Upload
darleen-mclaughlin
View
222
Download
0
Embed Size (px)
DESCRIPTION
First Stage: Glycolysis BASICS: Glycolysis doesn’t require oxygen (anaerobic)! Glycolysis doesn’t occur in the mitochondria, so it can happen in prokaryotes (lacking organelles). Glycolysis occurs in the cytoplasm. Glycolysis begins with glucose and ends with two pyruvate molecules, yielding minimal energy gain.
Citation preview
Chapter 7: Respiration
Respiration: The release of stored energy (sugar). Usually involves oxygen (the reason we breath is to release energy from our food).
Aerobic vs Anaerobic: Aerobic means in the presence of oxygen.
Mitochondrion
Inner Space
Inner Membrane Outer Membrane
Outer Space/
Intermembrane Space
First Stage: Glycolysis
BASICS:Glycolysis doesn’t require oxygen (anaerobic)!Glycolysis doesn’t occur in the mitochondria, so it
can happen in prokaryotes (lacking organelles). Glycolysis occurs in the cytoplasm.
Glycolysis begins with glucose and ends with two pyruvate molecules, yielding minimal energy gain.
First Stage: Glycolysis
1. Two ATP are invested to rearrange glucose.
2. When glucose is split into two 3-carbon compounds, energy is released.
3. Released energy is stored in 4 ATP (through substrate-level phosphorylation, or direct transfer of phosphate group).
4. NAD+ picks up e- and H+ to become NADH
Fig. 8.4b, p. 135
ATP
ATP
glucose
glucose-6-phosphate
fructose-6-phosphate
fructose-1,6-bisphosphate
2 ATP invested
ENERGY-REQUIRING STEPS OF GLYCOLYSIS
ADP
ADP
P
P
P
(see next slide)
Fig. 8.4c, p. 135
ATP
PGAL PGAL
ATP
NADH NADH
ATP ATP
2 ATP invested
ENERGY-RELEASING STEPS OF GLYCOLYSIS
2 ATP invested
NAD+
Pi
NAD+
Pi
3-phosphoglycerate 3-phosphoglycerate
2-phosphoglycerate 2-phosphoglycerate
PEP PEP
ADP ADP
1,3-bisphosphoglycerate 1,3-bisphosphoglycerateP P P P
P P
P P
P P
pyruvate pyruvate
to second set of reactions
substrate-level phosphorylation
substrate-level phosphorylation
H2O H2O
Second Step: Krebs Cycle
1. Two pyruvate molecules enter the mitochondrion (enter into the inner compartment of mito).
2. Coenzyme-A strips a carbon, yielding CO2.
3. Acetyl-CoA enters Krebs Cycle/Citric Acid Cycle, yielding more CO2.
4. Final yield: ATP, NADH, FADH2.
Fig. 8.5b, p. 136
Krebs Cycle
NADH
NADH
NADH
ATP ATP
ATPATP
ADP + Pi
INNER COMPARTMENT
OUTER COMPARTMENT
acetyl-CoA
free oxygen
6 Following its gradients, H+ flows back into inner compartment, through ATP synthases. The flow drives ATP formation.
1 Pyruvate from cytoplasm inters inner mitochondrial compartment.
3 NADH and FADH2 give up electrons and H+ to membrane-bound electron transport systems.
2 Krebs cycle and preparatory steps: NAD+ and FADH2
accept electrons and hydrogen stripped from the pyruvate. ATP forms. Carbon dioxide forms.
5 Oxygen accepts electrons, joins with H+ to form water.
4 As electrons move through the transport system, H+ is pumped to outer compartment.
Fig. 8.6, p. 137
oxaloacetate
malate
citrate
isocitrate
-ketogluteratefumarate
succinate
CoA
succinyl–CoA
ATP
NADH
NADH
NADH
NADH
FADH2
NAD+
NAD+
FAD NAD+ CoA
CoA
H2O
H2O
H2O
ADP + phosphate group (from GTP)
KREBS CYCLE
PREPARATORY STEPS
pyruvate
NAD+
CoAAcetyl–CoA
coenzyme A (CoA)
(CO2)
Step 3: Electron Transfer Phosphorylation
1. NADH and FADH2 transfer e- and H+ to inner membrane of mitochondria, buiding up concentration of protons in intermembrane space.
2. When protons flow through ATP synthases, up to 34 ATP are produced.
3. Oxygen will accept extra hydrogens, resulting in water.
Electron Transport Chain
ATP Synthase
Fig. 8.5b, p. 136
Krebs Cycle
NADH
NADH
NADH
ATP ATP
ATPATP
ADP + Pi
INNER COMPARTMENT
OUTER COMPARTMENT
acetyl-CoA
free oxygen
6 Following its gradients, H+ flows back into inner compartment, through ATP synthases. The flow drives ATP formation.
1 Pyruvate from cytoplasm inters inner mitochondrial compartment.
3 NADH and FADH2 give up electrons and H+ to membrane-bound electron transport systems.
2 Krebs cycle and preparatory steps: NAD+ and FADH2
accept electrons and hydrogen stripped from the pyruvate. ATP forms. Carbon dioxide forms.
5 Oxygen accepts electrons, joins with H+ to form water.
4 As electrons move through the transport system, H+ is pumped to outer compartment.
Possible Pathways
Glucose
Glycolysis
(if oxygen)
Aerobic Respiration (in mitochondria)
(no oxygen for yeast, bacteria)
Alcoholic Fermentation
(no oxygen, for muscle)
Lactate Fermentation
Alcoholic Fermentation (anaerobic)
If no oxygen is available, only glycolysis can occur.
In this case, pyruvate doesn’t enter the mitochondrion but rather is modified in the cytoplasm.
The result is ethanol and carbon dioxide.
Very little energy release as compared to aerobic respiration, so not an option for large, active animals.
Lactic Acid Fermentation (anaerobic)If no oxygen is available, only glycolysis can occur.
In this case, pyruvate doesn’t enter the mitochondrion but rather is modified in the cytoplasm.
The result is lactate.
Very little energy release as compared to aerobic respiration, so only used for short bursts of energy.