Module 5.2.2 Respiration Flashcards
What happens when ATP is hydrolysed?
The bonds between the 2nd & 3rd phosphate group break & a small amount of energy is released
ATP -> ADP +Pi + energy (35kJ)
Why is it beneficial that ATP is hydrolysed this way?
There is little wastage of energy
What is the purpose of respiration?
To turn ADP & Pi back into ATP so there is more energy
What are some of the reasons an organism has to respire?
Growth/repair/movement/cellular processes e.g. mitosis/active transport
What are the components of a mitochondrion?
Inner & outer membrane
Inter-membrane space
Matrix
Cristae
What does the outer membrane of a mitochondrion do?
Separates the outside environment & the inside of the organelle so it is the perfect condition for aerobic respiration
What does the inner membrane of a mitochondrion do?
Contains the electron transport chains & ATP synthase
What does the inter-membrane space of a mitochondrion do?
Proteins are pumped into it by electron transport chains
Small -> concentration increases quickly
What does the matrix of a mitochondrion do?
Contains enzymes for the Krebs cycle & mitochondrial DNA
What theory is supported by the existence of mitochondrial DNA?
The endosymbiosis theory
What is the endosymbiosis theory?
A theory that explains prokaryotic organisms evolved by absorbing mitochondria for aerobic respiration
How is mitochondrial DNA passed?
Maternally
What are the 3 stages of aerobic respiration?
The link reaction
Krebs cycle
Electron transport chain
What is glycolysis?
Splitting up glucose into pyruvate in the cytoplasm of the cell
Explain how glycolysis occurs in the cell?
1 glucose molecule, containing six carbons, is phosphorylated. 2 molecules of ATP are used to initially start the reaction which produces hexose bisphosphate. Because this molecule is unstable, lysis occurs, and it is broken down into 2 molecules of triose phosphate. These molecules are phosphorylated again and inorganic phosphate molecules, from the cytoplasm, enter and react with the triose phosphate to produce triose bisphosphate. The final stage of glycolysis is dehydrogenation. This is where 4 phosphate molecules are removed, making 4 molecules of ATP. This results in a net gain of 2 ATP molecules in each reaction. As well as this, 2 molecules of reduced NAD are produced from two hydrogen ions. Finally, 2 pyruvate molecules are formed as the resulting product.
For every one glucose molecule entering the reaction, what is produced?
2 molecules of ATP used, 4 produced (net gain of 2)
2 molecules of reduced NAD
2 molecules of pyruvate
What is the scientific name for the link reaction?
Oxidative decarboxylation
What is the link reaction?
A reaction that links glycolysis & the Krebs cycle together
Where does the link reaction occur?
In the matrix of the mitochondria
Explain what happens in the link reaction?
Pyruvate is decarboxylated & oxidised. This produces 2 molecules of carbon dioxide that can either be excreted or used in autotrophic organisms such as plants. As well as this, 2 hydrogen ions are released to form 2 molecules of reduced NAD. The final product, acetyl combines with coenzyme A to form 2 molecules of acetylcoenzymeA for the 2 molecule of pyruvate that are the beginning of the reaction
How is ADP phosphorylised?
ADP + Pi ——> ATP + H2O
IS ADP + Pi ——> ATP + H2O a condensation reaction?
Yes
What are the two different types of phosphorylation?
Substrate-level
Oxidative
What happens during substrate-level phosphorylation & what is it?
It is a single reaction involving direct transfer of a phosphate group from a donor molecule to ADP
Where does substrate-level phosphorylation occur in respiration?
Glycolysis -> triose bisphosphate -> ATP from ADP
Krebs cycle
Where does oxidative phosphorylation occur ?
Occurs in electron transport chains
What is oxidative phosphorylation?
A series of oxidative reactions that produce sufficient energy to form ATP from ADP & phosphate
Describe the Krebs cycle
AcetylCoA arrives at the Krebs cycle and unloads acetate. Acetate binds with oxaloacetate (4C) molecule. This forms a 6 carbon molecule, citrate. Citrate goes through dehyrdrogenation & decarboxylation to form a 5 carbon molecule, and a carbon dioxide & Reduced NAD are formed. This 5 carbon molecule also goes through dehydrogenation & decarboxylation to form a 4C molecule and release another molecule of CO2 & NADH. For the 4C molecule to turn back into oxaloacetate, it goes through substrate level phosphorylation to turn ADP to ATP, dehydrogenation where NAD & FAD turn into NADH & FADH2 and the cycle starts again
What happens to the NADH & FADH2 from the previous reactions?
They are used for oxidative phosphorylation
What is the final stage of aerobic respiration?
Oxidative phosphorylation
Where does oxidative phosphorylation occur?
The electron transport chains on the intermembrane space of the mitochondria
What are the electron carriers called?
Cytochromes
What does oxidative phosphorylation require & why to occur?
Oxygen to accept the electrons and hydrogen at the end from the NADH & FADH2
What is oxygen referred to in oxidative phosphorylation?
The terminal acceptor
What is oxidative phosphorylation based on?
Chemiostatic theory -> the movement of ions down an electrochemical gradient
What is an electrochemical gradient?
Has both an charge & concentration gradient
Per glucose molecule, how many molecules of NADH & FADH2 are produced?
NADH -> 10
FADH2 -> 2
Describe the process of oxidative phosphorylation
- Happens across the inner mitochondrial membrane.
- Each electron transport chain has four cytochromes
- Contains ATP synthase (not part of the ETC) -> where ATP is phosphorylated
- NADH & FADH2 arrive from previous reactions -> hydrogen atom they carry dissociates into electron & proton
- No longer reduced -> normal NAD & FAD & goes back to reactions it came from e.g. FAD goes back to Krebs
- Electrons move into ETC & move from 1 cytochrome to the next (goes through series of reduction & oxidation reactions) -> loses little bit of energy each time
- Electrons from NAD always enter 1st cytochrome, Electrons from FAD enter middle of the chain -> have less energy than NAD
- Energy from electrons used to pump protons left behind in the matrix into the inter membrane space
- Cannot diffuse back into matrix -> impermeable -> (high concentration of protons in intermembrane space)
- Oxygen (terminal acceptor) -> accepts 2 electrons left in cytochrome & 2 protons to make molecule of water
- Intermembrane space has high conc of protons & cant leave -> ATP synthase in membrane has ion channel allowing protons to diffuse back into matrix down electrochemical gradient -> protons lose little bit of kinetic energy (happens constantly) energy therefore stored builds up until enough energy produced to turn ADP & Pi into ATP
- Maximum yield of ATP not usually reached as it is used along the way -> e.g. active transport of pyruvate into matrix
What is the equation for oxygen making water?
2e- + 1/2 O2 + 2H+ ———-> H20
How many molecules of ATP can the 10 NADH molecules produce?
25
How many molecules of ATP can the 2 molecules of FADH2 produce?
3
Why is aerobic respiration favoured?
28 ATP molecules are produced (net) which is a lot more than anaerobic respiration can produce
