Carbohydrates Flashcards
What are three hexose sugars?
Glucose, fructose, galactose
What are two pentose sugars?
Ribose, deoxyribose
What are oligosaccharides?
3-10 monosaccharides joined by glycosidic bonds
What are polysaccharides?
> 10 monosaccharides joined by glycosidic bonds
What is the main polysaccharide in animals?
Glycogen
What are features of glycogen?
alpha-1-4, 1-6 glycosidic bonds; very dense; virtually insoluble as is hydrophobic so has very little water retention
Where is glycogen stored?
Muscle and liver
How much glycogen is stored in the muscles and liver?
Liver contains ~100g; muscle contains 300-500g depending on diet and training
When is muscle glycogen used?
During period of high intensity (70% VO2max) exercise of moderate duration
How long can muscle glycogen be used for?
60 minutes until it is depleted
When is liver glycogen broken down?
When glucagon causes release to increase glucose levels; especially important for brain as glucose can cross blood-brain barrier, whilst larger carbs cannot
What is the main polysaccharide in plants?
Starch
What are simple carbs?
Mono- and di-saccharides; sugars
What are complex carbs?
Oligo- and poly-saccharides; starches
What are the functions of carbs?
Energy store; fuels; sugars give backbone to RNA and DNA; structural elements in cell walls; linked to proteins and lipids; involved in key reactions
What might the daily carbs of elite athletes be like?
486g; based on 3 hours exercise (@2g/min = 360g) and 21 hours rest (@0.1g/min = 126g)
What are the main dietary carbs?
Starch; glycogen; dextrins (short chain polymers); maltose; sucrose; lactose; glucose; fructose
What allows glucose into cells?
Class 1 glucose transporters: GLUT 1, 2, 3, 4
Where does GLUT 1 act?
Foetal tissue and RBCs
Where does GLUT 2 act?
Liver
Where does GLUT 3 act?
Brains/ neurons
Where does GLUT 4 act?
Muscle/ adipose tissue
What are class 2 glucose transporters?
GLUT 5, 7, 9, 11
What are class 4 glucose transporters?
GLUT 6, 8, 10, 12
What is euglycaemia?
Normal blood glucose
How does insulin regulate blood glucose?
Hyperglycaemia triggers insulin release; insulin binds to receptor on cell surface; sets off cascade of signalling events; translocates more GLUT 4 to membrane; more glucose into cell
How does exercise act as a remedy in insulin-resistant people (T2DM)?
Exercise will localise GLUT 4 as uses different cell signalling to insulin; allows glucose to enter cell
