Three Stages In Cellular Respiration

Cellular respiration

There are three stages in cellular respiration: Glycolysis, the Krebs cycle and the electron transport chain.

The equation for cellular respiration is: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

Glycolysis

Glycolysis is multiple reactions that gain energy from glucose by splitting the glucose into 3 carbon molecules (Pyruvates). (Mason et al., 2016)

Glycolysis is anaerobic meaning it doesn’t require any oxygen to be carried out.

This is because energy can be made through fermentation; therefore it needs NAD+ in order for the process of Glycolysis to keep working.

The anaerobic process of fermentation causes the creation of lactic acid as a by product.

Glycolysis takes place in the cytoplasm of a cell

To begin the

In total the Krebs cycle contains 8 steps.

Before anything can happen one of the 3 Pyruvates created is oxidised. Meaning it is mixed with oxygen and creates CO2, which is then expelled from the body through respiration.

This leaves a two carbon molecule called acetyl coA. Two molecules of acetyl coA are used in the Krebs cycle per molecule of glucose. An NAD+ molecule then connects with the hydrogen to become NADH, creating two molecules of NADH that will be used later on.

At this stage enzymes bring together a phosphate and an ADP to create another ATP per Pyruvate molecule. Enzymes also join together the acetyl coA and Oxaloacetic to for citric acid.

Once the citric acid is created a molecule of water is then removed but also added back, causing the conversion citrus to isocitrate.

After this the substance then loses a molecule of CO2 and the five carbon molecule that remains is then oxidized, causing NAD+ to reduce to NADH.

The next step is then catalysed by a multienzyme complex that causes another molecule of carbon to be lost as CO2. Leaving a 4 carbon compound that is oxidised by the transfer of electrons to NAD+ forming NADH, this is then attached to coA by an unstable

The last step produces another molecule of NADH and regenerates oxaloacetate, which accepts a 2 carbon fragment from acetyl coA . This then means the cycle can repeat itself again.

Each time a carbon leave the Krebs cycle it creates energy. This energy is stored as NAD+ and FAD. The NAD+ and FAD each pick up hydrogen and electrons, turning them into NADH and FADH2. Each Pyruvate can yield 3 NADH and 1 FADH2 per cycle. The purpose of the Krebs cycle is to create these for the next stage, Oxidative Phosphorylation.

Oxidative Phosphorylation (the electron transport chain)

The FADH and NADH that were created in the Krebs cycle use their electrons to provide energy to electron transport chain that moves proteins along the inner membrane of the mitochondria.

These proteins swap the electrons to send hydrogen protons from the inside of the mitochondria to the outside.

This creates oxygen as I product which joins with the hydrogen’s from FADH and NADH to create H2O.

Once on the outside the protons want to come back inside the mitochondria.

This can be done through ATP snythase. This causes a spinning mechanism that forces ADP and phosphates together to form