Biochemistry high yield part 2

The medical biochemistry – FMGE

B2 – RIBOFLAVIN:-
 Coenzymes – FMN, FAD
 Used in oxidation reduction reactions
 Deficiency – cheilosis, glosittis, dermatitis
 Assessment of glutathione reductase in erythrocytes will be useful in
accessing riboflavin deficiency

NIACIN:-

 Coenzyme – NAD, NADP
 Pellagra preventive factor
 Niacin coenzymes synthesized from tryptophan
 Niacin deficiency results pellagra
 Pellagra symptoms – diarrhea, dementia, dermatitis – death “HD”
 Niacin inhibits lipolysis
 Niacin is used in treatment of hyperlipoprotenuria type_IIB. (increased
VLDL, increased LDL)

PYRIDOXINE:- B6

 Coenzyme – pyridoxine, pyridoxal pyridoxamine
 Pyridoxine used in transamination, decarboxylation, deamination.
 Active form is pyridoxal phosphate (PLP) transamination

It is required for the production of the monoamine neurotransmitters
serotonin, dopamine, norepinephrine and epinephrine, as it is the precursor
to pyridoxal phosphate: cofactor for the enzyme aromatic amino acid
decarboxylase. This enzyme is responsible for converting the precursors 5-
hydroxytryptophan (5-HTP) into serotonin and levodopa (L-DOPA) into
dopamine, noradrenaline and adrenaline. As such it has been implicated in
the treatment of depression and anxiety.

DEFICIENCY MANIFESTATIONS:-

1. neurological symptoms
2. excretion of xanthurenic acid in urine
3. drugs isoniazid and penicillamine can cause B6 deficiency.

Global institute of medical sciences www.gims-org.com


BIOTIN – B7

It is required for carboxylation reactions
Eg.:- 1. acetyl CoA carboxylase
2. propony CoA carboxylase
3. pyruvate carboxylase

PANTOTHENIC ACID:-

 also known as coenzyme –A
 deficiency – burning feet syndrome

FOLIC ACID:-

 it is important for one carbon metabolism
 the active form if tetrahydrofloate TH4 or THF
 the most common vitamin deficiency
 important for the synthesis of nitrogenous bases in DNA and RNA.
 Supplemented in pregnancy to prevent neural tube defects
 Deficiency of folic acid megaloblastic anemia.
 In folic acid deficiency FIGLU excreted in urine.
 (FIGLU- formiminoglutamate)

VITAMIN –B12 (COBALAMIN)

 The absorption of vit-B12 requires intrinsic factor, intrinsic factor
produced by gastric parietal cells
 Absorption of B12 into mucosal cells is Ca+2 dependent
 In mucosal cells B12 converts to methyl B12
 From the mucosal cells transported in the plasma by transcobalamins
i.e., Tc-I and Tc-II
 Methyl –B12 (mucosal cells) – 90% binds to Tc-I and 10% binds to
Tc-II
 Vit-B12 stores in liver, as deoxyadenosyl
 B12 (storage form of vit B12)

DEFICIENCY:-
 Methyl melanoic acidemia
 Pernicious anemia
 Neurological manifestations (optic neuropathy)



 Use schilling test to detect deficiency
 Vit-B12 deficiency - most common cause is malabsorption sprue .

HAEMOGLOBIN AND PORPHYRINS:-
METABOLISM:-

 Heme contains porphyrin molecule known as protoporphyrin IX
 Heme contains 4 pyrole rings
 The central atom of heme contains Fe
 The adult hemoglobin – α2,β2 – HbA1
 Fetal hemoglobin – α2 γ2 – HbF
 HbA2 – α2 δ2
 Glycosylated hemoglobin – Hb A1 C – α2 β2 –glucose (diabetes)
 Fetal Hb has more affinity towards O2 than adult – HbF – 100% ;
HbA1 – 95%.
 In heme if Fe2+ oxidizes to form Fe3+ known methehemoglobin

BIOSYNTHESIS OF HEME:-

 Heme synthesis take place in liver
 ALA synthase is rate limiting step in heme biosynthesis



HEME METABOLISM :-

 Bilirubin bound to albumin to form bilirubin albumin complex



 Enters liver for conjugation

 Bilirubin enters into intestine where it reacts with bacterial enzymes to
form stercobilin which enters into feces
 1 gm of Hb gives 35 mg of bilirubin
 Bilirubin- albumin complex binds to receptor LIGANDIN which in
present on hepatocytes

Porphyrias :-



CARBOHYDRATE METABOLISM:-

 Insulin dependent glucose transport – GLIT-4 skeletal muscle, adipose
tissue
 GLUT-1 – erythrocytes

GLYCOLYSIS CYCLE:-



 Location – cytosol of all most all the cells
 Glucokinase – liver, hexokinase – other tissues
 Hexokinase – low Km, glucokinase- High Km
 (PFK-1) Phosphofructokinase-1 – rate limiting step
 Spilitting – aldolase-A . 7 ATP in aerobic glycolysis and 2 ATP in
anerobic
 Glycolysis in RBC is always anerobic

