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Nutrition > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

what is the basic building block of all carbohydrates?

A

monosaccharides

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2
Q

what are the 4 types of carbohydrates, based on how many monosaccharides long they are?

A
  1. monosaccharides: basic unit
  2. disaccharides: made up of two monosaccharides
  3. oligosaccharides: 2-10 monosaccharides long (technically disaccharides are in this category)
  4. polysaccharides: over ten monosaccharides long
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3
Q

what are the 3 types of monosaccharides?

A
  1. gluctose
  2. fructose
  3. galactose
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4
Q

where is galactose found?

A

only in milk!!

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5
Q

what is the most common monosaccharide?

A

glucose

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6
Q

where is fructose found?

A

in sugary foods like molasses and berries

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7
Q

what are the 3 types of disaccharides? give what they are made of

A
  1. maltose = glucose + glucose
  2. sucrose = glucose + fructose
  3. lactose = glucose + galactose
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8
Q

describe digestion of carbohydrates in the mouth

A

salivary alpha amylase begins to breakdown carbohydrates; the longer in the mouth the more digestion occurs

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9
Q

does the digestion that happens in the mouth really play a large role in digestion of carbohydrates?

A

no; is negligible

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10
Q

does any digestion of carbohydrates occur in the stomach?

A

NO!!! the stomach contains NOTHING to digest carbs

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11
Q

describe the 4 steps of carbohydrate digestion in the small intestine

A
  1. when chyme enters the duodenum the duodenum secretes cholecystokinin (CCK)
  2. CCK acts on the pancreas to secrete digestive enzymes (pancreatic alpha amylase which breaks polysaccharides into oligosaccharides)
  3. oligosaccharidases along the brush border break down oligosaccharides into disaccharides
  4. disaccharidases along the brush border break down disaccharides into monosaccharides, which can finally be digested
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12
Q

give the 3 disaccharidases and what they do in the small intestine for digestion of carbohydrates

A
  1. maltase: breaks down maltose into 2 glucoses
  2. sucrase: breaks down sucrose into glucose + fructose
  3. lactase: breaks down lactose into one glucose and one galactose
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13
Q

where does digestion of carbohydrates mostly occur in the small intestine and why?

A

the jejunum; it is the longest part of the SI

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14
Q

how is absorption of carbohydrates accomplished?

A

through transporters

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15
Q

list and describe the 2 transporters that are responsible for absorption of carbohydrates into cells of the small intestine from the lumen of the SI

A
  1. sodium-glucose symporter: on the brush border; transports one glucose and one galactose into the cells along with 2 sodiums
  2. GLUT5: also on the brush border; will transport fructose into the cell via facilitated diffusion; nothing else transported into cell along with it
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16
Q

list and describe the 2 transporters that transport carbohydrates out of cells of the SI and into the blood stream for absorption

A
  1. GLUT2: transports glucose and galactose out of the cell

2. GLUT5: transports fructose out of the cell

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17
Q

in absorption of carbohydrates, what occurs after glucose, fructose, and galactose are transported out of the cells and into the bloodstream?

A

glucose, fructose, and galactose enter the hepatic portal system and travel to the liver, where fructose and galactose are converted to glucose

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18
Q

how is transport of glucose across cell membranes accomplished?

A

through 2 types of glucose transport proteins

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19
Q

what are the 2 types of glucose transport proteins?

A
  1. insulin independent

2. insulin dependent

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20
Q

name the 3 types of insulin independent glucose transport proteins

A
  1. GLUT1
  2. GLUT2
  3. GLUT3
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21
Q

name the one glucose dependent transport protein

A

GLUT4

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22
Q

where is GLUT1 found? (2)

A
  1. in small concentrations on every cell

2. in high concentration on erythrocytes and cells in the blood brain barrier

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23
Q

describe GLUT1’s affinity for glucose and what that means

A

GLUT1 has a high affinity for glucose, which means that is can transport glucose into cells no matter how low the blood glucose concentration is

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24
Q

why is GLUT1 found in high concentrations on erythrocytes and on cells in the blood brain barrier?

