2.8-2.9 Resp and photosynthesis Flashcards
Cells require energy for: (3)
Movement of organelles/cells
Synthesis of large molecules
Active trnsp
ATP yield from aerobic vs anaerobic
Aerobic = 38 ATP
Anaerobic = 2 ATP
Stages of aerobic respiration and location
Glycolysis (cytoplasm)
Link Pathway (mitochondrial matrix)
Krebs cycle (matrix)
Oxidative phosphorylation (cristae)
Glycolysis process
ATP required = 2
ATP produced = 4 (net 2)
NADH produced = 2
- Substrate level phosphorylation
Phosphorylation of glucose molecule to form fructose-1,6-biphosphate
Requires 2 ATP - Lysis
Lysis of F16BP to form 2x 3C sugars of glyceraldehyde 3 phosphate - Oxidation and ATP formation
- Each G3P undergoes oxidation to form 1 NADH
- Energy released is used to add Pi to remaining 3C compound
- Removal of 2 Pi groups from molecule by enzymes, add to 2ADP to form 2ATP
- Form pyruvate
Link pathway process
Oxidative decarboxylation
- Pyruvate from glycolysis enters mitochondrial matrix
- Enzymes remove 1 CO2 - decarboxylation
- Removal of 1 H, accepted by NAD+ to form NADH - oxidation
- Form acetyl group, reacts with Coenzyme A to form Acetyl-CoA
forms 2NADH, 2 CO2/ glucose
Significance of high energy bonds in acetylcoa
energy rich bonds are required to supply energy needed to form citric acid in krebs cycle.
Krebs cycle process
- Energy rich electrons are removed from organic molecules, transferred to electron carriers FAD+ and NAD+
- 2C Acetyl CoA + 4C oxaloacetate to from 6C citrate
- Oxidative decarboxylation releases 2CO2 (4CO2 in total) molecules per pyruvate, conversion from 6C to 5C, 5C to 4C releases CO2.
- Total produce 6NADH, 2 FADH2, 2 ATP per glucose (ATP produced by substrate level phosphorylation)
6C > 5C > 4C > 4C > 4C, reduction in C –> co2 produced. first 4C –> 4c is fADH, rest is NADH. 5C –> 4C has ATP
Oxidative phosphorylation in terms of chemiosmosis
Def chemiosmosis: use of proton gradient to generate ATP
Protons accumulate in intermembrane space
Proton gradient across inner membrane
Special channels coupled with ATP synthase permit H+ to pass through down concentration gradient
As H+ ions move through protein channels, ATP synthase uses energy of proton gradient to synthesize ATP through chemiosmosis
Oxidative phosphorylation process - essay
- NAD and FAD reduced to NADH and FADH by gaining electrons
- NADH produced in glycolysis, link and krebs, FADH2 only produced in krebs
- NADH2 and FADH 2 delivers electrons to ETC at inner membrane, mitochondrial cristae.
- Electrons release energy as they flow along the chain from one carrier to another
- Oxygen final electron acceptor (highest affinity)
- Proteins in inner membrane act as pumps, use energy from the electrons to pump protons into intermembrane space
- Protons accumulate in intermembrane space, high concentration of protons in intermembrane space, lower concentration in matrix - proton gradient across inner mitochondrial membrane between imspace and matrix is established.
- Protons pass through specialized channels in cristae coupled with ATP synthase
- ATP synthase makes use of energy from the proton gradient to convert ADP to ATP.
- Each NADH = 3 ATP, each FADH2 = 2 ATP
Total = 34 ATP
Adaptations of mitochondria
Inner membrane:
- Location of etc and atp synthase
- increased sa by folding into cristae, more ATP synthase = increase ATP synthesis
- Impermeable to protons, allowing a concentration gradient between intermembrane space and matrix
Intermembrane space:
- Small space in which protons accumulate, allows for high concentration of protons with resulting concentration gradient required for chemiosmosis to occur.
Matrix:
- contains enzymes required for krebs and link
Define respiration
Controlled release of energy from organic compounds to produce ATP
Aerobic vs anaerobic respiration
Oxygen v without oxygen
Produces CO2 and H2O vs produces ethanol and CO2 in yeast, lactic acid in mammals
Produces alot of energy 38ATP, produces less energy 2ATP
Lactic acid vs ethanol anaerobic resp
Produce lactic acid v produce co2 and ethanol
Lactic acid can be converted back into pyruvate when oxygen becomes available again v energy in ethanol is permanently unavailable
Lactic acid fermentation process and applications
Process
- Glycolysis: Glucose –> 2 Pyruvate 2 ATP + 2 NADH
- 2 Pyruvate –> 2 Lactate + 2 NAD+
Applications
- Supply small amount of ATP rapidly, maximize power of muscle contractions, eg sprinters
- Results in increased concentration of toxic lactate. After vigorous muscle contractions, lactate must be broken down with oxygen.
- Accumulation of toxic lactate results in muscle cramps and fatigue.
