metabolic pathways and ATP production Flashcards
glucose metabolism: explain the metabolism of glucose during glycolysis and gluconeogenesis, recall the key reactions in both pathways, and distinguish between the aerobic and anaerobic metabolism of glucose
where does glycolysis occur
cytoplasm
is glycolysis aerobic or anaerobic
anaerobic
give the basic reaction of glycolysis, including ATP and NADH
1x6C glucose → 2x3C pyruvate (+2ATP, 2NADH)
what is the production of ATP an example of
substrate-level phosphorylation: ATP production by transfer of high energy PO4 3- group from intermediate substrate to ADP
first stage of glycolysis and significance
glucose → glucose-6-phosphate + H+ (irreversible; hexokinase (glucokinase in liver); ATP → ADP)
second stage of glycolysis
isomerise glucose-6-phosphate to fructose-6-phosphate
third stage of glycolysis and significance of product
fructose-6-phosphate → fructose-1,6-bisphosphate (highly symmetrical; phosphofructokinase; ATP → ADP)
in molecular nomenclature, what is the difference between “bi” and “di”
“bi” is not joined and “di”is joined
fourth and fifth stages of glycolysis
ring opens to form 2x3C; isomerisation to form 2 glyceraldehyde-3-phosphate molecules
sixth stage of glycolysis
glyceraldehyde-3-phosphate → 1,3-bisphosphoglycerate (glyceraldehyde-3-phosphate dehydrogenase; NAD+ + Pi → NADH)
seventh stage of glycolysis
1,3-bisphosphoglycerate → 3-phosphoglycerate (phosphoglycerate kinase; ADP → ATP)
eighth stage of glycolysis
isomerisation of 3-phosphoglycerate to 2-phosphoglycerate (phosphoglycerate mutase)
ninth stage of glycolysis
2-phosphoglycerate → phosphoenolpyruvate + H2O (enolase dehydration)
tenth stage of glycolysis
phosphoenolpyruvate → pyruvate (pyruvate kinase; ADP → ATP)
what can glucose-6-phosphate be stored as
glycogen or pentose phosphates used for nucleotides
what can glycogen be synthesised from
UDP-glucose
how are sugars stored
glycogen, fatty acids and cholesterol
when are ketone bodies used
when the bodt is fasting (used by brain as cannot metabolise fatty acids)
diagram showing generation of molecules from different glycolysis and TCA intermediates
diagram form metabolism 9
when does gluconeogenesis occur and what does it prevent
when the body is fasting or intense exercise to prevent low [glucose] which could lead to hypoglycaemic coma
short term fasting
break down glycogen, release fatty acids from adipose, acetyl CoA converted to ketone bodies (used in muscle to produce glucose)
long term (12-18 hours) fasting
supplies exhausted
define gluconeogenesis
produces glucose from non-carbohydrate sources (lactate, amino acids, glycerol)
is gluconeogenesis the reversal of glycolysis
no - requires different enzymes
does gluconeogenesis require ATP
yes
where does gluconeogenesis occur
liver
diagram to show gluconeogenesis stages vs glycolysis
diagram from metabolism 9
what is the common starting point in gluconeogenesis
oxaloacetate
net loss of gluconeogenesis
6 ATP
first stage of gluconeogenesis
pyruvate → oxaloacetate (pyruvate carboxylase) in mitochondria
second stage of gluconeogenesis
oxaloacetate → phosphoenolpyruvate (phosphoenolpyruvate carboxykinase) in cytosol; limiting stage
third stage of gluconeogenesis
phosphoenolpyruvate → G3P → fructose-1,6-bisphosphate
fourth stage of gluconeogenesis
fructose-1,6-bisphosphate → fructose-6-phosphate (fructose-1,6-bisphosphatase) in cytosol
fifth stage of gluconeogenesis
fructose-6-phosphate → glucose-6-phosphate
sixth stage of gluconeogenesis
glucose-6-phosphate → glucose (glucose-6-phosphatase) in cytosol
sources of pyruvate
lactate (via LDH) and amino acids
source of oxaloacetate
ketogenic amino acids
sources of G3P
phosphoenolpyruvate, glycerol → DHAP
what happens to ATP and glucose demand in aerobic respiration
increase
pathways of aerobic metabolism
glucose secreted by liver into blood; muscle glycolysis increases (ATP production increases), gluconeogenesis increases (when ATP demand greater than supply), fatty acids increase (more available for B-oxidation)
what protein channels are required for cation balance in aerobic metabolism
Ca2+ATPase and Na+K+ATPase
aerobic pathways diagram
diagram from metabolism 9
when is anaerobic respiration required
when ATP demand is greater than oxidative phosphorylation supply and transport cannot keep up with glucose demand
pathways of anaerobic metabolism
muscle glycogen breakdown increases; glycolysis rate increases fo pyruvate accumulates and is stored as lactate in muscles; liver uses lactate to form pyruvate via LDH (gluconeogenesis) to be converted to glucose, preventing acidosis
anaerobic pathway diagram
diagram from metabolism 9
3 fates of pyruvate
alcoholic fermentation, lactate, generation of acetyl CoA
alcoholic fermentation
ethanal → ethanol by decarboxylases; produces NAD+ so glycolysis can continue
lactate production
pyruvate ⇌ lactate via lactate dehydrogenase (LDH), produces NAD+ so glycolysis can continue
creatine phosphate metabolism
creatine phosphate ⇌ creatine + ATP by creatine kinase
high levels of LDH or creatine kinase in plasma
tissue and muscle trauma, myocardial infarction
