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IHN: Biochemistry 2 > Vitamin C > Flashcards

Vitamin C Flashcards

(71 cards)

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1
Q

vitamin C aka

A

ascorbic acid or ascorbate

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2
Q

ascorbic acid (ascorbate) is synthesize from __ by many animals in __ or __

A

ascorbic acid (ascorbate) is synthesize from glucose by many animals in liver or kidney

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3
Q

is ascorbic acid produced by humans?

A

NO

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4
Q

2 food forms of vit C present in foods

A

ascorbic acid (AA)
dehydroascorbic acid (DHA)

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5
Q

best sources of vit c

A

fruits and veggies

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6
Q

other sources of vit c

A

animal organs (liver, kidney, brains)

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7
Q

__% AA, __% DHA

A

80-90% AA, 10-20% DHA

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8
Q

common sources of vit C

A

camu berry
tomato
peppers

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9
Q

tolerable upper limit (UL) is __ based on adverse effects of __

A

tolerable upper limit (UL) is 2 g/day based on adverse effects of osmotic diarrhea

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10
Q

can you reach UL from dietary vit C alone

A

no, it is only caused by excess supplementatin

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11
Q

excess vitamin c cause increased excretion of __ and __ which may increase __ formation

A

excess vitamin c cause increased excretion of oxalate and uric acid which may increase kidney stone formation

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12
Q

contraindications: people with __, __ anemia, or __ should aboid ascorbate supplements

A

contraindications: people with hemochromatosis, sideroblastic anemia (heme deficiency even with adequate iron), or thalassemia major (excess iron) should aboid ascorbate supplements

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13
Q

ascorbic acid acts as an __ (__ agent) and reacts with __

A

ascorbic acid acts as an electron donor (reducing agent) and reacts with oxidants

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14
Q

ascorbic acid can donate __ electrons
its free radical form is __

A

ascorbic acid can donate 2 electrons
its free radical form is stable

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15
Q

where is vit c absorbed

A

ileum and jejunum

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16
Q

2 methods of vit C absorption (overviews)

A
  1. ascorbate is coupled to sodium and transported directly by SVCT (sodium-dependent vit C transporter)
  2. GLUT requires extracellular oxidation of ascorbate to DHA
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17
Q

SVCT mechanism

A
  1. ascorbic acid goes through SVCT with NA+ and enters cell (against the gradient)
  2. Na+ leaves through ATPase
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18
Q

SVCT type of transporter

A

symporter: secondary active

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19
Q

why use SVCT and waste ATP

A

bc ascorbic acid is scarce in nature, so we must take advantage of it when available

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20
Q

vit C GLUT transport mechanism

A
  1. Asc –> DHA
  2. DHA is similar to glucose –> goes through GLUT into enterocyte
  3. enterocyte produces Asc
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21
Q

