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biochem > metabolism > Flashcards

metabolism Flashcards

1
Q

Hexokinase

A
  • located in most tissues but not liver nor B cells of pancrease
  • km is lower, higher affinity for substrate
  • Vmax is lower, so it reaches capacity quicker
  • it is not induced by insulin
  • G6P feedback inhibits
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2
Q

glucokinase

A

is only in liver, b cells of pancrease

  • it has a higher Km so lower affinity for substrate
  • higher vmax, so higher capacity
  • it is induced by insulin
  • it is not inhibited by G6P
  • it can be mutated causing maturity onset diabetes of the young MODY
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3
Q

electron transport inhibitors

A

complex 1: rotenone
complex III: antimycin A
Complex IV: cynanide, CO
Complex V (ATP synthase): oligomycin

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4
Q

uncoupling agents: 2,4 dinitrophenol, aspirin (overdose), thermogenin in brown fat

A

-the increase the permeability of membrane, causing a decrease in proton gradient and increase in oxygen consumption. ATP synthesis stops, but electron transport continues. produces heat

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5
Q

odd chain fatty acids yield 1 propionyl coA –> TCA cycle as succinyl coA–> gluconeogeneis and serve as a glucose sourse

what about even chain fatty acids?

A

-they yield only 1 acetyl coA equivalent and thus cannot produce new glucose

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6
Q

essential fructosuria

A
  • defect in fructokinase
  • autosomal recessive
  • benigh as fructose just goes into the blood and urine and doesnt build up like fructose intolerace with adolase B deficiency
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7
Q

fructose intolerance

A
  • autosomal recessive
  • deficiency in adolase B
  • F-1-P builds up cause a decrease in available phosphate, which results in inhibition of glycogenolysis and gluconeogensis
  • urine dipstick will be - as it only tests for glucose, instead test for reducing sugar
    symptoms: hypoglycemia, jaundince, cirrhosis and vomiting

treatment decrease intake of both fructose and sucrose

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8
Q

in the intestine glucose and galactose are taken up by what transporter?

A

SGLT1 (Na+ dependant)

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9
Q

In the intestine how is fructose taken up by in the enterocyte? and by spermatocytes

A

GLUT 5

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10
Q

What transporter transports glucose, galactose and fructose into the blood? and in b islet cells, liver, kidney

A

GLUT 2

note GLUT 2 is bidrectional and insulin-independant

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11
Q

GLUT 4

A

insulin dependant glucose transport in adipose tissue, skeletal muscle

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12
Q

GLUT 1

A

insulin INDEPENDANT transporter in RBC, brain and cornea

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13
Q

Galactokinase deficiency

A

-galactokinase deficiency
-relatively mild
-autosomal recessive
-galacitol can accumulate
symptoms
-galactose appears in blood and urine, infantile cataracts, may intially present as failure to track objects or to develop a social smile

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14
Q

Class galactosemia,

A
  • abscence of galactose-1-phosphate uridlytransferase
  • autosomal recessive
  • accumulated toxic substances, for example galicitol accumulates in the eye

symptoms: failure to thrive, jaundince, hepatomegaly, infantile cataracts, intellectual disability

treat exclude galactose and lactose from diet

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15
Q

essential amino acids

A

Glucogenic: methionine, valine, histidine

glucogenic/ketogenic : isoleucine, phenylalanine, threonine, tryptophan

ketogenic: leucine, lysine

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16
Q

ornithine transcarbamylase deficiency

A
  • most common urea cycle disorder
  • x linked recessive
  • often eveident in the first few days of life, but may be present with late onset
  • excess carbamoyl phosphate is converted to orotic acid (part of the pyrimidine synthesis pathway)

findings: increase orotic acid in blood and urine
- decrease BUN, symptoms of hyperammoneimia, no megloblastic anemia (unlike orotic acuduria)

