1 / 25

BB10a: Cells, Biomolecules & Genetics, 2003 Semester 1.

BB10a: Cells, Biomolecules & Genetics, 2003 Semester 1. Thursday 2 Oct. Lecture 4 Structures & functions of common carbohydrates Andrew Pearson. BB10A: Common carbohydrates. Basic units: called monosaccharides  are simple sugars such as glucose and fructose.

sage
Download Presentation

BB10a: Cells, Biomolecules & Genetics, 2003 Semester 1.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. BB10a: Cells, Biomolecules & Genetics, 2003 Semester 1. • Thursday 2 Oct. • Lecture 4 • Structures & functions of common carbohydrates • Andrew Pearson

  2. BB10A: Common carbohydrates Basic units: called monosaccharides  aresimple sugars such as glucose and fructose. The structures of monosaccharides can be drawn in different ways, to highlight different aspects: the Fischer projection is best for showing the stereoisomerism of the various substituents; but the Howarth projection is more useful to biochemists because it approximates the 3-D structures and helps explain stabilities.

  3. BB10A: Common carbohydrates Fischer projections

  4. Properties of monosaccharides. Containing many hydroxyl groups: sugars interact easily with water: they are hydrophilic & water-soluble. Containing many hydroxyl groups: sugars are highly oxidised and can be easily hydrolysed into fragments. Containing many hydroxyl groups: sugars are easily derivatised to give related molecules, including aminosugars, acetylated sugars, dimers, oligomers and polymers. BB10A: Common carbohydrates

  5. BB10A: Common carbohydrates

  6. BB10A: Common carbohydrates

  7. The relationship between the various isomers of sugars is not complicated to biochemists: Biomolecules like sugars are selected because of their 3-D structure, and the wrong isomer simply does not fit into binding sites. The distinction between D- and L- glucose is not something that many biochemists concern themselves with nowadays: some bacterial products contain the odd L-sugar, all others are D-. BB10A: Common carbohydrates

  8. Precise 3dimensional fit between a substrate and enzyme. Ionic interaction “Hydrophobic Interaction” H-bond Adapted From Voet & Voet

  9. BB10A: Common carbohydrates

  10. Disaccharides: two monosaccharides joined by O-glycosidic bond. Three occur naturally in stable form, Lactose in breast milk (sugar transport) Sucrose in plant sap (plant transport sugar) Trehalose in fungi and insect heamolymph (for transport) all others shown in books are digestion products of something bigger. BB10A: Common carbohydrates

  11. BB10A: Common carbohydrates

  12. BB10A: Common carbohydrates Disaccharides maltose trehalose sucrose cellobiose lactose

  13. BB10A: Common carbohydrates Glycogen, in animals, is similar but has a greater degree of branching.

  14. BB10A: Common carbohydrates Cellulose is a linear homopolymer of glucose, but unlike amylose the O-glycosidic bond is beta in cellulose; alpha in amylose.

  15. Cellulose: note the H-bonds. A tetrasaccharide from heparan sulphate: note the substituted sugars. Repeating unit of chitin: from insects and crustaceans

  16. The raffinose series at the end of a number of “unusual” plant storage polysaccharides. Our intestinal digestive enzymes are unable to cleave stachyose into smaller units – but anaerobes in our lower intestines can.. BB10A: Common carbohydrates

  17. BB10A: Common carbohydrates

  18. The difference in size between proteoglycans which are giant macromolecules and glycoproteins, which are small soluble protein macromolecules. BB10A: Common carbohydrates

  19. Just so stories: how furanosides and pyranosides got their names BB10A: Common carbohydrates

  20. Functions of Monosaccharides • broken down for energy (by either fermentation or respiration) • interconverted/carbon skeleton used for biosyntheses • solvation of hydrophobes: in aqueous transport media such as serum • transport form of energy in animal serum, plant sap and intracellularly in general.   BB10A: Common carbohydrates

  21. Oligosaccharides: • short branched heteropolymeric chains of • monosaccharides, often derivatised, • with high informational content in their normal • hydrated state. • Functions: • markers for outer surface of cell membranes • protein targeting markers in endoplasmic reticulum system • prevention of membrane protein flip-flop • formation of glycocalyx BB10A: Common carbohydrates

  22. Polysaccharides: long chains of monosaccharides, sometimes branched, either Homopolymers (only one type of monosacch.) (e.g. cellulose, glycogen, amylose, amylopectin) or heteropolymers(more than one monosacch.) (e.g. glycosaminoglycans, algal cell wall gels, peptidoglycan, chitin) BB10A: Common carbohydrates

  23. BB10A: Common carbohydrates • Functions: • energy reserves in plants: • (starch and some of the flatulogenic polymers) • energy reserves in animals: • glycogen • structural in all except animals: • chitin, celluloses, peptidoglycan • lubrication and shock-absorbing • in synovial fluids, connective tissues

  24. CHO function table BB10A: Common carbohydrates

More Related