Carbohydrates PDF

Carbohydrates Caner Geyik, PhD [email protected]  Objectives  Recognize the general structure of carbohydrates  Classify carbohydrates  Recognize disaccharides  Recognize polysaccharides  Explains carbohydrate modified protein structures and their functions...

Carbohydrates Caner Geyik, PhD [email protected]  Objectives  Recognize the general structure of carbohydrates  Classify carbohydrates  Recognize disaccharides  Recognize polysaccharides  Explains carbohydrate modified protein structures and their functions  Explain digestion of carbohydrates 2  Carbohydrates The carbohydrates are a group carbonyl compounds (aldehydes or ketones) that also contain several hydroxyl groups. Carbonyl 3  Carbohydrates The carbohydrates are a group carbonyl compounds (aldehydes or ketones) that also contain several hydroxyl groups. 4  Carbohydrates General formula (C.H2O)n There are many isomers  Isomer: Same formula, different structure  Fructose and Glucose formula= C6H12O6 5  Carbohydrates Classification (Number of units)  monosaccharide, disaccharide, oligosaccharide, polysaccharide  -ose suffix is added to name Monosaccharides Type of carbonyl group  Aldose, Ketose Number of carbons  triose, tetrose,… 6  Carbohydrates Classification (Number of units)  monosaccharide, disaccharide, oligosaccharide, polysaccharide  -ose suffix is added to name Monosaccharides Type of carbonyl group  Aldose, Ketose Number of carbons  triose, tetrose,… 7  Carbohydrates Monosaccharides Disaccharides Polysaccharides 8  Carbohydrates - Monosaccharides Aldoses: Aldehyde group  5 carbon: Aldopentose sugars  6 carbon: Aldohexose sugars 9  Carbohydrates - Monosaccharides Aldoses 10  Carbohydrates - Monosaccharides Aldoses 11  Carbohydrates - Monosaccharides Ketoses: ketone group  5 carbon: Ketopentose sugars  6 carbon: Ketohexose sugars 12  Carbohydrates - Monosaccharides Ketoses 13 14  Carbohydrates - Monosaccharides A hydroxyl (-OH) group is missing N-acetyl group is added to structure 15  Carbohydrates - Monosaccharides Glucose Contains carboxyl group Aldehyde group changed with hydroxyl group 16  Carbohydrates Monosaccharides Disaccharides Polysaccharides 17  Carbohydrates – Disaccharides A glycosidic bond between two monosaccharides producing a disaccharide 18  Carbohydrates – Disaccharides Glucose + Glucose Glucose + Galactose Glucose + Fructose 19  Carbohydrates Monosaccharides Disaccharides Polysaccharides 20  Carbohydrates – Polysaccharides Storage Structure  Glycogen  Cellulose  Starch  Chitin (N-acetyl glucosamine) 21  Carbohydrates – Polysaccharides Cellulose and Chitin Are Structural Polysaccharides Starch and Glycogen Are Storage Polysaccharides 22  Carbohydrates – Polysaccharides Glycogen Glycogenin protein in center, synthesis starts from this protein 1. Glucose is added to chain 2. Branches Degradation starts from the ends. More branch= more ends. More glucose can be taken back from more ends makes energy 23 production faster.  Carbohydrates – Polysaccharides Starch Amylose Amylopectin 24  Protein-Carbohydrate Structures Carbohydrate Rich  Proteoglycan  Glycosaminoglycan Protein Rich  Glycoprotein 25  Proteoglycan  Negatively charged heteropolysaccharide chains (Glycosaminoglycans, GAGs)  Associated with a core protein, forming proteoglycans 26  Glycosaminoglycans  Ability to bind large amounts of water, thereby producing the gel-like matrix  Extracellular Matrix (ECM)  Collagen  Elastin  Fibrillin-1  Fibronectin  Lubricating properties of mucous secretions 27  Glycoproteins  Glycoproteins are proteins to which oligosaccharides (glycans) are covalently attached  Glycosylation is the most common posttranslational modification of proteins.  Difference from proteoglycans:  Protein rich (%80+)  Glycan is short, does not contain repeating disaccharide units and is often branched 28  Glycoprotein Functions  Membrane-bound glycoproteins participate in a broad range of cellular phenomena  cell-surface recognition (other cells, hormones, and viruses)  cell-surface antigenicity (such as the blood group antigens) 29  Glycoprotein Functions  Extracellular matrix (ECM) components  Mucins of the gastrointestinal and urogenital tracts  In addition, almost all of the globular proteins present in human plasma are glycoproteins 30  Glycoprotein Structure  If the terminal sugar on the glycan is GalNAc, the blood group is A. If it is galactose, the blood group is B. If neither GalNAc nor galactose is present, the blood group is O 31  Digestion  Mouth and Intestines  Glucosidase enzymes: degrades glycosidic bonds In plants  Starch: Alpha glycosidic bonds  Cellulose: Beta glycosidic bonds 32  Digestion Carbohydrates  α-amilases  Distrupts α(1->4) bonds Oligosaccharides, Disaccharides  Humans can’t digest cellulose (beta bonds) Disaccharides  Intestinal disaccharidases :  Creates monosaccharides 33 Monosaccharides  Absorption of monosaccharides in intestine mucosal cells Sodium-dependent glucose cotransporter 1 (SGLT-1) Glucose and Galactose (with Na+ transport) GLUT-5 Fructose absorption GLUT-2 From intestine to blood 34  Carbohydrates  Central to energy metabolism  Blood glucose concentration is maintained at about 5 mM (90 mg/dL)  Essential for normal cerebral function  Below 3 mM (54 mg/dL) for long time = Confusion, coma  Above 8 mM (144 mg/dL) for long time = Vascular damage  After a meal, glucose concentrations in the portal venous blood can easily reach 20 mM (360 mg/dL) 35 Carbohydrates 36