A

because erythrocytes and the blood brain barrier REQUIRE glucose, so they have GLUT1 so they can get glucose no matter what the blood glucose concentration is

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25
Q

where is GLUT3 found?

A

on neurons in the brain and other neurons

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26
Q

describe GLUT3’s affinity for glucose

A

also has a high affinity for glucose like GLUT1

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27
Q

where is GLUT2 found? (2)

A
  1. on hepatocytes in the liver and

2. on pancreatic cells

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28
Q

describe GLUT2’s affinity for glucose

A

has a low affinity for glucose, meaning that glucose is only transported when there are high concentrations of blood glucose

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29
Q

when is blood glucose concentration usually high, allowing for GLUT2 to work?

A

just after a meal, and GLUT2 works because it is found on hepatocytes in the liver and all glucose from the diet goes to the liver first

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30
Q

where is GLUT4 found?

A

in muscle and adipose cells

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31
Q

when is GLUT4 expressed on muscle and adipose cells?

A

only when insulin is present

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32
Q

how does GLUT4 work?

A

glucose will only be transported into muscle and adipose cells when insulin is secreted

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33
Q

when and what causes insulin to be secreted?

A

insulin is secreted by the pancreas in response to high blood glucose which is sensed due to glucose transport via GLUT2

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34
Q

what is the main effect of insulin and why?

A

main effect is to lower blood glucose since it is secreted in response to high glucose levels

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35
Q

what are the 2 specific effects of insulin?

A
  1. GLUT4 expression (on muscle and adipose cells)

2. activation of metabolic pathways that utilize/store glucose (keep it out of the bloodstream)

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36
Q

when insulin is secreted and blood glucose is high immediately after a meal, what state is the animal in?

A

Fed State

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37
Q

when is glucagon secreted and what is it secreted by?

A

glucagon is secreted by the pancreas when insulin is not being secreted

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38
Q

what two things is the pancreas always secreting to regulate blood glucose levels?

A

insulin or glucagon

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39
Q

what is the main effect of glucagon?

A

to MAINTAIN blood glucose

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40
Q

what is the specific effect of glucagon?

A

activation of metabolic pathways that synthesize glucose and release glucose from storage (add removed glucose back to bloodstream for cells that require it)

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41
Q

how long will the fasted state last?

A

until all body reserves have been used up

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42
Q

what is the main goal of glycolysis?

A

to convert one molecule of glucose (a 6 carbon molecule) into 2 molecules of pyruvate (3-carbon molecules) for ATP (energy)

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43
Q

where does glycolysis take place and what does this mean?

A

takes place in the cytoplasm, meaning that any cell can perform glycolysis, do not need organelles like mitochondria to provide energy

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44
Q

what MUST happen in order for glycolysis to take place?

A

glucose MUST get into the cell

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45
Q

write out the entire process of glycolysis (11 steps)

A

every time you see this card, get a whiteboard and WRITE IT!!!! does not matter if studying for a quiz or exam or what, just DO IT

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46
Q

name the 4 ways of regulation of glycolysis

A
  1. glucose transport
  2. glucokinase
  3. phosphofructokinase-1
  4. pyruvate kinase
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47
Q

for what cells is the glucose transport regulation of glycolysis relevant for? why?

A

only on cells with GLUT2 and GLUT4 due to their low affinity for glucose meaning they require certain conditions in order for glucose to enter

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48
Q

describe the regulation of glycolysis that occurs via the glucose transporter GLUT2

A

GLUT2 will only transport glucose into liver and apncreatic cells when there are high concentrations of glucose outside those cells due to their low affinity for glucose; so glycolysis will only occur in those cells when there are high concentrations of glucose

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49
Q

describe the regulation of glycolysis that occurs via the glucose transporter GLUT4

A

GLUT4 will only tranposrt glucose into muscle and adipose cells when INSULIN IS PRESENT, so glycolysis will only occur in these cells when INSULIN IS PRESENT

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50
Q

describe the affinity for glucose of glucokinase, which catalyzes the first step of glycolysis in liver cells and what this means for glycosis

A

has a low affinity for glucose, so glycolysis will only be initiated in these cells when there are high concentrations of glucose inside those cells

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51
Q

describe the affinity for glucose of hexokinase, which catalyzes the first step of glycolysis in all cells except liver cells and what this means for glycolysis

A

has a high affinity for glucose, so will always be active in the presence of glucose

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52
Q

what does phosphofructokinase-1 do in glycolysis?

