Structure And Function Of Carbohydrates Flashcards
What is a carbohydrate
CH2O
It can have structural roles such as DNA and RNA, and other roles such as energetics like glucose and fructose (ATP)
Monomers of carbohydrates
Structural carbohydrates such as DNA and RNA: robins and deoxyribose (5 carbon structure, the only difference is at 2nd C there is a H-OH (ribose) bond rather than a H-H bond (deoxyribose)
Carbohydrates:
- types of isomers
Structural isomers: such as a change in compound from H to CH2OH in the respect of glucose to fructose
Stereoisomer: such as a switch in the position of the current compounds such as the switching of H-OH to OH-H in the respect of glucose to galactose
Glucose anomers
Alpha glucose where at carbon 1 the bond is positioned H-OH
Beta glucose where at carbon 1 the bond is positioned OH-H
Forming disaccharides
- sucrose and maltose
Sucrose is from the formation of alpha-glucose and fructose (reversed by invertase)
Maltose consists of 2 glucose molecules
Also lactose from glucose and galactose
Alpha glucose polymers
Alpha glucose polymers can have 1-4/1-6 linkages (numbers refer to the carbon number)
1-6 linkages make storage molecules more branched
Starch
- structure and function
Solely in plants as an energy store
Consists of amylopectin and amylose
Glycogen:
- structure and function
Solely in mammals as an energy store, mainly a 1-4 linkages
Cellulose:
- structure and function
Made from beta glucose with 1-4 linkages, cell wall of plant cells
Structure of glucose polymers
Cellulose only beta 1-4 linkages
Starch and glycogen only a 1-4 linkages
Form large fibres, aided by hydrogen bond formation between the bonds creating a rigid structure
Chitin:
- structure and function
Made from the chitin monomer a substituted glucose:
N-acetyl glucosamine (on carbon 2 the addition of N-acetyl)
Glycoproteins:
- structure and function
Addition of a glycan to a protein at specific residues such as Asn, Ser and Thr
Function: for structural purposes such as the mucous proteins (mucin)
Glycan contain sialic acid, these small sugars are polar and -ve charged
Functional role also for blog grouping e.g. for the B type galactose is attached to the blood (at proteins or lipids) or A type N-acetyl galactosamine (at proteins or lipids).
Proteoglycans
Contains Hyaluronan: consisting of aggregate core protein, chondritin sulfate, link proteins and keratan sulfate
Cartilage and the ECM
- consists of
The ECM is a organised combination of proteoglycans, cross-linked fibres of collagen and fibronectin
Proteoglycans:
- types
Chondroitin 6-sulfate Keratan sulfate Heparin Dermatan sulfate Hyaluronate Collectively known as glucosaminoglycans (GAGs)
Carbohydrate:
- energy quantity
4 kcal kg-1
Glucose:
- function
Oxidative respiration
Monosaccharide chemical structure
C6H12O6
Disaccharide chemical structure
C12H22O11
Formation of a disaccharide
By polymerisation called condensation reaction, leaving water
Breakdown of a disaccharide
Amylase, biological catalyst
Found in the mouth and gut, contains acid
Hydrolysis of starch
By a hydrolysis reaction with the presence of water
Can be broken down by hearing with acid (acid hydrolysis)
Glucose uptake
Via GLUT4 transporter
Glucose-1-P:
- use
Stored or broken decay depending on demand
Characteristics of storage compounds
Need to be energy rich, mobilisation and storable
Glycogen:
- location
- characteristics
Stored in the cytoplasm of liver and muscle
Glycogen is a branched polymer of glucose residues, consisting of a-1,6-glycosidic bonds and a-1,4-glycosidic bonds
30,000-50,000 glucose units (non reducing or reducing ends)
Glycogen breakdown:
- energy use
Breaking the glycosidic bond by adding orthophosphate to carbon 1 (phosphorylase)
This form alpha-D-glucose-1-phosphate + glycogen residue
Phosphorylase stops 4 residues away from a branching point
Debranching glycogen:
- movement
Transferase to shift three glucose residues
Debranching enzyme hydrolyses the alpha-1,6-glycosidic bond (alpha-1,6-glucosidase)
G1P to G6P:
- conversion
G1P needs to be converted G6P, via phosphoglucomutase
G6P can now enter glycolysis pathway or the pentose phosphate pathway (ribose)
Liver releases glucose
G6P + H2O via G6-phosphotase forms glucose and Pi
Glycogen synthesis
- G6P is converted to G1P
- Activation of G1P to UDP-glucose (via UTP for activation) also needs UDP-glucose pyrophosphorylase
- Formation of glycosidic bond (rls) with the help of glycogen synthase, removes uracil and adds to the glycogen chain
- Branching; glycogen-branching enzyme which adds a-1,6-branch points
