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Nutrchem > Carbohydrate Meta > Flashcards

Carbohydrate Meta Flashcards

(90 cards)

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1
Q

How quick is carbohydrate digestion and absorbtion?

A

30-90 mintes

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2
Q

How much monosaccharides can the liver remove from the portal vein

A

1/3

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3
Q

What are some sources of glucose

A
  1. Diet
  2. gluconeogenic precursors
  3. glycogen store
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4
Q

What is the fate of glucose in metabolism?

A
  • can be used to produce other carbohydrates (mammoary lactate, ribose for DNA)
  • sugar residues for other compounds (glycoproteins)
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5
Q

What cells are very dependent on glucose

A
  • brain
  • Rbc
  • Nerves
  • intestines
  • mucosa
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6
Q

What is nomal glucose levels

A

Upper end: 6mmol/L
Lower end : 4 mmol/L

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7
Q

What are the difference between glycolysis and complete oxidation of glucose?

A

Glycolysis
- Produces small amount of ATP
- Is an anaerobic process
- occurs in the cytoplasm

Complete oxidation
- occurs in the mitochandria
- Produces alot of ATP
- happens during aerobic conditions

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8
Q

What type of metabolism can occur in muscle cells and why

A

Muscles can undergo glycolysis, complete oxidation or storage of glycogen

  • muscle cells have mitochandria therefore metabolism can go all the way
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9
Q

What type of metabolism can occur is cardiac muscle

A
  • glycolysis –> cytoplasm existent
  • Completely oxidation –> yes mitochandria present
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10
Q

What type of metabolism can occur in hepatocytes?

A

-can do all types (glycolysis, complete oxidation and glycogen storage)

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11
Q

Describe the link between the muscle cells and the liver

A
  1. Glucose into the muscle –> G6P (can be converted to glycogen) –> pyruvate
  2. Pruvate has 2 fates: A. If we are reaching our VO2 max then it is converted into lactate and sent to liver B. Pyruvate can enter the mitochandria where it is converted to oxaloacetate the to citrate (this can occur more effiencient if we are well trained)
  3. A. Lactate enters the hepatocyte where it is converted into pyruvate where it can be converted into oxaloacetate then citrate –> where it can be converted to fat or CO2
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12
Q

What type of metabolism can occur in red blood

A

Glucose can only be converted to pyruvate then to lactate because they lack mitochandria

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13
Q

What type of metabolism can occur in the brain

A
  • complete oxidation of glucose BUT cannot store glycogen (big molecule)
  • can also oxidize ketones
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14
Q

What type of metabolism can occur in B-cells in pancreas

A
  • complete oxidation of glucose, very effiecient
  • High amount of mitochandria
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15
Q

What type of metabolism can occur in adipocytes

A
  • complete oxidation or synthesis of glycerol –> excess glucose to Acetyl CoA –> Fat storage
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16
Q

What organ can raise glucose level

A

the liver

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17
Q

Do skeletal, cardiac, adipose, brain tissues/cells released glucose to change blood glucose levels?

A

No, because the respond to the blood glucose changes but do not release glucose into the blood

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18
Q

Why store glycogen in a polymeric form rather than in free form?

A
  • want to store alot while keeping it readily avaible
  • Optimized degree of branching and chain length
  • more branching than amylopectin
  • uses less space and hold more water
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19
Q

What % of storage is glycogen in muscles and liver

A

muscles - 1%
Liver - 10%

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20
Q

What inhibits glycogensis

A
  • glycogenolysis and maximized glycogen stores
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21
Q

What are the 2 forms of glycogen synthase?

A

A (GYS1)
B ( GY2)

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22
Q

Describe gycogen sythase A

A
  • found everywhere in the body, RBC, brain, kidney adipose
  • more active when phosphorylated
  • Used in rapid response to an increase in blood glucose levels in fed state as well exercise
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23
Q

