Respiration

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Glycolysis (cytoplasm)

1. Phosphorylation

  • 1 ATP hydrolysed, phosphate goes to C6 = gluc-6-P converted fruc-6-P
  • Other ATP hydrolysed, phosphate C1 = fruc 1,6-bisphos & energy activates = hex 1,6-bis

2. Splitting of hexose 1,6-bisphosphate

  • Each molecule split into 2 triose phosphate

3. Oxidation of triose phosphate

  • 2 H atoms removed w/ use dehydrogenase & aided by NAD = NADH
  • 2 molecules NADH made & 2 molecules ATP formed (substrate-level-phosphorylation)

4. Conversion of triose phosphate to pyruvate

  • 4 enzyme-controlled reaction convert each TP to pyruvate
  • Another 2 molecules ADP phosphorylated ATP

each molecule glucose 4 ATP made, 2 used so net gain = 2 & 2 NADH + pyruvate made

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Energy

Metbolic reactions need energy:

  • active transport; move ions/molecules across membrane against conc grad
  • secretion; large molecules made to be exported by exocytosis
  • endocytosis; bulk movement large molecules into cell
  • synthesis of large molecules from smaller; ie proteins from amino acids
  • replication of DNA & synthesis of organelles before cell divides
  • movement; ie bacterial flagella
  • activation of chemicals; ie glucose phosphorylated @ beginning so more unstable + broken

Some energy from catabolic reactions = heat useful as reactions controlled by enzymes

Energy from photoautotrophs- use sunlight = large, organic molecules consumer & decomposers use (ie. plants, some protoctsists + bacteria)

Respiration releases energy used to phosphorylate ADP to ATP

 

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Anaerobic Respiration

- release of energy from substrates in absence of oxygen

  • oxygen = final e acceptor in OP but if absent ETC can't function so Krebs/link stops

  • only glycolysis occurs + only source ATP

  • NADH generated during oxidation has to be reoxidised so glycosis keeps operating increasing chance organism surviving under temp adverse conditions

EUK 2 pathways reoxidise NAD

  • fungi, like yeast, use ethanol fermentation
  • animals use lactate fermentation

neither produce any ATP but 2 mole of ATP per molecule glucose made by substrate-level phospo (glyco = 2 ATP, NADH, pyruvate per molecule glucose)

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Lactate Fermentation

pyruvate to lactate w/ help lactate dehydrogenase + donation H from NADH = NAD

occurs mammalian muscle tissue during vigorous activity when demand ATP high & is an oxygen deficit

  • NADH reoxidised to NAD+
  • pyruvate = H acceptor (accepts H atoms from NADH)
  • NAD = reoxidised & available accept more H atoms from glucose
  • glycosis can continue, generating enough ATP sustain muscle contraction
  • enzyme lactate dehydrogenase catalyses oxidation of NADH together w/ reduction of pyruvate to lactate

lactate carried in blood away from muscles to liver

when more O available lactate converted back to pyruvate- enter Krebs via link or directly

muscle fatigue caused by reduction in pH reduces enzyme activity in muscle not build up lactate

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Respiratory Substrates pt II

lipids; triglycerides hyudrolysed by lipase to f. acids + glycerol (converted glucose)

  • long chain HC so many H-C bonds
  • source of many protons for oxidative phospho = lots ATP made

  • each f. a combined w/ CoA needs energy from hydrolysis molecule ATP to AMP + 2Pi
  • f. a - CoA complex transported to matrix broken into 2 acetyl groups attached to CoA
  • during this NADH + FADH formed

  • acetyl groups released from CoA & enter Krebs where 3 NADH,, 1 NADH, 1 ATP made
  • lots NADH reoxidised @ ETC during ox phospho = lots ATP by chemiosmosis

on ave.

carbs = 15.8 kJ/g |  lipids = 39.4 kJ/g |  protein = 17.0 kJ/g

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ATP & Oxidative Phosphorylation

before OP 4 molecules ATP gained/made substrate level phosphorylation

more ATP made during OP as NADH + FADH reoxidised - 10 NADH, 2 FADH altogether

  • both provide e to ETC used OP
  • NADH also H ions contribute build up gradient for chemiosmosis but FADH H ions stay matrix but can combine w/ O2 make water

  • 10 molecules NADH theoret = 26 mole ATP during OP so each molecule NADH up to 2.6 mole ATP should be made
  • together w/ ATP total yield ATP molecules should be 30

rarely achieved bc;

