AP Biology Unit 3: Cellular Energetics

Enzymes

Enzymes

-biological catalysts - they speed up chemical reactions by lowering activation energy

-most enzymes are proteins —> enzymes need to have the right shape/structure to do their functions

-enzymes can denature under the right conditions = loss of function

Fermentation & Anaerobic Respiration

O2 is needed to do oxidative phosphorylation during cellular respiration. In low O2 conditions, cells can continue to make small amounts of ATP through anaerobic respiration.

-lactic acid fermentation(yeast + muscle cells)

-alcoholic fermentation(yeast + some bacteria)

Lactic acid fermentation

-yeast + some muscle cells

only glycolysis

glucose —> 2 pyruvate —> 2 lactate

products: 2 ATP

Alcoholic fermentation

- yeast + some bacteria

only glycolysis

glycolysis —> NAD+ regeneration but instead produce ethanol instead of 2 lactate

Environmental factors affecting enzyme function

-pH level/acidity: the more H+ ions, the more acidic. less H+ ions, more basic.

-temperature: colder = lower kinetic energy/molecule movement = slower reaction

-substrate concentration: more substrate = faster reaction unless all active sites of enzymes are occupied, then reaction rate would plateau

Enzyme inhibitors

Competitive inhibitor

• occupies the active site, competes with the substrate to occupy the active site

• can be counter-acted by adding more substrate

Noncompetitive/allosteric inhibitor

• occupies the allosteric site

• when bonded to the enzyme, the active site goes through a conformational change, making the substrate unable to bind effectively with the active site —> reaction blocked

• CANNOT be counter-acted by increasing substrate concentration

Photosynthesis

6CO₂ + 6H₂O —> C₆H₁₂O₆ + 6O₂

-plant cells only

-Matter is conserved

-endergonic: energy added in

LDR - Light-dependent reaction(photosynthesis)

photolysis: light used to split H₂O

• H₂O provides e^- to ETC(electron transport chain)

• O₂ released

• ATP/NADPH(e^- carrier made to power LIR

LIR - Light-independent reaction

- CO₂ from atmosphere - carbon is fixed into sugar

- ATP/NADPH from the LDR powers this process

Cellular Respiration

C6H12O6 + 6O2 —> 6CO2 + 6H2O

-exergonic: energy is released

-both plants and animals

1-Glycolysis(CR)

glucose —> 2 pyruvates

e^- carried by NADH

little ATP made

2-Citric Acid Cycle/Krebs cycle(CR)

2 pyruvate —> acetyl coA

-CO2 released

3-Oxidative Phosphorylation/ETC(CR)