Describe glycogen synthase B

A
  • Only in liver
  • Less active when phosphorylated
  • ensure that large pools of glycogen avaible for blood glucose concentration
    -Lower affinity for UDP- glucose and less sensitive to allosteric activiation by G6P
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24
Q

what activate glycogen phosphorylase

A
  • glucagon
  • epinephrine
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25
What is glycogenolysis
use of glycogen when blood glucose levels are low
26
What increases glycogensis
being in the fed state
27
What molecules start glycogensis
- high ATP and sugar - Insulin triggers the increase in glucose uptake - Glucose enters the cells and transforms to G6P to be used for glycogen storage - Lactate is perferred to be used as glycogen
28
What increases glycogenolysis
- fasting state
29
What triggers glycogenolysis
- Liver is depleted of glycogen - When no dietary glucose, glycogenolysis is initiated to supply glucose - Glucagon stimulates in the liver
30
What is the purpose of glycogen breakdown in the liver?
- To increase blood glucose levels or ATP
31
What is the purpose of glycogen breakdown in the muscle?
For atp for itself NOT THE BLOOD
32
What biomolecule is used for glycolysis
G6P
33
What organs contribute to the increase in blood glucose
- liver and kidney
34
How is glycogen phosphorylase activated in the skeketal tissue
- Phosphorylation control - Depending on the ratio of phorsphorylase a:b - A (more active, not sensitive to ATP) : B ( less active dephosphorylated form)
35
What activates glycogen phosphorylase in the liver?
- Allosteric control - Glucagon and epinephrine will bind to recpetor and cAMP will induce a response - Activating Glycogen phosphorylase
36
How is the rate of glycogen breakdown determined by enzymes in skeletal muscles?
Depends on ratio of phosphorylase A and B - Exercise can activate phosphorylase kinase that generate phosphorlyase A to stimulate breakdown of glycogen
37
Why are NAD+ and NADH important to reactions?
they are central for electron movement
38
What activates working muscles to stimulate glycolysis
NADH, Pi and ADP+AMP
39
What is regenerated in lactate formation
NAD+
40
What is the rate-determining step in aerobic metabolism?
PDH
41
How much ATP is formed during aerobic respiration?
34
42
What does an increased rate of glycolysis mean?
it means there is a depletion of NAD+
43
What tissue generate lactate and alanine
peripheral tissues
44
What does lactate to pyruvate generate?
NADH for gluoconeogensis
45
What factors impact weather pyruvate enters the CAC
- availbilty of oxygen - Metabolic state of the cell
46
How is pyruvate converted into acetyl CoA
via the PDC
47
What tranporter carrier pyruvate across the mitochandria
monocarboxylate carrier
48
What is the product and substrate of the CAC?
acteyl CoA to 2 CO2's
49
What molecules inhibit CAC
- pyruvate dehydrogenase activity - ATP avaibility - Excess NADH
50
Why would a cell have more mitochandria
to increase cellular respiration
51
What cells use the pentose pathway?
RBC, adipocyte, liver, and mammary glands
52
Where does the pentose pathway occur in the cell?
In cystol
53
What molecule does the pentose pathway generate
NADPH
54
How is glucose a regulator?
Regulated the activity of enzymes, transcription, hormone secretion, glucoregulatory neuron activity
55
How is a glucose a substrate?
Acts a signal molecule to control glucose and energy homeostasis
56
Where are some of the fates of glucose?
Glycogen stores, brain, adipose, muscle
57
What is the post prandial fate of monosaccharides?
- On the first pass most monosaccharides will be absorbed by the liver - insulin will initiate a response for use of monosaccharides for energy, glucose for glycogen stores Skeletal muscle - insulin will initiate uptake of glucose via GLUT 4 transporter - glucose will then be used for energy and for glycogen stores - fructose will also be absorbed Adipose tissue - GLUT 4 transporter will uptake, glucose will be used for energy, FA, glycerol, TG if excess glc Cardiac muscle - GLUT 4 transporter of glucose, glucose will be used for energy and glycogen synthesis Other -Glc can be up-taken (1&3) based on needs
58
Where and how much is the glucose uptaken
- 1/3 up-taken by the liver, high uptake due to GLUT 2 + glucokinase - 2/3 up-taken by peripheral tissues after insulin secretion
59
Which cells are insulin dependent?
Skeletal muscles and adipose tissue
60
Which cells are insulin independent?
Hepatocytes
61
How glucose transported to the blood stream from GIT?
- Via SGLUT transporters and GLUT transporters
62
GLUT 2 ( monosaccharide substrates, sites, affinity, capacity)
