5.2.2 Flashcards
What is glycolysis?
The breakdown of 1 glucose molecule into 2 pyruvate molecules
Is glycolysis aerobic or anaerobic?
Glycolysis is anaerobic
Where does glycolysis take place?
The cytoplasm of the cell
What are the four main steps in glycolysis?
Phosphorylation
Lysis
Phosphorylation
Dehydrogenation and formation of ATP
Describe the first phosphorylation in glycosis
Two molecules of ATP release one phosphate group each, which bind to a glucose molecule, forming hexose bisphosphate
Describe lysis in glycolysis
The formation of hexose bisphosphate destabilises the molecule, causing it to split into two triose phosphate (TP) molecules
Describe lysis in glycolysis
The formation of hexose bisphosphate destabilises the molecule, causing it to split into two triose phosphate (TP) molecules
Describe the second phosphorylation in glycolysis
Another phosphate group is added to each triose phosphate, forming triose bisphosphate. The phosphate groups come from free inorganic phosphate ions in the cytoplasm
Describe dehydrogenation and formation of ATP in glycolysis
Two phosphate groups are removed from each triose bisphosphate molecule, forming 4 ATP molecules. The two triose bisphosphate molecules are oxidised by the removal of hydrogen atoms, forming two pyruvate molecules. NAD coenzymes accept the hydrogens, reducing them
What type of phosphorylation is seen in glycolysis?
Substrate level phosphorylation
What is substrate level phosphorylation?
The formation of ATP without the involvement of an electron transport chain
What are the net products of glycolysis?
2 ATPs, 2 NADHs, and 2 pyruvates
What is the first step of AEROBIC respiration?
The link reaction
Where does the link reaction take place?
The mitochondrial matrix
How does pyruvate enter the mitochondrial matrix?
Active transport
What happens during oxidative decarboxylation of pyruvate?
Carbon dioxide is removed, as well as hydrogen
What accepts the removed hydrogens?
NAD, forming reduced NAD
What is formed after CO2 and hydrogen are removed?
An acetyl group
What happens to the acetyl group next?
It binds to coenzyme A, forming acetyl CoA
What are the net products of the link reaction?
2 CO2s, 2 NADHs, 2 acetyl CoAs
Where does the Krebs cycle take place?
The mitochondrial matrix
What is the first step in the Krebs cycle?
Acetyl CoA delivers an acetyl group to the Krebs cycle. The acetyl group combines with oxaloacetate (OAA) to form citrate (6C)
What is the second step in the Krebs cycle?
The citrate molecule undergoes decarboxylation and dehydrogenation producing one NADH and one CO2. A 5 carbon intermediate is formed
What is the third step in the Krebs cycle?
The 5 carbon intermediate undergoes further decarboxylation and dehydrogenation reations, regenerating OAA, so the cycle continues. Two more NADHs and one FADH2 is formed.
How many times does the Krebs cycle take place per glucose molecule?
2 times
What are the net products of the Krebs cycle?
2 ATPs, 4 CO2s, 6 NADHs, and 2 FADHs
How many ATPs does NADH cause the synthesis of?
3 ATPs
How many ATPs does FADH2 cause the synthesis of?
2 ATPs
What is the final stage of aerobic respiration?
Oxidative phosphorylation
What happens at the start of oxidative phosphorylation?
The hydrogen atoms that have been collected by NAD and FAD are delivered to electron transport chains in the membranes of the cristae of the mitochondria. The hydrogen atoms dissociate into hydrogen ions and electrons.
What do the electrons do in oxidative phosphorylation?
The electrons reduce and oxidise the electron carriers as they flow down the electron transport chain. This causes energy to be released. This energy is used to create a proton gradient leading to diffusion of protons through channel proteins lined with ATP synthase, resulting in the synthesis of ATP
What happens at the end of the electron transport chain?
The electrons combine with hydrogen ions and oxygen, which is the final electron acceptor, to form water. The electron transport chain cannot operate unless oxygen is present, so respiration that results in the complete breakdown of glucose is an aerobic process
Why is it called oxidative phosphorylation?
The phosphorylation of ADP to form ATP is dependent on electrons moving along electron transport chains. The electron transport chains require the presence of oxygen
How many ATP molecules are produced from aerobic respiration?
38 ATPs
What are obligate anaerobes?
Organisms that cannot survive in the presence of oxygen. Most obligate anaerobes are prokaryotes
What are facultative anaerobes?
Organisms that synthesise ATP by aerobic respiration if oxygen is present, but can switch to anaerobic respiration in the absence of oxygen
What are obligate aerobes?
Organisms that can only synthesise ATP in the presence of oxygen
What is fermentation?
Fermentation is a form of anaerobic respiration in which complex organic compounds are broken down into simpler inorganic compounds without the use of oxygen or the involvement of an electron transport chain
What is fermentation?
Fermentation is a form of anaerobic respiration in which complex organic compounds are broken down into simpler inorganic compounds without the use of oxygen or the involvement of an electron transport chain
What is the net ATP produced in fermentation?
2 ATPs
What is the net ATP produced in fermentation?
2 ATPs
What are the two main types of fermentation?
Alcoholic fermentation and lactate fermentation
Describe lactate fermentation in mammals
Pyruvate can act as a hydrogen acceptor, taking the hydrogen from reduced NAD, catalysed by lactate dehydrogenase. The pyruvate is converted into lactate and NAD is regenerated. This can be used to keep glycolysis going so a small amount of ATP is still synthesised.
What is the reason for oxygen debt?
Lactic acid is converted back to glucose in the liver, but oxygen is required for this
Why can’t lactate fermentation occur indefinitely?
The reduced quantity of ATP produced is not enough to maintain vital processes for long periods, and the accumulation of lactic acid causes a fall in pH leading to proteins denaturing.
Describe alcoholic fermentation in yeast
Alcoholic fermentation is irreversible, unlike lactate fermentation. Pyruvate is first converted into ethanal, catalysed by pyruvate decarboxylase. Ethanal then accepts a hydrogen atom from NADH, forming ethanol. The regenerated NAD can continue to act as a coenzyme and glycolysis can continue
What is a respiratory quotient?
A quality of a substrate to show the ratio between CO2 produced and O2 consumed
How is respiratory quotient calculated?
RQ = CO2 produced/ O2 consumed
What is the RQ of carbohydrates?
1.0
What is the RQ of proteins?
0.9
What is the RQ of lipids?
0.7
What does it mean if the RQ value is greater than 1?
Anaerobic respiration is taking place
What is used to measure RQ?
A respirometer
