cellular respiration harvesting chemical energy
DESCRIPTION
Cellular Respiration Harvesting Chemical Energy. ATP. Harvesting stored energy. Energy is stored in organic molecules carbohydrates, fats, proteins Heterotrophs eat these organic molecules food. glucose + oxygen energy + water + carbon. dioxide. respiration. ATP. +. - PowerPoint PPT PresentationTRANSCRIPT
Cellular RespirationHarvesting Chemical Energy
ATP
Harvesting stored energy• Energy is stored in organic molecules– carbohydrates, fats, proteins
• Heterotrophs eat these organic molecules food
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
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-
Coupling oxidation & reduction• REDOX reactions in respiration – release energy as they breakdown organic molecules
• break C-C bonds• strip off electrons from C-H bonds by removing H atoms
– C6H12O6 CO2 = the fuel has been oxidized• electrons attracted to more electronegative atoms
– in biology, the most electronegative atom? – O2 H2O = oxygen has been reduced
– couple REDOX reactions & use the released energy to synthesize ATP
C6H12O6 6O2 6CO2 6H2O ATP+ + +
oxidation
reduction
O2
Oxidation & reduction• Oxidation– removing H – loss of electrons– releases energy– exergonic
• Reduction– adding H – gain of electrons– stores energy– endergonic
C6H12O6 6O2 6CO2 6H2O ATP+ + +
oxidation
reduction
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!
H
Overview of cellular respiration• 4 metabolic stages– Anaerobic respiration
1. Glycolysis– respiration without O2
– in cytosol
– Aerobic respiration– respiration using O2
– in mitochondria
2. Pyruvate oxidation3. Krebs cycle4. Electron transport chain
C6H12O6 6O2 ATP 6H2O 6CO2+ + + (+ heat)
Glycolysis
glucose pyruvate2x6C 3C
• 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
10 reactions– convert
glucose (6C) to 2 pyruvate (3C)
– produces: 4 ATP & 2 NADH
– consumes:2 ATP
– net yield: 2 ATP & 2 NADH
glucoseC-C-C-C-C-C
fructose-1,6bPP-C-C-C-C-C-C-P
DHAPP-C-C-C
G3PC-C-C-P
pyruvateC-C-C
Overview
DHAP = dihydroxyacetone phosphateG3P = glyceraldehyde-3-phosphate
ATP2
ADP2
ATP4
ADP4
NAD+2
2Pi
enzyme
enzyme
enzyme enzyme
enzyme
enzyme
enzyme
enzyme
2Pi2H
2
Glycolysis summary endergonicinvest some ATP
exergonicharvest a little ATP & a little NADH
net yield2 ATP2 NADH
4 ATP
ENERGY INVESTMENT
ENERGY PAYOFF
G3PC-C-C-P
NET YIELD
-2 ATP
Pi
3
6
4,5
ADP
NAD+
Glucose
hexokinase
phosphoglucoseisomerase
phosphofructokinase
Glyceraldehyde 3-phosphate (G3P)
Dihydroxyacetonephosphate
Glucose 6-phosphate
Fructose 6-phosphate
Fructose 1,6-bisphosphate
isomerase
glyceraldehyde3-phosphatedehydrogenase
aldolase
1,3-Bisphosphoglycerate(BPG)
1,3-Bisphosphoglycerate(BPG)
1
2
ATP
ADP
ATP
NADH
NAD+
NADH
Pi
CH2
C O
CH2OH
P O
CH2 O P
O
CHOH
C
CH2 O P
OCHOH
CH2 O PO
CH2OP
O
PO
CH2
H
CH2OHO
CH2 POO
CH2OH
P O
1st half of glycolysis (5 reactions)
Glucose “priming” get glucose ready to split
phosphorylate glucose molecular
rearrangement split destabilized glucose
2nd half of glycolysis (5 reactions)
7
8
H2O9
10
ADP
ATP
3-Phosphoglycerate(3PG)
3-Phosphoglycerate(3PG)
2-Phosphoglycerate(2PG)
2-Phosphoglycerate(2PG)
Phosphoenolpyruvate(PEP)
Phosphoenolpyruvate(PEP)
Pyruvate Pyruvate
phosphoglyceratekinase
phosphoglycero-mutase
enolase
pyruvate kinase
ADP
ATP
ADP
ATP
ADP
ATP
H2O
CH2OH
CH3
CH2
O-
O
C
PH
CHOH
O-
O-
O-
C
C
C
C
C
C
P
P
O
O
O
OO
O
CH2
NAD+
NADH
NAD+
NADH
Energy Harvest G3PC-C-C-P
PiPi 6
DHAPP-C-C-C
– NADH production• G3P donates H• oxidizes the sugar• reduces NAD+
• NAD+ NADH– ATP production
• G3P pyruvate• PEP sugar donates P
– “substrate level phosphorylation”
• ADP ATP
Substrate-level Phosphorylation
P is transferred from PEP to ADPkinase enzymeADP ATP
H2O9
10
Phosphoenolpyruvate(PEP)
Phosphoenolpyruvate(PEP)
Pyruvate Pyruvate
enolase
pyruvate kinaseADP
ATP
ADP
ATP
H2O
CH3
O-
O
C
O-
C
C
C
P
OO
O
CH2
• In the last steps of glycolysis, where did the P come from to make ATP?– the sugar substrate (PEP)
ATP
Energy accounting of glycolysis
• Net gain = 2 ATP + 2 NADH– some energy investment (-2 ATP)– small energy return (4 ATP + 2 NADH)
• 1 6C sugar 2 3C sugars
2 ATP 2 ADP
4 ADP
glucose pyruvate2x6C 3C
ATP4
2 NAD+ 2
7
8
H2O9
10
ADP
ATP
3-Phosphoglycerate(3PG)
3-Phosphoglycerate(3PG)
2-Phosphoglycerate(2PG)
2-Phosphoglycerate(2PG)
Phosphoenolpyruvate(PEP)
Phosphoenolpyruvate(PEP)
Pyruvate Pyruvate
ADP
ATP
ADP
ATP
ADP
ATP
H2O
NAD+
NADH
NAD+
NADH
PiPi 6
But can’t stop there!
• Going to run out of NAD+
– without regenerating NAD+, energy production would stop!
– another molecule must accept H from NADH• so NAD+ is freed up for another round
PiNAD+
G3P
1,3-BPG 1,3-BPG
NADH
NAD+
NADH
Pi
DHAP
raw materials products
NADH
pyruvate
acetyl-CoA
lactate
ethanol
NAD+
NAD+
NADH
NAD+
NADH
CO2
acetaldehyde
Krebscycle
lactic acidfermentation
with oxygenaerobic respiration
without oxygenanaerobic respiration“fermentation”
How is NADH recycled to NAD+?
Another molecule must accept H from NADH
recycleNADH
which path you use depends on who you are…
which path you use depends on who you are…
alcoholfermentation