photosynthesis and cellular respirationsection 3 ch7: cellular respiration pg 131

Photosynthesis and Cellular Respiration Section 3

CH7: Cellular Respiration pg 131


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)


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.


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.



• 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)


• 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)




• 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


Glycolysis


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.


Pathway Reaction

Lactic Acid Fermentation

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


Two Types of Fermentation


Add this onto your Cellular Respiration illustration


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.


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.


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


Electron Transport ChainATP Production• Hydrogen ions diffuse through ATP synthase, providing

energy to produce several ATP molecules from ADP.


• 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.

The Role of Oxygen


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.


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.


SummaryCellular 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

photosynthesis and cellular respirationsection 3 ch7: cellular respiration pg 131

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