AP Bio Unit 3

Thermodynamics

first law of thermodynamics

• energy cannot be created nor destroyed

second law of thermodynamics

• every energy transformation increases the entropy of the universe

Enzymes

proteins

cannot change Free energy change

lower activation energy

• increase rate of reaction

active site → specifically designed area

• substrates can bind

• specifically shaped to the enzyme

• held by weak bonds (won’t stay forever)

• induced fit

  • active site can change shape to bind substrate

  • substrate turns into product

  • cycle reoccurs

enzymes speed up reactions that can happen on their owns

commonly end in -ase

catalysts → can be reused in a reaction

have ideal pH and temp. ranges

ionic concentration, pH, and temp. denatures enzymes

• change results in denaturation

• shape is distorted → cannot bind correctly

not consumed in reactions

Catalase → common enzyme found in all living cells, breaks down hydrogen peroxide

Temperature

enzyme activity increases w/ temp. to a certain point

more kinetic energy increases molecular motion → higher chance to bind with substrates

after certain temp. enzyme denatures (shape change)

Irreversible vs. Reversible Denaturation

Reversible: enzyme is able to restore the enzyme’s function to regain optimal shape

Irreversible: enzyme shape is permanently changed, catalytic ability destroyed (eggs)

Substrate Concentration

low substracte concentration = probability enzyme meets substrate decreases

• product produced at low rate

high substrate concentration = collision and reaction rate increase

saturation point: enzymes have all active sites interacting with substrates (peak)

• called enzyme saturation

Competitive vs. Noncompetitive Inhibition

Competitive: foreign molecule (not apart of cell or organism and not enzyme substrate)

• blocks active site

• prohibits substrate from binding

• inhibits reaction rate

Noncompetitive: foreign molecule binds away from active site (allosteric site)

• leads to ripple effect

• change of shape at active site

• susbstrate can so longer bind to active site

Metabolic Pathway

linked series of enzyme-catalyzed chemical reactions occurring within a cell

one molecule is altered through these steps

• leads to end product

• each step is catalyzed by a certain enzyme

• chain reaction

Enzyme Evolution

enzymes are proteins (genes)

• genes can be mutated

  • changes in amino acids of enzymes

Cellular Respiration

occurs in mitochondria

requires glucose and oxygen

outputs: carbon dioxide, water, and ATP

Glycolysis

inside cytoplasm

• oxidizes glucose into pyruvate

  • carbon of glucose stays present in pyruvate

• produces NADH and small amounts of ATP

  • NADH and FADH2 are main electron carriers

  • oxygen is FINAL electron acceptor

• not dependent on oxygen

• pyruvate enters mitochondria through CoA (Acetyl coenzyme A COA)

  • releases CO2

  • enters specifically mitochnodrial matrix

• NADH (coenzyme that can transfer electrons)

Krebs Cycle

aerobic (requires oxygen)

• CO2 released

• produces NADH and FADH2

• and ATP

ETC (Electrontransport Chain)

• electrons from NADH and FADH2 are transferred to proteins

  • generates protein gradient

  • proteins pumped to intermembrane space

  • ATP synthase

    • makes ATP by adding phosphate to ADP (adenosine diphosphate)

  • travel down electronchemical gradient

  • oxygen accepts final electrons

  • and can combine with 2 hydrogens

    • creates water

Fermentation

some use anaerobic respiration

does not produce as much ATP as aerobic respiration

others only use glycolysis 

• fermentation

  • making ATP where there is no oxygen

  • adds step after glycoysis

    • helps regenerate NAD+

Alcoholic Fermentation

• glycolysis occurs first

• pyruvate is used → produces CO2 and ethanol

  • acetaldehyde is also produced and is an electron acceptor

  • turns NADH to NAD+

Lactic Acid Fermentation

• start with glycolysis

  • produces ATP, NADH, and pyruvate

  • pyruvate turns into lactate

    • pyruvate becomes electron acceptor

    • so that NADH can be oxidized to NAD+

Photosynthesis

reactant: carbon dioxide and water

products: glucose and oxygen

chlorophyll → used to absorb plant and reflect green light

• found in chloroplasts

• light dependent and independent reactions

• light dependent occurs in thylakoid membrane

  • light is captures and water is split

    • 1/2O2 and H (electron)

• light independent reaction

• requires ATP and NADH

• occur in chloroplasts

  • specifically stroma

• CO2 enters stoma

  • enzyme converts CO2

  • ATP and NADPH

    • converts to glucose

• pigments from light dependent reactions absorbed into photosystems

  • electrons become excited w energy

  • electrons move to electron transport chain

    • water is split to move back into photosystem

    • H ions (protons) move inside and oxygen stays

  • as electrons move, the energy pumps hydrogen ions down the gradient

  • high concentration of H ions in enzyme

    • ATP synthase allows H ions to leave the membrane

    • produces ATP

  • electrons continue to move down chain

    • to photosystem I

    • in photosystem electrons are excited again w light

      • electrons accepted to NADP+

      • accepted w hydrogen → NADPH

        • NADPH: electron carrier

        • carriers electrons and hydrogen to light independent reactions

  • light independent reaction uses products of light dependent reaction

    • ATP, NADH, and CO2 to produce glucose