Respiration Flashcards
What is aerobic respiration?
The oxidation of glucose into carbon dioxide and water with release of energy
What is the equation of respiration?
Glucose + oxygen -> carbon dioxide + water (+energy)
What happens to energy in respiration
It is released or transferred, not produced
What does respiration occur in a series of?
Enzyme controlled steps - this means the release of energy is controlled
What nucleotide is ATP
Adenosine Triphosphate
What does ATP consist of
3 phosphate groups combined with adenine and pentose sugar, ribose
What type of energy store is ATP
The immediate, but short term energy store of cells
What is ATP synthesised from?
ADP (adenosine diphosphate) and inorganic phosphate (Pi) during phosphorylation
What happens when ATP is hydrolysed
ATP has a high free energy of hydrolysis meaning when it is hydrolysed a relatively large amount of energy is released
What happens when ATP is converted to ADP
Conversion yields energy. Conversions carried out my enzyme ATPases
Why is ATP a suitable energy store?
- hydrolysis of ATP molecules releases a small amount of energy so energy can be released in small manageable steps
- ATP hydrolysis is a single reaction releasing immediate energy and providing cell with control over energy
- ATP is small and soluble so can be transported around cell easily. Enables it to be transported from mitochondria to any part of cell
What are the uses of ATP
- energy for metabolic processes including synthesis of larger molecules
- movement
- active transport
- activates molecules via phosphorylation
Describe the structure of the mitochondria
- surrounded by a double membrane separated by intermembrane space
- outer membrane is permeable to most small molecules involved in cellular respiration
- inner membrane is highly folded forming cristae inc SA enabling more ATP to be produced.
- matrix contains many chemical compounds and some respiration reactions occur here
How is ATP produced in respiration
- substrate Level phosphorylation: direct transfer of a phosphorylated substance to ADP
- Oxidative phosphorylation: ATP is produced from ADP and Pi as electrons are transferred along a series of carriers
What are the stages of aerobic respiration
1 glycolysis
2 pyruvate oxidation (link reaction)
3 Krebs cycle
4 electron transport chain
What is glycolysis
The splitting of the hexose sugar (glucose) into two 3-carbon pyruvate molecules
What stage of respiration occurs aerobically and anaerobically
Glycolysis
Where does glycolysis occur
In fluid part of cytoplasm
What are the steps of glycolysis
1) activation of glucose by phosphorylating it. Makes glucose more reactive and uses up ATP as 2 phosphates come from hydrolysis of 2 atp molecules. Resulting molecule is fructose 1,6 bisphosphate
2) that then splits into two 3 carbon molecules of trios-phosphate, which is then oxidised through loss of hydrogen to form pyruvate with the production of 2 ATP molecules. The hydrogen atoms are collected by NAD which is reduced to form NADH.
3) overall the process from glucose to 2x pyruvate molecules results in the formation of 4 ATP and 2 NADH + H+, but the 2 ATP are used up in the process of glucose activation, so the net gain of ATP is only 2
What does the removal of hydrogen in stage 2 of glycolysis involve
Dehydrogenase enzymes in a process called dehydrogenation
What does the link reaction do?
Form a molecule called acetyl coenzyme A (acetyl CoA). This is necessary to allow the entry of a 2 carbon molecule into mitochondrial matrix
What is decarboxylation
Removal of a carbonyl group
What is dehydrogenation
The removal of hydrogen atoms
What is the process of the link reaction?
1) pyruvate is decarboxylated with the removal of one CO2
2) dehydrogenations occur with the removal of hydrogen leading to formation of NADH
3) The resulting 2 carbon (acetyl) group then combines with coenzyme A forming acetyl CoA
What other words exist for the Krebs cycle
The tricarboxylic acid cycle (TCA) and citric acid cycle
Where does Krebs cycle happen
In the matrix of mitochondria and involves a cyclical series of reactions
What happens at Krebs cycle
1) the 2 carbon acetyl CoA produced from link reaction enters cycle and combines with a 4C compound oxaloacetate forming 6C citric acid / citrate
2) Citrate undergoes decarboxylation resulting in 5C oxoglutarate. Dehydrogenation also occurs and hydrogen is released which reduces NAD to NADH
3) oxoglutarate is also decarboxylated resulting in formation of 4C oxaloacetate with loss of CO2 and the cycle continues
What does the reaction involved in converting oxogluterate to oxaloacetate involve?
Dehydrogenation. At two points hydrogen is released that reduces NAD to NADH. producing 2 molecules of NADH. At one point, hydrogen is released and used by a different hydrogen carrier, FAD and reduces FAD to FADH2
What is substrate level phosphorylation?
1 molecule of ATP is produced from the transfer of a phosphate group from an intermediate compound to ADP. ATP produced this way is referred to as substrate level phosphorylation
Why does krebs cycle turn twice?
