Lecture 1 - macros Flashcards
1
Q
CARBS:
- combination of which 3 atomes?
- generic formula?
- 3 types of saccharides. how long?
A
- carbon, hydrogen, oxygen
- (CH2O)n
- monosacs: simple sugars: glucose, fructose, galactose
- oligosaccharides: 2-10 monosacs
- polysaccharides: 3 or more (up to thousands) of sugar molecules
2
Q
- what are the 3 disaccharides?
- they are all ________ ________ –> formula
- what bond links them?
A
- sucrose = glucose + fructose
- lactose = glucose + galactose
- maltose = glucose + glucose
- structural isomers –> C12H22O12
- glycosidic bonds
3
Q
- give real life examples of polysacs?
- what is a complex carb?
- what is glycogen?
A
- starch: cereals, seeds, corn, pasta and pastries
- dietary starch representing most important dietary source of carb in diet –> take longer to break down = longer source of energy
- storage carbohydrate within mammalian muscle and liver
4
Q
what are the 3 stores of glucose (ish) in the body and how much?
- total CHO stored in body? = ? kcal?
A
- liver glycogen: 100g = 400 kcal
- blood glucose: 0.9g/L = 4g = 16 kcal
- skeletal muscle glycogen: 400g = 1600 kcal
TOTAL: 504g = 2016 kcal
5
Q
- muscle glycogen levels vary based on (2)
- liver glycogen goes from _____g to _____g during overnight fast
- what are the arrows btw the 3 sources of glucose in body? explain
A
- based on amount of muscle you have + amount of CHO you eat
- from 100g to 50g
- liver glycogen <–> blood glucose –> muscle glycogen. muscle glycogen cannot go back into blood bc no glucose-6-phosphatase to get glucose out
6
Q
what are the 4 roles of CHO in body?
A
- primarily serve as energy fuel, particularly during intense PA/exercise
- protein sparer: adequate CHO intake helps preserve tissue protein (no protein is used as energy)
- prevents ketosis: adequate CHO intake prevents need for utilizing ketones as fuel (high levels of ketones dangerous for diabetic)
- fuel for central nervous system: nervous system requires uninterrupted stream of CHO for proper function (120g glu/day to function)
4.
7
Q
when _________ stores are limited, excess sugar is converted and stored as what?
A
glycogen stores
stored as fat
8
Q
what are the 3 important CHO conversions?
A
- glycogenesis: synthesis of glycogen from glucose
- glycogenolysis: glucose formation from glycogen
- gluconeogenesis: glucose synthesis largely from structural components of nonCHO nutrients (protein –> glucose)
9
Q
explain the 5 steps of glycogenesis
A
- glucose uptake from blood via GLUT4 (for muscle) and GLUT2 (for liver)
- glucose is phosphorylated by hexokinase using ATP –> becomes glucose-6-phosphate which is trapped in the muscle + more reactive for further metabolic processes
- isomerization = essential step: glucose 6-phosphate to glucose-1-phosphate using phosphoglucomutase
- activation of glucose for glycogen synthesis: G1P + UTP becomes UDP glucose + PPi, using UDP-glucose pyrophosphorylase. ensures that glucose is energetically favorable for incorporation into glycogen
- glycogen synthase adds UDP glucose to chain, forming a-1,4 glycosidic bonds. for each glu unit added, 2 moles of ATP convert to ADP + Pi
10
Q
- key regulatory enzyme for glycogen synthesis?
- what type of bond is formed btw glucose molecules in glycogen?
- what steps ensures that glu is energetically favorable for incorporation into glycogen?
- how many moles of ATP needed to add 1 glu to glycogen chain?
A
- glycogen synthase
- a-1,4 glycosidic bond
- activation of glucose by UDP-glucose pyrophosphorylase
- 2 moles
11
Q
explain the 3 ish steps of glycogenolysis
A
- add inorganic phosphate to C1 of a glucose unit of glycogen, using glycogen phosphorylase –> cuts bond and releases G1P
- G1P –> G6P by phosphoglucomutase
3A. G6P enters glycolysis and becomes pyruvate (in muscle and liver)
3B. G6P + H2O –> glycose + Pi using glucose 6 phosphatase. only in liver. glucose goes to blood via GLUT2
12
Q
explain the 4 basic steps of gluconeogenesis
A
- lactate, glycerol or certain aa converted to pyruvate
- pyruvate –> oxaloacetate through pyruvate carboxylase. oxaloacetate –> phosphoenolpyruvate, through phosphoenolpyruvate carboxykinase (PEPCK, present in mitochondria and cytoplasm)
- PEP –> fructose-1,6-biphosphate
- F16BP –> glucose, which can enter circulation
13
Q
- _____A____ play a key role in regulating liver and muscle glycogen stores by controlling ____what?_____
- explain the 2 opposing roles of the 2 ____A_______
A
- hormones! –> control blood glucose levels
INSULIN: - secreted by b cells of pancreas when high blood sugar
- insulin stimulates glu uptake from blood into cell tissues + stimulates glycogen formation in liver = lowers blood sugar
GLUCAGON: - secreted by a cells of pancreas when low blood sugar
- stimulates glycogen breakdown in liver = raises blood sugar
14
Q
- what is the predominant CHO energy source during early stages of exercise?
- what happens after? as exercise intensity increases?
A
- muscle glycogen!
- as exercise intensity increases, there is an increase in demand for ATP in active skeletal muscle = increase demand for glucose = increase liver glucose release
15
Q
- at 75-90% of VO2 max –> ___which source of glu____ may supply up to ___% of total energy for active muscles
- how much is liver glycogen depleted after 1h vs 2h?
A
- blood glucose: 30%
- 1h: decrease liver glycogen 55% (not sure if 55% left or -55%)
- 2h: almost depletes glycogen stores of liver and active muscle au complet
16
Q
- at 50-60% and 25-30% of VO2 max: __which source of glu___ supplies ____% of energy in initial transition from rest to moderate exercise
- during next 20min, which source of glu supplies btw ___-____% of energy, with the remainder being provided by ____ ___________
A
- glycogen stored in active muscle supplies almost all energy in initial transition…
- liver and muscle glycogen supply btw 40-50% –> rest if fat catabolism
