C1.2 Respiration Flashcards
Adenosine Triphosphate structure
- 3 phosphate groups
- ribose sugar
- adenine (base)
ATP function
Cell energy currency, temporarily stores energy and used for transfter of energy between processes + different cell parts.
3rd phosphate group easily removed/reattached, releasing energy.
Properties of ATP which
make it suitable for storing/transfering energy
- Soluble in water: move freely in cytoplasm + other cell aqueous solutions.
- Stable at pH close to neutral (in cytoplasm).
- Can’t pass freely through PB of membranes. Movement between membrane-bound organelles controlled.
ATP as a coenzyme
Coenzymes are organic compounds that help enzymes by cycling between loaded and unloaded forms. ATP transfers chemical energy to enzymes, lowering the activation energy and triggering catalysis.
Mneumonic: BANG ME
Uses of ATP
Biosynthesis of macromolecules (e.g. polymers)
Active transport (e.g. endocytosis)
Nerve transmission (e.g. propagation of AP)
Growth and repair (e.g. mitotic division)
Movement (e.g. muscle contraction)
Emission of light (e.g. bioluminescence)
AP = action potentials
What are NAD+ and FAD?
Carrier molecules known as hydrogen/electron carriers (gain).
NAD+ + 2H+ + 2e– → NADH + H+
FAD + 2H+ + 2e– → FADH2
Glycolysis - step 1
Glucose is phosphorylated (6C) → fructose-1,6-biphosphate (6C, 2P)
(2ATP → 2ADP + 2Pi)
Glycolysis - step 2
Fructose-1,6-biphosphate (6C, 2P) undergoes lysis → 2x Triose phosphate (3C, P)
Glycolysis - step 3
Triose phosphate oxidised (dehydrogenase works w/ NAD+ (coenzyme) to remove H) → pyruvate (3C)
- NAD+ → NADH + H+ (reduced - accepts hydrogens, takes electrons to ETC)
- 2ADP + 2Pi → 2ATP (dephos. / ATP formation)
Link reaction (x2)
Pyruvate diffuses into matrix mitochondria and is decarboxylated (form CO2) + oxidised.
This forms NADH + H+ and an acetyl group (2C).
2C joins w/ coenzyme A → AcetylCoA
Krebs cycle (x2) - step 1
AcetylCoA + Oxaloacetate (4C) combine → Citrate (6C)
Coenzyme A goes back into Link Reaction.
Krebs Cycle (x2) - step 2
6C citrate → converted to 5C compound
Carbon dioxide = removed (decarboxylation)
Oxidation/dehydrogenation also occurs:
H is removed by NAD+ → NADH + H+
Krebs Cycle (x2) - step 3
5C molecule → converted to oxaloacetate (4C)
Decarboxylation + dehydrogenation occur (CO2, NADH + H+) FAD also reduced (remove H) → (FADH2).
Substrate level phosphorylation occurs: ATP produced by direct transfer of phosphate from an intermediate compound to ADP.
What does the Krebs Cycle produce (x2)?
KREBS HAPPENS x2 PER GLUCOSE = DOUBLE PRODUCT
- 2ATP
- 4CO2
- 2FADH2
- 6NADH + H+
ETC - step 1
NADH + H+ and FADH2 are oxidised - protons removed by dehydrogenase enzyme → NAD+ and FAD+ (reused in Krebs)
H atom → H+ and e-
ETC - step 2
e- move along the ETC (3 embedded proteins that act as electron carriers), losing energy at each carrier.
Energy used by protein pumps to move H+: matrix → intermem. space = create high electrochem. gradient.
ETC - step 3
Chemosmosis occurs:
H+ moves down gradient into matrix via a protein channel. Channel has ATP synthase attach, movement drives synthesis of ATP from ADP + Pi.
ETC - step 3 (final step of respiration)
In the matrix, 12H+ + 12e- + 6O2 (from blood) → 6H2O
* Oxygen = final electron acceptor
What is oxidative phosphorylation?
O = oxidation of NADH + H+ and FADH2 to form H+ and e- at the start of the ETC.
P = addition of a phosphate to form ATP (ADP+Pi → ATP) at the end of chemosmosis.
How much ATP is generated overall in aerobic + anaerobic respiration?
anaerobic = 2
Anaerobic respiration - step 1
Glucose → pyruvate (via glycolysis) + NADH
Without oxygen, NADH cannot be oxidized by the mitochondria, reducing the amount of available NAD.
Anaerobic respiration - step 2
Fermentation involves conversion: pyruvate → alt carbon compound via a reaction that oxidises NADH.
This process restores NAD, which is needed for glycolysis to keep making ATP without oxygen.
Without fermentation, glycolysis would stop = essential
Products of fermentation (- step 3)
Animals: lactic acid (lactate) – reversible (pyruvate can be reformed when oxygen is present)
Plants/yeast: ethanol + carbon dioxide – irreversible
Anaerobic cell respiration uses in animals and bacteria
Animals: used to maximise muscle contraction power (energy capacity exceeds oxygen levels)
Bacteria: lactic acid can be used to modify milk proteins, making certain yogurts + cheese
Anaerobic cell respiration uses in yeast
Bread – CO2 causes dough to rise via leavening (ethanol evaporates during baking process)
Alcohol – Ethanol is the intoxicating agent (concs above ~14% damage the yeast)
Variables affecting the rate of cell respiration
Temp/pH alter functionality of respiratory enzymes.
Glucose/oxygen availability influence reaction rates.
Inhibitors prevent enzyme-substrate interactions (e.g. cyanide blocks electron transfer in the ETC)
Carbohydrates - What is the energy yield? Is anaerobic respiration possible?
1) 17 kJ/g. About half of lipids. Energy is released by oxidizing C and H, carbohy. mass is more than 50% O, which doesn’t yield energy.
2) Yes - glycolysis uses sugars as the substrate and generates some ATP w/out needing oxygen.
Lipids - What is the energy yield? Is anaerobic respiration possible?
1) 37 kJ/g. Nearly 90% of lipid mass is C and H.
2) No - The first stage of respiration is fatty acids → acetyl groups in matrix, then fed into Krebs cycle. This only happen when oxygen is available.
Respiration formula
C6H12O6 +6 O2→6 CO2+ 6 H2O
C6H12O6→2 C3H6O3
C6H12O6→2 C2H5 OH + CO2
