Week 6

Question 1

glycogen is stored primarily in the

Answer 1

liver

skeletal muscle

Question 2

glycogen synthesis pathway summary

Answer 2

Glucose 6-P to Glucose 1-P
Glucose 1-P + UTP to UDPGIc
UDPGIc to terminal end of glycogen

Question 3

phosphoglucomutase

Answer 3

catalyzes isomerization of glucose 6-P to glucose 1-P

Question 4

UDPGIc pyrophosphorylase

Answer 4

glucose 1-p to UDPGIc

Question 5

difference between pathway for synthesis vs degradation of glycogen

Answer 5

they are the reverse of each other

Question 6

glycogen phosphorylase

Answer 6

releases glucose 1-P form glycogen

Question 7

glucose 6-phosphatase

Answer 7

converts glucose 6-P to free glucose

Question 8

key difference between liver and muscle glycogenolysis

Answer 8

an enzyme is required to de-phosphorylate glucose to be released from the liver

Question 9

Mechanisms for regulation of liver glycogen synthesis and degradation

Answer 9

• glucagon activation of GPCF

- epinephrine binding to alpha-adrenergic

Question 10

describe glucagon activation of GPCR

Answer 10

• activation of adenylate cyclase increases [cAMP] which activates protein kinase A which…
  a. phosphorylates glycogen phosphorylase which leads to glycogen degradation and
  b. phosphorylates glycogen synthase to inactivate

Question 11

describe epi binding alpha-adrenergic

Answer 11

PIP is cleaved to IP3 and DAG
- IP3 stimulates Ca release from ER which activate phosphorylase kinase to phosphorylate glycogen phosphorylase for glycogen degradation and calmodulin dependent kinase to phosphorylate glycogen synthase to inactivate
DAG activate protein kinase C

Question 12

regulation of glycogen synthesis and degradation in the skeletal muscle

Answer 12

not impacted by glucagon

• epi activation of GPCR
• Ca mediated muscle contraction
• elevated AMP

Question 13

describe epi activation of GPCR

Answer 13

activation of adenylate cylase increases [cAMP] which activates protein kinase A to

• phosphorylate phosphorylase kinase to phosphorylate glycogen phosphorylase for glycogen degradation
• phosphorylate glycogen synthase to inactivate it

Question 14

describe Ca mediated contraction

Answer 14

Ca calmodulin activates phosphorylase kinase to phosphorylate glycogen phosphorylase to lead to glycogen degradation

Question 15

describe impact of elevated AMP

Answer 15

allosterically activate glycogen phosphorylase to cause glycogen degradation

Question 16

substrates for glucogenogenesis

Answer 16

lactate
glycerol
amino acids (primarily alanine)
NOT ketogenic amino acids or fatty acids

Question 17

where is the lactate from that may be used for gluconeogenesis?

Answer 17

cori cycle

Question 18

where is the glycerol from that may be used for gluconeogenesis

Answer 18

released during lipolysis

Question 19

where are the amino acids from that may be used for gluconeogenesis?

Answer 19

skeletal muscle

Question 20

pyruvate carboxylase iin gluconeogenesis

Answer 20

mitochondrial enzyme that carboxylates pyruvate to OAA which is reduced to malate which is able to leave the mitochondria

Question 21

what does pyruvate carboxylase requires

Answer 21

acetyl-CoA for allosteric activation

biotin as cofactor

Question 22

phosphenol pyruvate carboxykinase in gluconeogenesis

Answer 22

cytosolic enzyme which converts cytosolic OAA to phospenol pyruvate

Question 23

what enhances transcription of phosphenol pyruvate

Answer 23

high cortisol levels

Question 24

what is required to overcome the clycolytic rxn catalyzed by pyruvate kinase to allow gluconeogenesis to occur

Answer 24

pyruvate carboxylase

phosphenol pyruvate

Question 25

fructose 1,6-bisphosphatase in gluconeogenesis

Answer 25

cytosolic enzyme which converts fructose 1,6-bisphosphate to fructose 6-phosphate

Question 26

what inhibits fructose 1,6-bisphosphatase

Answer 26

AMP | fructose 2,6-bisphosphtase

Question 27

what overcomes the irreversible glycolytic rxn catalyzed by fructose 1,6-bisphosphatase to allow gluconeogenesis to occur

