Lecture 7 Flashcards
What is ATP
Can be considered our energy currency.
The hydrolysis/Breaking of the phosphate bond in ATP (to convert into ADP) is what releases energy
Difference between ATP, ADP, and AMP
Number of phosphates
ADP = two phosphates
AMP = one phosphate
What is the ATP cycle
Describes the transfer of energy between complex and simple molecules in the body, with ATP as the mediator
We consume glucose but it can be stored as glycogen via anabolic reactions
Describe a catabolic reaction
Catabolic reactions transfer energy from complex molecules - glycogen, proteins, and triglycerides - to ATP and form simple molecules - glucose, amino acids, glycerol, and fatty acids. Heat is released
Describe an anabolic reaction
Anabolic reactions transfer energy from ATP to form complex molecules - glycogen, proteins, and triglycerides - from simple molecules - glucose, amino acids, glycerol, and fatty acids. Heat is released
What are the main categories of fuel
Carbohydrates - broken down to simple sugars (glucose)
Proteins - broken down to amino acids
Fats - broken down to simple fats
The course only focused on cellular respiration and glucose
What are the main categories of fuel
Carbohydrates - broken down to simple sugars (glucose)
Proteins - broken down to amino acids
Fats - broken down to simple fats
The course only focused on cellular respiration and glucos
How does glucose enter cells
We eat food (some energy is lost for this and in faeces), and glucose enters our blood. Then it enters cells, which is facilitated by insulin - which is released by pancreas’s beta cells in the islet of langerhaans.
Once in cells, it can be used immediately for cellular respiration for cellular work, or it can be stored for harder times (stored as glycogen in liver and skeletal muscle), as having high amounts of glucose within blood is not good (homeostasis). If this happens, when energy is needed, glucagon will be released by alpha cells in pancreas’s islets to turn it back into glucose in the blood stream
What is glycogen
It is formed via an anabolic reaction (heat release in this process) in liver and skeletal muscle, and can be broken down again to produce glucose (again, release of heat) when needed in bloodstream
ATP is used when transferring from glucose to glycogen and formed when glycogen goes back to glucose
Overall chemical reaction of aerobic respiration
C6H12O6 + 6O2 —> 6CO2 + 6H2O + Energy (as ATP)
Carbon is oxidised and oxygen is reduced
What are the steps of Cellular respiration
Glycolysis
Pyruvate oxidation
Citric acid/Krebs/TCA cycle
Electron transport chain (ETC)
What are the parts of the Mitochondrion?
Outer membrane
Inter membrane space
Inner membrane
Cristae
Matrix
Describe Glycolysis
Location: Occurs in the cytosol
Reactants (per glucose):
Glucose
2 ADP
2 NAD+ electron acceptor
(i.e. NOT OXYGEN)
Products:
2 Pyruvate acid molecules per glucose
4 ATP produced (2 ATP per pyruvate molecule)
2 NADH
2 H20
Net change:
- 2 pyruvate acid molecules, 2 ATP, 2 NADH, 2 H20
- 2 NAD+, and 1 glucose molecule lost.
Process:
Two ATP is invested in the glucose molecule, then the molecule splits in half, and NAD+ electron acceptors take electrons and hydrogen atoms from each of the two haves. Finally, 2 ATP is produced from each half, and 2 pyruvate acid molecules (3 carbon chains) are left
NAD+ - electron acceptor, NADH - electron donor
Elaborate on the third step of glycolysis
The third step of glycolysis include phosphofructokinase
Phosphofructokinase is an enzyme that can be rate limiting for glycolysis. It operates under a negative feedback kind of loop; it is inhibited by citrate and ATP, so when high levels of citrate and ATP subsequently less ATP and citrate produced
On the other hand, it can be stimulated by AMP (which accumulates when ATP is being used rapidly)
Allows for homeostasis (is a homeostatic mechanism - the maintenance of relatively constant conditions within physiologically tolerable limits)
Describe Pyruvate oxidation
Location: Matrix of mitochondria
Reactants: (per glucose)
2 Pyruvate acid molecules
2 O2 (OXYGEN)
2 NAD+
Coenzyme A
Products: (per glucose)
2 Acetyl CoA
2 CO2
2 NADH
(i.e. NO ATP)
Process:
In the presence of oxygen, the 2 molecules of pyruvate enter mitochondria, and each loses a carbon by reacting with O2 to produce CO2.
