8.2 Respiration Flashcards
What is oxidation and reduction?
Oxidation: loss of electrons
Reduction: gain of electrons
When Benedicts test is added to sugar molecules, what is reduced and oxidised?
Reduced: copper ions from benedicts and become atoms of copper by being given electrons - forms a red or organge precipitate
Oxidised: the sugar molecules that gave away its electrons
What are electron carriers capable of?
Substances that can accept and give up electrons as required
they often link oxidations and reductions in cells
What is the main electron carrier in respiration and photosynthesis?
Respiration: NAD
Photosynthesis: NADP (which is a phosphorylated version of NAD)
What is added to NAD to turn it into reduced NAD?
2 electrons
NAD initially has a positive charge and exists as NAD+
When it accepts 2 electrons it turns into NAD
The 2 electrons are from 2 hydrogen atoms and one of them splits into a proton and an electron
NAD+ accepts the electron and the proton (H+) is released
What is phosphorylation?
is the addition of a phosphate molecule to an organic molecule
What is the purpose of phosphorylation?
To make the phosphorylated molecule more unstable = more likely to react
What is a endergonic reaction?
a energy absorbing reaction
What happens in Glycolysis?
- ‘Sugar splitting’
- takes place in cytosol
- glucose is phosphorelated (required 2 ATP)
- Phosphorylated glucose split into 2 triose phosphate molecules
- Triose phosphate loses phosphate group to ADP making ATP
- Triose oxidises by losing H+ atoms to electrion carrer (co-enzyme NAD)
Overall
* Pyruvate formed
* ATP produced
* Reduced NAD made (NADH + H+)
* 2ATP used for phosphorylation
* 4 ATP made during glycolysis
* Net gain of 2 ATP
* Reduced NAD passes into ETC and can generate 6ATP per glucose
What happens in the Link reaction?
- if oxygen available, pyruvate enters the matrix of mitochondria
- Each pyruvate is decarboxylated and loses C as CO2
- 2C fragment = acetyl group
- Picked up by coenzyme A
- Oxidised by NAD
- 2C + CoA + NAD+ -> acetyl CoA + CO2 + NADH + H+
- Acetyl CoA enters Kreb’s cycle
Products: (All x2 because there are two pyruvates)
* carbon dioxide
* Acetyl coenzyme A
* Reduced NAD
What happens in the kreb cycle?
- 2 carboxylation + 4 oxidation
- Acetyle CoA combines with a 4C compound to form citric acid (6C)
- 6C compound undergoes a series of reaction eventually losing 2C to carbon dioxide (2 decarboxylation) and forming a 4C compound
- At the same time the compound is also oxidised 4 times by removing the H atoms so that NAD+ and FAD (both hydrogen carriers) are reduced
- The 4C compound is recycled to begin the kreb cycle again
Every cycle:
* reduction of NAD x3
* reduction of FAD x1
* decarboxylation x2
= 1 molecule of ATP generated
What happens in the ETC?
involves chemiosmosis and oxidative phosphorylation
- NADH + H+ and FADH2 donate their hydrogen to electron carriers
- NAD+ returns to the matrix
- the hydrogen atoms are split, to release 2 electrons
- the electrons pass from carrier to carrier, energy is released
- energy is used to pump protons across the inner membrane from the matrix into th eintermembrane space
- as electron continue to flow along the chain, more and more proton are pumped across the inner mitochondrial membrane
- a concentration gradient of protons build up (a store of potential energy)
- protons pass back from the intermembrane spae to the matrix down the concentration gradient through ATP synthase
- energy relsease is used by ATP synthase to phosphorylate ADP
- Electorn transferred to a terminal electron accept at the end of the chain
- Oxygen is the final electron acceptor in aerobic respiration
- oxygen is reduced by accepting the electron and forms covalent bond with hydrogen
- Hydrogen is removed = proton gradient across the inner mitochondrial membrane is maintained - chemiosmosis can continue
What are the order of things that happen in respiration and where do they occur?
- Glycolysis - cytosol of cell
- Link reaction - in the mitochondrial matrix
- the kreb cycle - still in the mitochondrial matrix
- ETC - mitochondria cristae
What is the role of oxygen?
- oxygen is the final electron acceptor in the mitochondrial ETC
- the reduction of the oxygen molecule invovles both accepting electrons and forming a covalent bond with hydrogen
- by using up hydrogen, the proton gradient across the inner mitochondrial membane is maintained so that chemiosmosis can continue
What is an adaptation?
a change in structure so that something carries out its function more efficiently
What are adaptations of mitochondria?
- Outer mitochondrial membrane separates the contents of the mitochondrion from the rest of the cell creating a compartment specialized for the biochemical reaction sof aerobic respiration
- The inner mitochondrial membrane is the site of oxidative phosphorylation. It contained ETC and ATP synthase, which carry thart out. Cristae are tubular projections of the inner membrane which increase the surface area available for oxidative phosphorylation
- The intermembrane space is where protons build up as a consequence of the ETC. the proton build up is used to produce ATP via the ATP synthase. The volume of the space is small so a concentration gradient across the inner membrane can be built up rapidly
- The matrix is the site of the Kreb cycle and the link reaction. The matrix fluid contains the enzymes necessary to support these reaciton systems
