Biology- 2.4 - Enzymes

?
Active Site
Few amino acids with complementary tertiary structure to substrate.
1 of 23
Turnover Number
No. reactions enzyme can catalyse per second.
2 of 23
Activation Energy
Minimum energy required for reaction to occur. Catalysts provide alternative pathway with lower activation energy. Enzymes act as catalysts by bringing substrates close enough to react.
3 of 23
Intracellular
Within cells, eg. metabolic pathway (p/s, respiration).
4 of 23
Extracellular
Outside of cells, eg. digestive enzymes (amylase, lipase, pepsin, trypsin).
5 of 23
Anabolic
Makes larger molecules, used energy.
6 of 23
Catabolic
Breaks down larger molecules, releases energy.
7 of 23
Cofactors
Substance that ensures enzyme-controlled reactions take place at an appropriate rate. Non-protein. Eg. amylase only digests starch with Cl-.
8 of 23
Prosthetic Group
Cofactor that is permanently bound by covalent bonds to an enzyme molecule (part of enzyme). Eg. Zn2+ is a prosthetic group in red blood cells (allows CO2 transportation).
9 of 23
Other Cofactors
Temporarily bind to either substrate/enzyme- ease formation of ES complexes= increased ROR.
10 of 23
Coenzymes
Type of cofactor, organic, not protein. Binds temporarily with active site either before or during the time that the substrate binds. Chemically changed during reaction so need to be recycled to original state. Eg. vitamins (B12 or folic acid).
11 of 23
Lock and Key Model
Substrate and active site are specific and complementary- fit perfectly. Tertiary structure gives complementary shape. Enzyme-substrate complex temporarily joined by non-covalent forces.
12 of 23
Induced Fit Hypothesis
Active site isn't fixed structure, substrate induces shape change. Active site is complementary, but subtle changes of shape to side chains (R groups) of amino acids= more precise. Binds more effectively with substrate (non-covalent forces).
13 of 23
Effect of Temperature on Enzyme Activity
Increases kinetic energy, more successful collisions, Vibrating breaks weak bonds holding tertiary structure together, active site shape changes, substrates don't fit well. Denatured= irreversibly changed shape, reaction stops.
14 of 23
Temperature Co-efficient
Increase in ROR when temperature increased by 10C. Q10= ROR at (T+10)C / ROR at TC.
15 of 23
Effect of pH on Enzyme Activity
Excess H+ ions attracted to negative groups (eg. amino acid R groups) and repel positive groups (H bonds). Interferes with binding of substrate and active site. If normal pH restpre, H bonds reform and active site shape reforms. Extreme pH,denatured.
16 of 23
Effect on ROR of increased substrate conc:
Increased ROR, more enzyme-substrate complexes formed. Reaches maximum rate when all active sites are occupied.
17 of 23
Effect on ROR of increased enzyme conc:
Increased ROR, more succesful collisions. Reaches maximum rate when substrate conc is limiting factor.
18 of 23
Advantages of Enzyme Degration
Eliminates abnormally shaped proteins. Eliminates if too many- regulating metabolism.
19 of 23
Why is the initial ROR the fastest?
Enzymes and substrates moving randomly, have more successful collisions. As reaction goes on, substrate conc decreases- ROR decreases.
20 of 23
Competitive Inhibitors
Reduces activity of enzyme by blocking active site due to it having a similar shape to substrate. Inhibitor unchanged by enzyme despite being in active site.
21 of 23
Non-Competitive Inhibitors
Reduces activity of enzyme by attaching to enzyme away from active site by disrupting tertiary structure which makes it no longer complementary.
22 of 23
Toxins
Toxins can inhibit/inactivate enzymes. Cyanide- inhibits aerobic respiration. Snake venom- prevents muscles relaxing, stay contracted= paralysis. Aspirin- prevents swelling by blocking cell signalling. Protease inhibitors- competitive inhibition.
23 of 23

Other cards in this set

Card 2

Front

Turnover Number

Back

No. reactions enzyme can catalyse per second.

Card 3

Front

Activation Energy

Back

Preview of the front of card 3

Card 4

Front

Intracellular

Back

Preview of the front of card 4

Card 5

Front

Extracellular

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

Biology
See all Biology resources »See all Enzymes resources »