12.3 - Oxidative Phosphorylation Flashcards
What happens to hexose sugars like glucose during aerobic respiration?
Hexose sugars are split during glycolysis, producing 3-carbon pyruvate molecules, which are then used in the Krebs cycle.
What is the fate of carbon dioxide produced during the Krebs cycle?
Carbon dioxide is a waste product of the Krebs cycle and is removed from the body during gaseous exchange.
Why are the hydrogen atoms produced in the Krebs cycle valuable?
The hydrogen atoms (specifically the electrons they carry) are valuable as a potential source of energy in aerobic respiration.
What role do the coenzymes NAD and FAD play in aerobic respiration?
NAD and FAD carry hydrogen atoms, along with their electrons, from the Krebs cycle to the next stage of respiration: oxidative phosphorylation.
What is oxidative phosphorylation, and why is it important?
Oxidative phosphorylation is the process where the energy from the electrons within the hydrogen atoms is conserved and used to form adenosine triphosphate (ATP), the energy currency of the cell.
What are mitochondria, and where are they found?
Mitochondria are organelles found in eukaryotic cells, involved in energy production through respiration.
Describe the structure of mitochondria.
- Mitochondria have a smooth outer membrane and an inner membrane that is folded into extensions called cristae.
- The inner space, known as the matrix, contains proteins, lipids, and traces of DNA.
What process occurs in the mitochondria, specifically within the cristae?
Oxidative phosphorylation, the process of ATP synthesis, occurs in the cristae of mitochondria, where enzymes and proteins involved in this process are located.
Why are mitochondria more abundant in metabolically active cells?
Mitochondria are more numerous in metabolically active cells, such as muscle, liver, and epithelial cells, because these cells have higher energy demands due to processes like active transport.
How do the mitochondria in metabolically active cells differ structurally?
In metabolically active cells, the mitochondria have more densely packed cristae, increasing the surface area for enzymes and proteins involved in oxidative phosphorylation, enhancing ATP production.
What is involved in the synthesis of ATP by oxidative phosphorylation?
The synthesis of ATP by oxidative phosphorylation involves the transfer of electrons down a series of electron carrier molecules, which together form the electron transfer chain.
Describe the chemiosmotic theory of oxidative phosphorylation
- The hydrogen atoms produced during glycolysis and the Krebs cycle combine with the coenzymes NAD and FAD.
- The reduced NAD and FAD donate the electrons of the hydrogen atoms they are carrying to the first molecule in the electron transfer chain.
- The electrons pass along a chain of electron transfer carrier molecules in a series of oxidation-reduction reactions.
- As the electrons flow along the chain, the energy they release causes the active transport of protons across the inner mitochondrial membrane and into inter-membranal space.
- The protons accumulate in the inter-membranal space before they diffuse back into the mitochondrial matrix through ATP synthase channels embedded in the inner mitochondrial membrane
- At the end of the chain the electrons combine with these protons and oxygen to form water.
- Oxygen is therefore the final acceptor of electrons in the electron transfer chain.
What is the main role of oxygen in respiration?
Oxygen acts as the final acceptor of hydrogen atoms produced in glycolysis and the Krebs cycle.
What happens if oxygen does not remove hydrogen atoms at the end of the electron transfer chain?
Without oxygen, the hydrogen ions (protons) and electrons would back up along the chain, causing the process of respiration to halt.
Why is the removal of hydrogen atoms by oxygen important in respiration?
It prevents the accumulation of hydrogen ions and electrons, allowing the continuous flow of electrons and the ongoing production of ATP in respiration.
What would be the consequence of oxygen not acting as the final electron acceptor?
The entire process of respiration would stop, as the electron transport chain would no longer function properly without the removal of hydrogen atoms.
What is the general principle regarding energy release in respiration?
The greater the energy released in a single step, the more of it is lost as heat, leaving less energy available for useful purposes.
Why is it beneficial for organisms to release energy gradually?
When energy is released a little at a time, more of it can be harvested for the benefit of the organism, enhancing efficiency.
How are electrons carried by NAD and FAD transferred during respiration?
The electrons are not transferred in one explosive step; instead, they are passed along a series of electron transfer carrier molecules.
What characterizes the series of electron transfer carrier molecules in terms of energy levels?
Each electron transfer carrier molecule is at a slightly lower energy level, allowing the electrons to move down an energy gradient.
What advantage does the transfer of electrons down an energy gradient provide?
It allows the energy to be released gradually, making it more useful for ATP synthesis and other cellular processes.
What types of substances can be oxidized by cells to release energy?
- Sugars are not the only substances that can be oxidized by cells to release energy.
- Both lipids and proteins may, in certain circumstances, be used as respiratory substrates without first being converted to carbohydrates.
How are lipids processed before respiration?
- Before being respired, lipids are first hydrolyzed to glycerol and fatty acids.
- The glycerol is then phosphorylated and converted to triose phosphate, which enters the glycolysis pathway and subsequently the Krebs cycle.
What happens to the fatty acid component of lipids during respiration?
- The fatty acid component is broken down into 2-carbon fragments, which are converted to acetyl coenzyme A.
- This acetyl coenzyme A then enters the Krebs cycle.
What are the products of lipid oxidation during respiration?
- The oxidation of lipids produces 2-carbon fragments of carbohydrate and many hydrogen atoms.
- The hydrogen atoms are used to produce ATP during oxidative phosphorylation.
Why do lipids release more energy than carbohydrates during respiration?
For this reason, lipids release more than double the energy of the same mass of carbohydrate.
What is the role of proteins as respiratory substrates?
- Protein is another potential source of energy.
- It is first hydrolyzed to its constituent amino acids.
- These amino acids have their amino group removed (a process called deamination) before entering the respiratory pathway at different points, depending on the number of carbon atoms they contain.
How do different amino acids enter the respiratory pathway?
3-carbon compounds are converted to pyruvate, while 4- and 5-carbon compounds are converted to intermediates in the Krebs cycle.
The processes that occur in the electron transfer chain are also known as oxidative phosphorylation. Suggest why this term is used
- The movement of electrons along the chain is due to oxidation
- the energy from the electrons combines inorganic phosphate and ADP to form ATP = phosphorylation
The surface of the inner mitochondrial membrane is highly folded to form cristae. State one advantage of this arrangement to the electron transfer chain
- provides a large SA of membrane incorporating the coenzyme (NAD/FAD) and electron carriers that transfer the electrons along the chain
The oxygen taken up by organisms has an important role in aerobic respiration. Explain this role
- Oxygen is the final acceptor of the electrons and hydrogen ions (protons) in the electron transfer chain
- without it the electrons would accumulate along the chain and respiration would cease
As part of which molecule does the oxygen taken into an organism leave after being respired
Water molecule
