Suggest why cells such as the liver contains large amount of mitochondria.
The liver performs many metabolic functions, hence the liver cells have high energy requirements and thus have a high number of mitochondria.
Explain what is meant by oxidative phosphorylation
- -It is a process in which ATP is derived as electrons are transferred from NADH and FADH2 to oxygen via a series of electron carriers of progressively lower energy levels.
- -Energy released from this electron transfer through a series of redox reactions is used to build up a proton gradient across the inner mitochondrial membrane.
- -Potential energy of this proton gradient is used to synthesize ATP via the ATP synthase.
Name two substances which enter the mitochondria and are oxidized.
2) Reduced nicotinamide adenine dinucleotide
Explain how the mitochondrial matrix is adapted for generating energy in the cell.
- -Circular DNA
- Circular DNA codes for electron carriers and mitochondrial enzymes needed for Link Reaction, Krebs Cycle and Oxidative Phosphorylation.
- -70S ribosome and tRNA
- Allow mitochondria to carry out protein synthesis independently of the cell.
- -Gel-like matrix contains soluble enzymes, organic acids and lipids
- Site where Link Reaction and Krebs Cycle occur.
- Lies next to inner mitochondrial membrane such that NADH & FADH2 of Link Reaction and Krebs Cycle can
- be channeled to Oxidative Phosphorylation
In the Krebs cycle, isocitrate dehydrogenase catalyses the oxidative decarboxylation of isocitrate to form alpha-ketoglutarate.
Explain what is meant by the term oxidative decarboxylation.
- -NAD oxidises isocitrate to alpha-ketoglutarate, itself being reduced to NADH.
- -In decarboxylation, isocitrate is decarboxylated to a 5-carbon alpha-ketoglutarate with the removal of 1 molecule of carbon dioxide.
Outline how gaseous exchange link the metabolic pathways between the chloroplast and mitochondrion of a plant cell.
- -In the thylakoid membrane of the chloroplast, oxygen is formed as a product of photolysis of water during the light-dependent reaction.
- - Oxygen diffuses out of the chloroplast and into the mitochondrial matrix where it acts as the final electron acceptor in the electron transport chain in oxidative phosphorylation to form water.
- - Carbon dioxide produced in aerobic respiration during the Krebs cycle or link reaction by decarboxylation is released into the cytosol and diffuses into the stroma of the chloroplast where it will be used for carbon fixation in the Calvin cycle.
Explain how oxygen concentration can remain constant in a plant cell.
- -Oxygen released by the chloroplast during the light-dependent reaction through the photolysis of water is used by the mitochondria as the final electron acceptor in the electron transport chain of oxidative phosphorylation
- -Compensation point is reached where both the rate of respiration and the rate of photosynthesis is the same, thus there is not net change in the concentration of oxygen.
Explain why there is no build up in the concentration of phosphate ions inside of the mitochondria as a result of an inward passage of phosphate ions.
- -Phosphate ions are used to produce ATP in oxidative phosphorylation or the Krebs cycle and these ATP subsequently leaves the mitochondria
- - The phosphate ions are also used in substrate-level phosphorylation in the Krebs cycle hence phosphate ions do not accumulate in the mitochondria.
What is structure X and how is it adapted for the synthesis of energy?
- -Structure X is the crista of the mitochodrion
- -Provides a large surface area for attachment of transport proteins electron carriers and proton pumps in sequential order and stalked particles with ATP synthase
Explain the importance of oxygen in oxidative phosphorylation.
- -Oxygen is the final electron acceptor of the electron transport chain in oxidative phosphorylation. In its absence, electron transport
- does not occur which is required to transfer hydrogen ions from the mitochondrial matrix into the intermembranal space.
- -A proton gradient cannot be generated for oxidative phosphorylation to occur if there is no oxygen.
Explain the role of FAD and NAD in oxidative phosphorylation.
- -Both FAD and NAD serves as an electron and hydrogen carrier.
- -FADH2 is a carrier from the Krebs cycle while NADH serves as a carrier from glycolysis, link reaction and Krebs cycle.
- -During oxidative phosphorylation, electrons are transferred from NADH or FADH2 to electron carriers of progressively lower energy levels, thus initiating oxidative phosphorylation.
Explain how ATP synthesis in animal cells can still occur in the absence of oxygen.
- -In the absence or lack of oxygen, lactate fermentation occurs in animal cells.
- -Lactate fermentation is the conversion of glucose to
- lactate/ lactic acid.
- -Reduced NAD from glycolysis reduces pyruvate to lactate, regenerating NAD+ so that glycolysis can
- continue to produce 2 net ATP from every glucose molecule.
-This occurs so that cellular activities can still continue in the absence of oxygen.
Explain the role of NAD in the Krebs cycle.
- -NAD is a coenzyme that removes protons and electrons from / oxidizes intermediates of the Krebs cycle,
- forming NADH
- -In the reduced state, NADH transfers the electrons to the electron transport chain on the inner mitochondrial membrane.
- -Each NADH gives rise to 3 ATP molecules via oxidative phosphorylation.
During glycolysis, 4 ATP is produced per glucose molecule. However, 2 ATP is used up for every glucose molecule during glycolysis.
Explain the function of the 2 ATP in glycolysis.
- - 1 ATP is used to phosphorylate glucose into glucose-6-phosphate. This is to supply glucose with enough energy to overcome the activation barrier or give it activation energy.
- - Another ATP is used to phosphorylate fructose-6-phosphate to fructose-1,6-bisphosphate so that it can be split into two molecules of triose phosphate.
Define the term respiration.
- -Respiration is the process by which organisms
- release energy from the breakdown of glucose in a series of stages.
- -This energy is used by cells to synthesize ATP from ADP and Pi
- -Subsequently, the energy released from the hydrolysis of ATP to ADP and Pi can be used to drive all the other biochemical reactions of the cell.