GLUT type of transport

A

facilitated diffusion

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22
Q

GLUT 1, 2, and 3 regulation

A

glucose
competitive inhibition

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23
Q

GLUT 4 regulation

A

insulin sitmulates

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24
Q

GLUT 1, 2, 3 location

A

osteoblasts
muscle
intestinal cells

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25
GLUT 4 location
adipose muscle cells
26
SVCT1 location
liver epithelial intestine kidney
27
SVCT 1 regulation
ascorbate: feedback inhibition of SVCT expression more ascorbate absorbed, less activity of SVCT
28
SVCT2 location
broad distribution (brain, retinal, and placenta cells)
29
SVCT1 knockout
total loss of ascorbate resorption in kidneys BUT intestinal absorption is unchanged
30
SVCT2 knock out
severe ascorbate deficiency in tissues KO IS LETHAL mice die at birth
31
__ transporters must exist, but remain unidentified
**efflux** transporters must exist, but remain unidentified
32
as more ascorbate is absorbed, __ has __ activity __ feedback
as more ascorbate is absorbed, **SVCT1** has **less** activity **negative** feedback
33
resorption of ascorbate in renal tubules by SVCT1 carrier is __
resorption of ascorbate in renal tubules by SVCT1 carrier is **saturable**
34
at vit C intakes of above __mg, all vit C is usually __
at vit C intakes of above **500 mg**, all vit C is usually **excreted**
35
ascorbate in blood is __ soluble and free in __
ascorbate in blood is **water** soluble and free in **plasma**
36
tissue concentrations of ascorbate are __ than plasma levels SO, ascorbate is actively transported __ a gradient into cells via a transporter
tissue concentrations of ascorbate are **way higher** than plasma levels SO, ascorbate is actively transported **against** a gradient into cells via a transporter
37
white blood cells have a concentration of ascorbate that is up to __ times __ than plasma
white blood cells have a concentration of ascorbate that is up to **80** times **higher** than plasma
38
RBC and WBC uptake (via GLUT1 and GLUT3) and transport __ in circulation
RBC and WBC uptake (via GLUT1 and GLUT3) and transport **DHA** in circulation
39
degradative oxidation of ascorbate occurs primarily in __ but also to some extent in __
degradative oxidation of ascorbate occurs primarily in **liver** but also to some extent in **kidneys**
40
oxalic acid is found mainly in
spinach, but also lots of other foods
41
oxalic acid acts as a magnet for __ molecules (like __)
oxalic acid acts as a magnet for **positively charged** molecules (like **Ca, Fe, Zn**)
42
degradation: vit C is __ to DHA, then destroyed by __
degradation: vit C is **oxidized** to DHA, then destroyed by **opening the ring**
43
ascorbate enzymatic role
reducing agent, iron and copper containing enzymes
44
ascorbate non-enzymatic role
anti-oxidant and, possibly, pro-oxidant (by reducing free Fe and Cu ions)
45
2 non-enzymatic mechanisms of ascorbate
1. antioxidant (free radical quenching) 2. potential functions (pro-oxidant, ROS formation)
46
enzymatic mehcanisms of ascorbate (6)
1. collagen synthesis (structural) 2. carnitine synthesis (metabolic energy) 3. catecholamine synthesis (hormonal) 4. peptide amidation (ie vasopressin) 5. epigenetic regulation (DNA and histone methylation) 6. transcriptional regulation (ie HIF)
47
ascorbate in collagen synthesis role:
ascorbate reduces heme iron (ferric --> ferrous) this restores enzyme activity
48
what enzyme activity is restored by ascorbate in collagen synthesis
prolyl hydroxylase
49
in collagen synthesis, ascorbate __ iron3+ to __
in collagen synthesis, ascorbate **reduces** iron3+ to **iron2+**
50
vit C is essential for __ synthesis
vit C is essential for **carnitine** synthesis
51
carnitine can be acquired from __ or synthesized from __ and __
carnitine can be acquired from **diet** or synthesized from **lysine** and **methionine**
52
ascorbate's role in __ synthesis explains the first sign of vit C deficiency: __
ascorbate's role in **carnitine** synthesis explains the first sign of vit C deficiency: **fatigue**
53
scurvy is associated with high circulating levels of __ and excretion of high levels of __
scurvy is associated with high circulating levels of **tyrosine** and excretion of high levels of **4-hydroxyphenyl pruvate**
54
premature infants also have high levels of __ and excretion of high levels of __ __ fixes this issue
premature infants also have high levels of **tyrosine** and excretion of high levels of **4-hydroxyphenyl pruvate** **ascorbate** fixes this issue
55
alkaptonuria is a mutation that inactivates __ this causes __ to accumulate in __ and turn it __ color
alkaptonuria is a mutation that inactivates **homogentisate dioxygenase** this causes homogentisate to accumulate in **urine** and turn it **black** color
56
depleted ascorbate prevents us from making __ and __
depleted ascorbate prevents us from making **catecholamines** and **dopamine**
57
epinephrine and norepinephrine are synthesized in __ and __ synthesis occurs in __ compartments
epinephrine and norepinephrine are synthesized in **neurons** and **adrenal gland** synthesis occurs in **vesicular** compartments
58
what is needed to convert norepinephrine to epinephrine?
SAM
59
ascorbate plays a role in hormone activation via
alpha-amidation
60
alpha-amidation is essential in __ activation
alpha-amidation is essential in **hormone** activation
61
hormone activation: ascorbate provides electrons in __ dependent mechanism
hormone activation: ascorbate provides electrons in **cytochrome b-561** dependent mechanism
62
vitamin c reduces several oxygen-centered __ and __
vitamin c reduces several oxygen-centered **radicals** and **reactive species**
63
vit C is an antioxidant due to the __ power of __
vit C is an antioxidant due to the **reducing** power of **ascorbate**
64
antioxidant function of ascorbate (3 things work together)
glutathione + Vit C + Vit E
65
assessment of vit C, best method
WBC content of vit C
66
assessment of vitamin C problems
no functional measure other than scurvy
67
vitamin C deficiency and symptoms
scurvy 4 Hs hemorrhage hyperkeratosis hypochondriasis hematologic abnormalities
68
earliest manifestations of scurvy are
dermatologic
69
some early signs of scurvy are
unspecific decreased appetite, fatigure, weakness
70
groups at risk
malnourished ppl: 1. cancer cachexia 2. low SES 3. drug and alcohol 4. elderly men 5. children 6. keto diet (no fresh fruits or veggies)
71
3 vitamin c controversial treatments (aka it does not work as a treatment)
CVD cancer common cold

IHN: Biochemistry 2 (38 decks)

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