Topic 8.1: Cell Respiration

8.1.1 State that oxidation involves the loss of electrons from an element, whereas reduction involves a gain of electrons; and that oxidation frequently involves gaining oxygen or losing hydrogen, whereas reduction frequently involves losing oxygen or gaining hydrogen.

OILRIG - Oxidation Is Loss, Reduction Is Gain
ELMO - Electron Loss Means Oxidation


8.1.2 Outline the process of glycolysis, including phosphorylation, lysis, oxidation and ATP formation

Glycolysis takes place in the cytoplasm.

The process phosphorylation simple oxidizes the glucose present with phosphate groups. It attaches itself to both ends of the glucose for it to become Hexose Biphosphate. This process requires ATP for the phosphate group to attach itself.

Lysis is the stage when the hexose biphosphate molecule becomes too unstable and breaks down into two triose phosphate.

This is the oxidation/ATP formation step. Each of the triose phosphate is oxidized to become a pyruvate molecule. With the addition of one hydrogen, it is passed on and reduce one NAD+ to NADH. Each Triose phosphate adds a phosphate group to the ADP reducing it to ATP. Note: Each Triose phosphate releases enough energy to form two ADP to ATP.

This is the full sequence of glycolysis in short.

8.1.3 Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs

This is the structure of a mitochondrion.

It is important to remember that Mitochondrion has a double membrane thus the existence of Cristae is to increase inner membrane surface area. Important for electron transport chain.


8.1.4 Explain aerobic respiration, including the link reaction, the Krebs cycle, the role of NADH + H+, the electron transport chain and the role of oxygen

There are 3 more stages in the aerobic respiration. This includes Link reaction, the Krebs cycle and the electron transport chain.

Link Reaction: Pyruvate is decarboxylated to become Acetyl CoA

The link reaction allows for pyruvate and Co-enzyme A to join together to form a complex. The carbon is decarboxylated (removal of carbon) as carbon dioxide. The remains forms Acetyl CoA. The NAD+ is reduced to NADH + H+.


Kreb's cycle: Oxidative decarboxylation of the acetyl group.

Acetyl CoA joins with a 4 carbon group to form citrate. CoA is then released to transport more pyruvate molecules. The C6 compound formed is called citric acid.

Citric acid is oxidatively decarbonxylated. A C5 group is now formed. The carbon is released as carbon dioxide. NAD+ is reduced to NADH + H+

The C5 grouped is also oxidatively decarbonxylated, forming a C4 group. The carbon is released as carbon dioxide. NAD+ is reduced to NADH + H+.

The final stage in the cycle requires the C4 group to regenerate back to its original form and accept acetyl CoA. This reduces NAD to NADH + H+ and FAD to FADH + H+. ADP also uses this energy to bind with a phosphate group to make ATP.

This is the whole process and shows how it is linked to the electron transport chain.

The hydrogen carriers (NADH + H+ and FADH + H+) provide electrons to the electron transport chain on the inner mitochondrial membrane. As the electrons cycle through the chain, they lose energy to translocate the hydrogen ions to the intermembrane space (creating a gradient). The hydrogen ions return to the matrix through ATP synthase mass producing ATP. Oxygen acts as the final electron acceptors for the electron transport chain to allow new electrons enter the chain. Oxygen combines with the hydrogen ions in the matrix to form water molecules.

8.1.5 Explain oxidative phosphorylation in terms of chemiosmosis

This is the electron transport chain.

• Oxidative phosphorylation describes the production of ATP from oxidised hydrogen carriers
• When electrons are donated to the electron transport chain, they lose energy as they are passed between submissive carrier molecules.
• The energy is used to translocate H+ ions from the matrix to the intermembrane space against the concentration gradient.
• The build up of H+ ions creates an electrochemical gradient, or proton motive force (PMF)
• The protons return to the matrix via a transmembrane exnzyme called ATP synthase.
• As the hydrogen ions return, they release energy which is used to produce ATP (from ADP + Pi)
• This process is called chemiomosis and occurs in the cristae
• The hydrogen ions and electrons bind with oxygen to form water molecules. 

8.1.6 Explain the relationship between the structure of the mitochondrian and its function

There are four structures in the mitochondrion which function to improve the reactions happening. Which include: Inner membrane, external double membrane, matrix and inter-membrane space

Inner membrane: The double folded inner membrane space forms cristae, this allows an increase of ATP synthesis thus more ATP produce
External double membrane: Contains appropriate proteins to allow the transport of molecules
Intermembrane space: Small space to increase the gradient difference.
Matrix: The right pH levels for the reaction and enzymes to work at optimal rate.