  • some protons leak across membrane reducing numb protons generate proton motive force
  • some produced is used a. transport pyruvate into mitochondria
  • some used for shuttle to bring H from NADH made during glycosis into the mitochondria
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Respiratory Substrates pt I

an organic substance that can be used for respiration

  • maj ATP produced during oxidative phospho protons flow through channels associated ATP synthase & H ions + e = H2O so more protons = more ATP
  • more H atoms in respiratory subst = more ATP when respired = more O2 needed respire


carbs; monosaccharides converted to glucose for respiration

  • theoretical yield 2870 kJ/mol & takes 30.6 kJ for 1 mol ATP
  • theoretically 1 mol glucose = nearly 94 mol ATP but actually around 30 w/ efficiency 32%
  • remaining energy released as heat maintains body temp = ECR proceeds

protein; excess a.a deaminated and rest changed glycogen/fat to store + later release energy

  • fast/starve/prolonged exercise protein from muscle hydrolyses to a.a respired
  • some convert to pyruvate, or acetate, carried to Krebs or enter directly
  • num H atoms per mole accepted by NAD + then used OP slightly more than num H atoms per mole of glucose
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Alcoholic Fermentation

pyruvate to ethanal (w/ help pyruvate decarboxylase so release CO2) to ethanol (ethanol dehydrogenase where NADH becomes reoxidised)

  • each pyruvate loses CO2 molecule, decarboxylated, to become ethanal which is catalysed by pyruvate decarboxylase that has coenzyme bound to it

  • ethanal accepts H atoms from NADH, becomes reoxidised as ethanal is reduced to ethanol (ethanol dehydrogenase)

  • reoxidised NAD can now accept more H atoms from glucose during glycolysis

yeast = facultative anaerobe- can live without oxygen but killed when conc ethanol 15%

  • rate growth faster under aerobic conditions
  • aerobic conditions to start w/ & then placed in anaerobic to undergo alcoholic fermentation
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Oxidative Phosphorylation & Chemiosmosis (cristae)

Involves e carriers embedded in inner membrane (folded cristae = large SA e carriers & ATP synthase enzymes)

Reduced NAD + FAD reoxidised = donate H atoms split into protons/electrions = e carriers

First e carrier accept electrons from reduced NAD = NADH - coenz Q reductase (aka NADH dehydrogenase)

Protons go into solution in matrix

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Mitochondria- electron transport chain

  • each e carrier (protein complexes arranged in etc) = enzyme associated w/ cofactor (nonprotein haem groups w/ iron atom)
  • cofactor accept & donate e bc iron atoms reduced gain e to Iron(II) / oxidised lose e to Iron(III); are oxidoreductase enzymes
  • some e carriers have coenzyme pumps protons from matrix to intermembrane space
  • inner membrane impermeable small ions, protons accumulate in space = proton gradient

ATP synthase enzymes (aka stalked particles)- large & protrude from inner membrane into matrix & allow protons pass through them

  • protons flow down proton gradient, through ATP synthase enzymes, from space to matrix (chemiosmosis)
  • force of flow drives rotation of part of enzyme allows ADP + Pi = ATP

Coenzyme FAD = reduced FAD in Krebs tightly bound to dehydrogenase embedded membrane

  • H atoms accepted by FAD don't get pumped into space, pass back to matrix
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Chemiosmosis

ETC- electron passed along chain e carriers & donated to molecular oxygen (final e acceptor)

~ chemiosmosis

  • as e flow along ETC energy released + used by coenzymes associated w/ carriers pump protons across to intermembrane space

  • builds up proton/pH/electrochem gradient so PE builds up in space
  • H ions can't diffuse lipid part inner membrane but can through ion channels (associated w/ ATP synthase) flow of ions = chemiosmosis

~ oxidative phosphorylation (formation ATP by ADP + Pi in presence oxygen)

  • as protons flow through ATP synth enzyme drives rotation of part of enzyne = ADP + Pi = ATP
  • e passed from last e carrier to molecular oxygen (final e acceptor)
  • H ions also join so oxygen reduced to water; 4H + 4e + O2 = 2H2O
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Link Reaction (matrix)

pyruvate from Glycolysis transported across inner & outer mitochond. membrane to matrix

- pyruvate decarboxylated + dehydrogenated w/ use pyruvate dehydrogenase & carboxylase

- removal of carboxyl group eventually becomes carbon dioxide

- NAD accepts H atoms = NADH

- CoA acceps acetate = acetyl CoA which carries acetate to Krebs Cycle

Note:

