8.2 Cellular Respiration Flashcards
Define phosphorylation.
Addition of a phosphate molecule (PO4)3- to an organic molecule.
Outline glycolysis.
- Phosphorylation: A hexose sugar is phosphorylated by two ATP to become hexose biphosphate
- Lysis: The hexose biphosphate splits into two triose phosphates (3C sugars) as the phosphate group makes it unstable
- Oxidation: Hydrogen removed from the triose phosphates via oxidation (NAD is reduced to NADH + H+)
- ATP Formation: Four ATP molecules are released as the triose phosphates are converted into pyruvate
Overall: One molecule of glucose results in 2 pyruvate, 2 (NADH + H+) and 2 ATP (net gain)
Outline the link reaction.
- Pyruvate is transported from the cytosol to the mitochondrial matrix in a reaction that produces (one) NADH + H+ via oxidation
- Pyruvate decarboxylated and oxidized to form an acetyl group called Acetyl CoA.
- Two high energy electrons are removed from pyruvate. These react with NAD+ to produce reduced NAD.
Outline the Krebs Cycle.
- In the matrix, acetyl CoA combines with a 4C compound to form a 6C compound called citric acid
- 6C undergoes oxidative carboxylation twice, producing two CO2 and creating 2 NADH+H+ from 2 NAD+, and creating the 4C compound called OAA
- OAA undergoes a series of reactions which result in an ADP becoming an ATP, FAD becoming FADH2, and NAD becoming NADH H+, and the OAA becoming the original 4C compound, starting the cycle over again.
What are the products of the link reaction?
Acetyl CoA, one CO2, and one NADH+H+
What are the products of one cycle of the Krebs Cycle?
2CO2, 3 NADH+H+, 1 FADH2, 1 ATP
What are two electron carriers used in cellular respiration?
NAD+ and FAD
Outline the electron transport chain.
- Electron carriers from the Krebs Cycle move towards the mitochondrial membrane and deposit their electrons and H+ ions.
- H+ ions are passed through the first channel while electrons move along the ETC and activate the next channel.
- More carriers deposit electrons and H+ ions with H+ moving through the second channel.
- Electrons continue along ETC but are losing energy. As they lose energy, they move back into the matrix, increasing the H+ concentration gradient.
Explain oxidative phosphorylation in terms of chemiosmosis
Oxidative phosphorylation describes the production of ATP from oxidised hydrogen carriers (as opposed to substrate level phosphorylation)
When electrons are donated to the electron transport chain, they lose energy as they are passed between successive carrier molecules
This 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 transmembran enzyme called ATP synthase
As they return they release energy which is used to produce ATP (from ADP and Pi)
This process is called chemiosmosis and occurs in the cristae
The H+ ions and electrons are combined with oxygen to form water, allowing the process to be repeated anew
What is the function of the outer membrane of the mitochondria?
Separates contents of the mitochondria from the rest of the cell.
What is the function of the inner membrane (including cristae)? How is it adapted to increase efficiency?
- Be a site for oxidative phosphorylation
- Contains ETC and ATP synthase
What is the function of the matrix? How is it adapted to increase efficiency?
- Be a site for the Krebs cycle and link reaction
- Contains the enzymes necessary to support these reactions
What is the function of mitochondrial DNA and ribosomes?
Synthesis of proteins and organization of mitochondria.
What is the function of the inter-membrane space? How is it adapted to increase efficiency?
- Be a site for the ETC.
- Volume of space is small so concentration gradient across inner membrane can be built up rapidly
What is the location, purpose, and ATP yield of glycolysis?
- Cytoplasm
- convert glucose (6C) to pyruvate (2*3C)
- 2 ATP
