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Photosynthesis and Cellular Respiration
CH7: Cellular Respiration pg 131
Section 3
Photosynthesis and Cellular Respiration
Section 3
Glycolysis
• The primary fuel for cellular respiration is glucose.
Equation for Photosynthesis
• 6CO2 + 6H2O + pigment + sunlight C6H12O6 + 6O2
Equation for Cellular Respiration
• C6H12O6 + O2  CO2 + H2O + ENERGY (ATP)
Photosynthesis and Cellular Respiration
Section 3
Glycolysis, continued
• In glycolysis, enzymes break down one six-carbon
molecule of glucose into two three-carbon pyruvate
molecules.
• The breaking of a sugar molecule by glycolysis results in
a net gain of two ATP molecules.
• This process of glycolysis is anaerobic, or takes place
without oxygen in the cytoplasm.
Photosynthesis and Cellular Respiration
Section 3
Glycolysis, continued
• Glycolysis is the only source of energy for some
prokaryotes.
• Other organisms use oxygen to release even more
energy from a glucose molecule.
– Metabolic processes that require oxygen are aerobic.
Photosynthesis and Cellular Respiration
Section 3
Glycolysis, continued
• Step 1, Breaking Down Glucose
– Two ATP molecules are used to break glucose into
two smaller units.
– Phosphate is attached to these 2 – three carbon
sugars (G3P)
Photosynthesis and Cellular Respiration
Section 3
Glycolysis, continued
• Step 2, NADH Production
– Each of the three carbon sugars (G3P) react with
another phosphate (not ATP)
– Hydrogen atoms from these compounds transfer to
two molecules of NAD+ resulting in 2 NADH
molecules (Hydrogen ion/proton and e- carrier)
Photosynthesis and Cellular Respiration
Section 3
Glycolysis, continued
• Step 3, Pyruvate Production
– In a series of 4 reactions, each of the 3 – carbon
sugars are converted into a 3 – carbon molecule of
pyruvate, resulting in 4 ATP molecules.
• BUT 2 ATP molecules were used in step one, so net total for
glycolysis is 2 ATP molecules
Photosynthesis and Cellular Respiration
Glycolysis
Section 3
Photosynthesis and Cellular Respiration
Section 3
Fermentation
• To make ATP during glycolysis, NAD+ is converted to
NADH.
– Organisms must recycle NAD+ to continue making ATP through
glycolysis.
• The process in which carbohydrates are broken down in
the absence of oxygen is called fermentation.
– Allowing glycolysis to continue supplying a cell with ATP in
anaerobic conditions.
Photosynthesis and Cellular Respiration
Pathway
Lactic Acid
Fermentation
Section 3
Reaction
PYRUVIC ACID + NADH LACTIC ACID + NAD+
*occurs in muscle cells for short term energy
production, also used in the
production of foods ex. yogurt, Kim chi, sauerkraut
Alcoholic
Fermentation
PYRUVIC ACID + NADH  ALCOHOL+ CO2 + NAD+
*occurs in yeast cells and is used in the production
of beer, wine and
bread
Photosynthesis and Cellular Respiration
Two Types of Fermentation
Section 3
Photosynthesis and Cellular Respiration
Section 3
Add this onto your Cellular Respiration illustration
Photosynthesis and Cellular Respiration
Section 3
Aerobic Respiration
• The first stage of aerobic respiration is the Krebs cycle,
a series of reactions that produce electron carriers
(NADH and FADH2).
• The electron carriers enter an electron transport chain,
which powers ATP synthase.
• Up to 38 ATP molecules can be produced from one
glucose molecule in aerobic respiration.
Photosynthesis and Cellular Respiration
Section 3
Photosynthesis and Cellular Respiration
Section 3
Kreb’s Cycle
• Pyruvate (from glycolysis) is broken down and
combined with other carbon compounds creating CoA.
– Releasing CO2
• The total yield of energy-storing products from the Krebs
cycle is 2 ATP, 6 NADH, and 2 FADH2.
Photosynthesis and Cellular Respiration
Section 3
Photosynthesis and Cellular Respiration
Section 3
Photosynthesis and Cellular Respiration
Section 3
Electron Transport Chain
• The second stage of aerobic respiration takes place in
the inner membranes of mitochondria
– ATP synthase are located here
• Electron carriers (NADH and FADH2), from the Krebs
cycle
– transfer energy in the form of e- and H+ into the electron
transport chain.
– e- are used to pump the H+ across the membrane to create a
concentration gradient
Photosynthesis and Cellular Respiration
Section 3
Photosynthesis and Cellular Respiration
Section 3
Electron Transport Chain
ATP Production
• Hydrogen ions diffuse through ATP synthase, providing
energy to produce several ATP molecules from ADP.
Photosynthesis and Cellular Respiration
Section 3
The Role of Oxygen
• End of the ETC, the e- combine with an oxygen atom
and two hydrogen ions to form two water molecules.
• If oxygen is not present, the electron transport chain
stops.
• The electron carriers are not recycled, so the Krebs
cycle also stops.
Photosynthesis and Cellular Respiration
Section 3
Efficiency of Cellular Respiration
• In the first stage of cellular respiration, glucose is broken
down to pyruvate during glycolysis, an anaerobic
process.
• Glycolysis results in 2 ATP molecules for each glucose
molecule that is broken down.
• In the 2nd stage, pyruvate EITHER passes through the
Krebs cycle OR undergoes fermentation.
– Fermentation recycles NAD+ but does not produce ATP.
Photosynthesis and Cellular Respiration
Section 3
Efficiency of Cellular Respiration cont’d
• Cells release energy most efficiently when oxygen is
present
• For each glucose molecule that is broken down, as many
as 2 ATP molecules are made during the Krebs cycle.
• The Krebs cycle feeds NADH and FADH2 to the ETC,
which can produce up to 34 ATP molecules.
Photosynthesis and Cellular Respiration
Section 3
Summary
Cellular
Respiration
Reactants
Products
Location
Gycolysis
Glucose, 2 ATP
2 Pyruvates,
2NADH,
4 (2) ATP
Cytoplasm
Krebs Cycle
2 AcetylCoA (CoA)
CO2, 6NADH,
2FADH2 ,2ATP
Matrix of
Mitochondria
ETC
6 NADH, 2FADH2,
O2
34 ATP, H2O,
6NAD, 2FAD
Inner
Mitochondrial
Membrane