A revision summary of OCR Biology Enzymes 2.1.4
Made by a student who achieved A* in A level Biology.
Covers all the points within the OCR Biology Specification.
Condenses 3 OCR specification books and class notes.
Enzymes – biological catalysts (speed up metabolic reactions). Temperature
- Globular proteins with tertiary structure. - Brownian Motion - Molecules move randomly & continuously
Lower the activation energy– energy required to start reaction. - ↑temp = ↑KE = ↑collisions = ↑successful collisions = ↑ESC
- ↑molecules with activation energy, ↑number of collisions, formed = ↑ESP. Faster rate of reaction & more product.
↑successful collisions. - Vmax = optimal temp
Regulate metabolism – sum of all reactions in an organism. - Denaturing = heat vibrates molecules straining bonds = breaks
- Anabolic – building of molecules (DNA) H & ionic bonds in tertiary structure = active site loses 3D
- Catabolic – breaking down of molecules (digestion) conformational shape = active site not complementary
Denaturing – bonds that hold tertiary structure are broken. Temp coefficient Q10 – how much rate of reaction (R) increases with
a temp (t) rise of 10°. Q10 = Rt / Rt – 10.
Lock and Key - Not temp sensitive reaction, Q10 = 1.
1. Specific substrate collides & bind with complementary active site. PH – measure of H+ ion conc. ↑H+ = ↓pH
2. forming enzyme-substrate complex (ESC) - H & ionic bonds between amino acid R-group hold proteins 3D
3. Enzyme provides alternative pathway with lower activation energy. tertiary structure. pH alters charges & tertiary structure
4. Interaction of R groups cause bond straining in substrate - ↓pH = ↑H+ ions = attracted to -ve ionic bonds in active site =
molecule. changes tertiary structure = no longer complementary = substrate
5. Enzyme product complex (EPC) formed, and 2 products released, cannot bind = ↓ESC
enzyme is unchanged. - Alters enzyme tertiary structure and denatures enzyme.
Induced-fit hypothesis – more evidence, new research - Vmax = Optimal pH = specific no. of H bonds for complementary
1. Active site of enzyme is flexible shape of active site.
2. Active site changes shape as substrate binds creating closer fit Renaturation – pH returns to optimal, protein resumes
3. Conformational shape change of active site as substrate bind Denaturing – active site no longer complementary, irreversible.
for closer fit & forms ESC Enzyme & Substrate Concentration
4. Interaction of R groups cause bond straining in substrate
molecule.
5. EPC - Products released. Binding caused a change in active site. ↑substrate conc = ↑collisions = ↑successful
collision = ↑ESC = ↑ESP = ↑rate of reaction.
Intracellular (enzymes)- work inside cells - Until enzyme conc is limiting factor.
- Hydrogen peroxide (catalase) → oxygen + water
- Catalase found in liver cells.
Extracellular (enzymes) – work outside cells to break polymers into
monomers.
- Proteins (trypsin)→ peptides→ amino acids.
- Trypsin produced in pancreas, secreted into small intestine.
- Starch (amylase)→ maltose(maltase)→ glucose.
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