  • 0 ATP produced
  • 1 NADH made per pyruvate 
  • 2 NADH made per glucose molecule
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Role of ATP

ATP - phosphorylated nucleotide 'universal energy currency'

High-energy intermediate compound, found in prokaryotes & eukaryotes

Contains:

  • adenosine (adenine + ribose)
  • 3 phosphate groups

Hydrolysed to ADP & Pi releasing 30.6 kJ energy per mol

Energy immediate available to cells in small, manageable amounts so won't damage + waste

Occurs in many small steps w/ energy each step joining ADP + Pi = ATP

Hydrolysis ATP coupled w/ synthesis reaction ie. proteins which require energy where energy released from hydrolysis = immediate source energy for these biolog processes

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Mitochondria

Mitochondria- organelles found in eukaryotes & site of link reaction, Krebs & oxidative phospho

  • inner & outer phospholipid membrane = envelope
  • outer = smooth
  • inner = folded into cristae = large SA

  • 2 membranes enclose & separate compartments within
  • between membranes = intermembrane space
  • matrix enclosed by inner membrane; semi-rigid + gel-like consists of mix proteins, lipids, mitochondrial DNA & ribosomes + enzymes

  • rod-shaped/thread-like mostly 0.5-1.0µm diameter & 2-5µm long but larger in athletes
  • metabolically active cells = more longer + densely packed cristae = more ETC + ATP synthase
  • can be moved around by cytoskeleton + some permanently positioned near site high demand
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Respiration & Energy

Respiration- process whereby energy stored in complex organic mole. used make ATP

Energy- the ability to do work

Anabolic- reactions build large molecules from smaller ones

Catabolic- larger molecules broken down to smaller

Energy:

  • exists as potential & kinetic energy
  • molecules that move = KE = diffuse down conc grad
  • large molecules = chemical portential energy
  • can't be made/destroyed & measured in joules w/ lots of forms

Energy needed to drive biolog. processes

Reactions occur in cells = metabolism

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Mitochondria- structure related to function

Matrix (link reaction/Krebs) contains:

  • enzymes catalyse stages reaction
  • molecules of NAD
  • oxaloacetate- accepts acetate from link reaction
  • mitochondrial DNA- code some mitochondrial enzymes/proteins
  • mitochondrial ribosomes- proteins assembled

Outer Membrane

  • phospholipid composition contains proteins- channel for ions, carrier for large+ enzymes

Inner Membrane

  • differ lipid composition from outer
  • impermeable most small ions including Hydrogen
  • folded into many cristae- increase SA
  • embedded electron carriers & ATP synthase enzymes
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Coenzymes

4 stages respiration; only glycolysis occurs in anaerobic conditions

  • first 3 stages H atoms removed oxidation reactions catalysed by dehydrogenase 
  • coenzymes help catalyse oxidation/reduction reactions
  • H atoms combine w/ coenzymes (NAD) carry them & later split into H ions & e
  • Delivering H to cristae reoxidises coenzymes so combine w/ more H atoms
  • OILRIG; + reactions are coupled, 1 oxidised other reduced

Nicotinamide Adenine Dinucleotide (NAD)

  • Organic, non-protein aids dehydrogenase carry out oxidation reactions
  • Made of 2 linked ribose, adenine & 2 phosphate groups
  • 1 contains adenine w/ other contains nicotinamide ring accepts H atoms
  • When accepts 2 H atoms w/ e = reduced & loses = oxidised

Coenzyme A (CoA)

  • Made from panthothenic aid, adenosine, 3 phosphate groups & cysteine
  • Carry ethanoate groups from pyruvate to Krebs cycle also acetate group from a/f acids
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Krebs Cycle (matrix)

1. Acetate offloaded from CoA & joins w/ 4C oxaloacetate forming citrate

2. Citrate decarbox & dehyd to 5C where pair H atoms accepted produce NADH 

3. 5C decarbox & dehyd to 4C where pair H atoms accepted produce NADH

4. 4C converted to another 4C & ADP phosphorylated to ATP

5. Second 4C converted to another 4C where pair H atoms removed to become reduced FAD

6. Third 4C dehyd & regenerates to oxyaloacetate where another NADH made

Note:

  • 1 turn of cycle for 1 pyruvate so each glucose molecule = 2 turns so double products
  • each molecule glucose; 6 NADH, 2 reduced FAD, 4 carbon dioxide & 2 ATP
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