cellular respiration and energy
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- Created by: Millie Smith08
- Created on: 16-04-23 17:37
metabolism
the inter-conversion of biomolecules using chemical reactions
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catabolic (degradative) reactions
production of chemical energy (ATP) and ion gradients
production of mechanical energy (muscle contraction)
production of reducing equivalents
production of biosynthetic precursors
production of mechanical energy (muscle contraction)
production of reducing equivalents
production of biosynthetic precursors
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anabolic (biosynthetic) reactions
storage of energy
production of macromolecules and cellular structures
production of macromolecules and cellular structures
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respiration
balances ATP and ADP
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the Gibbs free energy of the reaction is described by the following equation
∆G= ∆G°+RT ln〖([products])/([reactants])〗
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∆G° is the Gibbs free energy under standard conditions;
the temp is fixed at ~ 310.15 K (~37 °C) (for biological reactions) and R is a constant (8.314 J.K^-1.mol^-1)
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biological rxns are in a state of flux
chemicals are interconverted through a successive series of steps
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many reactions are endothermic
require energy
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reactions are often driven by
ATP or pyrophosphate hydrolysis (removal of products)
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ATP to ADP + Pi=
30.5 kJ mol^-1
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ATP to AMP + PPi
45.6 kJ mol^-1
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hydrolysis of ATP can change the equilibrium constant of a coupled reaction by
around 10^8 per hydrolysed ATP molecule
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ATP
negative charges of the phosphate groups repel each other
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Keq for [ATP]/ [ADP][Pi]=
roughly around 500M^-1 in the cell
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higher energy compounds such as phosphoenolpyruvate (PEP)
can be used to make ATP
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higher energy compounds such as glucose
can be activated by ATP
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most rxns involving phosphate groups require
a Mg^2+ cofactor
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metabolism needs to balance
energy (ATP), reducing agents and the amounts of small molecules
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NAD+ and NADP+ can be reduced to NADH or NADPH
these can be used to produce energy or for chemical reduction
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NAD+
oxidised version
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NADPH
protonated version
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why is NADPH often used in biosynthetic pathways?
because it is a reducing agent
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carbohydrates
monosaccharides can be classified by number of carbon atoms:
- trioses have 3 carbon atoms (glycolysis intermediates)
- tetroses have four carbon atoms
- pentoses have 5 carbon atoms (ribose and deoxyribose)
- hexoses have 6 carbons (glucose and fructose)
- trioses have 3 carbon atoms (glycolysis intermediates)
- tetroses have four carbon atoms
- pentoses have 5 carbon atoms (ribose and deoxyribose)
- hexoses have 6 carbons (glucose and fructose)
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aldehyde on carbon 2
aldohexose
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ketone on carbon 2
ketohexose
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what is the only diff between ketohexoses and aldohexoses ?
the orientation of the -OH group
they are epimers of each other
they are epimers of each other
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hexoses
relationships between various aldohexoses can be seen with Fischer projections
8 possible aldohexoses but only D-Glucose and D-Galactose are very abundant
D-Mannose is less common, other are uncommon
D-Fructose is a ketohexose found in fruit
8 possible aldohexoses but only D-Glucose and D-Galactose are very abundant
D-Mannose is less common, other are uncommon
D-Fructose is a ketohexose found in fruit
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ring closure of sugars in water
addition of alcohol group to aldehyde to form a hemiacetal
new chiral centre formed, which can have one or two groups (down or up; a- or b-)
these new isomers are called anomers
ring closure is reversible, however most sugars are present in the ring clos
new chiral centre formed, which can have one or two groups (down or up; a- or b-)
these new isomers are called anomers
ring closure is reversible, however most sugars are present in the ring clos
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furanose rings
ketohexoses (fructose)
5-membered (furanose) rings
ring closed form is usually more stable except where destabilising groups are present (eg phosphate- these groups repel each other and lead to ring open form)
5-membered (furanose) rings
