AP BIO UNIT 3 (2020-2025)

Enzymes

Biological catalysts that REDUCE ACTIVATION ENERGY to facilitate chemical reactions in cells

Denaturation of enzyme

Occurs when protein structure disrupted (by extreme temperature or pH outside optimal range), eliminates ability to catalyze reactions, can be reversible or irreversible

pH and temperature change effect on proteins

more efficient with higher temperature to a point, then starts to denature; pH or temperature outside of optimal range decreases efficiency; pH or temperature extremely out of range causes denaturation (reversible or irreversible)

Environmental pH effect on enzymes

Disruption of hydrogen bonds that provide enzyme structure, causing reduction in efficiency and/or denaturation

Relative concentration effect on enzymes

Determine how efficiently enzymatic reaction proceeds

Higher temperature effect on enzymes

Increase molecule movement speed, increasing frequency of collision between enzymes and substrate, which INCREASES THE RATE OF REACTION

Competitive inhibition

Molecules bind reversibly or irreversibly to ACTIVE SITE of enzyme, preventing reaction

Noncompetitive inhibition

Inhibitor binds to ALLOSTERIC SITE, changing shape/activity of enzyme

All living systems require

constant input of energy

Second Law of Thermodynamics

Energy input must exceed energy loss to maintain order and power cellular processes; cellular processes that release energy (exergonic) may be coupled with cellular processes that require energy (endergonic); loss of order or energy flow results in death

Energy pathways

Sequential for more controlled and efficient energy transfer. Product of reaction in metabolic pathway is reactant for next step in the pathway (e.g. glycolysis produces pyruvate which reacts in the Krebs cycle)

Photosynthesis

Captures energy from the sun and produces sugars

Photosynthesis first evolved in

Prokaryotic organisms; cyanobacterial photosynthesis created oxygenated atmosphere; prokaryotic photosynthetic pathways foundation of eukaryotic photosynthesis

Light-dependent reactions

Involve a series of reaction pathways that capture energy present in light to yield ATP and NADPH, which power the production of organic molecules

Chorophyll

Pigment in photosystems I and II that absorb energy from light and boost electrons to a higher energy level

Photosystem II

Comes first in thylakoid membrane; absorbs light to boost electrons to higher energy levels via chlorophyll; connected via ETC to PSI; special chlorophyll pair at core is P680

Photosystem I

Comes second in thylakoid membrane; absorbs light to boost electrons to higher energy levels via chlorophyll; connected via ETC to PSII; special chlorophyll pair at core is P700

Electron transport chain in photosynthesis

Electrons boosted in PSII by P680, travels down chain while PUMPING H+ IONS INTO THYLAKOID LUMEN FROM STROMA to build gradient (losing some energy), arrives in PSI and boosted again by P700 and transferred to acceptor molecule, reducing it

Chemiosmosis in photosynthesis

ATP synthesis via H+ (proton) ions flowing down gradient created by ETC (FROM THYLAKOID LUMEN INTO STROMA) through ATP synthase, which provides energy to phosphorylate ADP (PHOTOPHOSPHORYLATION); terminal electron acceptor is NADP+

Final stage of ETC in photosynthesis

After PSI, electron travels down short chain and is passed to NADP+ with another electron from the same pathway (reducing it) to CREATE NADPH

Calvin Cycle

In STROMA of chloroplast; uses energy captured in light reactions in form of ATP and NADPH to power production of carbohydrates/sugars (G3P, which forms glucose) from CO2 (and H+ ions)

Calvin Cycle Reactants and Products

18NADPH + 12ATP + 6CO2 make 2G3P makes 1 glucose (6 turns of cycle)

Fermentation and cellular respiration

Use energy from biological macromolecules to produce ATP and CHARACTERISTIC OF ALL FORMS OF LIFE

Aerobic cellular respiration

In MITOCHONDRIA, eukaryotes only, efficient (36 ATP) because OXYGEN MOST POWERFUL ELECTRON ACCEPTOR

Without oxygen, eukaryotic cells will

Die or cease to function because anaerobic respiration doesn’t produce enough energy to maintain life functions

Anaerobic cellular respiration

Happens without oxygen, used by prokaryotes, fermentation, produces less (2) ATP (ex. alcoholic, lactic acid, proprionic acid fermentation; acetogenesis)

Methanogenesis

Type of anaerobic respiration performed only by some archaebacteria that breaks down carbs into CO2 and methane; performed by some symbiotic bacteria in digestive tracts of humans, cows, etc. to break down CELLULOSE

Electron transport chain

Transfers energy from electrons in a series of coupled reactions that establish an electrochemical gradient across membranes

Electron transport chain in cellular respiration

Electrons delivered by NADH and FADH2 are passed to a series of electron acceptors as they move toward the terminal electron acceptor (oxygen in aerobic prokaryotes; other molecules in anaerobic prokaryotes); proton gradient formed ACROSS INNER MITOCHONDRIAL MEMBRANE (PLASMA in prokaryotes), separating high proton concentration (INTERMEMBRANE SPACE) from low proton concentration (MATRIX); flow of H+ back through membrane-bound ATP SYNTHASE via CHEMIOSMOSIS phosphorylates ADP and inorganic phosphate to ATP (OXIDATIVE PHOSPHORYLATION)

Electron transport chain reactions locations

Chloroplasts, mitochondria, prokaryotic plasma membranes

How can cellular respiration create heat instead of ATP?

By decoupling oxidative phosphorylation from electron transport; can be used by endothermic organisms to regulate body temperature (e.g. hibernating bears)

Glycolysis

Biochemical pathway that splits glucose to form TWO ATP from ADP and inorganic phosphate, NADH from NAD+, and pyruvate. Can occur with (goes to Krebs cycle) or without oxygen (goes to fermentation)

Aerobic respiration equation

C6H12O6 + 6 O2 + 36 ADP + 36 Pi -> 6 CO2 + 6 H2O + 36 ATP (produces most energy/ATP; carbon of glucose exhaled as CO2)

Lactic Acid Fermentation Equation

C6H12O6 + 2 ADP + 2 Pi -> 2 CH3CHOHCOOH (lactic acid) + 2 ATP

Alcoholic Fermentation Equation

C6H12C6 + 2 ADP + 2 Pi -> 2 C2H5OH (ethyl alcohol) + 2CO2 + 2 ATP

Reduce

To add electrons

Aerobic respiration

Glycolysis produces 2 ATP and pyruvate; pyruvate is transported from CYTOSOL to MITOCHONDRION for further oxidation in the KREBS/CITRIC ACID CYCLE in which ATP is made from ADP and electrons are transferred to coenzymes NADH and FADH2 (reduced), which transport them to ETC in INNER MITOCHONDRIAL MEMBRANE to create ELECTROCHEMICAL GRADIENT across membrane

Fermentation

Allows glycolysis to proceed in the absence of oxygen and produces organic molecules, including alcohol and lactic acid, as waste products. Much less efficient than aerobic/CAC (2 vs. 36 ATP) (e.g. lactic acid produced when exercising because not enough O2)

Variation at the molecular level in number/type

Provides organisms with the ability to respond to a variety of environmental stimuli and therefore survive/reproduce in different environments (ex. different types of phospholipids allow flexibility with temperature, different types of hemoglobin maximize oxygen absorption at different developmental stages, different chlorophylls = more wavelengths)