Then an electron is removed from each acid molecule to form an NADH. Then, a Coenzyme A attaches to each of the pyruvate acid molecules to produce Acetyl CoA.
Extra things to note about pyruvate acid cycle
The two NADH produced via glycolysis can enter the matrix via two different electron shuttles. Depending on the protein it goes through, you end up with 2 NADH or 2 FADH, which can lead to a small difference in the amount of ATP produced in the end
Describe the Citric acid cycle/Krebs cycle/TCA cycle
Location: Matrix
Reactants: (per glucose molecule)
2 Acetyl CoA
(2x) 4 chain carbon
6 NAD+
2 FAD
4 O2
Products:
2 ATP
6 NADH
2 FADH2
4 CO2
(2x) 4 chain carbons left over and recycled
Process:
The co-enzyme is removed from each Acetyl CoA and each two carbon chain is added to a four carbon chain to produce a six carbon chain. This is then partially broken down to produce 2 carbon dioxide per molecule (4 per glucose), and several electrons are captured by electron acceptors. Finally, an ATP is produced by each of the chains.
The citric acid cycle is a series of reactions: the product of one reaction is the substrate for the next (there are many intermediates).
It is when we have finished receiving the energy from the six carbons - but not done producing ATP
Important to recognise that there are intermediates within the citric acid cycle that feed into other pathways
Describe the Electron transport chain
Location: Across inner membrane of mitochondria
Reactants:
NADH
FADH2
O2
Products:
26-28 ATP
Process:
Electron carriers (NADH and FADH2) are oxidised to deliver electrons to proton pumps
Electrons are transferred from one electron carrier to the next in a series of redox reactions and as they move along each step they give up energy - used to cause H+ ions to cross from matrix to intercellular space.
Importantly, Oxygen (associated with complex 4) in the matrix will pull electrons from the final proton pump to be reduced into water - oxygen is required for this reason to keep the passage of electrons going.
When this occurs, the H+ ions concentration of the IMS will be high, and as a results the H+ ions will naturally and without energy travel back down the concentration gradient (chemiosmosis). The H+ will travel through a protein called ATP synthase, and will cause it to drive the bottom part of the protein to spin. This spinning will cause ADP and free phosphates in the matric to be used to produce ATP.
Remember that there are four protein complexes and some other facilitative ones (protein Q and Cyt c). Protein complexes 1, 3, and 4 are called protein pumps - transmembrane proteins that are able to transfer hydrogen ions from the matrix up into the inter membrane space. Complex 2 is a peripheral protein
FADH2 starts at complex 2 but ultimately passes down the same pathway.
ATP synthase protein is also on inner membrane
Where are the proteins involved in the electron transport chain
The proteins involved in the Electron transport chain are sitting on the inner membrane and are called complex 1, 2, 3, and 4. Complex 1, 3, and 4 are integral proteins, while Complex 2 protein is more of a peripheral protein.
What can impact the ETC
Cyanide can act on protein 4 to block passage of electrons to oxygen in the end, and if the reduction of oxygen is blocked the whole chain won’t work
Will cause mitochondria and like cell to die
In which process is most ATP produced from food
In the ETC
Describe substrate phosphorylation
ATP generated by direct transfer (from a substrate) of a phosphate group to ADP (using an enzyme). Glycolysis and citric acid cycle make ATP via substrate phosphorylation. Not very efficient
Describe oxidative phosphorylation
ATP is generated from the oxidation of NADH and FADH2 and the subsequent transfer of electrons and pumping of protons (doesn’t need substrate, deals with free phosphates)
How much ATP is produced in total from cellular respiration
30-32 ATP