ring closed form is usually more stable except where destabilising groups are present (eg phosphate- these groups repel each other and lead to ring open form)
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glycogen
the main storage polysaccharide in mammals ('animal starch')
composed entirely of glucose units linked by a-1,4 and a-1,6 links
glycosidic bonds are acetals
highly branched polysaccharide with an average chain length of 8 to 12 monosaccharide units
composed entirely of glucose units linked by a-1,4 and a-1,6 links
glycosidic bonds are acetals
highly branched polysaccharide with an average chain length of 8 to 12 monosaccharide units
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glycolysis
transport of glucose into cells
transport of glucose into cells
homeostatic blood glucose level is around 4.8 mM
transport into cells is mediated by a number of glucose transporters (GLUTs)
GLUT transporters have diff affinities for glucose
GLUT 1 and 3 – Km for glucose around 1mM. Mediates basal glucose uptake and fo
transport into cells is mediated by a number of glucose transporters (GLUTs)
GLUT transporters have diff affinities for glucose
GLUT 1 and 3 – Km for glucose around 1mM. Mediates basal glucose uptake and fo
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glycolysis
literally means 'sugar splitting'
it is a central pathway within the cell
there are 10 steps starting from glucose, divided into 3 stages:
1/ activation and rearrangement (3 steps)
2/ splitting into phosphorylated C3 sugars (2 steps)
3/ conversion of phos
it is a central pathway within the cell
there are 10 steps starting from glucose, divided into 3 stages:
1/ activation and rearrangement (3 steps)
2/ splitting into phosphorylated C3 sugars (2 steps)
3/ conversion of phos
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glycolysis stage 1
activates sugars for metabolism (energy is put in as 2x ATP) and allows formation of 2 x C3 sugars
phosphorylation causes ring opening of sugar to keto form
PFK1 is the main enzyme controlling glycolysis energy is being put into the system
the first step
phosphorylation causes ring opening of sugar to keto form
PFK1 is the main enzyme controlling glycolysis energy is being put into the system
the first step
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glycolysis stage 2
start off with fructose 1,6-bisphosphate in its ring open form
retro-aldol reaction= reverse of an aldol rxn (undertaken by aldolase enzyme)
end up with glyceraldehyde phosphate
aldolase breaks fructose-1,6-bisphosphate into dihydroxyacetone phosphate and
retro-aldol reaction= reverse of an aldol rxn (undertaken by aldolase enzyme)
end up with glyceraldehyde phosphate
aldolase breaks fructose-1,6-bisphosphate into dihydroxyacetone phosphate and
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glycolysis stage 3
each step is repeated twice as two molecules of glyceraldehyde-3-phosphate are each converted to pyruvate
products for stage 3 are 2x NADH and 4x ATP
net yield for ATP is 2 as 2 molecules of ATP have been put into the reaction
the last step here is the ta
products for stage 3 are 2x NADH and 4x ATP
net yield for ATP is 2 as 2 molecules of ATP have been put into the reaction
the last step here is the ta
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anaerobic respiration
typically occurs in muscle during anaerobic exercise (when you're doing a lot of work)
run out out pyruvate and therefore ATP
in the absence of oxygen, pyruvate is reduced to R-lactate (D-lactate)
eventually reduction to R-lactate will acidify everything
run out out pyruvate and therefore ATP
in the absence of oxygen, pyruvate is reduced to R-lactate (D-lactate)
eventually reduction to R-lactate will acidify everything
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the Cori cycle
recylces R-lactate to glucose (can't go back from R-lactate to glucose easily as do not have correct enzymes)
lactate is transported from muscle to liver in blood
lactate dehydrogenase in liver converts R-lactate to pyruvate
pyruvate is converted to gluco
lactate is transported from muscle to liver in blood
lactate dehydrogenase in liver converts R-lactate to pyruvate
pyruvate is converted to gluco
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gluconeogenesis
occurs primarily in the liver
2 x pyruvates required for each glucose
ATP, CO2 and pyruvate make oxaloacetate (in mitochondria)
oxaloacetate is exported to the cytosol and converted into phosphoenolpyruvate
2 x ATP and 1 x NADH also required
additional en
2 x pyruvates required for each glucose
ATP, CO2 and pyruvate make oxaloacetate (in mitochondria)
oxaloacetate is exported to the cytosol and converted into phosphoenolpyruvate
2 x ATP and 1 x NADH also required
additional en
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Other cards in this set
Card 2
Front
catabolic (degradative) reactions
Back
production of chemical energy (ATP) and ion gradients
production of mechanical energy (muscle contraction)
production of reducing equivalents
production of biosynthetic precursors
production of mechanical energy (muscle contraction)
production of reducing equivalents
production of biosynthetic precursors
Card 3
Front
anabolic (biosynthetic) reactions
Back
Card 4
Front
respiration
Back
Card 5
Front
the Gibbs free energy of the reaction is described by the following equation
Back
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