Biology: Digestive Enzymes

digestive enzymes are produced by

 

specialized cells in the digestive tract and pancreas.

WHAT IS THE DIGESTIVE TRACT 

the running of the digestive system

enzymes or groups of enzymes often

end in -ase.

carbohydrates si broken down by

Carbohydrase

     proteins is broken down by

     Proteases

lipids are broken down by

 Lipases

what is a saliva

Saliva is a fluid that is secreted by the salivary glands into the oral cavity.

what are the components of saliva

water, mucus, enzymes

The smell/sight of food and memory of taste act as 

stimuli for the excess secretion of saliva.

what is in saliva

water, salivary amylas, lingual lipase, mucus and lysozyme

how much water is in saliva

97% to 99.5%

salivary amylase is the

enzyme that begins starch digestion in the mouth

lingual lipase

enzyme that is activated by stomach acid and digests fat after the food is swallowed

mucus

binds and lubricates the mass of food and aids in swallowing

lysozyme

 enzyme that kills bacteria by destroying their cell wall

ph of saliva

6.8 to 7

what is gastric juice

he term used to describe the chemicals that are released by the stomach to help break down food.

how much gastric juice is produced a day

About 2 to 3 L per day of gastric juice is produced by the gastric glands.

what are the componets of the gastric juices

 

-             Mucus

-             Water

-             Hydrochloric acid (HCl)

-             Enzymes.

 

ph of gastric juice

from  1.5 to 3.5 - very acidic

Gastric juice has a

high concentration of hydrochloric acid 

pH of the hydrochloric acid

about 2

function of hydrochloric acid

o   Activates gastric enzymes.

o   Breaks up connective tissues and plant cell walls.

o   Helps liquefy food to form chyme.

o   Destroys most ingested microbes.

Hydrochloric acid: Activates

gastric enzymes.

Hydrochloric acid: breaks up

connective tissues and plant cell walls.

Hydrochloric acid:  Helps

liquefy food to form chyme.

Hydrochloric acid: Destroys

most ingested microbes.

the acidity of the hydrochloric acid

Hydrochloric Acid is dangerous, as it can burn the stomach.

what is there to prevent the stomach from burning

To prevent this, the stomach is coated in a slimy substance called mucus.

the main enzyme in gastric juice is

pepsin

what is pepsin

Pepsin is a type of protease that breaks down proteins in food into smaller polypeptides.

 Protein digestion is completed in

the small intestine.

salivary and gastric enzymes partially digest

protein

and salivary and gastric enzymes partially digest lesser amounts of

starch and fat in the stomach.

Most digestion and nearly all absorption occur after

 

the chyme has passed into the small intestine

bile is produce by_ and stored in the _

Bile, which is a substance, produced by the liver and stored in the gallbladder.

what is bile’s main role

bile’s main role is to emulsify fats (lipids), breaking them down into smaller droplets. 

what does emulsification mean

Emulsification means that a larger surface area of fats is exposed to enzymes that can digest them.

what is done to increase efficiency of lipid hydrolysis

o   This increases the efficiency of lipid hydrolysis, so the lipids are broken down faster and more efficiently.

pancreatic juice is a

alkaline (basic) mixture of water, enzymes, and sodium bicarbonate.

pancreatic juice contains

anylase, lipase, trypsin, nucleases

Pancreatic Juice: amylase

break down carbohydrates into simple sugars 

Pancreatic Juice: lipase

break down lipids into fatty acids and glycerol. 

Pancreatic Juice: trypsin

a protease enzyme, that break down proteins into smaller polypeptides and eventually, amino acids.

Pancreatic Juice: nucelase

 break down nucleic acids

carbohydrate digestion begins in the

mouth

 Salivary amylase breaks

down starch 

amylase works best at pH of

6.8 to 7.0 of oral cavity

Amylase quickly denatures on

contact with stomach acid

when amylase is denatured it is digested by

pepsin.

cellulose is

indigestible

When reaching the small intestine pancreatic amylase converts starch

to many disaccharides

what are some od the disaccharides that the pancreatic juice convert from starch

maltose, sucrose, and lactose.

protein digestion begins in the

stomach

protein digestion has an optimum of

pH of 1.5 to 3.5.

 Proteases are

 

enzymes that digest proteins. 

example of preotease

pepsin

 Pepsin digests into

10% to 15% of dietary protein

what is the deitary protein get digested into

shorter peptides and some free amino acids.

Proteins continue to digest in

the small intestine.

pepsin inactivated when  

it passes into the small intestine and mixes with the alkaline pancreatic juice (pH 8).

what takes over protein digestion

pancreatic enzymes trypsin take over the process by hydrolyzing polypeptides into even shorter peptides.

protein digestion with trypsisn means

hydrolyzing polypeptides into even shorter peptides.

Lipids: salivary glands in the mouth secrete

lingual lipase. 

lingula lipase is active in mouth, but more  

active in stomach along with gastric lipase. 

how much in percentage is lipids digested before the small intestine

10% to 15% of lipids digested before reaching small intestine.

Fat enters the small intestine as

large droplets exposed to lipase only at their surface.

 Bile from the liver emulsifies

lipids and breaks them into smaller droplets.