Answer 27

fructose 1,6-bisphosphatase

Question 28

fructose 2,6-bisphosphatase in the fed state

Answer 28

kinase termed phosphofructokinase-2 - generates fructose 2,6-bisphosphate that allosterically activates PFK-1 - dephosphorylated - kinase active, phosphtase inactive

Question 29

fructose 2,6-bisphosphatase in fasted state

Answer 29

phosphatase activity - generate fructose 6-phosphate - phosphorylate - kinase inactive, phosphatase active

Question 30

glucose 6-phosphatase in gluconeogenesis

Answer 30

dephosphorylates glucose 6-phosphate to free glucose that can be release form the liver

Question 31

what enzyme is use for both gluconeogenesis and glycogenolysis

Answer 31

glucose 6-phosphatase

Question 32

what are the pathways essential for glucose homeostasis

Answer 32

gluconeogenesis | glycogenolysis

Question 33

when are gluconeogenesis and glycogenolysis activated

Answer 33

when insulin to glycogen ratio becomes sufficiently reduced

Question 34

pathway responsible for supplying blood glucose levels until around 20 hours of fasting

Answer 34

glycogenolysis

Question 35

primary pathway for maintaining blood glucose after 20 hours of fasting

Answer 35

gluconeogenesis

Question 36

substrates for gluconeogenesis

Answer 36

lactate glycerol alanine and glutamine propionate

Question 37

this pathway is the reverse of glycolysis

Answer 37

gluconeogenesis

Question 38

lactate for gluconeogenesis comes from

Answer 38

anaerobic metabolism or the cori cycle

Question 39

glycerol for gluconeogenesis comes from

Answer 39

it is freed during fasting and through glycolysis

Question 40

the propionate for gluconeogenesis comes from

Answer 40

oxidation of fatty acids

Question 41

is acetyl-coA generated through fatty acid beta oxidation a substrate for gluconeogenesis?

Answer 41

no

Question 42

amino acids that can be transaminated for gluconeogenesis are released through

Answer 42

cortisol mediated protein metabolism

Question 43

gluconeogenesis is reverse of glycolysis except for

Answer 43

four regulatory steps that allow us to bypass irreversible steps of glycolysis

Question 44

irreversible steps of glycolysis

Answer 44

- the phosphorylation of glucose by glucose kinase or hexokinase - phosphorylation of fructose 6 phosphate by phosphofructokinase 1 - conversion of phosphoenolpyruvate by pyruvate kinase

Question 45

what allows the bypassing of the regulatory enzyme pyruvate kinase

Answer 45

combination of pyruvate carboxylase and phosphoenolpyruvate carboxy kinase

Question 46

overcome step catalyzed by phosphofructokinase 1 by using

Answer 46

fructose 1,6 bisphosphatase

Question 47

overcome rxn by glucose kinase or hexokinase

Answer 47

glucose 6 phosphatase which will dephosphorylate glucose 6 phosphate to general 3 glucose which ban be released into circulation

Question 48

liver glycogenolysis regulation

Answer 48

activated by glucagon and epinephrine

Question 49

liver glycogenolysis will

Answer 49

support blood glucose in fasted state

Question 50

muscle glycogenolysis regulation

Answer 50

activated by epi, AMP, Ca

Question 51

muscle glycogenolysis will

Answer 51

oxidize fuel for exercising muscle

Question 52

amp and calcium will be elevated in...

Answer 52

exercising skeletal muscle, those activating glycogenolysis

Question 53

muscle glycogen is not used to

Answer 53

support blood glucose - muscle lacks glucose-6-phosphate so cannot dephosphorylate glucose to release from cell

Question 54

difference between glut receptors in hepatic and skeletal muscle cells

Answer 54

glut2 in liver always in cell membrane | glut4 retained within cell until insulin is present

Question 55

difference in glucose phosphorylation in liver vs muscle cells

Answer 55

hexokinase responsible in muscle | glucokinase in liver

Question 56

glycogen receptor is present in the liver or skeletal muscle cells?

