5.2.2 Respiration Flashcards
What is ATP and what is its role in cells?
ATP or adenesine triphosphate in the universal energy currency for cells.
It provides energy for various cellular processes.
How ATP synthesised in respiration?
Pi and ADP combines to form ATP, using energy released in respiration.
Why is ATP synthesis considered an anabolic reaction?
Small molecules (ADP and Pi) are built up into larger ones (ATP)
What are the two main ways cells regenerate ATP during respiration?
Substrate-level phosphorylation - direct transfer of phosphate group, without involvement of an ETC (occurs in glycolysis & krebs)
Chemiosomsis - using movement of protons across a membrane to generate energy for ATP synthesis via ATP synthase (occurs in oxidative phosphorylation).
Name the two types of cellular respiration.
Aerobic respiration
Anaerobic respiration
What are the four stages of aerobic respiration in order?
- Glycolysis
- Link reaction
- Krebs cycle
- Oxidatve phosphorylation
Where does glycolysis occur and what does it produce?
Location: cytoplasm
Main products: 2 ATP, 2 reduced NAD & 2 pyruvate.
Where does the link reaction occur and what does it produce?
Location: Mitochondrial matrix
Main products: (per pyruvate) 1 acteyl coA, 1 reduced NAD and 1 CO₂.
Where does the Krebs cycle occur and what does it produce?
Location: Mitochondrial matrix
Main products: (per acetyl coA) 1 ATP, 3 reduced NAD,
1 reduced FAD and 2 CO₂.
Where does oxidative phosphorylation occur and what does it produce?
Location: Inner mitochondrial membrane of the cristae
Main products: 30-32 ATP and water
Is glycolysis an aerobic or anaerobic process?
Glycolysis is anaerobic - it does not require oxygen.
Describe the main steps of glycolysis.
(four stages)
- Phosphorylation of glucose - 2 ATP donate phosphate groups to glucose, forming hexose biphosphate (6C)
- Lysis - Hexose biphosphate molecule is split into 2 molecules of triose phosphate (TP)
- Phosphorylation of TP - A second phosphate is added to TP, converting them into 2 molecules of triose biphosphate.
- Dehydrogenation - A hydrogen is removed from each triose biphosphate (oxisised) = forming 2 red NAD , 2 pyruvate molecules and 4 ATP (substrate-level phosphorylation)
How does pyruvate reach the mitochondrial matrix for the link reaction?
By active transport via specific carrier proteins.
Describe the main steps of the link reaction.
(five stages)
- Decarboxylation - In mitochondrial matrix, each pyruvate is decarboxylated, removing 1 CO₂.
- Removal of CO₂ - CO₂ diffuses out of mitochondria as waste
- Oxidation of pyruvate - Two hydrogen atoms are removed from pyruvate to form 2C molecule acetate.
- Reduction of NAD - The hydrogen aroms removed are used to reduce NAD, forming NADH (an electron carrier).
- Formation of acetyl CoA - Acetate binds to coenzyme A, forming acetyl coenzyme A.
What is the role of acetyl CoA?
It delivers the acetyl group to the Krebs cycle.
Describe the main steps of the Krebs cycle.
(five stages)
- Acetly CoA (2C) merges with oxaloacetate (4C) to form a molecule of citrate (6C)
- Citrate is decarboxylated, releasing two molecules of CO₂.
- Citrate is also dehydrogenated (oxidised), releasing hydrogens that reduce 3 NAD and 1 FAD.
- One ATP is synthesised directly by substrate-level phosphorylation - per acetyl CoA.
- Oxaloacetate is regenerated from citrate to repeat cycle.
What is the role of NAD and FAD in the Krebs cycle?
Act as oxidsing agents
They are reduced - accept electrons & protons
The reduced coenzymes later donate these electrons & protons to the ETC for oxidative phosphorylation
What is the electron transport chain (ETC)?
A series of electron carrier molecules in the inner mitochondrial membrane, releasing energy in stages
What are the differences between NAD and FAD?
- NAD accepts 1 electron and 1 proton but FAD accepts 2 protons and 2 electrons.
- NAD participates in all three stages, but FAD only accepts in the Krebs cycle.
What are the reactants in oxidative phosphorylation?
Reduced NAD, Reduced FAD, Oxygen
ADP and inorganic phosphate (Pi)
Describe the main steps of oxidative phosphorylation.
(seven stages)
- NADH and FADH₂ release hydrogen, transfering H⁺ and high energy electrons (e⁻) into the mitochondrial matrix.
- The e⁻ are passed along a series of electron carrier molecules in the ETC embedded in inner mitochondrial membrane, releasing energy as transferred.
- The energy is used to actively transport H⁺ across inner mitochondrial membrane from matrix into intermembrane space.
- Accumulation of H⁺ in intermembrabe space sets up steep electrochemical gradient of H⁺ across inner membrane.
- H⁺ diffuses back into matrix down electrochemical gradient through ATP synthase.
- This releases energy and catalyses the synthesis of ATP from ADP and Pi.
- Oxygen is final electron acceptor & combines with H⁺ and e⁻ to form water - help maintain proton gradient.
What is chemiosmosis in oxidative phosphorylation?
The diffusion of protons across partially permeable inner mitochondrial membrane.
Down their electrochemical gradient through ATP synthase, catalysing ATP synthesis.
How much ATP is produced in oxidative phosphorylation per glucose molecule?
Between 30-32 ATP
What is the total ATP yield from one glucose molecule in aerobic respiration?
2 ATP produced in glycolysis
0 ATP in link reaction
2 ATP in Krebs cycle
30-32 in Oxidative phosphorylation
So, 34-36 ATP molecules in total.