17
Q

amino acid derivatives of:

phenylalalnine

A

tyrosine –> thyroxine
tyrosine –> dopa –> dopamine–> NE –> epi

  • B6 to go from dopa to DA
  • vitamin C to go from DA to NE
  • need SAM to go from NE - Epi
18
Q

amino acid derivatives of:

tryptophan

A
  • niacin (need B6) –> NAD +/NADP+

- serotonin –> melatonin

19
Q

amino acid derivatives of:

histidine

A

histamine (need B6)

20
Q

amino acid derivatives of:

glycine

A

porphyrin (need B6 to make) –> heme

21
Q

amino acid derivatives of:

glutamate

A

with B6 it makes GABA

makes glutathione

22
Q

amino acid derivatives of::

arginine

A

Creatine
urea
NO

23
Q

phenylketonuria

A
  • decrease phenylalanine hydroxylase or decreased tetrahydrobipterin cofactor (malignant PKU)
  • tyroside becomes essential
  • leads to excess phenyl ketones in urine
  • AR
  • screen 2-3 days after birth due to normal maternal enzyme still around

findings:
-intellectualy disability, growth retardation, seizures, fair skin, eczema, musty body odor.

treat: decrease Phe foods, and increase tyrosine in diet

24
Q

what are some phenylketones

A

phenylacetate, phenylactate phenylpruvate

25
Q

maternal PKU

A
  • lack of proper dietary therapy during pregnancy. Findings in infant:
  • microcephaly
  • intellectual disability
  • growth retardation
  • congenital heart defects
26
Q

alkaptonuria (ochronosis)

A

-autosomal recessive
-benign
congential deficiency of homegentisate oxidase in the degradative pathway of tyrosine to fumarate

findings: dark connective tissue, brown pigmented sclerae, urine turns black on prologued exposure to air, may have debilitating arthralgias (homogentisic acid is toxic to cartilage)

27
Q

homocystinuria

A

autosomal recessive
-multiple types

  1. cystathione synthase deficiency (treatment: decrease methionine, and increase cysteine, increase B12 and folate in diet)
  2. Decrease affinity of cystathione synthase for pyridoxal phosphate (treatment increase B6 a lot and increase cysteine in diet)
  3. homocysteine methyltransferase (methionine synthase) deficiency (treatment: increase methionine in diet).

all forms result in excess homocysteine

findings :
-increased homecysteine in urine, intellectual disability, osteoporosis, tall stature, kyphosis, lens subluxation (downward and inward), thrombosis, and atherosclerosis (stroke and MI).

28
Q

cystinuria

A
  • autosomal recessive
  • hereditary defect of renal PCT and intestinal amino acid transporter for cysteine, ornithine, lysine and arginine COLA
  • leads to excess cystein in urine and can lead to precipitation of hexagonal cysteine stones
  • urinary cyanide nitroprusside test is diagnostic,

treatment: alkalization (potassium citrate, acetozolamide) and chelating agents increase solubility of cystine stones, good hydration

cystine is made of two cysteines connected by a disulfide bond

29
Q

maple syrup urine disease

A

blocked degradation of branched amino acids (isoleurcine, leucine and valine) due to decreased alpha ketoacid dehydrogenase (B1). causes and increase in alphaketoacids in the blood especially those of leurcine

  • autosomal recessive
  • causes severe CNS defects, intellectual disability, and death

restrict the diet of iso, leu and valine
-thiamine supplementation

30
Q

glycogen

A

branches have alphae (1,6) bonds and linkages have alpha (1,4) bonds.

31
Q

gycogen breakdown

A
  1. glycogen phophorylase cleaves glucose-1-phosphate residues off branched glycogen until four remain before a branch point
  2. then 4-alpha glucanotransferase (debranching enzyme) moves three glucose-1-p from branch to the linkage (long chain)
  3. then a-1,6-glucosidase (debranching enzyme) cleaves off the last glucose 1-p on the branch

note a small amount of glycogen is degraded in lysosomes by alpha-1,4-glucosidase (acid maltase)

32
Q

1g protein or carbohydrte =

A

4kcal

33
Q

1 f fat =

A

9kcal

34
Q

1 g alcohol

A

= 7 kcal

biochem (8 decks)

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