carbohydrate metabolism glycolysis and the TCA Flashcards
what is an anabolic pathway
pathway concerned with the synthesis of cellular components
makes bonds
what is a catabolic pathway
pathway that is involved with the degradation of cellular components
exergonic process which breaks bonds
increases entropy
what is oxidation
loss of electrons
gain of oxygen
loss of hydrogen
what is reduction
gain of electrons
loss of oxygen
gain of hydrogen
where are the acid anhydride bonds located in ATP
they are located between the phosphate-oxygen-phosphate in the triphosphate molecule of ATP
where are the phosphate ester bonds located in the ATP molecule
between the ribose oxygen and the phosphate of the triphosphate group
why is ATP the currency of energy
due to its unstable energy rich nature of the acid anhydride bond
why are the acid anhydride bonds full of energy
due to the charge repulsion because of the adjacent phosphate groups
and because of the resonance of phosphate ions
which molecules have energy
sugar
starch
protein
what is oxidation according to biochemical definitions
we can remove an electron and protons(H+ ions)
what is TCA
tricarboxylic acid cycle/krebs cycle/citric acid cycle
what is the most common fuel in mammals
glucose
what is the only fuel the brain uses
glucose
describe the structure of glucose
it is a 6 carbon sugar that has a tendency to remain in ring formation
what occurs in glycolysis
glucose broken into 2 molecules of pyruvate
what products are produced when glucose is fermented
ethanol
C02
lactate
what products are produced when we have complete oxidation of glucose
6h20 and 2c02
what are microbes called when they can survive in no oxygen
facultative anaerobes
what do animals display
anerobiosis
what is anaerobiosis
tolerate small amounts of anaerobic activity
where does glycolysis occur
in the cytosol
what are the two phases of glycolysis
the investment phase and the return phase
what occurs in the investment phase of glycolysis
we use 2 molecules of ATP to produce fructose 1,6 bisphosphate
what occurs in the return phase of glycolysis
we get some ATP BACK and pyruvate is produced
how does glucose enter the cell
via transport proteins GLUT4
what is the first stage of glycolysis
glucose enters the cell
glucose reacts with ATP- phosphorylated withe the enzyme hexokinase to produce glucose-6 phosphate
why can glucose 6 phosphate not get out of the cell
because it is charged
why can glucose 6 phosphate be broken down easily
due to the instability of the molecule due to the negative charge
what conditions does hexokinase require
magnesium- type 2 and crowns disease can lack this
which enzyme catalyses the isomerisation of G6P
phosphoglucose isomerase
what is isomerism
the same empirical formula but a change in the shape
what are the stages of isomerism of g6p
- first the carbon 6 ring is opened- has an aldove
- catalyse isomerisation occurs and the aldose is converted to a ketose
- formation of the cyclic fructose 6 phosphate
what then happens to fructose 6 phosphate
- it reacts with ATP and phosphofructokinase(PFK) to produce fructose1,6 bisphosphate, ADP, H+
- this reacts with aldolase to produce glyceraldehyde 3 phosphate (gap) and dihydroxyacetone phosphate(DHAP)
what is the rate determining step for glycolysis
the phosphorylation of fructose 6 phosphate to fructose 1,6 phosphate by phosphofructokinase
what are the two products aldolase produces
GAP AND DHAP
how do we convert dihydroxyacetone phosphate into glyceraldehyde 3 phosphate
by the enzyme triose phosphate isomerase which forms aldose and then forms glyceraldehyde 3 phosphate
what is the ATP consuming summary
- hexokinase
- phosphoglucose isomerase
- phosphofructosekinase
- aldose
- triose phosphate isomerase
what does the second stage of glycolysis start with
glyceraldehyde 3 phosphate +NAD + pi and the enzyme glyceraldehyde 3 phosphate dehydrogenase to form 1,3bisphosphogltcerate + NADH+H+
what molecule has a high phosphorylation transfer potential
1,3bisphosphogltcerate
what happens to the 1,3 bisphosphogltcerate
reacts with ADP+H+ and phosphoglycerate kinase to from 3 phosphoglycerate and ATP
what then happens to 3 phosphoglycerate
it reacts with phosphoglycerate mutate to form 2 phosphoglycerate
what does 2 phosphoglycerate react with
endolase and a hydrolysis reaction to form ATP and pyruvate
what can the reversible reaction of pyruvate form
phophophenolpyruvate (PEP) +ADP+H+
which molecule must be regernated from the metabolism of pyruvate
NAD
at the end of glycolysis what do we have
used 2 ATP molecules
created 4 ATP molecules THEREFORE net gain of 2ATP, 2PYRUVATE
how can NAD be regenerated
- pyruvate to lactate
- pyruvate to acetylCoA
- pyruvate to acetaldehyde-> ethanol which oxidises NADH
how does pyruvate become acetyl coenzyme A
by the enzyme pyruvate dehydrogenase
and through oxidative decarboxylation
where is acetylcoenzyme A found
in the matrix of the mitochondria
what is the main role of the krebs cycle
to harvest high energy electrons from carbon compounds
what is the first stage of the krebs cycle
citrate synthase
how is citrate synthesised in the cycle
acetylcoA(2C) enters and is condensed and reacts with oxaloacetate(4C) to form citrate COA and then the coA leaves the molecule to form citrate(6C)
what is the second stage of the krebs cycle
citrate first undergoes dehydration, then isomerisation to form cis citrate and then hydration again to form isocitrate. aconitase reacts in both steps
what is the third stage of the krebs cycle
isocitrate(6C) undergoes oxidative decarboxylation which forms alpha ketoglutarate(5C) with the help of the enzyme isocitrate dehydrogenase
ALSO RELEASES NADH
what is the rate determining step of the krebs cycle
the overall formation of a ketoglucarate
WHAT IS STAGE 4 OF THE KREBS CYCLE
oxidative decarboxylation from a ketoglutarate(5C) to succinylCOA(4C)
RELEASES NADH
what is step 5 of the krebs cycle
substrate level phosphorylation from Succinyl COA to succinate
this forms ATP with the help of the enzyme succinylCOA synthase
what is step 6 of the krebs cycle
dehydrogenation/oxidation from succinate(4C) to fumarate (4C)
releasing FADH2
what is step 7 of the krebs cycle
hydration of fumarate to malate by fumerase
what is step 8 of the krebs cycle
dehydrogenation/oxidation from malate to oxaloacetate with malate dehydrogenase
RELEASING NADPH
which step of the krebs cycle is irreversible
1,3,4
