Energy Production

Learning outcome 1: To describe the structure, hydrolysis and synthesis of ATP

Structure: ATP (Adenosine triphosphate) is the primary energy currency of cells. It consists of an adenine base, a ribose sugar, and three phosphate groups. The structure of ATP can be represented as:

Adenine + Ribose + 3 Phosphate groups

Hydrolysis: of ATP is the process by which the energy stored in the bonds between the phosphate groups is released. This occurs when the third phosphate group is removed, creating adenosine diphosphate (ADP) and inorganic phosphate (Pi):

ATP + H2O → ADP + Pi + energy

Synthesis: of ATP, also known as cellular respiration, is the process by which cells generate ATP from the breakdown of organic molecules, such as glucose. This occurs in the mitochondria of eukaryotic cells and in the cytoplasm of prokaryotic cells. The process can be summarized as:

Glucose + Oxygen → CO2 + H2O + ATP

Overall, In the cell, the ATP is continuously hydrolyzed to ADP and Pi to release energy for various cellular processes, and it is continuously synthesized to keep the energy balance in the cell.

Learning outcome 2: To differentiate substrate-level phosphorylation from oxidative phosphorylation

Substrate-level phosphorylation and oxidative phosphorylation are two different ways that cells can generate ATP.

Substrate-level phosphorylation is the process by which the energy released during the metabolic reactions of enzymes is used to phosphorylate ADP to form ATP. This process occurs during glycolysis and the citric acid cycle. It does not require oxygen and it is anaerobic.

Oxidative phosphorylation, on the other hand, is the process by which cells generate ATP using the energy released during the oxidation of organic molecules, such as glucose, in the presence of oxygen. This process occurs in the mitochondria of eukaryotic cells and in the cytoplasm of prokaryotic cells. During this process, electrons are transferred from the organic molecule to oxygen, creating water and releasing energy. This energy is then used to pump protons across a membrane, creating a proton gradient. The flow of protons back across the membrane through ATP synthase generates ATP. This process is aerobic.

In summary, substrate-level phosphorylation generates ATP through the energy released by enzymes during metabolic reactions, while oxidative phosphorylation generates ATP through the energy released by the oxidation of organic molecules in the presence of oxygen.

Learning outcome 3: To identify the components of the electron transport chain

The electron transport chain (ETC) is a series of protein complexes and electron carriers that are located in the inner mitochondrial membrane of eukaryotic cells and in the plasma membrane of prokaryotic cells. The ETC is responsible for the transfer of electrons from organic molecules, such as glucose, to oxygen during cellular respiration, and it is a key component of oxidative phosphorylation. The ETC includes the following components:

NADH dehydrogenase (or NADH-ubiquinone oxidoreductase): This enzyme complex accepts electrons from NADH and transfers them to the next component of the ETC.

ubiquinone (or coenzyme Q): This electron carrier picks up the electrons from NADH dehydrogenase and transfers them to the next component of the ETC.

cytochrome b-c1 complex (or succinate dehydrogenase): This enzyme complex transfers electrons from ubiquinone to cytochrome c.

cytochrome c: This electron carrier picks up the electrons from the cytochrome b-c1 complex and transfers them to the next component of the ETC.

cytochrome c oxidase (or cytochrome aa3 complex): This enzyme complex accepts electrons from cytochrome c and transfers them to oxygen, creating water and releasing energy.

ATP synthase: This enzyme complex uses the energy released during the ETC to generate ATP by pumping protons across a membrane, creating a proton gradient.

Overall, The ETC is a series of protein complexes and electron carriers that transfer electrons from organic molecules to oxygen, releasing energy that is used to generate ATP through oxidative phosphorylation.

Learning outcome 4: To describe processes involved in electron transport chain and oxidative phosphorylation

The ETC begins with the transfer of electrons from NADH, a product of glucose metabolism, to the first complex of the ETC, NADH dehydrogenase. This complex transfers electrons to ubiquinone, an electron carrier which then passed to cytochrome b-c1 complex (or succinate dehydrogenase). This complex in turn passes the electrons to cytochrome c, another electron carrier that transfers electrons to cytochrome c oxidase (or cytochrome aa3 complex).

The cytochrome c oxidase complex is the final electron acceptor of the ETC, it accept electrons from cytochrome c and transfer them to oxygen, creating water and releasing energy. This energy is used to pump protons (H+) across a membrane creating a proton gradient, this process is called chemiosmosis.

The protons flow back across the membrane through ATP synthase, an enzyme complex that generates ATP. This process is known as oxidative phosphorylation, it uses energy from the electron transport chain to generate ATP, the energy currency of the cell.

Overall, The electron transport chain and oxidative phosphorylation are closely linked processes that occur in the mitochondria of eukaryotic cells and in the cytoplasm of prokaryotic cells. They involve the transfer of electrons from organic molecules to oxygen, releasing energy that is used to generate ATP through the process of chemiosmosis.