3. Energy Production: Key Concepts
• Primary energy yielding compounds:
• Glucose
• Fatty Acids
• Glycerol
• Amino Acids
• ATP= Energy Currency
ATP
3
4. Basic Metabolic
Pathway
• Key Compounds that Enter
• Glucose
• Fatty Acids
• Glycerol
• Amino Acids
• Key End Product
• ATP
Glucose
Pyruvate
Acetyl CoA
TCA
(Krebs)
Cycle
Electron Transport Chain
4
5. Glucose
• Glycolysis
• Some ATP
• Glycolysis is anerobic pathway
Glucose
Pyruvate
Acetyl CoA
TCA
(Krebs)
Cycle
Electron Transport Chain
Glycolysis
ATP
5
6. Glucose:
Inadequate
Oxygen
• Cori cycle
• Pyruvate converted to lactate
• Lactate sent to liver
• Regenerates glucose
• Little ATP produced (when no
oxygen)
Pyruvate
Acetyl CoA
TCA
(Krebs)
Cycle
Electron Transport Chain
Glycolysis
ATP
Glucose
Anaerobic Lactate
ATP
Cori
Cycle
7. Fermentation (Anaerobic Respiration)
• Some prokaryotes that live in low oxygen environments rely on
anaerobic respiration (fermentation) to breakdown food.
• Fermentation and cellular respiration begin the same way, with
glycolysis but in fermentation the pyruvate made in glycolysis
does not go to Krebs cycle and ETC.
7
10. Fats/Lipids
• Main form of fats
• Triglycerides
• Triglycerides:
• Glycerol
• Fatty Acids (only go down the
pathway which requires
oxygen)
Pyruvate
Acetyl CoA
TCA
(Krebs)
Cycle
Electron Transport Chain
Glycolysis
ATP
Anaerobic
ATP
Glucose
Glycerol Lactate
Cori
Cycle
Fatty
Acids
10
11. Amino acids
• Amino acids
• Glucogenic
• Ketogenic
• Amino Acids are stored in
muscle or different tissues
but we don’t use those
amino acids for energy. We
use amino acids from the
protein we eat in our food.
Pyruvate
Acetyl CoA
TCA
(Krebs)
Cycle
Electron Transport Chain
Glycolysis
ATP Glucose
Anaerobic Lactate
ATP
Cori
Cycle
Glucogenic A.A
Ketogenic A.A
11
13. Glycolysis
• Glycolysis is an oxygen independent pathway
• Glycolysis is the degradation of glucose
• Glycolysis can produce ATP in the absence of oxygen
• Glycolysis consists of two stages
• Energy investment phase
• Energy generation phase
13
17. Summary of Glycolysis
• Single glucose molecule produces 2 molecules of pyruvate, 2
molecules of ATP, 2 molecules of NADH and 2 molecules of water.
• 2 ATP’S are used in steps 1-3, 2 ATP molecules are generated in step 7
and 2 more ATP’s are generated in step 10.