A

converts fructose 6-phosphate into fructose 1,6-bisphosphate in the first committed step of glycolysis

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53
Q

what does it means when we refer to the first committed step of glycolysis?

A

after the conversion of fructose 6-phosphate into fructose 1,6-bisphosphate, the only pathway that can now occur is glycolysis, the product must move on in conversion to pyruvate

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54
Q

how is phosphofructokinase-1 regulated (2)

A
  1. inhibited by a buildup of ATP

2. reactivated by fructose 2,6-bisphosphate

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55
Q

when phosphofructokinase-1 is inhibited by a buildup of ATP, what happens to the glucose that would have entered glycolysis

A

it is stored as glycogen

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56
Q

can the liver hold all the stored glycogen in the world? what does this mean?

A

no, so phosphofructokinase-1 is reactivated by fructose 2,6-bisphosphate

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57
Q

when is fructose 2,6-bisphosphate synthsized?

A

when insulin is present

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58
Q

what does pyruvate kinase do?

A

converts phosphoenol pyruvate into pyruvate in the final step of glycolysis

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59
Q

how is pyruvate kinase regulated (2)

A
  1. activated by fructose 1,6-bisphosphate becauase products are now committed to glycolysis
  2. inhibited by glucagon
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60
Q

how much ATP is produced by glycolysis?

A

4 ATP

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61
Q

how much ATP is used by glycolysis?

A

2 ATP

62
Q

how much ATP is 1 NADH + H+ molecule worth?

A

1 NADH + H+ is worth 2.5 ATP

63
Q

how much ATP comes from the NADH + H+ molecules produced in glycolysis?

A

2 NADH + H+ molecules x 2.25 = 5 ATP

64
Q

how much NET ATP is produced from one molecule of glucose undergoing glycolysis? is this a lot?

A

net 7 ATP from one molecule of glucose, which isn’t a lot

65
Q

what is glycogen? (2)

A
  1. a complex polymer of glucose molecules

2. the storage form of glucose in the LIVER and MUSCLE

66
Q

where is the glucose chain attached in glycogen?

A

to glycogenin

67
Q

what is glycogenin?

A

a core protein where glucose attaches in glycogen

68
Q

why is glycogen highly branched?

A

to allow miltiple glucoses to be able to attach for storage and use

69
Q

describe the structure of glycogen

A

chain of glucoses that are linked via alpha 1,4-linkages on the straight chain and glucoses are linked by alpha 1,6-linkages at the branched points

70
Q

why does the liver store glucose as glycogen? she’s selfless

A

to be able to releace glucose into the bloodstream during the fasted state to maintain blood glucose levels (the selfless. altruistic angel)

71
Q

how much glycogen does the liver store?

A

enough to maintain blood glucose levels during an overnight fast

72
Q

why does the muscle store glucose as glycogen? selfish

A

for a quick energy soure when needed, selfish

73
Q

when do both the liver and muscle store glucose as glycogen?

A

after a meal, in the fed state

74
Q

give the 4 steps of the glycogenesis pathway

A
  1. glucose in coverted to glucose 6-phosphate by glucokinase in the liver and hexokinase in the muscle and the conversion input of one ATP to one ADP
  2. glucose 6-phosphate is converted to glucose 1-phosphate by phosphoglucomutase
  3. glucose 1-phosphate is converted to UDP-glucose by UDP-glucose phosphorylase and the conversion input of one UDP to PPi
  4. UDp-glucose is converted to (Glucose)n+1, or added to glycogen chain, by glycogen synthase and the input conversion of (Glucose)n to UDP
75
Q

what is UDP glucose?