MS: Glucose, galactose, mannose, and fructose Sites: Small intestine, B-pancreas and liver Affinity: low Capacity: high
63
GLUT 4 ( monosaccharide substrates, sites, affinity, capacity)
MS: Glucose Site: Adipose, muscle, Affinity: // Capacity: high
64
Where is insulin released?
B-cells in the pancreas
65
Where is glucagon released?
A- cells in the pancreas
66
What does insulin do?
Stimulate hepatic uptake and storage
67
What response does glucagon have on the liver?
Increase liver output of glucose but can be catabolic
68
Where are the A and B cells found ?
Islet of langerhans
69
Explain how glucagon raises blood sugar
- decrease in bloods glucose - breakdown glycogen into glucose in the liver - breakdown fats to fatty acids and ketones in the liver (ketogenesis) - breakdown non carbohydrates to produce glucose (gluconeogensis) Increases blood glucose concentration
70
Explain how insulin promotes energy storage?
Raising blood glucose levels Anabolic effects - uptake of skeletal muscles and adipose tissue for energy - convert glucose to glycogen for storage -promote synthesis of muscle - promote synthesis of fat
71
How is GLUT 4 impacted by insulin?
Once insulin binds to its receptor, it send a response to the transporter to move to the membrane of the cell and to bring the extra cellular glucose into the cytoplasm
72
What does the rate of glucose transport depend on in muscle and adipose tissue?
How long glut 4 is on cell surface and amount
73
Explain the process of how insulin is secreted.
- glucose enters the cells via GLUT 2 and gets phosphoryl aged by glucokinase - Pyruvate is made and undergoes the transformation inside the mitochondria (PDH -> A CoA -> CAC) - the increase of ATP: ADP ratio cause depolarization, which opens up the CA+ channels. Ca2+ fusion of insulin vesicle to be released via exocytosis
74
How is insulin production coupled with glucose
Via ATP production
75
What can stimulate insulin production?
GLUCOSE -certain aa -Parasympathetic stimulation -incretin hormones
76
Does fructose cause an insulin response, why or why not?
Fructose enters cells via GLUT 5 which not present in the pancreas therefore I’ll not initiate a response
77
What enzymes/transporters senses blood glucose levels?
GLUT 2 and glucokinase/ rate of glycolysis
78
Explain glucose homeostasis during the fed state
- pancreas will increase insulin production and decrease glucagon production - increased glucose utilization (glycogenesis and lipogenesis ) and decrease glucose production (gluconeogensis and glycogenolysis ) - muscle will uptake glucose and utilize
79
Explain glucose homeostasis during the fasted state
- Pancreas will produce glucagon and decrease insulin production - liver will increase glucose production (lipogenesis and glycogenesis ) and decrease glucose utilization ( gluconeogenesis and glycogenolysis ) - muscle will decrease uptake and utilization
80
What are normal glucose ranges
4-6mmol/l 70-110 mg/dl
81
What is insulin resistance?
Increase insulin secretion for the same response in GLUT 4 transporters
82
What does insulin resistance lead to?
Hyperglycaemia and hyperinsulimeia
83
What are Catecholamines effect on glucose levels?
Increased glycogenolysis and gluconeogenesis
84
What are Glucocorticoids effect on glucose levels?
Increased hepatic glucose output & expression of gluconeogenic genes
85
What are the effects of Tri-iodothyronine (T3) on glucose levels?
Can modulate or amplify many other hormones & actions, increases gene expression for enzymes to regulate metabolism (both anabolic & catabolic systems; INCR BMR)
86
What happens to glucose metabolism during starvation
- Increased glucagon secretion - increase glycogenolysis and gluconeogensis - decreased up p take of glucose by muscles and adipose, switches to fat oxidation
87
What is glycemic index?
The incremental area under the blood glucose response curve of a 50 g carbohydrate portion of a test food expressed as a percent of the response to the same amount of carbohydrate from a standard food taken by the same subject
88
What’s the difference between a high glycemic response and a low glycemic response?
Low glycemic response has a smaller more controlled increase in blood glucose but high glycemic response and a high spike in blood glucose filled by a dip which leads to a drop. High glycemic response put pressure on the pancreas to produce more insulin
89
What is glycemic load?
takes into account BOTH GI and the amount of food in a given serving GL=GI/100x(gofCHO/serving)
90
What is the glucose sparing effect?
Glucose uptake by muscle and adipose tissue decreases and switches to lipid fuels

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