c1.3 - respiration Flashcards
respiration
set of metabolic reactions that take place in organisms + break down respiratory substances
e.g: glucose into smaller inorganic molecules, like water + CO2
linked to synthesis of ATP
why respiration described as catabolic process
complex molecules (respiratory substrates) broken down into smaller, simpler molecules
why organisms need to respire
produces chemical energy in ATP for variety of processes
e.g: active transport, metabolic reactions, muscle contraction
releases heat energy for thermoregulation
aerobic respiration
takes place in presence of O2 + produced CO2, water + ATP
C6H12O6 + 6O2 -> 6CO2 + 6H2O
four main stages of aerobic respiration + where they occur
glycolysis - cytosol
link reaction - mitochondrial matrix
krebs cycle - mitochondrial matrix
electron transport chain - inner mitochondrial matrix
stages of glycolysis
- glucose (hexose sugar) phophorylated to hexose bisphosphate by 2x ATP
- hexose bisphosphate splits into 2x triose phosphate (TP)
- 2 molecules of TP oxidised to 2x pyruvate
net gain of 2x reduced NAD (NADH) + 2x ATP per glucose
equation to summarise glycolysis
glucose + 2NAD + 2ADP + 2Pi -> 2 pyruvate + 2NADH + heat
how does pyruvate from glycolysis enter mitochondria
active transport
link reaction
- oxidative decarboxylation + dehydrogenation of pyruvate to form acetate
net gain of CO2 + 2x reduced NAD - acetate combines w/ coenzyme A (CoA) to form acetyl coenzyme A
equation to summarise link reaction
pyruvate + NAD + CoA -> acetyl CoA + reduced NAD + CO2
krebs cycle
series of oxidation-reduction reaction in matrix of mitochondria in which acetyl CoA is oxidised generating reduced NAD, reduced FAD, ATP + CO2
function of krebs cycle
means of releasing energy from carbon bonds to provide ATP, reduced NAD + reduced FAD (with release of CO2)
how many NAD + FAD does complete oxidation of 1 glucose molecule yield
10 reduced NAD
2 reduced FAD
electron transport chain
series of electron carrier proteins that transfer electrons in a chain of oxidation-reduction reaction, releasing energy
what happens in ETC
electrons released from reduced NAD + FAD undergo successive redox reactions
energy released is coupled to maintaining proton gradient or is released as heat
oxygen acts as final electron acceptor
role of reduced NAD + FAD in ETC
source of electrons + protons
how chemiosmosis produces ATP during aerobic respiration
protons flow down conc gradient from intermembrane space into mitochondrial matrix via ATP synthase
ATP synthase phophorylates ADP to form ATP as protons flow through it
role of O2 in ETC
final electron acceptor
O2 + 4H+ + 4e- -> 2H2O
how many ATP produced per oxidised NAD in aerobic respiration
3 ATP
how many ATP produced per oxidised FAD in aerobic respiration
2 ATP
anaerobic respiration
takes place in absence of oxygen
less ATP formed than aerobic
product of anaerobic respiration in animals
lactic acid
anaerobic respiration in animals
only glycolysis continues
reduced NAD (product of glycolysis) transfers H to pyruvate, forming lactic acid + regeneration NAD
catalysed by enzyme lactate dehydrogenase
products of anaerobic respiration in plants + microorganisms
ethanol + CO2
anaerobic respiration in plants + microorganisms
only glycolysis continues
pyruvate decarboxylated to form ethanal
ethanal accepts H for reduced NAD making ethanol
NAD regenerated for glycolysis
yield of ATP in aerobic v anaerobic respiration
aerobic - 30 to 32 ATP
anaerobic - 2 ATP
why is max yield of ATP in aerobic respiration never reached
ATP lost due to leaky membranes
energy required to move pyruvate + ADP into mitochondrial matrix
2 types of molecules that can be used as alternative respiratory substrates
(amino acids from) proteins
(glycerol + fatty acids from) lipids
how lipids used in respiration
hydrolysed to glycerol + fatty acids
glycerol converted to a 3C sugar + enter glycolysis
fatty acids broken down into 2C acetate fragments which enter krebs cycle as acetyl CoA
how proteins used in respiration
hydrolysed to amino acids
amino acid deaminated in liver forming keto acids + ammonia
keto acids enter glycolysis + krebs cycle