Answer 56

liver

Question 57

During an overnight fast, what is a major source of blood glucose? - dietary glucose - gluconeogenesis - glycerol from lipolysis - hepatic glycogenolysis - muscle glycogenolysis

Answer 57

hepatic glycogenolysis

Question 58

glycogen is stored in the

Answer 58

liver and skeletal muscle

Question 59

phosphoglucomutase

Answer 59

isomerizes glucose 6-P to glucose 1-P | part of glycogen synthesis

Question 60

UDPG1c pyrophosphorylase

Answer 60

add UTP to glucose 1-p to make udpGlc | part of glycogen synthesis

Question 61

glycogen synthase

Answer 61

adds UDPGlc to the terminal end of glycogen | part of glycogen synthesis

Question 62

glycogen phosphorylase

Answer 62

releases glucose 1-P from glycogen | part of glycogen degradation

Question 63

glucose 6-phosphatase

Answer 63

glucose 6p to free glucose

Question 64

regulation of liver glycogen synthesis and degradation

Answer 64

glucagon activation of GPCR epinephrine binds alpha-adrenergic

Question 65

glucagon activation of GPCR in liver

Answer 65

actates adenylate cyclase ot increase cA

Question 66

summary of glucagon activation of GPCR in liver

Answer 66

glycogen phosphorylase is activated and glycogen synthase is inactivated

Question 67

epinephrine binding alpha adrenergic in liver

Answer 67

cleaves PIP to IP3 and DAG to stimulate the release of Ca from ER which will activate phosphorylase kinase to phosphorylate glycogen phosphorylase and degrade glycogen and phosphorylate glycogen synthase to inactivate it

Question 68

substrates for gluconeogenesis

Answer 68

lactase from cori cycle glycerol from lipolysis aa from alanine from skeletal muscle

Question 69

are fatty acids or ketogenic amino acids substrates for gluconeogenesis

Answer 69

no

Question 70

pyruvate carboxylase

Answer 70

mitochondrial enzyme that carboxylates pyruvate to OAA which can be reduced to malate leave the mitochondria

Question 71

pyruvate carboxylase requires

Answer 71

acetyl-coA for allosteric activation | biotin as a cofactor

Question 72

phospoenol pyruvate carboxykinase

Answer 72

cytosolic enzyme that converts cytosolic OAA to phosphoenol pyruvate

Question 73

transcription of phosphoenol pyruvate carboxykinase is enhanced by

Answer 73

high levels of cortisol

Question 74

required to overcome the glycolytic rxn catalyzed by pyruvate kinase

Answer 74

pyruvate carboxylase and phosphoenol pyruvate carboxykinase

Question 75

fructose 1,6-bisphosphatase

Answer 75

cytosolic enzyme that converts fructose 1,6-bisphosphate to fructose 6-phosphate

Question 76

regulations of fructose 1,6 bisphosphatase

Answer 76

inhibited by AMP an fructose 2,6 bisphosphate

Question 77

overcomes irreversible glycolytic rxn catalyze by phosphfructokinase-1

Answer 77

fructose 1,6-bisphosphatase

Question 78

fructose 2,6 bisphosphatase

Answer 78

reduces the amount of fructose 2,6 bisphosphate which will reduce the allosteric activation of PFK1 and enhance the rxn catalyzed by fructose 1,6 bisphosphatase

Question 79

fructose 2,6 bisphosphatase in fed state

Answer 79

kinase activity and is phosphotructokinase generate fructose 2,6 bisphosphate to allostrically activate PFK1

Question 80

fructose 2,6 bisphosphatase in fed state in fasted state

Answer 80

phosphatase activity generates fructose 6-phosphate

Question 81

enzyme used for both gluconeogenesis and glycogenolysis

Answer 81

glucose-6 phosphatase

Question 82

If unregulated, what pairs of enzymes would represent a futile cycle?

Answer 82

Fructose 1,6-bisphosphatase and phosphofructokinase-1

Question 83

Alanine can be shuttled from the skeletal muscle to the liver where it is deaminated to generate pyruvate. When glucagon is high, pyruvate is primarily used as a substrate for which pathways?

Answer 83

gluconeogenesis

Question 84

The skeletal muscle primarily provides substrate for gluconeogenesis through which of the following processes?

Answer 84

protein catabolism

Question 85

When insulin levels are high, what is true of glycogen synthase

Answer 85

it is dephosphorylate and active

Question 86

What are the two major contributors to maintaining blood glucose levels during fasting?

Answer 86

hepatic glycogenolysis and gluconeogenesis

Question 87

The process of gluconeogenesis primarily takes place in which tissues?

Answer 87

liver

Question 88

Newborn screening results show a biotinidase deficiency in a 2-day old infant. This deficiency impairs the infant’s ability to reuse and recycle biotin. Due to this enzymatic deficiency, the activity of which enzymes is likely impaired?

Answer 88

pyruvate carboxylase