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exci 258 final exam 2022 > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

how do the GLUT transport glucose

A

by facilitated diffusion, down a concentration gradient (carrier is needed but not E)

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2
Q

describe GLUT 1 (tissue distribution and important features)

A

most tissues (brain, RBCs and placenta esp.)
low km (1mM); high affinity allows near constant uptake

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3
Q

describe GLUT 2 (tissue distribution and important features)

A

liver, kidneys, intestine and pancreatic beta cells
high km (15-20mM), responds only to high [glucose] like post prandial blood levels

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4
Q

describe GLUT 3 (tissue distribution and important features)

A

low levels in most tissues (high expressions in neurons)
low km (<1mM), allows preferential uptake during hypoglycemia

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5
Q

describe GLUT 4 (tissue distribution and important features)

A

muscle, adipose tissue
medium km (2.5-5mM), insulin dependency in recruitment of GLUT 4 from intracellular stores

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6
Q

what is km and affinity

A

km is the concentration of glucose at which uptake velocity is half maximal

affinity is the degree of attraction that glucose has to the transporter

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7
Q

what happens to the GLUT transporters when blood glucose levels are high

A

glut 2 is activated and so insulin is secreted, Glut 4 will then be able to take glucose out of the circ and into the cell to bring the circ blood glucose levels down

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8
Q

what will the slope look like for a GLUT that has high affinity in a graph that shows transport rate and [blood glucose]

A

very steap rise; at low [ ] it will reach 50% max very fast and very soon

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9
Q

why is it needed for GLUT 1 to have a high affinity

A

since RBC deliver O2 to tissues and takes away CO2, it needs cte energy and so it needs to be delivering glucose constantly even at severe hypoglycemia

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10
Q

what would happen if GLUT 2 had a km of 1mM instead of 15-20

A

insulin would be released constantly at low blood glucose levels and would bind to skeletal m. so in 10 min, your blood glucose would go from 5 to 2.5 (intense hypoglycemia)

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11
Q

what is the normal range of blood glucose at rest

A

4-8 mM

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12
Q

what relies 100% on glucose for ATP production and metabolism and can only manufacture ATP thru glycolysis

A

red blood cells

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13
Q

why is it so important that rbc gets their ATP from glucose and glucose transporters

A

since the rbc don’t have a mitochondria, that produces a significant amount of ATP, it needs to rely on glucose metabolism instead

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14
Q

why do neurons have a high rate of metabolism

A

because every A.P that fires needs ATP quickly so they rely on glycolysis and they need to function 100% of the time

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15
Q

GLUT w high km and low affinity are most efficient during what conditions

A

transient periods of hyperglycemia

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16
Q

how does the liver bring circ blood glucose back to normal levels after hyperglycemia

A

it takes its up glucose from circ at 10-15mM and stores it as glycogen

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17
Q

when do the beta cells start producing insulin and where will the insulin go

A

when the blood glucose is at high levels
and insulin will go to bind to skeletal m. and adipose tissue

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18
Q

what GLUT is found in higher concentration in the pancreas GLUT 2 or 1

A

GLUT 2

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19
Q

what is lactose broken into and what is it broken by

A

its broken into galactose and glucose by lactase

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20
Q

what is sucrose broken into and what is it broken by

A

glucose and fructose and by sucrase enzyme

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21
Q

what sugar monomer can’t go thru glycolysis

A

galactose (it can only be stored as glycogen)

22
Q

what monomer is already in the circ and what monomer is taken up by the villa in the small intestines

A

glucose

fructose

23
Q

t/f sugar monomers all have their diff and specific transporters

A

true

24
Q

what do all the sugar monomers encounter as soon as they enter the cell

A

ATP hydrolysis rx

25
Q

what will determine if the substances go down to glycogenesis or glycolysis and when would each happen

A

if the cell has ATP needs (exercise) or not (excess carbs after a big meal will need to be stored)

26
Q

what is the diff btw glucokinase and hexokinase

A

glucose kinase is only found in the liver and hexokinase is found in skeletal m and they both speed up the phosphorylation of glucose to g-6-p

27
Q

what is the common hub of galactose, glucose and fructose

A

G-6-P

28
Q

what is the enzyme for phosphorylation of fructose and galactose

A

fructokinase
galactokinase

29
Q

what is the fate of glucose in the liver

A

can either be stored as glycogen or go back into circulation

30
Q

what does glucose-6-phosphorylase do and where is it found solely

A

it will catalyze the G-6-P back into glucose so it can go back out into circ
it is only found in the liver (it can also do the same for fructose and galactose)

