A2C1 - Chapter 3 - Respiration WIP Flashcards
(35 cards)
What is respiration?
A set of metabolic reactions that take place in organisms and break down respiratory substances, such as glucose, into smaller inorganic molecules, like water and carbon dioxide.
This is linked to the synthesis of ATP.
Why is respiration described as a catabolic process?
Complex molecules (respiratory substrates) are broken down into smaller, simpler molecules.
Why do organisms need to respire?
It produces chemical energy in ATP for a variety of processes including active transport, metabolic reactions and muscle contraction.
It releases heat energy for thermoregulation.
Define aerobic respiration.
A form of cellular respiration that takes place in the presence of oxygen and produces carbon dioxide, water and ATP.
Overall:
C6H12O6 + 6O2 –> 6CO2 + 6H2O
Name the four main stages of aerobic respiration and state where they occur.
Glycolysis = Cytosol
Link Reaction = Mitochondrial Matrix
Krebs Cycle = Mitochondrial Matrix
Electron Transport Chain = Inner Mitochondrial Membrane
(GLKE)
Outline the stages of glycolysis. (3 steps)
- Glucose (hexose sugar) phosphorylated to hexose bisphosphate by 2 ATP (which simultanously become ADP + Pi)
- Hexose bisphosphate splits into 2x TP.
- 2x TP oxidised to 2x pyruvates. (NAD becomes reduced NAD/2ADP + 2Pi –> 2ATP)
Net gain of 2 NADH and 4 ATP per glucose. (4-2 because we used 2 in step 1 hence net gain of 2 ATP not 4)
Write an equation to summarise glycolysis.
Glucose + 2NAD + 2ADP + 2Pi –> 2 Pyruvate + 2NADH + 2ATP + Heat
How does pyruvate from glycolysis enter the mitochondria?
Active Transport
Outline the link reaction. (only occurs in mitochondrial matrix) (5 steps)
- Pyruvate (3C) from glycolysis is transported into the mitochondrion.
- One carbon is removed from pyruvate as CO₂ (decarboxylation), leaving 2C.
- That 2C molecule is oxidised — meaning hydrogen atoms are removed from it.
- Those H atoms are picked up by NAD⁺, reducing it to reduced NAD (NADH).
- The resulting 2C molecule is now an acetyl group, which combines with Coenzyme A, forming Acetyl CoA.
What is decarboxylation?
The removal of Carbon Dioxide, performed by decarboxylase enzymes.
Write an equation to summarise the link reaction.
Pyruvate + NAD + CoA –> Acetyl CoA + NADH + CO2.
What is the krebs cycle?
A series of oxidation-reduction reactions in the matrix of the mitochondria in which acetyl coenzyme A is oxidised generating NADH, reduced FAD and carbon dioxide.
How many times does the krebs cycle occur for one glucose molecule?
Twice because 1 glucose molecule can form 2 Acetyl CoA
Where does the krebs cycle occur?
Mitochondrial Matrix
Outline the stages of the krebs cycle.
- Acetyl CoA (2C) enters the cycle
→ Combines with oxaloacetate (4C)
→ Forms citrate (6C) - Citrate (6C) is converted to a 5C acid.
→ Hence 1 CO₂ is lost (decarboxylation) de
→ 1 NAD+ → NADH (reduction) na - 5C compound → 4C compound
→ Another CO₂ lost (decarboxylation) de
→ Another NAD+ → NADH na - 4C compound is rearranged back to oxaloacetate (4C)
→ ADP + Pi → ATP (via substrate-level phosphorylation) a
→ FAD → FADH₂ fa
→ NAD⁺ → NADH na
What is the function of the krebs cycle?
To release energy held in carbon bonds to provide ATP, reduced NAD and reduced FAD (with the release of CO2).
How many NAD and FAD does the complete oxidation of one glucose molecule yield?
10 reduced NAD and 2 reduced FAD.
What is the final stage of this respiration looney tunes parade?
The Electron Fucking Transport Chain.
What is the Electron Transport Chain?
A series of electron carrier proteins that transfer electrons in a chain of oxidation-reduction reactions, releasing energy.
Where is this guy located? (The ETC)
Inner Mitochondrial Membrane (cristae)
What happens in the electron transport chain (briefly)?
Electrons released from reduced NAD and FAD undergo successive redox reactions.
The energy released is coupled to maintaining the proton gradient or is released as heat.
Oxygen acts as the final electron acceptor.
Describe the role of reduced NAD and reduced FAD in the electron transport chain.
They are the source of electrons and protons.
Outline the steps for the Electron Transport Chain.
Step 1: NADH donates its electrons (dehydrogenation) to the first proton pump.
Releasing hydrogen atoms that split into protons (H⁺) and electrons (e⁻).
The protons are pumped across the inner membrane into the intermembrane space.
Step 2: Electrons move to the next proton pump.
As they do, they release energy, which is used to pump more protons from the matrix to the intermembrane space.
Step 3: The electrons move through another pump.
A third proton pump is used to pump two more protons into the intermembrane space, creating the proton gradient (more protons outside than inside the matrix).
Step 4: The terminal electron acceptor (oxygen) grabs the electrons.
Oxygen combines with two protons and the two electrons to form water (H₂O).
Step 5: The protons (H⁺) flow back into the matrix through ATP synthase (the stalked particle).
This flow of protons is called chemiosmosis, and it’s used to phosphorylate ADP into ATP.
Hence: ATP Production:
NADH generates 3 ATP because it goes through three proton pumps.
FADH₂ generates 2 ATP because it only enters at the second pump and therefore uses two proton pumps.
How does chemiosmosis produce ATP during aerobic respiration?
Protons flow down their concentration gradient from the intermembrane space into the mitochondrial matrix via ATP synthase.
ATP synthase phosphorylates ADP to form ATP as protons flow through it.
