respiration Flashcards
what are the four key stages of aerobic respiration
-glycolysis
-link reaction
-Krebs cycle
-oxidative phosphorylation
what is ATP
nucleotide derivative
-composed of the base adenosine, pentose sugar, 3 phosphate groups
where does glycolysis occur
cytoplasm
glycolysis
first stage of aerobic and anaerobic respiration, however it is an anaerobic process (doesn’t require any energy/oxygen).
glycolysis involves 3 steps:
1. phosphorylating glucose to glucose phosphate, using ATP
2. glucose phosphate forms two molecules of triose phosphate
3. oxidation of triose phosphate to produce pyruvate. this produces two ATP molecules each, as well as reducing NAD into reduced NAD.
what are the products of glycolysis
2x pyruvate
net gain of 2 ATP
2x reduced NAD
where does the link reaction take place and why
mitochondrial matrix
-contains specific enzymes to catalyse steps of the reaction and contains molecules of NAD
link reaction
Glycolysis supplies pyruvate. Both molecules of pyruvate enter into the mitochondrial matrix via active transport.
Pyruvate is decarboxylated, CO2 is released.
Pyruvate is oxidised to acetate. The enzyme pyruvate dehydrogenase oxidises pyruvate, removing an H+ and forming acetate. NAD is present to take up the released hydrogen, forming reduced NAD.
Acetate combines with coenzyme A (CoA) making a molecule called acetyl-coenzyme A (acetyl-CoA). Acetyl-CoA will transport acetate to the Krebs cycle
what are the products of the link reaction
occurs twice for every glucose molecule, so:
-2x acetyl CoA
-2 carbon dioxide released
-2 reduced NAD
where does the Krebs cycle take place
mitochondrial matrix
krebs cycle
-acetylcoenzyme A (2C) reacts with a 4C molecule, releasing coenzyme A and producing a 6C molecule that enters the krebs cycle
-in a series of redox reactions, the krebs cycle generates reduced coenzymes (reduced NAD and reduced FAD) and ATP by substrate-level phosphorylation, a carbon dioxide is also lost.
what are the products of the krebs cycle
kreb cycle turns two times per molecule of glucose, therefore per molecule of glucose:
-2 ATP molecules
-6 reduced NAD molecules
-2 reduced FAD molecules
-4 carbon dioxide molecules
what happens if there is an absence of oxygen in Krebs and link
all FAD and NAD will be reduced so none will be available to take up the protons produced during Krebs, so enzymes will stop working
where does oxidative phosphorylation take place
inner mitochondrial membrane
oxidative phosphorylation
the hydrogen atoms produced during glycolysis and the Krebs cycle combine with the coenzymes NAD + FAD
the reduced NAD + FAD donate the electrons of the hydrogen atoms they are carrying to the first molecule in the ETC
the electrons pass along a chain of electron transfer carrier molecules in a series of oxidation-reduction reactions. as the electrons flow along the chain, the energy they release causes the active transport of protons across the inner mitochondrial membrane and into the inter-membranal space
the protons accumulate in the inter-membranal space before they diffuse back into the mitochondrial matrix through ATP synthase channels (produces a Pi to catalyse ADP to produce ATP) embedded in the inner mitochondrial membrane
at the end of the chain the electrons combine with these protons and oxygen to form water
-oxygen is therefore the final acceptor of electrons in the ETC
what are the products of oxidative phosphorylation
many molecules of ATP and the production of water from oxygen
why is oxygen important in aerobic respiration
oxygen acts as the final electron acceptor. Without oxygen the electron transport chain cannot continue as the electrons have nowhere to go. without oxygen accepting the electrons (and hydrogens) the reduced coenzymes NADH and FADH2 cannot be oxidised to regenerate NAD and FAD, so they can’t be used in further hydrogen transport.
where does anaerobic respiration take place
cytoplasm of the cell only
the pyruvate produced in glycolysis is reduced to form what in plants and microbes
ethanol and carbon dioxide
-by gaining the hydrogen from the reduced NAD
the pyruvate produced in glycolysis is reduced to what in animals
lactate
-by gaining the hydrogen from the reduced NAD
in anaerobic respiration, what happens once the hydrogen from reduced NAD has been gained
NAD becomes oxidised so that it can be reused in glycolysis and ensure more ATP is continued to be produced
efficiency of aerobic and anaerobic respiration
aerobic:
-total yield of ATP from one glucose molecule should be 38 molecules of ATP, approx 32% efficient
anaerobic:
-even less efficient, only 2 ATP molecules are produced from one molecule of glucose
