harvesting stored energy
DESCRIPTION
glucose + oxygen energy + water + carbon. dioxide. respiration. ATP. +. 6H 2 O. +. 6CO 2. + heat. . C 6 H 12 O 6. +. 6O 2. COMBUSTION = making a lot of heat energy by burning fuels in one step. ATP. glucose. O 2. O 2. fuel (carbohydrates). Harvesting stored energy. - PowerPoint PPT PresentationTRANSCRIPT
Harvesting stored energy• Glucose is the model
– catabolism of glucose to produce ATP
C6H12O6 6O2 ATP 6H2O 6CO2+ + +
CO2 + H2O + heatfuel(carbohydrates)
COMBUSTION = making a lot of heat energy by burning fuels in one step
RESPIRATION = making ATP (& some heat)by burning fuels in many small steps
CO2 + H2O + ATP (+ heat)
ATP
glucose
glucose + oxygen energy + water + carbondioxide
resp
iratio
n
O2 O2
+ heat
enzymesATP
2
ATP = adenosine triphosphate-the energy “currency” of cells
ATP stores energy in the bonds between phosphates
3
Energy Currency of Cells
When the bond between phosphates is broken:
ATP ADP + Pi
energy is released
ADP = adenosine diphosphatePi = inorganic phosphateThis reaction is reversible.
ATP
Really high energy bond
ADP + Pi
How do we harvest energy from fuels?• Digest large molecules into smaller ones
– break bonds & move electrons from one molecule to another• as electrons move they “carry energy” with them• that energy is stored in another bond,
released as heat or harvested to make ATP
e-
+ +e-
+ –loses e- gains e- oxidized reduced
oxidation reduction
redox
e-
How do we move electrons in biology?• Moving electrons in living systems
– electrons cannot move alone in cells• electrons move as part of H atom• move H = move electrons
pe
+
H
+H
+ –loses e- gains e- oxidized reduced
oxidation reduction
C6H12O6 6O2 6CO2 6H2O ATP+ + +oxidation
reductionH e-
Moving electrons in respiration• Electron carriers move electrons by
shuttling H atoms around– NAD+ NADH (reduced)– FAD+2 FADH2 (reduced)
+ Hreduction
oxidation
PO–
O–
O
–O
PO–
O–
O
–O
CC
O
NH2
N+
H
adenine
ribose sugar
phosphates
NAD+
nicotinamideVitamin B3niacin
PO–
O–
O
–O
PO–
O–
O
–O
CC
O
NH2
N+
HNADH
carries electrons as a reduced molecule
reducing power!
How efficient!Build once,use many ways
H
8
Steps of Respiration
The complete oxidation of glucose proceeds in stages:
1. glycolysis2. pyruvate oxidation3. Krebs cycle4. electron transport chain & chemiosmosis
9
Glycolysis
glucose pyruvate2x6C 3C
That’s not enoughATP for me!
• Breaking down glucose – “glyco – lysis” (splitting sugar)
– ancient pathway which harvests energy• where energy transfer first evolved• transfer energy from organic molecules to ATP• still is starting point for ALL cellular respiration
– but it’s inefficient • generate only 2 ATP for every 1 glucose
– occurs in cytosol
intermembranespace inner
membrane
outermembrane
matrixcristae
Mitochondria — Structure• Double membrane energy harvesting organelle
– smooth outer membrane– highly folded inner membrane
• cristae– intermembrane space
• fluid-filled space between membranes– matrix
• inner fluid-filled space– DNA, ribosomes– enzymes
• free in matrix & membrane-bound
mitochondrialDNA
What cells would have a lot of mitochondria?
Mitochondria – Function
What does this tell us about the evolution of eukaryotes?Endosymbiosis!
Dividing mitochondriaWho else divides like that?
Advantage of highly folded inner membrane?More surface area for membrane-bound enzymes & permeases
Membrane-bound proteinsEnzymes & permeases
bacteria!
pyruvate acetyl CoA + CO2
Oxidation of pyruvate
NAD3C 2C 1C[2x ]
• Pyruvate enters mitochondrial matrix
– 3 step oxidation process– releases 2 CO2 (count the carbons!)– reduces 2 NAD 2 NADH (moves e-)– produces 2 acetyl CoA
• Acetyl CoA enters Krebs cycle
Wheredoes theCO2 go?Exhale!
14
3. Krebs Cycle-oxidizes the acetyl Co-A-occurs in the matrix of the mitochondria
15
Krebs Cycle
After glycolysis, pyruvate oxidation, and the Krebs cycle, glucose has been oxidized to:
- 6 CO2
- 4 ATP- 10 NADH- 2 FADH2
These electron carriers proceedto the electron transport chain.
• Electron Transport Chain – series of proteins built into
inner mitochondrial membrane– yields ~36 ATP from 1 glucose!– only in presence of O2 (aerobic respiration)
O2Thatsounds morelike it!
NAD+
Q
C
NADH H2O
H+
e–
2H+ + O2
H+H+
e–FADH2
12
NADH dehydrogenase
cytochrome bc complex
cytochrome coxidase complex
FAD
e–
• Electron carriers pass electrons & H+ to ETC– H cleaved off NADH & FADH2– electrons stripped from H atoms H+ (protons)
• electrons passed from one electron carrier to next in mitochondrial membrane (ETC)
• flowing electrons = energy to do work– transport proteins in membrane pump H+ (protons)
across inner membrane to intermembrane space
H+ H+ H+
H+
ADP + Pi
H+ H+
H+
H+ H+
H+H+H+
ATP
Chemiosmosis:
• Set up a H+
gradient• Allow the protons
to flow through ATP synthase
• Synthesizes ATP
ADP + Pi ATP
“proton-motive” force
H+
H+
O2+
Q C
ATP
Pyruvate fromcytoplasm
Electrontransportsystem
ATPsynthase
H2O
CO2
Krebscycle
IntermembranespaceInner
mitochondrialmembrane
1. Electrons are harvested and carried to the transport system.
2. Electrons provide energy
to pump protons across the membrane.
3. Oxygen joins with protons to form water. 2H+
NADH
NADH
Acetyl-CoA
FADH2
ATP4. Protons diffuse back in
down their concentrationgradient, driving the synthesis of ATP.
Mitochondrial matrix
21
H+
H+
O2
H+
e-
e-
e-
e-
ATP
Cellular respiration
2 ATP 2 ATP ~36 ATP+ +
~40 ATP
21
Oxidation Without O2Respiration occurs without O2 via either:
1. anaerobic respiration-methanogens (CO2 CH4)-sulfur bacteria (SO4 H2S)
2. fermentation-ethanol (yeast)-lactic acid (animal cells)
Pyruvate is a branching pointPyruvate
O2O2
mitochondriaKrebs cycleaerobic respiration
fermentationanaerobicrespiration
Fermentation (anaerobic)• Bacteria, yeast
1C3C 2Cpyruvate ethanol + CO2
Animals, some fungipyruvate lactic acid
3C 3C
beer, wine, bread
cheese, anaerobic exercise (no O2)
NADH NAD+
NADH NAD+
back to glycolysis
back to glycolysis
24
Catabolism of Protein & FatIn the absence of carbohydrates, animals
can break down other molecules:
-proteins: amino acids converted to a molecule that enters glycolysis or the Krebs cycle
-fats: fatty acids enter Krebs cycle (produces more energy than glucose)
25