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Physiology > Sugars and Shunts and Shuttles > Flashcards

Sugars and Shunts and Shuttles Flashcards

1
Q

Name the monosaccharides

A

Glucose, Galactose, Fructose

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2
Q

What is the purpose of monosaccharides

A

Form di, oligo, polysaccharides

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3
Q

What is the most important dietary carb

A

Free monosacchardies, which are not abundant in the diet

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4
Q

What is the preferred form of sugar for absorption?

A

Monosaccharide. Poly and Di-saccharides hydrolyzed to monosaccharides

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5
Q

What hydrolyzes di- and poly-saccharides?

A

Carbohydrases in intestinal lumina

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6
Q

Name the di-saccharides

A

Maltose, Sucrose, Lactose

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7
Q

What is maltose

A

Glucose + Glucose a-1,4 linkage

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8
Q

What is sucrose

A

Fructose + Glucose

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9
Q

What is lactose

A

Galactose + Glucose B-1,4 linkage

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10
Q

Where does digestion of diasaccharides take place

A

Upper GI

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11
Q

What hydrolyzes maltose?

A

Maltase

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12
Q

What occurs after maltose is hydrolyzed?

A

2 glucose moelcles enter the glycolysis cycle

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13
Q

What does glucokinase enzyme trigger?

A

GLycogen synthesis (liver)

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14
Q

What does hexokinase enzyme trigger?

A

Glycolysis (cytoplasm)

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15
Q

What enzyme hydrolyzes sucrose?

A

Sucrase

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16
Q

Where is the majority of fructose metabolized?

A

Major pathway: liver

Minor pathway: muscle

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17
Q

How is fructose metabolized?

A

Fructose fructokinase -> Fructose 1 phosphate -> Aldolase B -> DHAP + Glyceraldehyde glyceraldehyde kinase -> Glyceraldehyde 3 phosphate -> glycolysis

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18
Q

What are the properties of fructokinase?

A

Low Km (high affinity), will not phosphorylate glucose, is not affected by starvation or insulin (fructose removed from diabetic patients at normal rate)

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19
Q

Should fructose be given to diabetic patients to replenish carbohydrate scores?

A

No, the removal of fructose is slow and accumulation of fructose will lead to cataracts (accumulation in lens).

In diabetic patients, glucose is also converted to fructose via the sorbitol pathway resulting in excess fructose -> cataracts

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20
Q

What is the minor route of fructose metabolism?

A

In muscle, hexokinase can phosphorylate fructose to fructose 6 phosphate

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21
Q

What hydrolyzes lactose?

A

Lactase

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22
Q

How is galactose metabolized?

A

Galactose galactokinase -> Galactose 1 phosphate galactose 1 phosphate uridyl transferase -> GLucose 1 Phosphate phosphoglucomutase -> Glucose 6 phosphate

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23
Q

What is the hepatic function test?

A

Measures the amount of galactose/glucose in blood after an injection of galactose. Measures rate of utilization by the liver

24
Q

Is galactose required in the diet?

A

No, Glucose 1-phosphate can be converted to galactose

25
What is galactose an important precursor for?
Lactation & Lactose
26
What bonds are broken during fiber digestion?
B 1,4 linkages
27
What are the characteristics of cellulose?
Straight chain of 1500 glucose rings Most abundant material on Earth Beta configuration is not digestible by mammalian enzymes
28
How do ruminants utilize cellulose?
Microbes have symbiotic relationship, use cellulase to create VFAs that can be converted to glucose
29
What is a negative about ruminantion?
Gas and heat loss, ruminant digestion of cellulose is not effective
30
What is the purpose of the reticulum?
Holds food that is regurgitated later for rumination.
31
Where are the microbes killed?
Abomasum (4th stomach)
32
What type of fermentation is rumination?
Anaerobic
33
What is the pentose phosphate pathway?
A cystolic process that generates NADPH and 5-carbon (pnetose) sugars
34
Does the Hexose Monophosphate Shunt create ATP?
No, 10-20% of G6P is metabolized by pentose pathway to create NADPH for lipid synthesis.
35
What does the HMP pathway produce?
NADPH for lipid biosynthesis and riboses
36
What are the phases of the HMP pathway?
Oxidative (non-reversible, produces NADPH) | Non-oxidative (reversible, interconverts 3,4,5,6 carbon sugars)
37
Why can muscles not run only the oxidative phase?
Muscles lack the rate limiting enzyme. | Muscles can run the non-oxidative phase for ribose production
38
What tissue has the highest activity level of HMP pathway?
Liver and Adipose because of fatty acid synthesis
39
What tissues does HMP pathway occur?
Red blood cells, Liver, Adipose, Endocrine tissues (hormones and cholesterol)
40
What is NADPH used for?
Fatty acid and cholesterol synthesis
41
What is the rate limiting enzyme of the HMP pathway?
Glucose-6-phosphate dehydrogenase
42
What are the oxidative steps of the HMP pathway?
G6P *glucose 6 phosphate dehydrogenase* -> 6-phosphogluconolactone *Gluconolactonase* -> 6-phosphogluconate *6-phosphogluconate dehydrogenase* -> Ribulose 5 phosphate
43
What animals have a deficiency of the rate limiting enzymes?
Weimereiner dogs
44
What regulates the HMP pathway?
NADP/NADPH
45
How many NADPH does the oxidative phase of the HMP pathway produce?
2
46
What vitamin is needed to continue the non-oxidative steps?
Thiamine (B1)
47
Can Ribulose-5-phosphate be glucogenic?
Yes. Ribulose 5 phosphate *phosphopentose isomerase* -> Ribose 5 phosphate -> Fructose 6 phosphate
48
What are the non-oxidative steps of HMP pathway?
Ribulose 5 phosphate *phosphopentose isomerase* -> Ribose 5 phosphate -> Fructose 6 phosphate, nucleotides
49
When is the recycled G6P turned in to glucose vs repeating the HMP cycle?
Liver: G6P to Glucose during gluconeogenesis | Adipose and other tissue: Recycled to HMP
50
How many NADPH total is created during HMP pathway?
6
51
1 G6P molecule will produce how many NADPH?
6. 3 G6P + G3P -> 2 G6P + 6 NADPH
52
What is the purpose of the malate-aspartate shuttle?
To carry NADH across mitochondria matrix and ultimately electrons to ETS
53
What is the purpose of the glyercol 3-phosphate shuttler?
To carry FADH across inner mitochondria membranes and ultimately electrons to ETS
54
Where does the glycerol-3-phosphate shuttle move Glycerol phosphate?
Inner mitochondrial membrane
55
How many net ATP is produced fro the Glyercol 3 phosphate shuttle?
- 1 (one NADH used, one FADH created)
56
In what tissues can fructose be catalyzed in to Fructose 1 phosphate
Liver, Kidney, Intestine
57
What upregulates fructokinase?
High levels of fructose

Physiology (45 decks)

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