Energy in a diet
SACCHARIDES / LIPIDS / PROTEINS
60 : 30 : 10
17 kJ/g 37 kJ/g 17 kJ/g
4 kCal/g 9 kCal/g 4 kCal/g
-CH(OH)- -CH2- -CH(NH2)-
CO2, H2O CO2, H2O CO2, H2O, NH3
Oxidation of a hydrocarbon skeleton- individual steps
alkane
alkene
alcohol
aldehyde
carboxylic acid
CO2 + H2O
CH3-CH3
CH2=CH2
CH3-CH2-OH
CH3-CHO
CH3-COOH
2 CO2 + 2 H2O
Saccharides in a diet
• starch predominates (75% of a dry mass of cereals, 65% in potatoes)
� 20% amylose (non-branched, spiral, 200 – 300 glc)
� 80% amylopectine (up to 1000 glc, branched at every 20-25 glucose unit)
• glycogen in meat (branched at every 8-10 glc unit)
• „sugar“ = disaccharide sucrose (Glc-Fru)
• milk sugar = disaccharide lactose (Gal-Glc)
• fiber = indigestible polysaccharides (cellulose, pectin)
DISACCHARIDES
SALAME
• SAcharose (= sucrose)
• LActose
• MaltosE
saccharose has not reducing properties
The figure has been adopted from J.Koolman, K.H.Röhm / Color Atlas of Biochemistry, 2nd edition, Thieme 2005
α-Glc(1→4)Glc β-Gal(1→4)Glc α-Glc(1→2)β- Fru
free anomeric (= hemiacetal) hydroxyl ⇒ reducing properties
POLYSACCHARIDES
• homopolysaccharidesstarch, glycogen, cellulose, inuline
• heteropolysaccharidesglycoproteins, proteoglycans
• branched
• unbranched
• storagestarch, glycogen,inuline
• structuralcellulose, proteoglycans
amylose (maltose)n amylopectine
STARCH (Glc)n
The figures have been adopted from Harper´s Biochemistry
α(1→4) glycosidic bonds α(1→4) glycosidic bonds
α(1→6) glycosidic bonds
GLYCOGEN (Glc)n
The figure is found at http://students.ou.edu/R/Ben.A.Rodriguez-1/glycogen.gif (October 2007)
nonreducing end reducing end
OH
CELLULOSE
ββββ-Glc(1→4)Glc
The figures are found at http://web.chemistry.gatech.edu/~williams/bCourse_Information/6521/carbo/glu/cellulose_int_2.jpghttp://www.kjemi.uio.no/14_skole/modul/Evina_organisk/Org_K3fig14_cellulose.JPG (October 2007)
Monosaccharides
• form phosphoric acid esters („phosphates“) in cells
• their carbon skeleton is partially oxidized : -CH(OH)-(less energy produced when it is oxidized in metabolism)
• energy source – Glc, Fru, Gal / energy storage - glycogen
• conversion to other saccharides(components of nucleotides, glycoproteins)or saccharide derivatives(aminosugars, uronic acids – in proteoglycans)
• conversion to fat (energy storage)
• important intermediates of their metabolism:� glyceraldehyde-3-phosphate� dihydroxyacetone phosphate (DHAP)� 1,3-bisphosphoglycerate
anhydride bond
Monosaccharides
glucose
� energy production (glycolysis)
� energy storage (glycogen or conversion to fat)
� conversion to other saccharides, e.g. ribose (pentose phosphate cycle)
� conversion to glucuronic acid (oxidation of glucose)
fructose
� conversion to glucose� energy production (glycolysis)
� energy storage (conversion to fat)
galactose
� conversion to glucose and lactose� synthesis of glycoproteins and proteoglycans
ribose
� nucleotide synthesis
http://www.medicographia.com/2010/01/advanced-glycation-end-products-ages-and-their-receptors-rages-in-diabetic-vascular-disease/
Glycated hemoglobin
fructose
Adopted from Trends in Biochemical Sciences, reference edition, volume 6, page 209.Elsevier/North-Holland Biomedical Press, 1981.
