Respiration

The release of energy from food (usually glucose) using enzymes

There are two forms of respiration- aerobic (requiring oxygen) and anaerobic (does not require oxygen)

Aerobic Respiration

Requires oxygen

C6H12O6 + 6O2 6CO2 + 6H2O + 2820kj energy

Relatively efficient

About 40% of the energy in glucose is converted to ATP. The high efficiency is due to the fact that glucose is completely broken down.

Aerobic respiration begins in the cytoplasm, but most of the energy is produced by reactions that take place in the mitochondria.

Anaerobic RespirationOtherwise called fermentation, it occurs in the absence of oxygen

Plant cellsGlucose Ethanol + Carbon dioxide + 210kj

Animal cellsGlucose lactic acid +150kj

Less efficient than aerobic respiration because glucose is not fully broken down

The end products, alcohol and lactic acid can be dangerous if they build up.

Fermentation is the basis of much of the biotechnology industry. Industrial fermentation is carried out in sterile vessels called bioreactors.

• Brewing• Baking• Environmental clean up.

Differences between aerobic and anaerobic respiration

Aerobic Anaerobic

Oxygen necessary Oxygen not necessary

Occurs in mitochondria Occurs in cytoplasm

Large amt of ATP made Small amt of ATP made

Total breakdown of glucose

Partial breakdown of glucose

End products; carbon dioxide and water

End products; carbon dioxide and lactic acid or alcohol

Biochemistry of Respiration

• There are two stages involved in respiration– Glycolysis, which takes place in the cytosol

and which does not require oxygen– Krebs cycle reactions and the Hydrogen

(electron) transport system, take place in the mitochondria, and require oxygen

Glycolysis (Anaerobic)

GLUCOSE (6C)

PYRUVIC ACID (3C)PYRUVIC ACID (3C)

2ATP→2ADPThe energy released activates the glucose to break down to a high energy sugar which then converts to two triose sugars.

TRIOSE SUGAR(3C) TRIOSE SUGAR (3C)

NAD→NADH2NAD→NADH2

ADP→ATP ADP→ATP

Two hydrogens are removed and are picked up by NAD and are converted to NADH2

H2O

H2O

Water formed in

the Hydrogen

Carrier System

There is a low yield of ATP from glycolysis

The Krebs CycleIf enough oxygen is present, both the hydrogen atoms and Pyruvic acid enter a mitochondria

PYRUVIC ACID (3C)

ACETYL COENZYME A (2C)

2H NAD→NADH2CO2

CO2

2H NAD→NADH2

CO2

6H4Hs attach to 2NAD

2H follow a different path

ATP

For every 2 hydrogen

removed, three molecules of ATP

are formed

Released 2H is stored as NADH2, and is transferred to the Hydrogen transport system, where water is made

Hydrogen (electron) Transport Systems

• A number of electron accepting molecules are found on the cristae of the mitochondria. Due to the large surface area, a large number of systems fit on the membranes of the cristae.

• NADH2 is converted to NAD and a pair of high energy electrons and a pair of hydrogen ions are released.

• The electrons are passed from one carrier to the next losing energy as they move.

• After three steps in the process, enough energy is produced to convert 3ADP to 3ATP. The production of ATP in this process is called oxidative phosphorylation.

• At the end of the system, low energy electrons combine with hydrogen ions and oxygen to produce water

• 2 electrons + 2H+ + ½ O2 → H2O