Process and applications of Ethanol fermantation
Process
- Glycolysis: Glucose –> 2 Pyruvate 2 ATP + 2 NADH
- 2 Pyruvate –> 2 Acetaldehyde + 2CO2
- 2 Acetaldehyde –> 2 Ethanol + 2NAD+
Applications
- Yeast in bread making - flour + water + yeast creates CO2 which causes bread to rise. EtOH produced is evaporated during baking
- Production of bioethanol - Starch and cellulose present in sugarcane and corn is first broken down into sugars. yeast converts sugars into ethanol in large fermenters. Ethanol produced can be purified by distillation.
Recall how to draw absorption vs action spectrum for photosynthesis
Absorption spectrum - absorption/% against wavelength of light/nm
Action spectrum - relative photosynthesis rate against wavelength of light/nm
400-700nm
Factors affecting rate of photosynthesis
Increase in light intensity increases rate of photosynthesis until a plateau is reached at higher light intensities where another factor becomes limiting factor.
- Light needed for light indep reactions
- High light intensity may bleach chlorophyll, slow down photosynthesis
Increase in temp increases rate of photosynthesis to an optimum, above which rate drops
- temp affects enzyme (rubisco) activity
- increase to optimal temp - optimal rate of carbon fixation. Higher temp - do not work effectively
Increase in CO2 conc increases rate of photosynthesis until a plateau is reached at higher CO2 levels.
- CO2 is needed for calvin cycle for carboxylation of RuBP
- under normal conditions, CO2 is conc for limiting factor for rate of photosynthesis.
Light dependent stage
- definition
- location
- Explain photosystem structure, accessory and primary pigments
Use of light energy to carry out photolysis of water to provide the protons and electrons required to carry out redox reactions to produce ATP and reduce NADP to NADPH
Thylakoid membrane
Photosystem:
Reaction-center complex surrounded by light-harvesting complexes. Light harvesting complex funnel energy of photons to reaction center. Reaction center also contains pigments which absorb light energy to promote electrons to a higher energy level before donating them to ETC.
Light harvesting complex contains accessory pigment - traps light energy, channels it to primary pigment.
Reaction center contains primary pigments - donates high energy electrons to ETC (Chlorophyll a in P680 and P700)
Light dependent stage - essay
- Photolysis of water in thylakoid space
- P680+ accepts electrons
- Photon hits accessory pigment, energy passed among pigment molecules until it excites P680 in reaction center
- 2 excited electrons from P680 to primary electron acceptor
- Electrons pass through redox reactions from primary electron acceptor to subsequent carrier along ETC
- Energy from excited electrons going down ETC used to pump protons
- H+ accumulate in thylakoid
- Steep proton gradient, diffusion down through ATP synthase produce ATP
- P700 accepts electrons passing from PS II from ETC
- Light excites P700, produces 2 excited electrons
- Electrons transferred to electron acceptor, donate to electron carriers.
- Transferred from P700 down ETC to Fd then to NADP
NADP + H+ in stroma to form NADPH with NADP reductase. - Cyclic - electrons from PS I are excited and pass down ETC to PS I.
Cyclic vs noncyclic phosphorylation
Pathway of electrons
First e donor
Last e acceptor
Products
PS involved
High concentration of H+ due to
PEEPH
Photophosphorylation vs Oxidative phosphorylation
LLEEED
Location
Light energy
Energy for synthesis comes from
Electron donors
Electron acceptors
Direction of proton flow (inwards outwards)
Light independent stage - essay
Occurs in stroma
Carbon fixation
- CO2 added to ribulose-1,5-biphosphate, catalyzed by Rubisco
- Form unstable 6C compound, splits into 2 glycerate-3-phosphate
Reduction
- Glycerate-3-phosphate reduced to triose phosphate using NADP and ATP
- ATP provides PO4, NADPH provides hydrogen
Regeneration of RuBP
- 5 of 6 G3P is converted back to RuBP
- 1 of 6 G3P is converted to 6C sugar molecule used to build carbohydrates.
Fixing of 3 CO2 molecules requires = 9ATP, 6 NADPH
Role of hydrogen ions during photosynthesis
ATP synthesis
- Photolysis
- energy from excited electrons produced by photosystem II and I used to pump protons into thylakoid
- concentration gradient
- chemiosmosis
NADPH synthesis
- NADP reacts with H+ in stroma to form NADPH
ATP and NADPH used for synthesis of TP from Glycerate 3 phosphate
Structure of chloroplast and functions
Small internal volume of thylakoid - quickly increase H+ conc gradient
Suitable pH of stroma, contains enzymes - optimal pH for greatest activity of Rubisco
Photosynthetic pigments arranged into photosystems on thylakoid membrane, many grana - increase SA for light absorption
Lamellae connect grana - increase photosynthetic efficiency
Double membrane surrounding chloroplast - permeable to CO2, ATP, O2, sugars, other products of photosynthesis
