RESPIRATION Flashcards
Respiration
Process whereby energy stored in complex organic molecules is used to make ATP, organic molecule= contains carbon
Examples of uses of energy
Active transport- against concentration gradient
Secretion
Endocytosis
Anabolism- forming larger molecules from smaller, simpler molecules
ATP
Adenosine triphosphate Phosphorylated nucleotide -contains energy within bonds -phosphate group removed 30.6 kj/mol energy released -hydrolysis
Energy released from reactions
ATP + H2O –> ADP + Pi
ADP + H2O –> AMP + Pi 30.6 kj/mol ^^
AMP + H2O –> A + Pi 14.2
Why is energy released in small amounts
Prevents cell damage
Glycolysis
Cytoplasm
Overview- 1. glucose broken down to 2 molecules of pyruvate, 2. process common to aerobic + anaerobic respiration
1st stage of glycolysis
Phosphorylation of glucose (addition of phosphate on glucose)
ATP –> ADP + Pi
Hexose sugars + 2Pi –> hexose bisphosphate
Glucose cant leave cell as changed shape
2nd stage of glycolysis
Split phosphorylated glucose (unstable)
Hexose bisphosphate –> trios phosphate (3C)
Dehydrogenase enzymes remove H from TP, forms rNAD
3rd stage of glycolysis
Oxidation of TP to form pyruvate
2x Pi from TP –> 2x ATP
Removal of Pi –> 2x pyruvate
ADP + Pi –> ATP (substrate level phosphorylation)
End products glycolysis
2 ATP
2 rNAD
2 pyruvate
Link reaction
Mitochondrial matrix
Overview- pyruvate actively transported into mitochondrion to acetyl coenzyme A
No ATP produced
Cycle happens twice for every glucose molecule entering glycolysis
Link: Decarboxylation
Removal of carboxyl group
CO2 diffuses out of cell
Link: Dehydrogenase
Removal of hydrogen
Reduce coenzyme NAD
Coenzyme A + acetate –>
Acetyl coenzyme A
End products of link reaction
2 rNAD
2 CO2
2 acetyl coenzyme A
Krebs cycle
Mitochondria matrix
Overview- 6C –> 4c compound using enzymes
Stages of Krebs cycle
- acetyl release from acetyl CoA from link
- acetyl (2C) combines with oxaloacetate (4C) forming citrate (6C)
-citrate decarboxylated + dehydrogenated= CO2 + rNAD + 5C compound - 5C compound decarboxylated + dehydrogenated = CO2 + rNAD + 4C
- 4C combines with CoA
ADP + Pi –> ATP (substate LP)
4C dehydrogenated= diff 4C + rFAD - new 4C= dehydrogenated –> oxaloacetate (1st molecule) + rNAD
End products of Krebs
2 ATP
4 CO2
6 rNAD
2 rFAD
What are coenzymes
Non-protein compounds
Importance of coenzymes: Hydrogen carriers (NAD + FAD)
Accepts hydrogen atoms from dehydrogenase enzymes (=reduced)
Carry hydrogen to electron transport system for oxidative phosphorylation
Importance of coenzymes: Coenzyme A
Carries acetate group made from pyruvate (from Krebs) to form acetyl coenzyme A
Oxidative phosphorylation (location + overview)
Inner membrane of mitochondrial matrix
Overview- formation of ATP (+ Pi to ADP), presence of oxygen= final electron acceptor
Oxidative phosphorylation process
- NAD reduced to form 2H, release 2e-
- 2e- enters e- transport chain (protein carrier)
- protein carriers in mitochondrial matrix
- 2H diffuse through protein carriers into inner membrane space
- chemiosmosis- H+ ions diffuses through channel proteins (ATP synthase), down proton gradient
- Pi + ADP –> ATP
- oxygen final e- acceptor
Electron transport chain
H atoms removed from rNAD + rFAD by enzymes
rNAD + rFAD oxidised (donate H atom, recycled)
H atoms split into H + e-
- e- carrier accepts e-= reduced
-protons enter matrix
E- passed along e- carrier chain on inner mitochondrial matrix –> oxygen (final e- acceptor)
Chemiosmosis
- e- passed along protein carriers, energy released pumps protons from matrix to inner membrane
- proton gradient form
- increased concentration of protons in inner membrane space
- protons diffuse through protein channels (ATP synthase)
- flow of electrons= chemiosmosis
Oxidative phosphorylation
Protons flow through ATP synthase Joins ADP + Pi --> ATP End of e- transport chain, e- combines with H+ ions + oxygen to form water Oxygen= final acceptor Oxygen reduced to water 2H+ + 2e- + 1/2 O2 --> H2O
Summary of ATP losses + gains
Theoretical + real values
rNAD generates 3 ATP
rFAD generates 2 ATP
rNAD –> 2.5 ATP
rFAD –> 1.5 ATP
Factors to explain losses + gains of ATP
Some protons leak across membrane of mitochondria
Some ATP used to actively transport pyruvate into mitochondria
Some ATP used to transport rNAD made in cytoplasm during glycolysis
Anaerobic respiration
No oxygen to act as final e- acceptor
= no oxidative phosphorylation, link or Krebs (rNAD + rFAD cant be regenerated)
- only glycolysis
- cytoplasm
- mitochondria not used
Alcoholic fermentation
Absence of oxygen, pyruvate decarboxylated forming CO2 + ethanol (pyruvate decarboxylase)
Ethanal accepts H atoms from rNAD (-2H) –> NAD as ethanal reduced to ethanol
Ethanal dehydrogenase
Regeneration of NAD= glycolysis
NET 2 ATP from glycolysis (substate level phosphorylation)
NAD doesn’t enter mitochondria for oxidative phosphorylation
Effect of lowering pH
Muscle fatigue
Enzymes affected by pH
Process of lactate fermentation
- vigorous exercise- not enough oxygen for aerobic respiration
- pyruvate (from glycolysis) accepts H-atoms from rNAD + is converted to lactate (3C)- lactate dehydrogenase
- lactate diffuses into bloodstream to liver
- after exercise- lactate oxidised in liver back to pyruvate- respired aerobically to CO2 + H2O in link + Krebs
- net 2 ARP produced in glycolysis- substrate level phosphorylation
Oxygen debt
Oxygen needed to oxidise lactate
-deep breathing after exercise
Lactate –> pyruvate or glucose in living using oxygen
Lactate= fall in pH causing proteins to denature
