metabolism

Question 1

Hexokinase

Answer 1

• 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

Question 2

glucokinase

Answer 2

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

Question 3

electron transport inhibitors

Answer 3

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

Question 4

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

Answer 4

-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

Question 5

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?

Answer 5

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

Question 6

essential fructosuria

Answer 6

• 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

Question 7

fructose intolerance

Answer 7

• 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

Question 8

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

Answer 8

SGLT1 (Na+ dependant)

Question 9

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

Answer 9

GLUT 5

Question 10

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

Answer 10

GLUT 2

note GLUT 2 is bidrectional and insulin-independant

Question 11

GLUT 4

Answer 11

insulin dependant glucose transport in adipose tissue, skeletal muscle

Question 12

GLUT 1

Answer 12

insulin INDEPENDANT transporter in RBC, brain and cornea

Question 13

Galactokinase deficiency

Answer 13

-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

Question 14

Class galactosemia,

Answer 14

• 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

Question 15

essential amino acids

Answer 15

Glucogenic: methionine, valine, histidine

glucogenic/ketogenic : isoleucine, phenylalanine, threonine, tryptophan

ketogenic: leucine, lysine

Question 16

ornithine transcarbamylase deficiency

Answer 16

• 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)

Question 17

amino acid derivatives of:

phenylalalnine

Answer 17

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

Question 18

amino acid derivatives of:

tryptophan

Answer 18

• niacin (need B6) –> NAD +/NADP+

- serotonin –> melatonin

Question 19

amino acid derivatives of:

histidine

Answer 19

histamine (need B6)

Question 20

amino acid derivatives of:

glycine

Answer 20

porphyrin (need B6 to make) –> heme

Question 21

amino acid derivatives of:

glutamate

Answer 21

with B6 it makes GABA

makes glutathione

Question 22

amino acid derivatives of::

arginine

Answer 22

Creatine
urea
NO

Question 23

phenylketonuria

Answer 23

• 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

Question 24

what are some phenylketones

Answer 24

phenylacetate, phenylactate phenylpruvate

Question 25

maternal PKU

Answer 25

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

Question 26

alkaptonuria (ochronosis)

Answer 26

-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)

Question 27

homocystinuria

Answer 27

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).

Question 28

cystinuria

Answer 28

- 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

Question 29

maple syrup urine disease

Answer 29

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

Question 30

glycogen

Answer 30

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

Question 31

gycogen breakdown

Answer 31

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)

Question 32

1g protein or carbohydrte =

Answer 32

4kcal

Question 33

1 f fat =

Answer 33

9kcal

Question 34

1 g alcohol

Answer 34

= 7 kcal