5.2.2 - Aerobic Respiration | Conjunto de Fichas

Pregunta	Respuesta
What are the Mitochondria?	- The site for the last 3 stages of Respiration. - they have a double membrane, the inner membrane is folded to form cristae, which maximises the surface area available for respiration. - the intermembrane space contains enzymes used in aerobic respiration - the fluid interior is the matrix - they contain mitochondrial DNA, allowing them to produce their own enzymes & reproduce
Why Is cellular respiration necessary?	- Active Transport - Secretion - large molecules in some cells are released by exocytosis - Replication of DNA & synthesis of organelles before cell division - Movement e.g. of bacterial flagella, muscle contractions
Describe the structure of ATP	- An adenosine group attached to a ribose sugar & three phosphate molecules Image: cc989528-903b-46de-822f-d8d1fc4fa11d.gif (image/gif)
Explain the importance of Coenzymes - specifically NAD & Coenzyme A	Coenzymes aid in the oxidation & reduction of reactions, and are electron acceptors. NAD accepts hydrogen atoms & carries them to the mitochondrial membrane where they are later split into protons & electrons for the ETC. It is also used in Glycolysis, Krebs Cycle, & anaerobic respiration. Coenzyme A carries acetyl groups from the link reaction to the Krebs cycle.
Where does Glycolysis take place and why?	Glycolysis takes place in the cytoplasm as glucose molecules can not cross the mitochondrial membrane, by breaking glucose into 2 molecules of pyruvate, this enables it to cross the membrane for the Link Reaction.
What happens in Glycolysis?	1. 2 molecules of ATP are used to phosphorylate glucose, the 2 phosphate molecules released are added to glucose to form hexose bisphosphate (6C) 2. HB is unstable so splits into 2 molecules of triose phosphate (3C). 3. Each TP molecule is oxidised, 2 NAD accept 2 hydrogen atoms to form 2 reduced NAD & 2 pyruvate molecules. 4. 4 ATP are produced but the net gain is 2, as 2 ATP were used at the start.
Where does the Link Reaction take place?	The Link Reaction takes place in the mitochondrial matrix. It links anaerobic glycolysis to the aerobic stages of respiration in the mitochondria.
What happens in the Link Reaction?	1. 2 pyruvate molecules are actively transported into the matrix. 2. Pyruvate is decarboxylated & dehydrogenated, NAD accepts 1 hydrogen atom 3. The removal of CO2 leaves a 2 carbon compound called acetate. 4. Coenzyme A binds to acetate to form acetyl-coenzyme A. 5. Acetyl CoA delivers the acetyl group to the Krebs Cycle. 6. No ATP molecules are formed during the Link Reaction, remember, the link reaction occurs twice for each molecule of glucose.
What are the products of the Link Reaction per glucose?	- 2 CO2 molecules (released as waste or used by plants for photosynthesis) - 2 Reduced NAD (go to oxidative phosphorylation to synthesise ATP)
Where does the Krebs Cycle take place?	The Krebs Cycle occurs in the Matrix, involving a series of oxidation & reduction reactions. this cycle happens once per pyruvate so twice per glucose.
What happens in the Krebs Cycle?	1. CoA releases the acetyl group. The acetyl group combines with oxaloacetate (4C) to form citrate (6C). 2. Citrate is decarboxylated & dehydrogenated with the help of NAD accepting a hydrogen. this forms reduced NAD & alpha-ketogluterate (5C) 3. The AK is further dehydrogenated & decarboxylated to form a 4C compound (+ Red. NAD) 4. ATP is produced by the direct transfer of a phosphate group from one 4C intermediate to another - this is substrate level phosphorylation. 5. the 4C is dehydrogenated twice & the H atoms are accepted by FAD to form reduced FAD, & NAD to form reduced NAD. 6. the 4C is converted to oxaloacetate which is used in the next Krebs Cycle.
What are the products of the Krebs Cycle, per glucose?	- 2 CO2 molecules - 2 ATP molecules - 6 Reduced NAD - 2 Reduced FAD
Where does Oxidative Phosphorylation take place?	In the inner mitochondrial membrane, it is used to make ATP using energy carried by electrons in reduced NAD &FAD, these coenzymes are also re-oxidised to be used again as electron acceptors.
What happens in Oxidative Phosphorylation?	1. Hydrogen atoms are released from red. NAD & FAD, this oxidises them to NAD & FAD. 2. The Hydrogen atoms split into protons & electrons. 3. Electrons move along the electron transport chain, as they move through the carriers they lose energy. 4. The energy lost is used to pump protons from the matrix into the intermembrane space. 5. this forms a proton gradient, with a higher concentration in the intermembrane space. 6. Protons move by facilitated diffusion down this gradient through ATP synthase 7. this movement of protons drives the synthesis of ATP from ADP + Pi. 8. At the end of the transport chain, in the matrix, the protons combine with electrons & oxygen to form water - Oxygen is the final electron acceptor.
What is Chemiosmosis?	the process of movement of hydrogen ions (protons) across a membrane due to the movement of electrons through the electron transport chain.
Describe the differences between NAD & FAD:	NAD: - takes part in all stages of cellular respiration - NAD accepts 1 hydrogen molecule - Reduced NAD is oxidised at the start of the ETC - results in the synthesis of 2.5 ATP molecules FAD: - FAD only accepts hydrogen ions during the Krebs Cycle - FAD accepts 2 hydrogens - Reduced FAD is oxidised further along the ETC - Reduced NAD results in the synthesis of 1.5 ATP
What is a Respiratory Substrate?	A biological molecule that can be broken down in respiration to release energy
What respiratory substrate releases the most energy & why?	Lipids have the highest energy value because most ATP is made in Oxidative Phosphorylation which uses H atoms from Red. NAD & FAD. Lipids contain the most hydrogen atoms per uni of mass & therefore more ATP can be synthesised from its Hydrogen atoms.
What is a Respiratory Quotient?	RQ = Volume of CO2 produced / Volume of O2 consumed
What are the respiratory quotients of Carbohydrates, Proteins & Lipids?	1.0, 0.9, 0.7
What does a Respiratory Quotient of 0.7-1.0 indicate?	That conditions are normal, this shows some lipids & carbohydrates are being respired, (proteins are normally respired only in times of starvation or during exercise.
What does a Respiratory Quotient larger than 1.0 indicate?	That there is a lack of oxygen, therefore the cell is respiring anaerobically which uses lots of glucose molecules very quickly to synthesise 2 molecules of ATP per glucose.
Why do plants have a low Respiratory Quotient?	Because the CO2 released in respiration is used in photosynthesis.

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