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258 - physiology > Lecture 2: Glucose transport, glucose and glycogen > Flashcards

Lecture 2: Glucose transport, glucose and glycogen Flashcards

1
Q

what is the Gibbs free energy value for ATP

A

-7.3

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2
Q

true or false: all derivatives of ATP and ADP and ADMp have negative free energy values

A

True

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3
Q

is glucose tranported into the cell through energy in most cells

A

no , down a concentration gradient by facilitated diffusion

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4
Q

is a protein carried needed for glucose transport? is the energy needed?

A

protein yes

energy no

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5
Q

what are the 2 most commonly studied glucose carriers and do they require insulin

A

glut (no insulin) and glut 4 (insulin dependent)

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6
Q

true or false: most post absorptive glucose uptake by cells does not require insulin

A

true

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7
Q

where is the glut 4 (insulin dependant) located

A

skeletal muscles, adipose and heart tissue)

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8
Q

do all glut receptors/carriers require insulin

A

no

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9
Q

are all glucose transporters membrane-bound?

A

no , glut 4 is in vessicles in the skeletal, adipose amd heart tissue

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10
Q

which glut receptors are membrane bound

A

glut 1
glut 2
glut 3

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11
Q

which receptor is in vesicles

A

glut 4

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12
Q

Where is glut 1 receptors located

A

most tissues (brain, RBS, placenta)

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13
Q

where are glut 2 receptors located

A

liver, kidneys, intestine, pancreatic b cells

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14
Q

where are glut 3 receptors located

A

low levels in most tissues but high expression in neurons

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15
Q

where are glut 4 transporters located

A

msucle, adipose and heart

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16
Q

affinity defintion

A

degree of attraction that glucose has to tranposter

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17
Q

km defintion and why

A

concentration of glucose at which uptake velocity is half maximal

this is the point the transporter is most active phase

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18
Q

features of Glut 1

A 
LOW KM (1 mM)
HIGH AFFINITY (NEAR CONSTANT UPTAKE) = glucose binds very easily to transporter
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19
Q

what glucose transporter has a near constant uptake

A

glut 1

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20
Q

features of glut 2

A 
High Km (15-20 mM)
respond only to high glucose concnetration
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21
Q

when is glut 2 very active

A

POST PRANDIAL BLOOD LEVELS

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22
Q

explain glut 1:

A

high concentration in the brain cells and rbc
They are constantly taking up glucose therefore there is a strong attraction and you do not need a high concentration of it to activate the transporter

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23
Q

explain glut 2 transporter

A

After eating, there is a high concentration of glucose in the cell.
The liver will take excess carbs of glucose and store it as glycogen to lower the glucose blood level
RESPONDS FAVORABLY TO HIGH CONCENTRATIONS OF GLUCOSE
will not activate at low levels of glucose or it will cause you to uptake too much glucose

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24
Q

which transporter responds favourably to high concentrations of glucose

A

glut 2

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25
Q

what is typical blood glucose concentration

A

4-8 MM

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26
Q

features of glut 3

A 
low Km (less than 1), high affinity 
allows for preferential uptake of glucose during hypoglycemia
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27
Q

which transporter allows preferential uptake of glucose during hypoglycemia

A

glut 3

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28
Q

glut 4 features

A

medium km (2.5-5), insulin dependancy in recruitment of glut 4 from intracellular stores

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29
Q

true or false: all gluts are ACTIVE MEDIATED transporters

ie. transport glucose up concentration gradient only

A

false
PASSIVE
down concentration gradient

30
Q

STUDY THE GRAPH OF GLUCOSE TRANSPORTERS AND KM

A

.

31
Q

ranks these in increasing order of KM

glut 1,2,3,4

A

glute 1
glute 3
glute 4
g;ute 2

32
Q

Tissues with low km and high affinity use which 2 glut transporters

A

glut 1 and glut 3

33
Q

what is the function of tissues with low km and high affinity

A

protect from any negative affects of hypoglycemia (ex: syncope)

34
Q

true or false: RBC have no mitochondria which is why they need near constant uptake of ATP

A

true

35
Q

true or false and explain: RBC and neuron are not only fueled by glycolysis

A

false, RBC metabolism is solely on glyoclysis so there needs to be an intake of glucose in the cell (dont need alot of energy and responds to low concerntration)

36
Q

explain how RBCs and Neurons protect themselves from hypoglycemia

A

SInce they have such a high afinity and low km, they do not need a lot of glucose to function correctly
Even during periods of low concentration (2.5 MM of glucose, they will still take up atp)