31
Q

what are the steps of glycogenesis

A

1) blood glucose levels are high activating the Liver GLUT sys allowing glucose to enter liver
2) glucose encounters 1st enzyme (glucokinase) and becomes G-6-P and ATP becomes ADP
3) G-6-P encounters enzyme that moves P from 6th C to 1st C
4) G-1-P encounters enzyme and becomes uridine diphosphate glucose and UTP lets go of 2 P to add to G-1-P
5) UDP glucose w enzyme glycogen synthase gets stored as glycogen

32
Q

what is the UTP’s purpose in glycogenesis

A

it prepares glucose to bind to the glycogen unit that’s in skeletal m. and it needs E to push the rx forward

33
Q

what enzyme pushes the rx from G-1-P to UDP-glucose

A

UDT-glucose pyrophosphorylase

34
Q

what is the role of glycogenin

A

it acts as the anchor and the backbone of the glycogen tree so that it attaches to something that won’t be metabolized

35
Q

what is the difference btw an alpha-1,4 and alpha-1,6 bond and what enzyme help the formation of each

A

1,4 is the bond found in btw each glucose monomer forming the main linear branch with the glycogen synthase and the 1,6 is when the branch branches off the main linear twig with a branching enzyme

36
Q

what is a non reducing end and what enzyme is it sensitive to

A

first one that will be broken off when glucose is needed for energy
glycogen phosphorylase

37
Q

why can’t the reducing end broken off

A

because it attaches to glycogenin and so it would be free in the cell if the bond was broken off

38
Q

what enzyme is activated when you need glucose to be broken off glycogen and form G-1-P

A

glycogen phosphorylase

39
Q

t/f the glycogen mol is reduced one residue at a time

A

true

40
Q

what enzymes break down and attach the 1,6 bond

A

branching enzyme will help build the 1,6 bond when you need to store more glucose as glycogen by helping the branching from the main linear branch
debranching enzyme will break down one branch 1,6 and then activate the phosphorylase enzyme which will start breaking off the non reducing end off

41
Q

what hormone activates the glycogen synthase and branching enzyme and by doing what

A

insulin, by allowing glucose to enter the cell and to promote storage of glucose as glycogen during rest or after major meal

42
Q

what enzymes are stimulators of glycogenolysis

A

de branching and glycogen phosphorylase

43
Q

what 2 hormones stimulate the de branching and glycogen phosphorylase enzymes and where do they each come from

A

epinephrine (medulla of adrenal gland) and glucagon (alpha cells of pancreas)

44
Q

when there are high levels of AMP in the m. what does that mean

A

it means there are low levels of ATP and the m. needs a substrate to get ATP so it will start breaking down the stored glycogen (it happens at high needs of E)

45
Q

what does glycogen phosphorylase a and b do

A

a: will stimulate glycogenolysis when P is bound to it
b: will inhibit glycogenolysis when P is not bound to it

46
Q

what does the glycogen synthase do when its phosphorylated

A

it will inhibit glycogenesis

47
Q

what do the hormones epi and glucagon activate in glycogenolysis and how do they do it

A

the activate the cAMO dependent protein kinase that will activate phosphorylase enzyme by adding a P and will inhibit glycogen synthase by adding a P as well

48
Q

when is the cAMP activated

A

it is activated during high I exercise to start breaking down glycogen

49
Q

with low I exercise what happens concerning glucose utilization

A

no need for glycogen to be broken down bc it has enough w only uptake of glucose and breakdown of fats (no need for ATP and no need to activate epi and glucagon)

50
Q

with moderate I exercise what happens concerning glucose utilization

A

gradual drop in glycogen content in liver and skeletal m., need additional substrate for more ATP (glucose or glycogen) and phosphorylase a is activated by epi and glucagon so starts breaking down non reducing ends

51
Q

with high I exercise what happens concerning glucose utilization

A

huge amounts of epi and glucagon binding to the m. and liver cells with even more phosphorylase enzymes activated
immediate demand for this type of carb as a source of energy
at 25% of glycogen, fatigue levels are really high

52
Q

t/f at this point, only carbs are used for E during exercise

A

false, fat metabolism is coming in and helping to manufacture ATP for E usage to help carbs not be the only ones

exci 258 final exam 2022 (3 decks)

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