Adopted from the texbook by Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
sources of blood glucose after a meal and during fasting
and starvation
Content of liver glycogen during a day
Adopted from the textbook by Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
18:3 <0,5%18:3 <0,5%18:3 10%18:3 1%18:3 1%18:3 1,5%PUFA
ωωωω-3
18:2 1,5%18:2 63%18:2 20%18:2 8%18:2 9%18:2 2,5%PUFA
ωωωω-6
18:1 7%18:1 21%18:1 59%18:1 72%18:1 42%18:1 25%MUFA
12:0 45%
14:0 17%
16:0 9%
16:0 6%
18:0 4%
16:0 4%
18:0 1,5%
16:0 11%
18:0 2,5%
14:0 1%16:0 24%18:0 14%
14:0 10%16:0 26%18:0 12%
SFA
coco-nut
oilsunflower
oilrapeseed
oilolive
oillardbutter
Composition of sample fats
adopted from http://www.internimedicina.cz/pdfs/int/2009/12/05.pdf
Free fatty acids(FFA)
Esterified fatty acids
= triacylglycerol(TAG)
or triglyceride
ωωωω-9
ωωωω-6
ωωωω-3
oleic acid
linoleic acid
alpha - linolenic acid
gamma - linolenic acid
eicosapentenoic acid (EPA)
arachidonic acid
docosahexenoic acid (DHA)
18
18
9
9 12
18
18
The figure is found at http://courses.cm.utexas.edu/archive/Spring2002/CH339K/Robertus/overheads-2/ch11_cholesterol.jpg (Jan 2007)
Fatty acids (FA)
• saturated fat contains saturated FA(more energy: -CH2-CH2-)
• monounsaturated fat / polyunsaturated fat(less energy – partially oxidized: -CH=CH-)
• even number of carbons (synthesized from C-2 precursor)
• separated cis double bonds: -CH=CH-CH2-CH=CH-
• short chain fatty acids (SCFA): less than 6 carbons
• medium chain fatty acids (MCFA): 6 – 12 carbons
• long chain fatty acids (LCFA): more than 12 carbons
• very long chain fatty acids (VLCFA): more than 22 carbons
The figure was adopted from: J.Koolman, K.H.Röhm / Color Atlas of Biochemistry, 2nd edition, Thieme 2005
Fat in a diet
fat (triacylglycerols) and phospholipids contain:
• saturated fatty acids (SFA)
• monounsaturated fatty acids (MUFA)
• polyunsaturated fatty acids (PUFA) = essential FA
� omega-6 (ω-6, n-6)
� omega-3 (ω-3, n-3) - in fish oil: EPA, DHA
• trans fatty acids (TFA)
cholesterol
• found in animal fat
Fatty acids (FA)
• in cells they are bound to Coenzyme A → „acyl-CoA“
binding place
• more reduced carbon skeletonthan saccharides: -CH2-
• FA are components of triacylglycerols, phospholipids, cholesterol esters (= hydrolyzable lipids)
• FA are used for energy production (β-oxidation) or
energy storage in a form of triacylglycerols = neutral fat
• FA can be converted to ketone bodies, eicosanoids
The figure was accepted from the book: Grundy, S.M.: Atlas of lipid disorders, unit 1. Gower Medical Publishing, New York, 1990.
blood lipids
Proteins in a diet
• animal proteins (all amino acids)
• plant proteins (less common: Met, Lys, Trp)
• essential amino acids:
� branched chain - Val, Leu, Ile
� aromatic - Phe, Trp
� basic - His, Arg, Lys
� secondary alcohol group containing - Thr
� sulfide group containing - Met
Amino acids (AA)• contain other elements: nitrogen (all AA), sulfur (Cys, Met)
� when AA are degraded ammonia NH3 (and H2SO4) are produced
� NH3 is toxic ⇒ it must be converted to urea→ excreted with urine
• AA are primarily used for proteosynthesis
• other use:
� synthesis of N-containing compounds (heme, nucleotides, signal molecules – hormones, neurotransmitters)
� direct energy production (Krebs cycle) or indirec energy production during fasting: after conversion to glucose(gluconeogenesis)
� energy storage after conversion to fat
• the use of AA as energy substrates consumes energybecause ammonia must be detoxified !