Carbohydrates Flashcards
Carbohydrates are highly oxidisable or not l
Yes they are
Carbohydrate functions
Structure in cell walls and ECM of animal cells. Store energy as starch in plants and glycogen in animals. Cell to cell communication eg ABO blood groups
Types of monosaccharides
Glucose fructose galactose
Disaccharide
Formed from monomers that are linked by glycosidic bonds
Glycosidic bonds
Covalent bond formed between hydroxyl group and anomeric carbon of different monosaccharide
Anomeric carbon
Anomers are mirror images of each other( left and right handed forms ). Stabilises the structure of glucose. Only residue that can be oxidised
Types of disaccharide
Maltose lactose sucrose
Sucrose is a reducing sugar true or false and why
False because no free anomeric carbon
Polysaccharides
Polymers of medium to high molecular weight
Types of polysaccharides
Homopolysaccharides - single monomer species
Heteropolysaccharides- have two or more monomer species
Starch contains
Amylose mainly straight and amylopectin (75% of it) (got alpha 1-4 chains and 1-6 chains). Non reducing ends
What is more extensively branched glycogen or starch
Glycogen
Glycogen is in what part of the body
Liver (replenish blood) and skeletal muscle (produces atp for contraction)
Why store glucose in polymers
Compactness, have lots of non reducing ends so can be readily synthesised and degraded, form hydrated gels and not rlly in solution - omsotically inactive
What do carbohydrates attached to proteins do
Communication between cells, protect it from degradation, influence folding, increase solubility
Glycosaminoglycans
Found in mucus, un branched polymers made from units of hexuronic acid and amino sugar which alternates through the chains
Proteoglycans
Carbohydrate part muchhh more than protein. Formed from GAGs. They are macromolecules found on surface of cells or in between cells in the ECM. Form part of connective tissue
Glycoproteins
V similar to proteoglycans but protein part more than glucose. Found in blood and in cells in secretory system
Carbohydrate digestion order
Mouth- salivary amylase
Duodenum- pancreatic amylase
Jejunum (small intestine)- mucosal cell surface enzymes
Glucose is absorbed how
Using glucose symport and sodium potassium pump in epithelial cells of the small intestine
Fructose is absorbed how
Uses GLUT5 transporter. Then goes down the conc gradient high in gut lumen low in blood
Cellulose and hemicellulose break down
Don’t get digested but they get broken down. Increase faecal bulk and decrease transit time. Break down yields CH4 and H2 (farts)
Disaccharide deficiencies
Genetic, cramps because struggle to break down. Enzyme tests to see if they are working. Lactose intolerance
Fate of absorbed glucose
Goes from epithelial cells into blood then to liver. Converted into glucose-6-phosphate which cannot diffuse out of cell because GLUT transporters won’t take it so it is trapped. Enzymes work on it. Then go through blood as glucose to other tissues
What enzyme is better for glucose- glucokinase or hexokinase
Hexokinase (low Km but low Vmax)
In skeletal muscle what does glycogen get broken down into
Lactate because of glycolysis
Synthesis of glycogen
1- glycogenin binds glucose to form short chains then glycogen synthase extends the chains
2- chains broken by glycogen branching enzyme and react hard via alpha1-6 bonds to give branch points
Degradation of glycogen
Glucose monomers are removed by glycogen phosphoylase one at a time from non reducing ends as G1P. Then glucose is removed then reattached at the nearest non reducing end. Glucosidase then removes the final glucose by breaking a alpha1-6 link to release free glucose
What happens to pyruvate at the end of glycolysis
Converted into ethanol and carbon dioxide, lactate or carbon dioxide and water
What coenzyme is needed in glycolysis
NAD and NADH
What is glycolysis
Catabolic pathway that saves some potential energy from glucose by forming ATP through substrate level phosphorylation.only way energy can be made when oxygen is in short supply
Process of glycolysis
Glucose to F-1,6-BP (Used 2ATP) then to G3P to PEP to pyruvate or to DHAP. Produces 4 ATP
When is cori cycle used
When the muscles don’t receive oxygen fast enough to make ATP so ATP is made via substrate level phosphorylation which produces lactate. Lactate converted and then the liver repaid oxygen debt to molecules
Gluconeogenesis is
Process that transforms non carbohydrate substances such as glycerol, amino acids, lactate into glucose
What is cori cycle
Interaction between muscle and liver with glucose
How can glycolysis and gluconogenesis be independently controlled
Bypass reactions that sidestep the irreversible ones of glycolysis. Prevents them cancelling each other out
What other sugars can be added to glycolysis
Galactose at beginning (converted into glucose 6P) and then fructose at second stages (converted into fructose 6P) or from liver converted into GAP or DHAP
