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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 Presentation
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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
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