Anaerobic respiration

Respiration without oxygen

2 different types of “Respiration”make up all of Cellular Respiration

What happens if there is no available electron acceptor?

Glucose

2 pyruvate

2 ATP

2 ADP 2 NAD+

2 NADH

Aerobic respiration: The NADH then passes its high energy e- to the electron transport chain (becoming NAD+ again) and eventually to O2

Anaerobic respiration: Without O2, NADH has nowhere to donate its e- to, NAD+ cannot be regenerated, and glycolysis stops

glycolysis

Anaerobic respiration With no oxygen oxidative phosphorylation and

Krebs cycle cannot take place. (Cells without mitochondria cannot respire aerobically – e.g. red blood cells)

In anaerobic respiration glycolysis takes place as usual yielding pyruvate and a small amount of ATP.

If pyruvate levels were allowed to build up it stop glycolysis and inhibit ATP production, also the reduced NAD produced must be oxidised back or else the cell would run out of it – again stopping ATP production.

Process of Cellular Respiration

Anaerobic respiration

All living organisms break down sugars to get energy. In humans this breakdown usually

occurs with oxygen.

Anaerobic respiration can be represented by the equation

C6H12O6 2C2H5OH + 2CO2

glucose alcohol

energy

For example, our own muscles resort to anaerobic respiration when oxygen is not delivered to them fast enough.

The energy released by anaerobic respiration is considerably less than the energy from aerobic respiration.

Anaerobic respiration takes place at some stage in the cells of most living organisms.

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Anaerobic respiration is widely used by many micro-organismssuch as bacteria and yeasts.

Bacteria and yeasts are microscopic single-celled organisms.

Bacteria are to be found everywhere, in or on organisms,in water, air and soil

Yeasts are usually found in close association with vegetable matter such as fruit

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1. In Muscle Cells - During extraneousactivities, the oxygen in the muscle tissue isdecreased to an extent that aerobicrespiration does not occur at a sufficientrate. Hence, there is a buildup of lactic acidand your muscles get tired

2. In Yeast - The fermentation end product isethyl alcohol, and CO2

Anaerobic respirationglucose

triose phosphate

oxidisedNAD

reducedNAD

pyruvateethanal ethanol

reduced oxidised

NAD NAD

alcohol dehydrogenase

Producing ethanol from pyruvate regenerates oxidised NAD and allows glycolysis to continue

Anaerobic respirationglucose

triose phosphate

oxidisedNAD

reducedNAD

pyruvate lactate

reduced oxidised

NAD NAD

lactate

dehydrogenase

Producing lactate from pyruvate regenerates oxidised NAD and allows glycolysis to continue

Anaerobic respiration First CO2 is removed from pyruvate to

produce ethanal. Alcohol dehydrogenase converts ethanal

to ethanol by adding hydrogen taken from reduced NAD.

Process used by humans for many thousands of years to produced risen breads and alcohol for drinking.

Anaerobic Respiration refers to theoxidation of molecules in the

absence of oxygen to produce energy

It is also knownAs Fermentation

Anaerobic fermentation

Fermentation: An alternative set of reactions that can follow glycolysis in the absence of oxygen as a final electron acceptor.

Extremely inefficient: no Kreb’s cycle, no ETC. Glycolysis produces a net of 2 ATP’s per glucose molecule

Glucose2

Pyruvate

2 NAD+ 2 NADH

2 ADP 2 ATP

Fermentationby-product

Intermediate accepts electrons from NADH

FERMENTATION PATHWAYS ALLOWS CELLS TO REGENERATE NAD+ FOR GLYCOLSIS

2 types of fermentation

Fermentation Lactic Acid

Fermentation

Alcohol Fermentation

2 types of fermentation

Glucose

2 Pyruvate

2 NAD+ 2 NADH

2 ADP 2 ATP

2 Lactate

Pyruvate accepts electrons from NADH

LACTIC ACID FERMENTATION OCCURS IN HUMANS

Glucose

2 Pyruvate

2 NAD+ 2 NADH

2 ADP 2 ATP

2 Ethanol 2 Acetylaldehyde

2 CO2

ALCOHOL FERMENTATION OCCURS IN YEAST