- A process that requires the presence of oxygen and producing ATP (energy).
- It uses fat, carbohydrate and protein to produce energy.
- Aerobic means oxygen dependent and aerobic metabolism refers to an energy-generating system under the presence of oxygen as opposed to anaerobic.
- Anaerobic metabolism does not dependent upon the presence of oxygen.
- Oxygen act as the final electron acceptor in the Electron Transport Chain (ETC) which later combines with hydrogen to form water, H20.
- ATP synthesis takes place via aerobic breakdown of energy substrates through the coupling of respiratory chain and oxidative phosphorylation.
- Aerobic metabolism includes in terms of energy sources carbohydrates and lipids and to a less extent proteins.
- In exercise, aerobic metabolism predominates supplying a large amount of energy at low power during exercise exceeding 1 min.
- Aerobic occurs in cytosol and mitochondria matrix
- End of product yields 38 ATP
- This metabolism undergoes Glycolysis, Krebs cycle, and Electron Transport Chain
glycolysis
- occurs in cytosol
- begins catabolism by breaking glucose into two molecule of pyruvate
- occurs whether oxygen is present or not
- other product form are 2 molecule of ATP and 2 NADH+ H+
link reaction / transition reaction
- conversion of pyruvate to acetyl coenzyme A
- it is treated as part of the Krebs Cycle
- the date of pyruvate depends upon the PRESENCE or ABSENCE of oxygen
- if PRESENT, pyruvate enters the mitochondrion where it is completely oxidized to form carbon dioxide and water
PYRUVATE IS CONVERTED INTO ACETYL COA
- pyruvate molecules are translocated from cytosol into mitochondria
- As pyruvate enters the mitochondria, a multienzyme complex modifies pyruvate to acetyl CoA which later enters the Kreb Cycle in matrix
- In these series of reactions, pyruvate undergoes a process known as oxidative decarboxylation which converts pyruvate to Acetyl CoA
krebs cycle
- role: To provide hydrogens (electrons) that can be used in the electron transport chain to provide energy for the formation of ATP
- It is the second stage of aerobic metabolism
- occurs in mitochondria
- this cycle begins when acetate from acetyl CoA combines with oxaloacetate to form citrate
- oxaloacetate is recycled and the acetate is broken down to carbon dioxide
- each cycle produces 1 ATP by substrate level phosphorylation, 3 NADH, 1 FADH2 (another electron carrier) per acetyl CoA
- conclusion if there are two molecules of acetyl CoA enter Krebs Cycle for each molecule of glucose, the cycle turn twice for each glucose molecule giving:
- 6 NADH + H+
- 2 FADH2
- 2 ATP
- 4 CO2
electron transport chain
Electron Transport Chain (ETC) is the chain of electron acceptors embedded in the inner membrane of the mitochondria
- ETC synthesis ATP by Oxidative Phosphorylation which is the final stage in aerobic metabolism
- the exergonic transfer of electrons (redox) to oxygen (final electron acceptor) leads to the Oxidative Phosphorylation
- The Oxidative Phosphorylation is the process in which ATP is formed as a result of the transfer of electrons from NADH + H+ OR FADH2 to oxygen by a series of electron carriers
electron transport chain pathway
- the electrons of NADH enter the chain at NADH dehydrogenase complex (complex I)
- Two electrons are transferred from NADH to the NADH dehydrogenase complex and reduced it, NADH will oxidized to NAD+
- NADH dehydrogenase complex passes the electron to the next electron carrier, ubiquinone
- as the electron transferred, free energy is released
- the free energy is used to pump proton from the matrix into intermembrane space building up proton concentration gradient
- ubiquinone transfer electron to cytochrome reductase
- From cytochrome reductase, electron is picked up by cytochrome c
- electron from cytochrome c transferred to cytochrome oxidase and passes it to oxygen, the final electron acceptor in the chain
- another source of electron for transport chain is FADH2 BUT the elctron carried have lower free energy
- FADH2 is oxidized to FAD and released electrons and protons
atp synthesis by chemiosmosis
Chemiosmosis is the diffusion of ions across a selectively permeable membrane . It relates to the generation of ATP by the movement of hydrogen ions across a membrane during cellular respiration
- as the hydrogen ion concentration becomes higher on the intermembrane space, this creates PROTON MOTIVE FORCE
- PMF drives the synthesis of ATP by ATP synthase complex
- the whole process known as oxidative phosphorylation