Prof Nirupama Mallick
Agricultural & Food Engineering Department
What is Respiration?
 The process of converting Food Energy into Chemical
Energy (ATP).
 ATPs are used to power the metabolic processes.
 It is almost the reserve process of photosynthesis, which
requires light energy for producing food, using carbon
dioxide and producing oxygen.
 Respiration is the chemical process opposite of
photosynthesis because it releases energy from food, and uses
oxygen and produces carbon dioxide.
Photosynthesis vs Respiration
Photosynthesis
Produces food
Respiration
Stores energy
Uses water
Uses food
Releases energy
Produces water
Uses CO2
Produces CO2
Releases O2
Occurs in light
Only in cells containing
chloroplasts
Uses O2
Occurs at all time
Occurs in all cells
The Overall Equation for
Respiration
• A common fuel molecule for cellular
respiration is glucose
Glucose
Oxygen
Carbon
dioxide
Water
Energy
Oxidation
[Glucose loses electrons (and hydrogens)]
Glucose
Oxygen
Carbon
dioxide
Reduction
[Oxygen gains electrons (and hydrogens)]
Water
What is ATP?
•
Energy currency of the cell
•
Adenosine Triphosphate
– 5-Carbon sugar (Ribose)
– Nitrogenous base (Adenine)
– 3 Phosphate groups
•
The chemical bonds that link the phosphate
groups together are Covalent high energy
bonds
•
When a phosphate group is removed to form
ADP and P, small packets of energy are
released.
•
As ATP is broken down, it gives off usable
energy to power chemical work and gives off
some nonusable energy as heat.
What are the Stages of
Cellular Respiration?
• Glycolysis
• Krebs Cycle
• Electron Transport Chain (ETC)/
Oxidative Phosporylation
Where Does Cellular
Respiration Take Place?
• It actually takes
place in two
parts of the cell:
Glycolysis occurs
in the Cytoplasm
or Cytosol
Krebs Cycle &
ETC Take place in
the Mitochondria
Review of Mitochondria
Structure
• About 1 micron
diameter
• Smooth outer
Membrane
• Folded inner
membrane
• Folds called Cristae
• Space inside cristae
called the Matrix
Intermembrane
space
Cellular Respiration
2
2
34
GLYCOLYSIS
 Glyco = sweet
Lysis= splitting
 Embden-Meyerhoff-Parnas (EMP) Pathway
 Anaerobic (does not require Oxygen)
 10 steps all occurring in cytosol or cytoplasm
GLYCOLYSIS
Glycolysis Summary
Takes place in the Cytosol (cytoplasm)
Doesn’t Use Oxygen
Requires input of 2 ATP
Glucose splits into two molecules of
Pyruvate or Pyruvic Acid
Produces 2 NADH and 4 ATP
Net Production: 2 NADH and 2 ATP
Pyruvic acid from glycolysis is first
converted into Acetyl-CoA
Pyruvate
dehydrogenase
Net Production: 2 NADH
Releases 2 CO2
Krebs cycle
• Krebs cycle- was discovered by
Sir Hans Krebs
Also called Citric acid cycle or
Tricarboxylic Acid (TCA) cycle
Requires Oxygen (Aerobic)
• Takes place in matrix of mitochondria
•
•
Krebs Cycle Summary
•
Cyclical series of oxidation reactions
•
Turns twice per glucose molecule
•
•
Each turn of the Krebs Cycle also produces
3NADH, 1FADH2, 1ATP and 2CO2
Therefore, For each Glucose molecule, the
Krebs Cycle produces 6NADH, 2FADH2,
2ATP and 4CO2
Electron transport chain (ETC)
• Discovered by Eugene Kennedy & Albert
Lehninger (1948)
• Catalyzes a flow of electrons from NADH/
FADH2 to O2
1) direct transfer of electron as in the
reduction of Fe3+ to Fe 2+ and Cu2+ to Cu+
2) transfer as a hydrogen atom (H+ & e-)
• Electron transport is coupled with formation
of proton gradient → used for ATP synthesis
Electron transport chain (ETC)
Consists of 5 complexes:
– Complex I (NADH dehydrogenase)
– Complex II (Succinate dehydrogenase)
– Complex III (Ubiquinone-Cytochrome
bc1 complex)
– Complex IV (Cytochrome oxidase)
– Complex V (ATP synthase)
Electron transport chain
(ETC)
Complex I : NADH to Ubiquinone
Complex II : Succinate to Ubiquinone
Complex III :Ubiquinone to Cytochrome c
Complex IV : Cytochrome c to Oxygen
Chemiosmosis
• The steps that transport protons from
Intermembrane space to matrix
establishing a proton chemiosmotic
gradient.
• It is an energy-coupling mechanism
that uses energy stored in the form of
an H+ gradient across a membrane to
generate ATP.
ATP synthase
F1
F0
ATP Synthesis
• Inner mitochondrial membrane is
impermeable to protons.
• Proton can re-enter the matrix only through
proton-specific channels (F0).
• The proton-motive force that drives protons
back into the matrix provides the energy for
ATP synthesis, catalyzed by the F1 complex
associated with F0.
Electron Transport Chain
Summary
Occurs Across Inner Mitochondrial
membrane
• Uses coenzymes NAD+ and FAD+ to
accept e- from glucose
• NADH = 3 ATP’s
• FADH2 = 2 ATP’s
• 34 ATP Produced
• H2O Produced
Total number of ATP produced
Glycolysis
4 ATP
2 molecules NADH
6 ATP
Pyruvate DH complex
2 molecules NADH
6 ATP
TCA cycle
2 ATP
6 molecules NADH
18 ATP
2 molecules FADH2
4 ATP
TOTAL ATP produced
40
ATP utilized in glycolysis 2
NET ATP PRODUCED 38
Fate of PYRUVATE in the absence of oxygen:
Fermentation
NADH
Pyruvate
decarboxylase
Lactate
dehydrogenase
NADH
Alcohol
dehydrogenase
Alcohol
fermentation
occurs in yeasts,
and some bacteria
Lactic acid fermentation
occurs in animal muscle
cells, some fungi and
bacteria to make yogurt
Fermentation
 Occurs when O2 NOT present
(anaerobic)
Requires NADH generated by glycolysis
Called Lactic Acid fermentation in
muscle cells, some fungi and bacteria,
produces lactic acid)
Called Alcoholic fermentation in yeast
(produces carbon dioxide and ethanol)
Net Gain: only 2 ATP
Cellular respiration can “burn” other kinds of
molecules besides glucose
– Diverse types of carbohydrates
– Fats
– Proteins
Food
Polysaccharides
Sugars
Glycerol
Fats
Fatty acids
Proteins
Amino acids
Amino groups
Glycolysis
AcetylCoA
Krebs
Cycle
Electron
Transport
Some commercial use of
fermentation: wine and beer.
Yeasts in the process of “budding”
or reproducing.
Carbon dioxide in beer and cake- due to yeast fermentation