyme activity lower at lower temperature less kenetic energy less sucessful collision
- Higher temperature protein looses specific 3D structure of active site so no longer has a complementory fit
9
Q
pH effect on enzymes
A
- About 7.5 pH in the small intestine
- About 1.5 pH for the stomach (Pepsin)
- 4-5 pH for digestive lysosomal enzymes
- Could effect charges of the R group activity decrease if not in optimal
- Tertiary structure temporaly altered so enzymes substrate cannot occour
10
Q
Increase in substrate concentrations effect on enzyme
A
- Causes an increase in substrate concentration initially
- Enzyme becomes saturated with the substrate so the reaction rate decreases and this reaches Vmax
11
Q
Enzyme kenetics (Km)
A
- Concentration of substrate where the rate of reaction is half maximal
- Inverse meaasure of how tightly bound the enzyme binds to its surface
- Higher Km lower affinity to substrate greated concentration of substrate to reach Vmax
- Lower Km stronger binding
12
Q
Competitive inhibitor
A
- Competes with substrate to bind to the active site
- Effect is reversible or irreversible (covalent bonding)
13
Q
Non competitive inhibitor
A
- Binding to the allosteric part of the enzyme causing a conformational change
- Blocks catalytic activity and the bindingis reversible
14
Q
Enzyme cofactors
A
- Provide the active site with additional reactive groups
- Essential ions - activator ions (loosely bound) or metal ions (tightly bound)
- Coenzymes - Co-substrates (loosely bound) or prosthetic groups (tightly bound)
15
Q
Essential ions
Activator ions
A
- Reversibly bind to enzymes and participate in substrate binding
16
Q
Essential ions
Metal ions
A
- Cations that are tightly bound to an enzyme and participate in catalysis
17
Q
Coenzymes
Cosubstrates
A
- Weak temporarily bound to enzyme
- Altered during course of reaction and dissociate from active site
- NAD and NADP+
18
Q
Coenzymes
Prosthetic groups
A
- Tightly bound to enzyme via covalent bonding
- Must be regenerated each catalytic cycle e.g. heamoglobinand oxygen
19
Q
Holoenzyme
A
- Catalytically active enzyme together with cofactor
20
Q
Apoenzyme
A
Protein part of enzyme without its cofactor not activated
21
Q
Oxidoreductases
A
Transfer electrons from one molecule (oxidant) to another one (reductant)
22
Q
Hydrolases
A
Cleave/break specific types of covalent bonds, transferring groups to water
23
Q
Transferases
A
Transfer of specific functional groups from one molecule (donor) to another one (acceptor)
24
Q
Isomerase
A
Convert one isomer to another
25
Lyases
Break a chemical bond between two parts of a molecule (other than hydrolysis or oxidative bond breaking)
26
Translocases
Assisting in moving molecules, usually across a cell membrane
27
Ligases
Join two molecules by forming a new chemical bond