A

the primed glucose that is ready to be added to an existing glycogen chain

76
Q

how does glycogen synthase work?

A

only adds glucose to existing glycogen chain at alpha-1,4-linkages

77
Q

since glycogen is highly branched, what else is required in the glycogenesis pathway?

A

branching enzyme

78
Q

how does branching enzyme work?

A

once a glucose chain is at least ELEVEN glucoses long, a segment of SEVEN glucoses will be removed and will be added to another chain at an alpha-1,6-linkage that is itself at least 4 glucoses away from an existing branch

79
Q

what creates chains in glycogen?

A

alpha-1,4-linkages

80
Q

what creates branches in glycogen?

A

alpha-1,6-linkages

81
Q

in what two ways is glycogenesis regulated?

A
  1. through glucose transport

2. through glycogen synthase

82
Q

what must happen in order for glycogenesis to occur?

A

glucose MUST get into the cell

83
Q

describe how glycogenesis is regulated via glucose transport in liver cells

A

GLUT2 has a low affinity for glucose, so glucose will only get into the cell when there are high concentrations of blood glucose, so glycogenesis will only happen when there is high blood glucose (Fed state)

84
Q

describe how glycogenesis is regulated via glucose transport in muscle cells

A

GLUT4 is insulin dependent, so glucose will only enter muscle cells when insulin is present, so glycogenesis will only occur in these cells when insulin is present (Fed state)

85
Q

will glycogenesis happen in the Fasted state?

A

NO!! glycogenesis will only occur in the Fed state

86
Q

describe how glycogenesis is regulated via glycogen synthase

A
  1. glycogen synthase in inactive when it is phosporylated, so the enzyme protein phosphatase-1 (PP1) dephosporylates it to become active
  2. conversely, protein kinase A (PKA) phosphorylates glycogen synthase to inactivate it
87
Q

when is protein phosphatase-1 activated? what does this indicate and what is the result?

A

by insulin, in the fed state, indicates that glycogenesis can occur and dephosphorylates glycogen synthase

88
Q

what is protein kinase A (PKA) activated by? what does this indicate and what is the result?

A

activated by glucagon, indicating a fasted state where glycogenesis should NOT occur, so it phosphorylates glycogen synthase and prevents glycogenesis from occurring

89
Q

what determines if glycolysis or glycogenesis occurs?

A

the excess ATP produced by glycolysis inhibits phosphofructokinase-1, which shuttles everything back to glucose-6 phosphate and causes glycogenesis to occur instead

90
Q

where does glycogenesis occur?

A

in the cytosol; like glycolysis

91
Q

what is glycogenolysis?

A

the breakdown of glycogen

92
Q

what is glycogen broken down into in the liver through glycogenolysis? what can use this? selfless

A

glucose, whole body can use

93
Q

what is glycogen broken down into in the muscle through glycogenolysis? what can use this? selfish

A

glucose 6-phosphate, only muscles can use

94
Q

describe the 3 steps of glycogenolysis in the LIVER

A
  1. (Glucose)n is converted to glucose 1-phosphate by glycogen phosphorylase, with the input on an inorganic phosphate (Pi) and releasing (Glucose)n-1, or the glycogen chain with one less glucose molecules
  2. glucose 1-phosphate is converted to glucose 6-phosphate by phosphoglucomutase
  3. glucose 6-phosphate is converted to glucose by glucose 6-phosphatase, with the input of one H2O and the release of a Pi, then the glucose enters the bloodstream
95
Q

describe the 2 steps of glycogenolysis in the MUSCLE

A
  1. (Glucose)n is covnerted to glucose 1-phosphate by glycogen phosphorylase with the input of an inorganic phosphate (Pi) and the release of (Glucose)n-1
  2. glucose 1-phosphate is converted to glucose 6-phosphate by phosphoglucomutase, and this glucose 6-phosphate enters glycolysis for energy production in the muscles
96
Q

what does glycogen phosphorylase do in glycogenolysis?

A

removes alpha-1,4-linkages

97
Q

at the same time as the pathway is occurring in glycogenolysis, what is also working?

