5.2.2 - Respiration Flashcards
What is respiration?
a process where glucose is broken down to release energy (generated in the form of ATP)
What is the equation for respiration?
glucose + oxygen -> carbon dioxide + water
C6H12O6 + 6O2 -> 6CO2 + 6H2O
Why is cellular respiration needed?
to produce ATP for processes like... -active transport -photosynthesis -cell division -movement of vesicles -phagocytosis etc
Describe the structure of a mitochondrion
- double membrane where inner mitochondrial membrane is folded to form cristae
- matrix containing mitochondrial DNA and ribosomes (needed for protein synthesis to make any enzymes needed)
Where does glycolysis occur?
cytoplasm
What is glycolysis?
the breakdown of glucose into pyruvate
What are the products of glycolysis (per one molecule of glucose)?
2x pyruvate
2x ATP
2x redNAD
What happens during glycolysis?
glucose glucose phosphate fructose phosphate fructose bisphosphate 2x triose phosphate 2x triose bisphosphate 2x triose phosphate 2x pyruvate
Where does the link reaction occur?
matrix of mitochondria
What is the link reaction?
the conversion of pyruvate into acetyl coA
What happens in the link reaction?
pyruvate -> acetyl group -> acetyl CoA
- dehydrogenation (pyruvate looses Hs and NAD gains them so is reduced)
- decarboxylation (CO2 is lost)
- coenzyme A added
What are the products of the link reaction (per one molecule of glucose)?
2x acetyl CoA
2x redNAD
Where does the Krebs Cycle occur?
matrix of mitochondria
What happens in the Krebs Cycle?
- acetyl CoA and OAA forms citrate
- citrate is decarboxylated (looses CO2) and dehydrogenated (looses H as NAD is reduced) to form a 5C intermediate
- 5C intermediate is decarboxylated (looses CO2) and dehydrogenated (looses H as NAD is reduced) to form a 4C intermediate
- 4C intermediate is converted into a different 4C intermediate as ADP is phosphorylated
- 4C intermediate is converted into another 4C intermediate as FAD is reduced
- 4C intermediate is converted into oxaloacetate (OAA) as NAD is reduced
- OAA can be reconverted into citrate, allowing the cycle to continue
What are the products of the Krebs Cycle (per one molecule of glucose)?
2x ATP
2x redFAD
6x redNAD
What coenzymes are used in cellular respiration?
- NAD
- FAD
- coenzyme A
What is substrate level phosphorylation?
phosphorylation when a phosphate group is directly transferred from one molecule to another
eg. during glycolysis and the Krebs Cycle
What is oxidative phosphorylation?
phosphorylation when energy from electrons from reduced coenzymes (NAD and FAD) is used to synthesise ATP
Where does oxidative phosphorylation occur?
inner mitochondrial membrane (cristae)
What happens in oxidative phosphorylation?
- in the matrix of the mitochondria, redNAD and redFAD are dehydrogenated into NAD and FAD and hydrogen atoms
- these Hs are dissociated into H+ and e-
- these e- move down an electron transport chain in the inner mitochondrial membrane, loosing energy as they do so
- this energy is used by a proton pump move the H+ ions across the inner membrane into the intermembrane space, creating a proton (electrochemical) gradient across the inner membrane
- the H+ ions then move back across the inner membrane through ATP synthase (known as chemiosmosis)
- this turns ATP synthase on so that ADP can be phosphorylated into ATP
- the H+ ions and e- then combine with oxygen (aka the final electron accepter) to produce water (this is catalysed by cytochrome oxidase)
How do metabolic poisons disrupt oxidative phosphorylation?
- they bind to electron carriers, which inhibits the electron transport chain
- reduces chemiosmosis
- inhibits Krebs Cycle as NAD and FAD are not regenerated
How much ATP is produced across all of aerobic respiration?
38
Why is less ATP produced than the theoretical maximum?
- some ATP is used for active transport (of pyruvate and H+ ions from glycolysis into the mitochondrion)
- some energy is released to surroundings (eg. as heat)
- not all of the H+ ion movement across the membrane is used to generate ATP/goes through ATP synthase (eg. H+ leak through membrane)
- not all redNAD produced is used to make ATP
What are the stages in aerobic respiration?
- glycolysis
- link reaction
- Krebs Cycle
- oxidative phosphorylation
What are obligate anaerobes?
organisms that only respire anaerobically
eg. prokaryotes like clostridium
What are obligate aerobes?
organisms that only respire aerobically
eg. mammals
What are facultative anaerobes?
organisms that can respire both aerobically and anaerobically (depending on the conditions)
eg. yeast
What are the two types of anaerobic respiration?
lactate fermentation
alcoholic fermentation
Where does lactate fermentation occur?
cytoplasm of muscle cells
in mammals
What happens in lactate fermentation?
- pyruvate is converted into lactate (lactic acid)
- catalysed by lactate dehydrogenase
- redNAD is oxidised
What happens to the lactate produced from lactate fermentation when there is oxygen again?
-lactate is converted back into glucose in the liver
Where does alcoholic fermentation occur?
yeast
What happens in alcoholic fermentation?
- pyruvate is decarboxylated to form ethanal (catalysed by pyruvate dehydrogenase and pyruvate decarboxylase)
- ethanal is reduced to ethanol (catalysed by ethanal dehydrogenase)
- redNAD is oxidised
What would happen if too much ethanol was produced in alcoholic fermentation?
-cell membranes would dissolve in the ethanol
Why do organisms respire anaerobically?
- 2xATP are still produced in glycolysis
- NAD is regenerated (which is needed in glycolysis, so allows glycolysis to continue)
Why does anaerobic respiration produce less ATP than aerobic respiration?
- ATP is only produced from glycolysis (only 2 molecules of ATP)
- Krebs cycle, oxidative phosphorylation, etc can’t occur (oxygen is needed as a final electron acceptor)
RQ=
volume of CO2 produced
____________________
volume of O2 used
What molecules are normally used in respiration?
carbohydrates and lipids
When are proteins used in respiration?
during starvation
What substrate is being used for respiration if there is a RQ value of 1?
carbohydrates
What substrate is being used for respiration if there is a RQ value of 0.7?
lipids
What substrate is being used for respiration if there is a RQ value of 0.8-0.9?
proteins
-range because there are different R groups in different amino acids
(or a mixture of carbohydrates and lipids)
Why do lipids release more energy than carbohydrates when used as a respiratory substrate?
- lipids have more H atoms
- so can form more redNAD
- which forms more ATP
What does a RQ value of more than 1 mean?
anaerobic respiration is occuring
What is a respirometer used for?
to find the rate of respiration
-measured the volume of O2 produced/CO2 used
What is the function of soda lime in a respirometer?
absorbs CO2
What is the function of the syringe in a respirometer?
used to reset the respirometer at the end of each trial
What does it mean when the bubble/coloured liquid in the glass tube of the respirometer moves left?
- more O2 is used than CO2 is produced (in aerobic conditions
- how much O2 is absorbed (in anaerobic conditions)
What does it mean when the bubble/coloured liquid in the glass tube of the respirometer moves right?
-more CO2 is produced than O2 is used (in aerobic conditions)
What causes the bubble/coloured liquid to move in a respirometer?
changes in pressure from O2/CO2 being used/produced
