Biochemistry Flashcards
Newborn infants have a well-established risk of
vitamin K deficiency.
1-Fetal intestine is sterile, so it cannot synthesize vitamin K.
2-Breast-fed infants have a low vitamin K status because
placental transfer of vitamin K is poor and human milk contains
low levels of vitamin K.
3-The concentrations of plasma clotting factors are low in infants
due to immaturity of the liver.
Anemia and convulsions are manifestations of PLP deficiency.
Pyridoxal phosphate (PLP) acts as a coenzyme for many reactions in amino acid metabolism as
1-Heme biosynthesis
2-Conversion of glutamic acid to GABA
Patients with Von Gierkeʾs disease suffer from
hypertriacylglycerolemia.
Severe hypoglycemia stimulates epinephrine secretion, which
stimulates lipolysis in adipose tissue and increases the release of
free fatty acids
Impaired gluconeogenesis results in amplified triacylglycerol
synthesis because glucose 6-P is utilized for synthesis of TAG.
Hyperammonemia has a toxic effect on the brain and central
nervous system
The toxicity of hyperammonemia is thought to result, in part, from a shift in the equilibrium of the glutamate dehydrogenase reaction towards the direction of glutamate formation
The brain is particularly sensitive to hyperammonemia, because it depends on the citric acid cycle to maintain its high rate of energy production.
According to the clinical manifestations, two groups can be observed in porphyrias.
Neuropsychiatric manifestation: the accumulation of ALA which cause injury to sympathetic nerves and somatic nerves
Photosensitivity: results from accumulation of porphyrins in the skin
The key enzymes of the Krebsʾ cycle.
a) Citrate synthase
b) Isocitrate dehydrogenase
c) α-ketoglutarate dehydrogenase
Three causes of hypercholesterolemia
Diet rich in saturated fat, carbohydrates and cholesterol
Obesity
Hypothyrodism
Diabetes mellitus
Three genetic causes of gout
Defects of PRPP synthetase
Von Gierke’s disease
Lesh-Nyah Syndrome
Case (1):
A thirty years old female suffering from leukemia
presented with severe pain in the joints of her feet. Also,
she suffers from renal colic. She went to her doctor who
referred her for laboratory investigation. The results
showed high serum uric acid level with the presence of
urate crystals in her urine.
- What is the most possible diagnosis?
- Four other causes of hyperuricemia?
- What is the drug of choice in treating hyperuricemia?
How does it act?
Gout
High purine diet, kidney disease, starvation, excessive consumption of alchohol
Allopurinol
Allopurinol competitively inhibits the enzyme xanthine
oxidase
A 27-day-old baby presented at the Emergency
Department with severe bleeding from her umbilicus and
nose. The parents used direct pressure but were unable to
stop the bleeding. Coagulation studies showed prolonged
prothrombin time and delayed clotting time. The
condition was diagnosed as a vitamin deficiency.
1.What is the most probable vitamin deficient?
2.What are the causes for deficiency of this vitamin in newly
born?
3.Mention three other causes for deficiency of this vitamin ?
Vitamin K
Fetal intestine is sterile, so it cannot synthesize vitamin K.
Placental transfer of vitamin K is poor.
Human milk contains low levels of vitamin K.
The concentrations of plasma clotting factors are low in infants due to immaturity of the liver
Failure of absorption: steatorrhea
Failure of utilization: incase of liver disease
Dicumarol: competitive inhibitor to vitamin K
Causes of steatorrhea
Deficiency of pancreatic lipase
deficiency of bile salts or obstruction in bile duct
Defect in intestinal epithelium
Compare tissue fat and depot fat in site, main function, composition and amount and affect of diet
Tissue fat:
Every cell
Enter in structural elements of cell not used in energy
Phospholipids glycoproteins and cholesterol
Constant and not affected by diet
Depot fat:
Adipose tissue
Energy storage
TAG with SFA
increase by overfeeding and decreases by fasting
On biochemical basis explain vomiting and watery diarrhea
in lactose intolerance
Cause: lactase deficiency
bacterial fermentation of lactose to mixture of gases and acids.
treatment: stop lactose
Vitamin C deficiency manifestations
Defective blood vessels: capillaries are fragile leading to increase tendency for bleeding
Swollen, tender gums
Defective of teeth: teeth fall out
Anemia: sue to bleeding
Defective healing of wounds
Vitamin D functions, causes of deficiency and manifestations
Increase absorption of calcium by intestine
Increase reabsorption of calcium by kidney
Helps bone calcify
Causes: decrease intake, decrease absorption, low exposure to sunlight, defective vitamin d activation like in liver disease
Manifestation:
Rickets in kids: large heads, sclerosis and bend femurs
Osteomalacia in adults: to females of multiple pregnancies, more prone to fractures and bone aches.
Vitamin A deficiency causes, manifestations
Causes: decrease intake, decrease absorption, decrease of RBP
Manifestations:
In eye: night blindness, softening of the cornea
In skin and muocus membrane: Respiratory tract infection, skin becomes rough and scaly
Delayed on growth of bone
Delayed eruption of teeth
Increase risk of cancer
Functions of vitamin A
regulation of growth and differentiation of all tissues
Growth of bone and cartilage
Growth of teeth enamel
Component of visual pigments
Von Gierke’s disease cause, manifestation
Deficiency of glucose 6-phosphatase
Lactic acidosis: deficiency of gluconeogenesis
deficiency of gluconeogenesis and glycolysis
hepatomegaly and enlarged kidney
hypertriacylglyceroloemia;
hypercholesterolemia: increase of FA oxidation
Phenylketonuria cause, characteristics and treatment
Due to deficiency of phenylalanine hydroxylase
Elevated phenylalanine: metabolites appear in urine giving it a musty scent
CNS manifestation: the metabolites interfere with brain neurotransmitter. Retardation at the age of one
Hypopigmentation: of hair and iris
treatment: must be treated in first 10 days to prevent retardation and treatment for the rest of life
Restrict phenylalanine and give tyrosine
Phenylketonuria cause, characteristics and treatment
Due to deficiency of phenylalanine hydroxylase
Elevated phenylalanine: metabolites appear in urine giving it a musty scent
CNS manifestation: the metabolites interfere with brain neurotransmitter. Retardation at the age of one
Hypopigmentation: of hair and iris
treatment: must be treated in first 10 days to prevent retardation and treatment for the rest of life
Restrict phenylalanine and give tyrosine
