Pancreatic juice/Bile + large intestines

Describe the activity of pancreatic juice Trypsinogen and trypsin Chymotrypsinogen and chymotrypsin Proelastase and elastase 1 Procarboxypeptidase and carboxypeptidase Pancreatic amylase Prolipase and pancreatic lipase Nuclease (and nucleotidase and nucleosidase) Alkaline fluid Bile

How is pancreatic juice formed ?

•Epithelium secretes bicarbonate ions and water. this Mix with enzymes to produce pancreatic juice

What is the PH differences between pancreatic juice and gastric juice ?

Pancreatic = 7.5-8.8

Gastric = 1-2.2

What are the 4 main peptidases that are only activated in the small intestine which protects the pancreas.

1. Trypsinogen

2. Chymotrypsinogen

3. Proelastase

4. Procarboxypeptidases\

How is Trypsinogen activated ?

activated to trypsin by enteropeptidase in the small intestine

How is Chymotrypsinogen activated ?

1.activated to chymotrypsin by trypsin

How is Proelastase activated to ?

to elastase 1 by trypsin

How is Procarboxypeptidases activated to ?

carboxypeptidases by trypsin

Pancreatic amylase breaks α-glycosidic bonds in starch. Why does this occur ?

To increase the yield of Maltotriose and maltose in amylose

To increase the yield of glucose and dextrin from amylopectin

How is amylase broken down to pass thru the intestines ?

by trypsin

What does pancreatic lipases breakdown ?

Triglycerides into two free fatty acids and one monoacylglycerol

released in its active form

What are the 3 enzymes of the pancreatic juice to digest nucleic acids?

Nucleases , Nucleotidases , Nucleosidases

Nucleases (release)

Made in pancreas

Examples are Deoxyribonucleases and ribonucleases

Breaks down phosphodiester bonds between nucleotides

Nucleotidases

Made in small intestines

Breaks down Nucleotides → → nucleosides and a phosphate

Nucleosidases

made in small intestines

Hydrolyse nucleosides → → pentose sugar and nitrogenous base

Where is bile made and stored

Made - liver

Stores - gallbladder

What is bile made off ?

oWater

oBicarbonate ions

oBilirubin

oCholesterol

oBile salts for emulsification

When chyme enters the duodenum, what enzyme is realeased ?

CCK

What happens in the presence of CCK ?

the hepatopancreatic sphincter opens and bile flows through the common bile duct to the duodenum

What happens in the absence of CCK ?

the hepatopancreatic sphincter remains closed and bile is directed to the gallbladder via the cyst duct

How is CCK production unregulated ?

in the presence of fat

How is carbohydrates absorbed in the small intestines?

They diffuse through the cytoplasm by facilitated diffusion and co transport from the apical side to the basal side

How is fructose absorbed ?

Transported from the lumen into the enterocyte by facilitated diffusion thru GLUT5.

Goes across basal membrane to blood by GLUT2.

How is amino acids absorbed ?

In the small intestines via sodium cotransporter

How are lipids absorbed ?

Transported into epithelial cells by simple diffusion.

The capillary network transports absorbed nutrients to the hepatic portal system

The lacteal absorbs molecules too large to pass into capillaries like chylomicrons

How is water absorbed ?

osmosis

it diffuses is response to osmotic gradient made by absorbed electrolytes

→ Water passes directly across the membrane but rates of absorption are increased by aquaporins

What are the 2 types of vitamins + examples?

FAT SOLUBLE - A,D,E,K

WATER SOLUBLE - 9 (B and C)

How are the fat-soluble vitamins absorbed?

Enter duodenum along with dietary fats

Incorporated into chylomicrons and absorbed at lacteal

How are the water-soluble vitamins absorbed?

Easily absorbed by intestinal epithelium

What is the function of the large intestine in terms of absorption ?

Bile salts absorbed in caecum and transported to the liver

• Vitamins synthesised by gut bacteria are absorbed in the large intestine

• Vitamin K for blood clotting

• Biotin for glucose metabolism

• Vitamin B5 for hormone and synthesis of neurotransmitters (acetylcholine, - pinephrine, and serotonin)

What is the function of the large intestine in terms of Detoxification ?

Organic molecules

• Bilirubin is converted to other molecules by gut bacteria and absorbed

• Excreted by urinary system

Toxins – ammonia and hydrogen sulphide

• absorbed at large intestine are transported to liver for detoxification

• Ultimately excreted by urinary system

What are the other 2 functions of the small intestines ?

Defecation and Water absorption and compaction of faeces