37
Q

which glut transporter works best for periods of transcietn HYPERGLYCEMIA/post prandial

A

glut 2

38
Q

which glut transporter works better in periods of hyperglycemia

A

glute 2

39
Q

which glute receptor works best for periods of normal blood sugar

A

glute 4

40
Q

which glut receptors work best with hypoglycemic conditions

A

glute 1 and glute 3

41
Q

explain why tissues with high km and low affinity are good for hyperglycemia

A

Glut 2 (in liver, b cells) have an extremely high rate of transport but only at high concentrations of blood glucose therefore it will take up a lot of glucose as glycogen and secreting insulin to allow glycogen storage in muscles

42
Q

what are the two pathways for glucose/sucrose etc

A

can be stored as glycogen

go to glycolysis

43
Q

true or false: the skeletal muscles can only take up glucose?

A

false, it can take up glucose, fructose and galactose

44
Q

fructose, galactose and glucose all need ATP

A

true

45
Q

When ATP is broken down with galactose, what does galactose become

A

galactose 1 phosphate

46
Q

when atp is broken down, what does the glucose become

A

glucose 6 phosphate

47
Q

when atp is broken down, what does frcutose become

A

fructose 6 phsophate

48
Q

true or false, all sugars need to go through phosphorylation for reactions within the cell

A

true

49
Q

what is fructose made from

A

sucrose and glucose

50
Q

what is galactose made from

A

glucose and lactose

51
Q

what is the enzyme that converts galactose to galactose 1 phosphate

A

galactokinase

52
Q

what is the enzyme that converts glucose to glucose 6 phosphate

A

glucokinase (liver)

hexokinase

53
Q

what is the enzyme that converts fructose to fructose 6 phosphate or fructose 1 phosphate

A

fructokinanse (1)

hexokinase (6)

54
Q

is glucokinase found anywhere in the body?

A

no , only found in the liver

55
Q

is hexokinase found in the liver?

A

no

56
Q

true or false: hexokinase can be used only for glucose

A

false, can also be used for fructose

57
Q

true or false: glucose 6 phosphatase enzyme is only found in the liver

A

true

58
Q

function of glucose 6 phosphatase

A

Allows stores carbohydrates in the liver to be reprocessed into glucose (phosphate from glucose 6 phosphate binds to the enzyme) and allows glucose to leave the liver cells and enter the blood circulation

convert monosacharrides (fructose and galactose) to glucose for export

59
Q

What is the only way we can constantly maintain blood circulation levels of blood glucose

A

through glucose 6 phosphate being reprocessed to glucose by the enzyme and exiting the liver

60
Q

is the process of glycogenesis reversible and if so what is it called

A

yes and glycogenolysis

61
Q

what is glycogenesis

A

new formation of glycogen in tissues to be stored

62
Q

explain glycogenesis in the liver

A

After eating, liver is going to take high levels of glucose.
It enters the cell and gets converted to glucose 6 phosphate by GLUCOKINASE=spontanously
Once converted to glucose 6 phosphate it can go up the pathway to become glycolysis, down the pathway to be glycolosis or it can go back out into the blood by phosphotase (glucose6phosphostase)

63
Q

what is glycogenolysis

A

breakdown of glycogen for energy when needed

done by glucose 6 phosphotase

64
Q

what is the last step needed to store the glucose as glycogen

A

need UTP instead of ATP

65
Q

Explain glucose into glycogen

A

1) glucose into glucose6 phosphate by hexokinase everywhere in the body and glucokinase in the liver(ATP drives reaction)
2) Glucose 6 phosphate to glucose 1 phophshate
3) Glucose 1 phoshphate into UDP glucose (UTP drives reaction)
UTP is broken down, UDP binds to the glucose
4) UDP-glucose is stored AS GLYCOGEN by glycogen syntahse

66
Q

what is UTP

A

high energy compound (purine with ribose and 3 phosphates)

67
Q

what is the enzyme responsible for accelerating UDP glucose into glycogen

A

GLYCOGEN SYNTHASE

68
Q

do all glut receptors/carriers require insulin

A

no

69
Q

what hormone is going to stimulate glycogen synthase and why

A

insulin

and increased insulin stimulates uptake og glucose into the cell that will be stored as glyocgen

70
Q

what is glycogenin

A

protein that acts as an achor that allows glucose to bind and start to form the glycogen tree

258 - physiology (21 decks)

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