A

debranching enzyme

98
Q

how does debranching enzyme work in glycogenolysis?

A

when only FOUR glucoses remain on a branch, a chain of THREE are removed and will be added at the end of another chain, while the ONE remaining glucose is release as free glucose to go through glycogenolysis; removes alpha-1,6-linkages

99
Q

how is glycogenolysis regulated?

A

through glycogen phosphorylase, using the same enzymes as glycogenesis

100
Q

describe regulation of glycogen phosphorylase for glycogenolysis

A
  1. glycogen phosphorylase is inactive when it is DEphosphorylated, so protein kinase A phosphorylates and activates it
  2. protein phosphatase-1 dephosphorylates and inactivates glycogen phosphorylase
101
Q

what causes secretion of protein phosphatase-1 and deactivation of glycogen phosphorylase through dephosphorylation? relate to glycogenesis

A

the presence of insulin, which indicates that there is extra glucose and glycogenesis occurs instead and PP-1 dephosphorylates and activates glycogen synthase instead

102
Q

what causes secretion of protein kinase A and activation of glycogen phosphorylase through phosphorylation? relate to glycogenesis

A

PKA is activated by glucagon (greater effect in the liver) and epinephrin (greater effect in muscle). This indicates that there is a fasted state and glycogenolysis must occur instead of glycogenesis, so PKA also deactivates phycogen synthase by phosphorylation

103
Q

can glycogenesis and glycogenolysis occur at the same time? why?

A

nope! they are regulated conversely by the same enzymes. Protein kinase A deactivates glycogenesis and activates glycogenolysis through phosphorylation and protein phosphatase-1 activates glycogenesis and deactivates glycogenolysis through dephosphorylation

104
Q

what is gluconeogenesis?

A

biosynthesis of glucose

105
Q

where does gluconeogenesis occur? (2)

A
  1. liver

2. kidney

106
Q

what is the goal of gluconeogenesis?

A

to maintain blood glucose

107
Q

what is the onnly source of energy that can be broken down and stored in anaerobic conditions?

A

glucose

108
Q

when does gluconeogenesis occur and where?

A

when fasting longer than what the liver has glycogen stored for, gluconeogenesis occurs first in the LIVER and if continue on to extreme starvation, gluconeogenesis will occur in the kidneys as well

109
Q

what are the 3 precursors for gluconeogenesis?

A
  1. lactate/lactic acid
  2. glycerol
  3. amino acids
110
Q

when is lactate produced?

A

due to the anaerobic metabolism of glucose

111
Q

how is lactate produced?

A

one glucose is converted to 2 molecules of pyruvate through glycolysis and then the pyruvate is converted to lactate which enters the bloodstream and is removed by the liver

112
Q

under what conditions/locations is lactate most often produced? (2)

A
  1. when exercising anaerobically or during fight or flight response
  2. in erythrocytes, which are RBCs with no mitochondria, so they use lactate instead
113
Q

how and when is glycerol produced?

A

from the breakdown of fats (triglycerides); when fatty acids are removed from glycerol to mobilize fat in the fasted state, glycerol is released from adipose and is removed by the liver (from the bloodstream)

114
Q

how and when are amino acids produced in the body to be a precursor for gluconeogenesis?

A
  1. produced from the breakdown of protein

2. major source of energy during extreme starvation, when there are no more fat stores

115
Q

what kind of muscle is broken down first to be a precursor for gluconeogenesis? why?

A

skeletal muscle; least essential. keep heart beating and brain getting energy first

116
Q

when do the precursors of amino acids and lactate enter gluconeogenesis? where does this occur?

A

at the first step when pyruvate is converted to oxaloacetate by pyruvate carboxylase with the input of a bicarbonate and the input conversion of one ATP to ADP + Pi; in the mitochondria

117
Q

when does the precursor glycerol enter gluconeogenesis? where does this occur?

A

when one glyceraldehyde 3-phosphate is converted into one dehydroxyacetone phosphate by triose phosphate isomerase; in the cytosol

118
Q

when does gluconeogenesis move out of the mitochondria and into the cytosol?

