carbohydrate and lipid metabolism Flashcards
formation of enolate anions
formed from alpha beta systems, alpha carbon is slightly acidic so a strong base reacts with it to form enolates
formation of acetals and ketals
alcohol attacks ethers twice to form carbons with ether linkages under acidic conditions (AASPEN + extra activation)
what is an acetal
carbon with 2 ethers and one hydrogen
what is a ketal
carbon with 2 ethers and 2 hydrogens
formation of imines
addition of primary amines to carbonyl group of aldehyde/ketone followed by acid catalysed elimination of water
what is an aldol reaction
produces an enolate from an aldehyde or ketone which then attacks another carbonyl compound to form a beta-hydroxyl carbonyl compound
what is an elimination reaction
nucleophile attacks the hydrogen instead of the carbon to form an alkene
what are the two types of monosaccharides
aldoses and ketoses
what are the three common sugars
d-glucopyranose (all OH equatorial) , d-galactose (OH-4 axial, all others equatorial) , d-mannopyranose (OH-2 is axial, others equatorial)
define axial
above/below
define equatorial
away from the ring
what is a lipid
defined by a physical property rather than a common structural feature, natural and not very water soluble
hydrolysable lipid characteristics
tri-acyl glycerides
used for energy storage
contain alcohols and fatty acids
non-hydrolysable lipid characteristics
steroid hormones - bile acids etc
define metabolism
sum of all biochemical reactions
define catabolism
large biochemical molecules being broken into smaller ones
define anabolism
small biochemical molecules joined to larger ones
what is ATP used for
energy carrier within the cell, froduced by food catabolism
what is NAD (nicotinamide adenosine dinucleotides) used for
redox factor - enzyme catalysed reduction mechanism, H added across carbonyl to form alcohol
NAD structure
nicotinamide, ribose, adenine and ADP
FAD (flavin adenosine dinucleotide) structure
riboflavin, adenosine diphosphate
what is FAD used for
redox factor - reduction is enzyme catalysed, H added across carbonyl to form alcohol
AcetylCoA structure
2-aminoethanethiol, pantothenic acid and phosphorylated ADP
role of AcetylCoA
acyl carrier, HS group can form thioesters
steps in glucose metabolism
- digestion
- glycolysis - 2 pyruvate and 4 ATP
- pyruvate - acetylcoa
- citric acid cycle
- electron transport chain
products of the citric acid cycle
- 1 FADH
- 3 NADH
- 1 GTP
- 2 CO 2
what is the electron transport chain
a series of biochemical reactions that use electrons and hydrogen from NADH/FADH2 (from citric acid cycle) which are passed through carriers to pump H+ into the intermembrane space and then back into the matrix through ATP synthase
products of the electron transport chain
for each AcetylCoA: 10 ATP are formed
glycerol head of lipids metabolism
oxidised - catalysed by ATP and converted to pyruvate for citric acid cycle
fatty acid chains metabolism
- combined with CoA and dehydrogenated to FADH2
- hydrated to form 2nd alcohol,
- dehydrogenated to ketone to form NADH
- release of another CoA
- loop continues until all C2 groups broken down to produce acetylcoa which goes through citric acid cycle
anabolic reactions of acetylcoa
- lipogenesis
- cholesterol biosynthesis
- ketogenesis
lipogenesis
- fatty acid synthesis from acetylcoa
- acetyl acp + malonyl acp condensated
- Acetoacetyl ACP is hydrogenated using NADPH
- beta hydroxybutyryl ACP dehydrated
- crotonyl acp hydrogenated with nadph
- forms butyryl acp
ketogenesis
- 2 acetylcoa join - acetylacetylcoa
- forms 3-hydroxy-emethylglutayl (also used for cholesterol)
- this forms ketone bodies
metabolism of carbon portion of amino acids
- triaglycerols via fatty acid synth
- glucose via gluconeogenesis
- ATP via citric acid
- ketogenesis
metabolism of nitrogen portion of amino acids
- elimination
- biosynth of non-essential amino acids or other nitrogen compounds
deamination (Schiff base)
oxidation and hydrogenation of an amine to form imine
trans-amination
interchanging of amino group of an alpha amino acid with a keto group from an alpha-keto acid
excess amino acids
transferred to glutamate and converted to urea by glutamate dehydrogenase and the urea cycle
what is oxidative stress
generation of high levels of toxic oxidising molecules which cause tissue damage
how are reactive oxygen species usually neutralised
glutathione (GSH)
hyperglycaemia induced superoxide production
increased glucose through citric acid cycle, increasing NADH, increasing ETC.
problems with superoxide overproduction
increasing superoxide inhibits GADPH which diverts glycolysis metabolites to the 4 pathways of hyperglycaemic damage (polyol, hexosamine, PKA, AGE)
polyol hyperglycaemic damage pathway
increased glucose = increased aldose reductase = increased sorbitol = increased NADPH = reduced GSH = reduced protection
PKC hyperglycaemic damage pathway
excess DHAP converted to DAG that activates PKC which activates other proteins that use NADPH to produce superoxides
AGE (advanced glycation end-products) hyperglycaemic damage pathway
DHAP and GAP levels increase and degrade to methylglyoxal which reacts with lysine to form imines - can inactivate proteins
what is methylglyoxal
reactive electrophile which can alkylate amino groups on proteins and nucleic acids to disrupt their function
w is methylglyoxal detoxified
glyoxalase pathway - it is reduced to lactic acid by glutathione
