MBBS Biochemistry

1. Dr. SOHIL TAKODARA

3.  50-150gms of fat per day
 90% Tri Acyl Glycerol(TAG)/Triglycerides(TG),
 10% ( Cholesterol. Phospholipids, Fatty
Acids(FA))
 Common dietary sources: Milk, Curd, paneer,
sweets, ghee, butter, oils, eggs

4.  Energy – 1 gm fat ( 9 Kcal)
 TAG- Emergency source of energy
(Starvation)
 Phospholipids-Insulation, surfactant etc
 Biological membrane formation
 Cholesterol- Steroid hormones, Bile Acids
 Lipoproteins- Lipid transporters of the body

5. TRI ACYL GLYCEROLS (TG/Neutral Fat)
Glycerol + Fatty acid ----> TAG
CH2-OH HOOC-R
CH-OH + HOOC-R’ ------->
CH2-OH HOOC-R’’

6. • Lingual Lipase
Mouth
• Gastric Lipase
Stomach
• Pancreatic juice
• Lipase and colipase
• Phospholipase A2
• Cholesterol Esterase
• Bile salt
Intestine

7.  Lingual lipase- Dorsum of the tongue
 Secreted on Saliva
 Very little digestion
 Action continues in stomach ( pH= 2.5-5)
 It Splits TAGs into Fatty Acids and Glycerol

8.  Gastric Lipase- Chief cells of gastric mucosa
 Digests around 30% of TAG
 Acts on Sn-3 ester linkage of TAGs containing
short and medium chain FA (Butter,Ghee)
 Produces 1,2 Diacylglycerol ( DAG) and Free
Fatty Acids ( FFA)

10. Pancreatic
Juice
Lipase
/colipase
Phospho
lipase A2
Cholesterol
esterase
Bile salt

12.  Its essential for efficient lipid digestion
 Bile salts- Synthesized in Liver, Secreted in
Bile
 Sodium and potassium salt of Bile acids
 Mixed micelle formation of Bile salt, PL,
cholesterolesters

18.  BREAKSDOWN Cholesterolesters into free
fatty acids and free cholesterol

19.  ACTS ON PHOSPHOLIPID (LECITHIN)
 PRODUCES LYSOLECITHIN AND FREE
CHOLESTEROL

20. LIPASES SITE OF ACTION SUBSTRATE PRODUCTS
Lingual and
gastric lipase
Mouth,Stomach Medium chain FA
+ TG (Milk)
FFA,DAG
Pancreatic
Lipase
Duodenum Longchain FA
containing TG
FFA,Glycerol,2M
AG
Phospholipase A2 Small Intestine Phospholipids at
Sn-2
FFA,Lysolecithin
Intestinal Lipase Small Intestine TAG with
medium chain
FA
FFA,Glycerol
Lipoprotein
Lipase
Capillary walls TAG in
Chylomicron,
VLDL
FFA,Glycerol
Hormone
sensitive Lipase
Adipose tissue TAG stores FFA,Glycerol

22.  Digested lipid products are packed into
micelle and move towards intestinal mucosa
 Bile salts undergo enterohepatic circulation
for reutilization (1 % excreted)

23.  2-acyl glycerol gets reconverted to TAG
 1-acyl glycerol is broken into FFA and
glycerol
 Long chain utilizes this glycerol to form TAG
 TAGs, PL, CE are incorporated with Apo A and
Apo B48 forms a and circulated

26. DISORDERS
Steatorrhea- excretion of fatty foul smelling stools.
Defective digestion - chronic disease of pancreas
surgical removal of pancreas
defective bile synthesis(
OBSTRUCTIVE JAUNDICE)
gall stones
Defective absorption- intestinal diseases-
Enteritis
Tropical sprue
Crohn’s disease

28. Chyluria- milky urine
due to abnormal connection between lymphatic drainage of
intestine and urinary tract - chylous fistula
Chylothorax- milky pleural fluid
Chyle may leak into the pleural cavity from the thoracic duct
or its tributaries as a result of trauma (stabwounds, crush
injuries, surgical injury) or obstruction by tumour. It is
commonly mistaken for pus. Chyle contains fat globules.
Colipase defeciency- steatorrhoea
Cholelithiasis – failure to keep cholesterol in solution by bile
salts.
FSV def manifestations are common.