C1.2 Cell Respiration Flashcards
(21 cards)
Aerobic Respiration
The process of breaking down nutrients and food in the presence of oxygen in order to produce energy (in the form of ATP) using enzymes and producing the byproducts CO2 and H2O.
Nutrients and Food
glucose, fatty acids, proteins [basically carbon-hydrogen containing organic molecules]
Energy in Cellular Respiration
- energy in cellular respiration is transferred in small quantities rather than one big release
- if energy was transferred in one big release, there would be a lot of energy lost as heat loss to the surroundings
- instead, energy is transferred into ATP in many small steps
- this minimizes heat loss and these small steps maximize energy storage of ATP
ATP (Adenosine triphosphate)
- produced during respiration
- directly fuels many biological reactions
- “universal energy currency”
ATP = suitable energy source
- contains chemical energy locked up in its structure (in the form of 3 phosphate bonds)
- energy can be released from ATP in small manageable quantities through hydrolysis of ATP to ADP - useful for energy requiring processes in the cell
- very reactive molecule, taking part in cell respiration and metabolism (lone pair of electrons in phosphate bonds)
- Small (easy to transport) can be moved easily through facilitated diffusion (polar and soluble)
- cannot simply move through cell membranes, keeping it trapped by cells (under control)
condensation
water is released, and energy is required to form ATP from ADP and P(ion)
hydrolysis
hydrolysis of ATP splits into ADP by removing one phophate group using water. Energy contained in the covalent bond is released.
Phosphorylation
- addition of phosphate group from ATP (which gets hydrolysed to ADP +P) with the help of kinase enzyme
- dephosphorylation = phosphatase
Phosphorylated intermediates
- In many metabolic reactions, ATP reacts with other metabolites with the help of enzymes in order to form phosphorylated intermediates
- this phophorylation makes them more reactive for the process in which they need to take part in
Sliding filament theory
1) Myosin heads are activated by the splitting of ATP (hydrolysis), causing change in position of heads.
2) Myosin heads are attracted to and attach to exposed binding sites of actin to form cross-bridges
3) As myosin forms cross bridges, ADP is released and the myosin bends due to loss of energy. The bonding is towards the center of the sarcomere and the actin is moved inwards. (powerstroke)
4) After powerstroke, myosin binds to ATP and this allows the detachment of the myosin heads from the actin attachment site. No binding sites exposed (relaxed state)
muscle relaxation
- muscle attached to bones through tendons (connective tissue)
- one bone acts as anchor (immovable origin)
- other bones moves as result of muscle contraction
- muscle can only contract or pull (not push) so muscles work in pairs
- antagonistic mucle action - a muscle pulls in one direction at a joint, and the other pulls in opposite direction to move bones
Anaerobic vs Aerobic
Anaerobic:
1) in cytoplasm
2) produces byproducts lactic acid or ethanol+CO2
3) Doesn’t undergo Krebs cycle
4) 2 mol of ATP
5) incomplete glycolysis (doesn’t use oxygen)
6) Only carbs can be used as substrates
Aerobic:
1) in mitochondria and cytoplasm
2) produced byproducts CO2 and water
3) Undergoes Krebs cycle
4) 32-36 ATP
5) complete glycolysis
6) carbs, proteins, and lipids can be used as substrates
Glycolysis
1) 1 ATP undergoes phosphorylation forms glucose-6-phosphate
2) 2nd ATP undergoes phosphorylate fructose 1,6 - bisphosphate
3) Splits into 2 triose phosphate molecules
4) 2 P added to form 2 triose 1,3-bisphosphate molecules
5) 1st two ADP to ATP forms 2 glycerate 3-phosphate
6) 2nd two ADP to ATP form 2 pyruvate
Net:
2 ATP converted to ADP
4 ADP converted to 4 ATP
2 NAD+ converted to 2NADH+2H
4-2=2 ATP net
Link Reaction
After glycolysis, pyruvate enter mitochondrial matrix through active transport for link reaction
1) Decarboxylation of pyruvate to acetate (2CO2 produced, 1 per pyruvate)
2) Binding of enzyme CoA to acetate forms acetyl coA
3) Oxidation of acetate
4) Reduction of NAD+ to NADH +H
Net:
2 acetyl CoA
2 CO2
2 NADH
Krebs cycle
1) Acetyl CoA (2 carbon) combines with oxaloacetate (4 carbon) to form 6 carbon citrate
2) Citrate undergoes oxidation and decarboxylation releasing 1 CO2 and 1 NADH, forming 5C molecule
3) 1 CO2 and 1 NADH released between 5C and 4C
4) After 4C, ADP converted to 1 ATP, FAD+ to FADH2 and NAD+ to NADH
Undergoes cycle two times because 2 acetyl CoA
Net:
- 4 CO2
- 2 ATP
- 2 FADH2
- 6 NADH
ETC
1) Offloading of electrons from NADH+H to the 1st ETC complex
2) offloading releases energy which is used for the active transport of 2 H+ ions from the matrix to the intermembrane space
3) 2 electrons move from complex 1 to 2, again releasing energy to transfer to H+ ions
4) Two electrons move from complex 2 to 3, releasing energy for two more H+ ions
5) Finally, electrons from complex 3 move to final acceptor (oxygen) and reduces half molecule of oxygen. (2 H+ ions transferred when reduced).
It takes two cycles to fully reduce O2 molecule to H2O
Chemiosmosis
- While electrons move down ETC, energy is released in small amounts and used to pump protons out of the matrix and into the intermembrane space
- this creates a proton gradient (high conc of protons in intermembrane space than matrix)
- protons move down gradient through facilitated diffusion using enzyme ATP synthase
- as protons move passively down gradient, ATP synthase harnesses this energy allowing the phosphorylation of ADP to form ATP.
ATP synthase
complex of integral proteins located in mitochondrial inner membrane
catalyzes the synthesis of ATP from ADP and phosphate, driven by flow of protons.
Anaerobic respiration uses
- short rapid bursts of energy
- when oxygen supply runs out in respiring cells
- in oxygen deficient environments (waterlogged soil)
- variety of fermented foods (yoghurt, bread, cheese)
Anaerobic respiration power contraction
- ATP needs to be supplied at a faster rate to maximize power contractions for exercises that demand ATP at a faster rate
- lactic acid accumulates in muscle tissue
- this accumulation can affect pH in muscle tissue inhibition myosin-actin interactions and prevent further muscle contraction
Anaerobic process
Pyruvate releases two CO2, 2 ethanal, alcohol dehydrogenase (2 NADH oxidised to 2 NAD), 2 ethanol
Pyruvate, lactate dehydrogenase (2 NAD oxidised to 2 NADH), 2 lactate