IRREVERSIBLE STEPS:-

 Hexokinase
 PFK-1
 Pyruvate kinase ( deficiency hemolytic anemia )

INHIBITORS:-

 Glycerol dehyde 3 phosphate dehydrogenase – iodo acetate ,arsenate
 Enolase – fluoride
 Phospphotriose isomerase - bromohydroxy acetone phosphate
 End product of aerobic glycolysis – pyruvate
 End product of anaerobic glycolysis – lactate
 Glycolysis in erythrocytes is always anaerobic
 Number of ATP under aerobic glycolysis 7
 Number of ATP under anaerobic glycolysis 2
 PFK-1 is regulated by PFK-2
 A product of glycolysis – 2,3 BPG combines with hemoglob9in and
unloads O2 to tissues.
 Increase 2,3-BPG shifts O2 /Hb dissociation curve to right
 Decrease 2,3-BPG shifts O2/Hb dissociation curve to left.

PDH COMPLEX:

 Location – mitochondria
 Enzyme complexes:-
1. E1 – pyruvate dehydrogenase – TPP
2. E2 – dihydro lipoyl transacetylase – lipoamide ,CoA
3. E3 – dihydro lipoyl dehydrogenase – NAD, FAD
 Inhibitors – arsenic poisoning

TCA CYCLE:-



 Location – mitochondria
 Citrate synthase - rate limitin step

 NADH produce in :-

1. iso citrate dehydrogenase
2. α-ketoglutarate dehydrogenase
3. malate dehydrogenase

 FADH produced by succinate dehydrogenase
 GTP produced by succinate thiokinase

INHIBITORS:-

1. Aconitase – fluroacetate
2. Α-keto glutarate dehydrogenase – arsenate
3. Succinate dehydrogenase – malonate
 Number of ATP produced from 1 Acetyl Co-A is 10.

GLUCONEOGENESIS:-

 Synthesis of glucose from non-carbohydrate compounds.
 160 gms of glucose required per day (whole body)
 120 gms of glucose is required brain
 Location:- initial step mitochondria ; key step – cytosol
 Rate limiting step – pyruvate carboxylase



 Alanin glucogenic aminoacid
 Glucagon stimulates gluconeogenesis, insulin inhibits
 Αlpha- cells secrets glucagone
 Alcohol inhibits gluconeogenesis induces hypoglycemia

GLYCOGEN METABOLISM

 Liver glycogen maintains blood glucose
 Muscle glycogen is used ony for muscle
 Glycogenesis in muscle starts with hexokinase
 Glycogenesis in liver starts with glucokinase
 Glycogen in protein produced by liver acts as initiator of glycogen
synthesis
 The tyrosine residue of glycogenin adds glucose from UDP-G to form
glycogen primer
 Glycogen synthatase – rate limiting step in glycogen synthesis



 Glycogen phosphorylase breaks glycogen at α1-4 residues.
 Glucagons stimulates glycogen breakdown in liver
 Epinephrine stimulates glycogen breakdown in muscle
 Calcium promotes glycogen breakdown by Ca+2 colmodulin complex
 Glucose 6 phosphatase deficiency –Von Girek’s disease
 Lysosomal α (1, 4) glucosidase deficiency – Pompe’s disease – heart is
more commonly involved – death occurs due to heart failure.
 De-branching enzyme deficiency Anderson’s disease
 Muscle glycogen phosphorylase deficiency –MC Ardle’s disease
 Liver glycogen phosphorylase Her’s disease
 Phosphofructokinase – Taruri’s disease – erythocytes, hemolysis

HMP PATHWAY:-

 HMP pathway is only pathway which synthesizes NADPH in RBC
(required for antioxidant reaction)
 Rate limiting step – glucose 6 phosphate dehydrogenase
 Deficiency of glucose 6 phosphate dehydrogenase – hemolytic anemia
 HMP pathway – synthesis of riboses
 Transketolase dependent on TPP – decrease TPP – Werick’s
korsakoff syndrome
 Glucose 6 phosphate dehydrogenase deficiency is resistant to malaria
 Deficiency of xylitol dehydrogenase – essential pentosuria
GLACTOSE METABOLISM:-
 CLASSICAL GALACTOSEMIA
 Infants
 Deficiency of galactose 1-phosphate Transferase uradyl.
 Increase galactitol by aldose reductae – cataract diagnosis – elevated
galactose 1-phosphate uridyl transferase

FRUCTOSE METABOLISM:-
 Deficiency of fructokinase essential fructosuria
 Deficiency of aldolase-B hereditary fructose intolerance
 Mucopolysaccharidoses-I – Iduronidase – Hurler’s syndrome
 Mucopolysaccharidoses-II – iduronate sulfatase – Hunter’s syndrome
 Mucopolysaccharidoses-III – sanfilippo syndrome
 β- glucuronidase – sly syndrome (Mucopolysaccharidoses-VII)


Biochemistry high yield part 2

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Biochemistry high yield part 2