2.3. Hidratos de carbono y lípidos

Hidratos de carbono Monosacáridos están interconectados por reacciones de condensación , a fin de formar disacáridos y polímeros de polisacáridos .

Hidratos de carbono Monosacáridos Glucosa Ribosa fructosa Disacáridos Sacarosa (Glucosa + Fructosa) Maltosa (glucosa+glucosa) Lactosa (glucosa+galactosa Polisacáridos Almidón (vegetal) Amilosa Amilopectina Glucógeno (almidón animal) Celulosa (paredcelular)

Polisacáridos - Celulosa Pared celular leña 1 micrometer 1 micrometer Figure :3-4 Title: Cellulose structure and function Caption: Cellulose is composed of glucose subunits. Compare with Fig. 3-3c and note that every other glucose molecule in cellulose is “upside down.” Unlike starch, cellulose has great structural strength, due to the difference in bonding and to the arrangement of parallel molecules of cellulose into long, cross-linked fibers. Plant cells often lay down cellulose fibers in layers that run at angles to each other, resulting in resistance to tearing in both directions. The final product can be incredibly tough, as testified by this 3000-year-old bristlecone pine in California's White Mountains. Question Many types of plastic are composed of molecules derived from cellulose, but engineers are working hard to develop plastics based on starch molecules. Why might starch-based plastics be an improvement over existing types of plastic? CH2OH H OH CH2OH H OH O O H H H OH H H OH H H H O O O OH H H O OH H H O H H H H O O H H OH CH2OH H OH CH2OH

Polisacáridos - almidón 100 micrometers Los granos de almidón en células de plantas CH2OH CH2OH O O H H H H H H OH H O OH H H OH H OH O CH2OH CH2OH CH2 CH2OH O O O O H H H H H H H H H H H H OH H O OH H O OH H O OH H O H OH H OH H OH H OH Figure :3-3 Title: Starch is an energy-storage polysaccharide made of glucose subunits Caption: (a) Starch globules inside individual potato cells. Most plants synthesize starch, which forms water-insoluble globules consisting of many starch molecules and makes up the bulk of this potato. (b) A small portion of a single starch molecule. Starch commonly occurs as branched chains of up to half a million glucose subunits. (c) The precise structure of the blue highlighted portion of the starch molecule in (b). Note the linkage between the individual glucose subunits for comparison with cellulose (Fig. 3-4).

Amilosa o amilopectina

Polisacáridos: el glucógeno

Lípidos Ácidos grasos+ Glicerina Gesättigte Fettsäuren Ungesättigte monoungesättigt polyungesättigt cis trans z.B. Phospholipide, Steroide, Triglyceride

saturados ( sin dobles enlaces C = C) Lípidos Figure: 3-UN5 Title: Saturated fat saturados ( sin dobles enlaces C = C)

Lípidos Glicerina Ácido graso Triglicérido C OH H C O HO CH etc. CH2 Figure :3-6 Title: Synthesis of a triglyceride Caption: Dehydration synthesis links a single glycerol molecule with three fatty acids to form a triglyceride.

Lípidos Riesgos para la salud de las grasas trans y grasas saturadas

Los lípidos son más adecuados para el almacenamiento de energía a largo plazo que los hidratos de carbono.

Figure: 30-1 Title: Fat provides insulation Caption: These walruses can withstand the icy waters of the polar seas because a thick layer of fat beneath the skin insulates them from the cold.