17
18. Transition (Acetyl CoA Reaction)
• Occurs in the mitochondrial matrix
• Reactants = 2 pyruvates, 2 co-enzyme A (CoA), 2 NAD+
• Products = 2 Acetyl CoA, 2 NADH + H, 2CO2
18
20. Structure of Mitochondria
20
• Rod shaped double
membrane bound organelle
• The membranes are made up
of phospholipids and proteins
21. Outer Membrane
• It is smooth and composed of equal amount of phospholipids
and proteins
• It has a large number of special proteins known as porins (allow
movement of molecules upto 5000 Daltons)
21
22. Inner Membrane
• More complex
• Folded into number of folds many times known as Cristae
• Folding helps to increase surface area
• Cristae and the proteins of the inner membrane helps in the
production of ATP’s (Electron Transport System)
22
24. Matrix
• Complex mixture of proteins and enzymes which are important
for synthesis of ATP molecules, mitochondrial ribosomes,
tRNA’s and Mitochondrial DNA
24
25. Mitochondrial DNA
• Mitochondria have a small amount of DNA of their own
• Human mtDNA have 16500 DNA base pairs which contains 37
genes
• All these genes are essential for normal function of
mitochondria
• Mutations in the mtDNA leads to a number of diseases
25
26. Citric Acid Cycle (Krebs Cycle)
• Second stage of cellular respiration
• The usable energy found in food molecules is released mainly
in this cycle
• It takes place only in the presence of oxygen
• It occurs in the matrix of cell mitochondria
26
28. Summary
• Citric acid cycle uses one molecule of Acetyl CoA (one glucose
molecule generates two molecules of Acety CoA) to generate one
ATP, 3 NADH, one FADH2, two Carbon dioxide and 3H+ ions
• Two additional molecules are also generated in the conversion of
pyruvic acid two Acetyl CoA prior to the start of the cycle
• The NADH and FADH2 molecules generated here are then passed
to the final step of oxidative phosphorylation (ETC) to generate more
ATP’s
28
29. Electron Transport Chain
• ETC is actually a series of protein complexes and electron carrier
molecules within the inner membrane of mitochondria
• Electrons are passed from one member of the transport chain to
another in a series of redox reactions
• Energy released in these reactions is captured as a proton gradient,
which is then used to make ATP in a process called chemiosmosis.
• Together, the electron transport chain and chemiosmosis make
up oxidative phosphorylation
29
30. Steps of ETC
1. Delivery of electrons by NADH and FADH2:
• Reduced electron carriers (NADH and FADH2) from other steps
of cellular respiration transfer their electrons to molecules near
the beginning of the transport chain
• In the process, they turn back into NAD+ and FAD, which can
be reused in other steps of cellular respiration
30
31. 2. Electron transfer and proton pumping
• As electrons are passed down the chain, they move from a higher to
a lower energy level, releasing energy
• Some of the energy is used to pump H+ ions, moving them out of the
matrix and into the intermembrane space
• This pumping establishes an electrochemical gradient
31
32. 3. Splitting of oxygen to form water:
• At the end of the electron transport chain, electrons are transferred to
molecular oxygen, which splits in half and takes up H+ to form water.
4. Gradient-driven synthesis of ATP:
• As H+ ions flow down their gradient and back into the matrix, they
pass through an enzyme called ATP synthase, which harnesses the
flow of protons to synthesize ATP
32
35. What does the ETC do for the cell ?
• Two functions
1. Regenerates electron carriers (NAD+ . FAD):
• NADH and FADH2 pass their electrons to the electron transport
chain, turning back into NAD+ and FAD
• This is important because the oxidized forms of these electron
carriers are used in glycolysis and the citric acid cycle and must
be available to keep these processes running
35
36. 2. Makes a proton gradient:
• The transport chain builds a proton gradient across the inner
mitochondrial membrane, with a higher concentration of H+ in the
intermembrane space and a lower concentration in the matrix
• This gradient represents a stored form of energy, and it can be
used to make ATP
36
37. Summary
• Electrons are donated to ETC by NADH and FADH2
• Electrons are passed along the chain from one protein complex
to another until donated to oxygen forming water
• During the passage of electrons, protons are pumped out of the
mitochondrial matrix across the inner membrane into then
intermembrane space
37
38. • These protons produce an electrochemical gradient that causes
proton to flow down the gradient and back into the matrix through
ATP synthase
• This movement of protons provide energy for the production of ATP
38
NADH from Glycolysis cannot directly travel into Mitochondria. It either enter with shuttle DHAP and give G3P which will further reacts with NAD to give NADH2 in the matrix. Thus we get loss of one ATP. If the shuttle service used is OAA ( Oxalo acetate) then the NADH reacts with it and give us Malate which travels inside the mitochondria to the inside matrix where this Malate reacts with NAD to give us NADH so no loss of ATP occurs.