A

once pyruvate has been converted to oxaloacetate

119
Q

how many molecules of each precursor must enter into gluconeogenesis and why?

A

2 of each because it comes from 2 pyruvate molecules which will eventually become two glyceraldehyde 3-phosphate molecules that then move on

120
Q

at what kind of steps is gluconeogenesis regulated?

A

at the steps that differ from glycolysis

121
Q

by what 4 enzymes is gluconeogenesis regulated? what do these enzymes normally do?

A
  1. pyruvate carboxylase, which converts pyruvate into oxaloactate
  2. phosphoenol pyruvate carboxykianse, which converts oxaloacetate into phosphoenol pyruvate
  3. Fructose 1,6-bisphosphatase, which converts fructose 1,6-bisphosphate into fructose 6-phosphate
  4. glucose 6-phosphatase, which converts glucose 6-phosphate into glucose
122
Q

how does pyruvate carboxylase contribute to regulation of gluconeogenesis?

A

it is activated by increase in breakdown of fat, which indicates that some time has passed after the last meal so something needs to be done to maintain blood glucose, so this enzyme is activated to start gluconeogenesis

123
Q

how does phosphoenol pyruvate carboxykinase contribute to regulation of gluconeogenesis? (2)

A
  1. it is activated by glucagon and glucocorticoids like cortisol (under stress) and contributes to maintaining blood glucose levels
  2. it is inhibited by insulin, which indictaes that the body has plenty of glucose, and when inhibited, it by passes the pyruvate kinase reaction on glycolysis to prevent addition of glucose to the bloodstream
124
Q

how does fructose 1,6-bisphosphatase contribute to regulation of gluconeogenesis?

A

it is inhibited by fructose 2,6-bisphosphate, which normally activates phosphofructokinase-1 in glycolysis so we can use the glucose we have instead of making more

125
Q

how does glucose 6-phosphatase contribute to regulation of gluconeogenesis?

A

it is inhibited by insulin, because now we want to use the glucose, not make it

126
Q

give the 11 steps of gluconeogenesis

A
  1. in the mitochondria, amino acids and lactate enter and 2 pyruvate molecules are converted to 2 oxaloacetates by pyruvate carboxylase and input of a bicarbonate and inpit conversion of one ATP to ADP + Pi
  2. now in the cytosol, 2 oxaloacetates are converted to 2 phosphoenol pyruvates by phosophoenol pyruvate carboxykinase, input conversion of one GTP to GDP and release of CO2
  3. 2 phosphoenol pyruvate are converted to 2-phosphoglycerate by enolase and input of H20
  4. 2 molecules of 2-phosphoglycerate are converted 2 3-phosphoglycerates by phsophoglycerate mutase
  5. 2 3-phosphoglycerates are converted to molecules of 1,3-bisphosphoglycerate by phosphpglycerate kinase and input conversion of one ATP to one ADP
  6. 2 molecules of 1,3-bisphosphoglycerate and glycerol if it is the precursor are converted to 2 molecules of glyceradehyde 3-phosphate by gluceraldehyde 3-phosphate dehydrogenase and input conversion on one NADH + H+ to NAD+ and and Pi is released
  7. one of the glyceraldehyde 3-phosphate molecules is converted to dihydroxyacetone phosphate by triose phosphate isomerase
  8. one molecule of glyceraldehyde 3-phosphate and one molecule of dihydroxyacetone phosphate is converted to 1 molecule of fructose 1,6-bisphosphate by aldolase
  9. fructose 1,6-bisphosphate is converted to fructose 6-phosphate by fructose 1,6-bisphosphatase
  10. fructose 6-phosphate is converted to glucose 6-phosphate by phosphoglucose isomerase
  11. glucose 6-phosphate is converted to glucose by glucose 6-phosphatase with the input of H2O and release of a Pi
127
Q

why is the normal blood glucose range so narrow?

A

because major deviations can cause death

128
Q

why do ruminants have a lower normal blood glucose range?

