BioChem Lab - Experiment 9: CHEMICAL DIGESTION OF FOODS

Food digestion

•to ensure that large food molecules (carbohydrates, proteins, and lipids) are broken down to smaller subunits that make them up.

carbohydrates, proteins, and lipids

are broken down to smaller subunits that make them up.

Importance of Digestion

•This makes them easier to be absorbed within the intestines and transported through the vasculature of the body to the tissues and cells where those molecules can then be used.

Digestive enzymes

•greatly enhance the rate at which covalent bonds that link subunits together to form polymeric biomolecules are broken.

digestive tract

These are produced in different segments of the alimentary canal

based on specificity

Enzymes act on their substrates ____________________

polysaccharides, lipase for lipids, etc.

Enzymes act on their substrates based on specificity

salivary amylase (ptyalin)

Carbohydrates are the first type of molecule to be chemically digested in the alimentary canal, as chemical digestion begins in the oral cavity through a salivary enzyme called

maltose

Salivary amylase begins the breakdown of the polysaccharide amylose (starch, the principal storage carbohydrate in plants) into the disaccharide

short-lived action

Salivary amylase has a

low gastric pH

In fact, it is swallowed with chewed food and subsequently inactivated by extremely ?

7; 6.4-7.0

Amylase has an optimum pH around __, and the pH of saliva is generally between 6.4-7.0

stomach

Chemical digestion of proteins start in the ?

gastric juice

The stomach produces a mixture of fluids called

induced by smell, site, and taste of food

The stomach produces a mixture of fluids called gastric juice in response to neural stimulation

Gastric juice

contains several substances, but the two most important for initiating protein digestion are hydrochloric acid (HCl) and the protease pepsin.

hydrochloric acid (HCl) and the protease pepsin

Gastric juice contains several substances, but the two most important for initiating protein digestion are ?

HCL

•is secreted by parietal cells in the gastric mucosa.

(1) the low pH denatures the tertiary structures of ingested protein, making them easier to digest enzymatically, and (2) the low pH is required for the activation of pepsin

The low pH (~2) of the gastric juice aids protein digestion in a couple of ways:

pepsinogen

Pepsin is produced by chief cells of the gastric pit in the molecule’s inactive form called

proteolytic activity

Pepsin is produced by chief cells of the gastric pit in the molecule’s inactive form called pepsinogen, but once it diffuses into the lumen of the stomach the acidic conditions enable it to have a weak ?

37°C

For humans digestive enzymes, they work best at temperatures of ______ and will be drastically impacted by temperatures above or below this temperature.

above 60°C; denaturated

Factors Affecting Enzyme Activity

• •Being heated ________ will lead to the protein being _______ and thus, will no longer function properly.

• cooled down

• decrease the activity

• no activity

• 0°C

Factors Affecting Enzyme Activity

• •Conversely, being ___________ will progressively _________ for some enzymes to the point of __________ once a temperature of __________ is reached.

pH and sensitivity of the molecule

Enzymes also function within an optimal range based on _______________

pH

is an indication as to where within the pathway of digestion the enzyme will principally function.

Iodine test and Benedict’s test

Digestion of starch is tracked based on the result of ?

blue-black or purple color

If starch is present, it will give a _________________ in Iodine test

blue solution

If starch is present, it will give a ____________ in Benedict’s test.

disaccharide maltose

If digestion has occurred by the action of amylase, starch is broken down into the ?

fraying occurs and formation of bubbles occurred

Egg white digestion acted by pepsin is observed when ?

pH ~ 2.2; 42°C

Pepsin works best in acidic conditions ? and at temperature near ?.

around 8.0

Pepsin becomes irreversibly inactive at high pH ?