There are 2 molecules of Acetyl CoA for every molecule of glucose
What does the Krebs cycle produce?
2 molecules of ATP directly, 6 pairs of hydrogen atoms to form 6 molecules of NADH, 2 pairs of hydrogen atoms to form 2 molecules of FADH2
What will NADH and FADH2 do at ETC?
Yield more ATP
Where does the electron transport system take place?
In and on the inner mitochondrial membranes
Where do the hydrogens in the ETC come from>
Produced by Krebs cycle, link reaction and glycolysis by process of dehydrogenation
What is the ETC system made of?
A number of cytochromes and co enzymes which have the ability to pass on the electrons produced from the splitting of the hydrogen atom into electrons and protons, and the energy in the hydrogen and electrons is converted into ATP, the form of energy that the cells can use
How are electrons able to move along the chain?
Each carrier downstream has slightly stronger reducing power than the one before it
Describe what happens during electron transport system
1) NAD and FAD feed in pairs of hydrogen from the link reaction, Krebs cycle and glycolysis
2) The H atoms split into their protons and electrons between coenzyme Q and cytochrome b
3) the cytochromes involved contain iron, the electrons go to cytochromes
4) NAD passes in the H atoms at an earlier stage than FAD. FAD feeds in between the flavoprotein and cytochrome Q
5) Following the cytochrome Q stage, hydrogen dissociates into electrons and protons and ETC functions as an electron carrier
6) Oxygen acts as a final acceptor of H atoms, it is vital to the whole process, without it only glycolysis could occur.
7) oxygen combines with hydrogen to form water - a waste product of respiration. This is catalysed by cytochrome oxidase
8) cytochrome oxidase is inhibited by cyanide
9) The formation of ATP by the oxidation of the hydrogen atoms is oxidative phosphorylation
10) As the H atoms are released from their carriers (FAD and NAD), the carriers are regenerated to return to glycolysis, link reaction, or Krebs cycle
What is substrate level phosphorylation?
The method by which glycolysis and Krebs cycle produce ATP. ADP molecule is phosphorylated when a phosphate group is transferred from another molecule
What happens in oxidative phosphorylation?
ATP is made using free phosphate groups. The energy required to achieve this is derived from a series of REDOX reactions in the ETC. NADH feeds its electrons into the chain at an earlier stage that reduced FAD so NADH produces 3 ATP molecules and reduced FAD produces 2
How many ATP molecules are produced in glycolysis?
8
How many ATP molecules are produced in the link reaction?
6
How many ATP molecules are produced in Krebs cycle?
24
Why is only 30-36 molecules of ATP really made?
Reduced NAD from glycolysis can’t enter mitochondrion easily, so it passes its electron onto an FAD molecule that then enter ETC
What is used for respiration when glucose stores are low?
Fat and protein
What happens when triglycerides are hydrolysed into fatty acids and glycerol?
Glycerol enters the glycolysis pathway, and Krebs cycle is where fatty acids enter respiratory pathway
What happens to fatty acids?
undergo a process called beta oxidaton. This involves 2 carbon fragments being broken off fatty acid chains and being converted to acetyl CoA
Where do many respiratory substrates enter respiration?
At the acetyl CoA stage, therefore it is often referred to as the ‘hub’
What happens when there is no oxygen?
Krebs cycle and electron transport chain cannot take place. Glycolysis will continue to produce 2 ATP molecules from each molecule of glucose
How is hydrogen removed in anaerobic respiration?
They are combined with the pyruvate to form ethanol or lactate in fermentation. The ethanol or lactate don’t yield energy, they just mop up excess hydrogen ions
Where does anaerobic respiration take place?
In the cytoplasm so substances don’t have to diffuse in and out of mitochondrion, in addition to it only being a very short part of aerobic pathway
What is the equation of anaerobic respiration in animals?
Glucose -> lactate + energy
Where is anaerobic respiration most likely to happen?
In skeletal muscle as a consequence of exercise
What does excess lactate cause?
fatigue and cramp like pains
How is lactate removed?
Oxygen is required and lactate is converted back into glucose or metabolised in other ways. This is where the term oxygen debt comes from
Why is breathing rate high after exercise/
to repay the oxygen debt
What is the equation of anaerobic respiration in plants/fungus
glucose -> ethanol + carbon dioxide + energy
What are the products of anaerobic respiration in plants/fungus?
End product is ethanol, carbon dioxide is a waste product. Ethanol isn’t converted back to pyruvate but i eliminated as waste
What is RQ?
Respiratory quotient
what is the equation for the RQ?
RQ = (volume of CO2 released)/(volume of O2 molecules consume)
THIS ISN@T FINISHED LOL
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