A

a majority of the carbs from their diet are not broken down to glucose so ruminants rely solely on gluconeogenesis

129
Q

compare the blood glucose range of a chicken to other animals

A

much higher and no one knows why

130
Q

where does blood glucose come from? (3)

A
  1. dietary carbohydrates in the fed state
  2. liver glycogen in the fasted state
  3. gluconeogenesis in the fasted state
131
Q

does muscle glucose 6-phosphate contribute to blood glucose?

A

nope

132
Q

when does glucose become blood glucose?

A

when it enters the bloodstream

133
Q

what are the 4 gluconeogenesis precursors that contribute to blood glucose?

A
  1. lactate
  2. amino acids
  3. glycerol
  4. proprionate
134
Q

describe the cyclical nature of lactate contributing to blood glucose

A

glucose is broken down to lactate in anaerobic conditions and then travels through the bloodstream to the liver where it is converted to glucose which then tracels through the bloodstream and is broken down to lactate again

135
Q

describe how glycerol contributes to blood glucose

A

when fat is broken down, glycerol is released which travels through the bloodstream to the liver where it is converted to glucose which travels to cells for use

136
Q

describe how amino acids contribute to blood glucose

A

protein in muscle if broken down into amino acids which travel through the bloodstream to the liver where they are converte to glucose which travels through the bloodstream to cells for use

137
Q

what is the precursor for gluconeogenesis for ruminants and nonruminant herbivores?

A

propionate

138
Q

where does proprionate come from?

A

microbial fermentation

139
Q

describe how proprionate contributes to blood glucose

A

proprionate is absorbed from the rumen wall then travels through the hepatic portal vein to the liver where it is converted to glucose and sent to cells for use

140
Q

in what 5 ways is blood glucose regulated?

A
  1. glucose transport
  2. glucokinase
  3. insulin
  4. glucagon
  5. other hormones like GH, ACTH, and epinephrine
141
Q

when are the glucose transporters GLUT2 and GLUT4 active?

A

when trying to lower blood glucose

142
Q

how do GLUT2 and GLUT4 regulate blood glucose? the abridged version

A

only active in high concentrations of glucose (GLUT2) and presence of insulin (GLUT4), lower blood glucose by transporting out of bloodstream and into cells

143
Q

how does glucokinase regulate blood glucose when there are large amounts of blood glucose?

A

glucokinase will prevent glucose from leaving the cells when blood glucose is high by converting it to glucose 6-phosphate for glycolysis

144
Q

how does glucokinase regulate blood glucose when there are low amounts of blood glucose?

A

this means gluconeogenesis or glycogenesis has occured, so glucokinase is inactive and glucose can enter the bloodstream instead of getting used by liver cells

145
Q

how does insulin regulate blood glucose (generally and then give 3 mechanisms)

A

lowers blood glucose

  1. activates GLUT4 to remove glucose from blood
  2. activates glycogenesis by activating PP-1 and activate glycolysis which will keep glucose from returning to bloodstream
  3. inhibits gluconeogenesis and glycogenesis which also prevents glucose from returning to blood
146
Q

how does glucagon regulate blood glucose? (generally and then give 2)

A

opposite of insulin, maintains blood glucose

  1. activates gluconeogenesis and glycogenolysis to allow glucose to enter blood
  2. inhibits glycolysis and glycogenesis, keeps liver and muscles from storing or using glucose
147
Q

how does growth hormone regulate blood glucose?

A

enhances gluconeogenesis to provide energy for growth as more glucose enters the bloodstream

148
Q

how does ACTH regulate blood glucose?

A

stimulates release of glucocorticoids, like cortisol from adrenal cortex and cortisol enhances gluconeogenesis so glucose enters the blood

149
Q

how does epinephrine regulate blood glucose?

A

stimulates/activates glycogen phosphorylase for glycogenolysis and glucose enters the blood

150
Q

what cells secrete insulin?

A

pancreatic beta cells

151
Q

what cells secrete glucagon?

A

pancreatic alpha cells

Nutrition (19 decks)

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