Carbohydrates Flashcards
why are carbohydrates important?
-Important in fuel and energy source and in recovery, preventing fatigue
how are glucose levels in blood measured and what do different levels mean?
can be measured in mmol/L
-Different levels- after waking up healthy range is 4-7 mmol, 5-normal blood glucose level (euglycemia- wants to be maintained)
-After exercise blood glucose levels decrease -lower glucose levels show lower physical conditions after exercise- in a worse state
What is hypoglycaemia?
low blood glucose levels
what is hyperglycaemia
high blood glucose levels
what is glycolysis?
-requires high blood plasma glucose levels
–1 glucose molecule is broken down into 2 pyruvate molecules to create 2 ATP molecules
how can consuming carbs increase glycolysis?
- it increases plasma glucose levels, allowing glycolysis to take place
-high carb diets improve physical condition and recovery during exercise
what are carbs made up of?
-carbon, hydrogen, oxygen (CHO)
what are the 3 different forms of carbohydrates and give examples?
-Monosaccharides-simplest form of sugar, 3-7 carbons eg.glucose, fructose and galactose
-Disaccharides- 2 monosaccharides joined by glycosidic link, eg.sucrose, lactose, maltose
-polysaccharides- larger sugar molecules, many monosaccharides joined together(more than 10), eg,cellulose, starch, glycogen
what is the general formula for carbs
CH2O)n n=number of carbons
-For every carbon there is 2 hydrogens and 1 oxygen
how does microvilli in small intestine help with carbohydrate absorption
increase SA of SI which allows for carbs to be absorbed and digested
Describe the process of the breakdown of carbohydrates from the mouth to the intestine?
-Saliva-contain salivary amylase- an enzyme- can break down starch into dextrins and maltose
-Then broken down into maltose alone by pancreatic amylase
-Lactose and sucrose can’t be broken down by salivary amylase-remains in same form until small intestine
-In small intestine sucrase breaks down sucrose into fructose and glucose
-Maltose broken down by maltase into glucose
-Lactose broken down into galactose and glucose by lactase
(monosaccharide units)
Describe how monosaccharide units are absorbed into the bloodstream after being broken down?
-Sodium glucose transporters in small intestine allow monosaccharides to be transported across microvilli and be absorbed through small intestine into blood stream where it can be transported to required area
-Specific sodium glucose transporters allow specific monosaccharides to be transported across microvilli
-GLUT2- then transports to bloodstream-not specific-general to all monosaccharides
what happens when glucose from digested carbohydrates enter the blood stream
-insulin is released from pancreas and enters blood
-glucose and insulin arrive at muscles
what are the 3 main storage sites of carbs in the body?
-Skeletal muscle (40g)
-Liver (100g)
-Blood (3-5g)
what is the function of the storage sites apart from storage and what is their limitation?
-Storage sites work together to maintain equilibrium of euglycemia if glucose levels are high or low)
-Storage sites are limited- so just be replenished daily thru consumption of carbohydrates
Describe how the liver helps maintain blood glucose levels?
–Glycogen is broken down into glucose- glycogenolysis-60%
-can produce glucose without glycogen thru gluconeogenesis-40%
-glucose is required as is the brain’s only source of fuel
describe how hormones control low and high blood glucose levels?
-When blood glucose is high-initiates release of insulin from pancreas
-this stimulates glucose uptake from blood into tissue cells and stimulates glucose to be converted into glycogen in the liver, lowering blood glucose levels
-When low stimulates pancreas to release glucagon which stimulates glycogen breakdown into glucose which is released into blood raising blood glucose levels
How is glucose taken up into skeletal muscle cells?
-glucose entry into cell is moderated by gradient
-needs transporters to allow passage into cell- are 5 glucose transporters:
GLUT1, GLUT2, GLUT3, GLUT4,GLUT5
what are the 2 pathways for glucose uptake into skeletal muscle?
insulin dependant and independent pathway
describe the insulin dependant pathway
GLUT4 is main transporter involved in uptake of glucose into muscles
-Glucose binds to insulin receptor on the plasma membrane of muscle cell
-GLUT4 transporter then receives signal for increase in glucose and insulin
-Causes translocation of the vesicles on GLUT4 molecule to plasma membrane
-Allows glucose to be transported into muscles
describe the insulin independant pathway
-occurs as a result of exercise
-exercise begins and energy demand increases in muscles
-vesicles can still translocate to membrane, allowing glucose to enter however insulin is not required as we may not be increasing blood plasma levels
what is glycemic index?
- represents blood glucose response to meal
-Is high soon after intake of food then decreases as time increases
-food classified into high, moderate or low GI:
0-100- high-above 70, moderate=55-70, low= below 55
What is the difference between low GI and high GI foods?
Low GI- emptied from stomach slowly and is slowly digested through the whole digestive tract
High GI- empties from stomach rapidly and is quickly digested in the first portion of the digestive tract
what is the effect of GI on glucose and insulin levels?
-high GI food cause higher blood glucose and insulin levels than low GI foods however as time increases, levels decrease and plateau with low and high GI foods
what is the effects of consuming low GI foods compared to high GI foods?
-Low GI foods- cause fuller feeling for longer as there is a longer stimulation of nutrient receptors in the gastronomical tract as food takes longer to digest
-High GI foods can cause reactive hypoglycemia to occur due to increase at start causes sharp increase in glucose and insulin then levels rapidly drop to below initial value
why can fatigue occur within athletes?
-Hypoglycemia (consumption of carbs during exercise prevents this)
-muscle glycogen depletion (consuming a low carb diet will increase muscle glycogen depletion during exercise, increasing fatigue)
-dehydration
