AP/IB Biology - Cell Respiration & Photosynthesis

Cell Respiration & Photosynthesis
BIO STUDY GUIDE (Ch. 9.1-9.5, 10.1-10.3)
I) CELLULAR RESPIRATION
A) Catabolic Pathways
A.1) Fermentation: partial degradation of sugar that occurs w/o oxygen
A.2) Cellular Respiration: oxygen is used
A.3) Redox Reactions (Oxidation-Reduction that exchanges electrons)
Oxidation: loss of electrons (energy must be added)
Reduction: addition of electrons. (-) charged electrons added to atom reduce amount of (+) charge of that atom
A.4) Stepwise Energy Harvest via NAD+ & ETC (FOODNADHETCOXYGEN)
Each electron travels with a proton, hydrogen atom
NAD+: functions as an oxidizing agent  Hydrogen atom transferred here first  most versatile electron acceptor
Traps electrons from glucose by enzymes (dehydrogenases) to remove pair of hydrogen atoms(2 electrons & 2 protons) from substrate to oxidize it, then the enzyme delivers the 2 electrons & 1 proton (the other is released as hydrogen ion) to its coenzyme NAD+
The NAD+ has now neutralized its charge and is reduced to NADH
Electron Transport Chain: Break the fall of electrons to oxygen in several steps  Built in inner membrane of mitochondrion  exergonic  prevents from losing energy at once
Electrons from food move by NADH to top of chain and at the bottom, oxygen capture these electrons along w/ hydrogen nuclei forming water electrons move down from one carrier mol. to the next losing little energy fall down a energy gradient to stable location where its more electroneg.
A.5) Stages of Cellular Respiration (GLYCOSISCITRIC ACID CYCLEOXIDATIVE PHOSPHORYLATION)
Glycosis: Occurs in Cytosol  Begins degradation process by breaking down glucose into 2 compounds called pyruvate
CAC (Krebs Cycle): Occurs in mitochondrial matrix  completes breakdown by oxidizing a derivative of pyruvate to CO2
Oxidative Phosphorylation: ATP synthesis in which energy is released at each step of chain and stored in mitochondrion  powered by redox reaction of ETC a lot of ATP takes place in inner membrane of mitochondrion and is made up of ETC and chemiosmosis
Substrate-level Phosphorylation: small amount of ATP formed in few reaction of glycosis & CAC
B) Glycosis harvest chemical energy by oxidizing glucose to pyruvate
B.1) Energy investment phase cell actually spends ATP but is repaid with dividends during energy payoff phase
B.2) Energy Payoff Phase
ATP is produced by substrate-level phosphorylation & NAD+ is reduced to NADH by electrons released from oxidation of food(glucose)
C) CAC completes energy-yielding oxidation of glucose
C.1) If molecular oxygen is present, pyruvate enters mitochondrion where enzymes of CAC complete oxidation of organic fuel
C.2) Before CAC, pyruvate is converted into acetyl CoA through 3 reactions
Pyruvate's carboxyl group is removed and given off as mol. of CO2 (CO2 that's released in respiration) remaining two-carbon fragment is oxidized forming acetate. enzyme transfers extracted electrons to NAD+ storing energy as NADH coenzyme A is attached to acetate by an unstable bond making it reactive
The product is thus acetyl CoA is now ready to feed it acetyl group in the CAC cycle for further oxidization
D) Oxidative Phosphorylation
D.1) Pathway of Electron Transport
Located in inner membrane of mitochondrion in cristae (folding=increase surface) electrons from NADH and FADH2 pass through the electron transport chain (ETC) to oxygen, which is reduced to water
Electron carriers alternate betwn reduced and oxidized states as they accept & donate electrons. Each component of the chain becomes reduced when it accepts electrons from upper level, which has lower affinity for electrons. It then return to oxidized form as it passes electrons to downhill, a more electronegative level. D.2) Chemiosmosis
Inside inner membrane of mitochondrion are many copies of proteinATP Synthase
ATP Synthase: enzyme that makes ATP from ADP & inorganic phosphate
Uses energy of an existing ion gradient to power ATP synthesis
Chemiosmosis: Process in which energy is stored in form of hydrogen ion gradient across membrane to drive cellular work such as synthesis of ATP diffusion of ions
E) Fermentation
E.1) Types of fermentation
Alcohol Fermentation: pyruvate is converted to ethanol
Lactic Acid Fermentation: pyruvate us reduced directly by NADH to form lactate as an end product w/o release of CO2
II) PHOTOSYNTHESIS
A) Chloroplasts: Site of Photosynthesis in plants
A.1) Chlorophyll: Color in leaves embedded in thylakoid membrane
A.2) Stomata: pores in which CO2 and oxygen go through
A.3) Thylakoids: membranous sacs & includes chlorophyll mols., ETC, & ATP synthase
A.4) Stroma: dense fluid w/in chloroplasts
B) Two Stages of Photosynthesis
B.1) Light Reactions (photo): covert solar energy to chemical energy  Light-dependent
Light absorbed by chlorophyll drives transfer of electrons & hydrogen from water to an acceptor NADP+
NADP+: Temporarily stores energized electrons
Water is split in process and thus this process gives off O2 as by-product
Uses solar power to reduce NADP+ to NADPH by adding a pair of electrons along with hydrogen nucleus (H+)
Also generate ATP using chemiosmosis to power addition of phosphate group to ADP: photophosphorylation
Thus light energy is converted to chemical energy in two forms
NADH: source of energized electrons
ATP: versatile energy currency of cells
B.2) Calvin Cycle(synthesis): Makes sugar by using NADH & ATP  light-independent
Incorporates CO2 from air into organic mol. already present in chloroplast: Carbon Fixation
Recycles ADP & NADH to make more
C) Light Reactions
C.1) Photosystems: composed of a reaction center surrounded by a number of light-harvesting complexes (pigment molecules)
Photosystem II
Chlorophyll a: absorbs best in red & blue and least in green  P680
Photosystem I
Chlorophyll b: yellow-green  P700
C.2) ETC produces from light energy ATP & NADPH membrane-bound proteins in organelle
PSII absorbs light excited electron passes from chlorophyll to primary electron acceptor electron acceptor: special chlorophyll a mol. needs to replace electron in chlorphyll enzymes extracts electron from H2) & supplies them to chlorophyll splits H2oO combines w/ another O to form O2O2 release in atmosphere
C.3) Noncyclic Photophosphorylation dominant route of electron flow
2 steps: in PSII & PSI
PSII generates energy as ATP
PSI generates reducing power as NADPH
C.4) Cyclic Photophosphorylation
Uses PSI but not PSII
Electrons cycle back to PSII to make more ATP but no NADPH & oxygen
C.5) Comparison between Chemiosmosis in Chloroplasts & Mitochondria
Chloroplasts & Mitochondria produces ATP in same way : Chemiosmosis
Mitochondria transfer chemical energy from food molecules to ATP
Chloroplasts transform light energy into chemical energy in ATP
D) Calvin Cycle (anabolic) (similar to CAC(catabolic) as they both regenerate starting material after mols enter and leave cycle)
D.1) Need products of light reactions
D.2) End Product is Glyceraldehyde-3-phosphate (G3P) energy rich 3 carbon sugar
D.3) 3 Phases
Carbon Fixation
Rubisco: enzyme which fixes carbon from air (most important and abundant)
Reduction
Regeneration of CO2 acceptor (RuBP)
E) Photosynthesis summary
E.1) Light reactions produced ATP produced NADPH consumed H2O produced O2 as byproduct
E.2) Calvin cycle consumed CO2 produced G3P (sugar) regenerated ADP regenerated NADP