Question

In regards to the digestive system-

Review digestion of carbohydrates:

Enzyme	Site of digestion/absorption

Review of digestion of proteins:

Enzyme	Site of digestion/absorption
Pepsin
Trypsin
Chymotrypsin

Review digestion of fats:

Enzyme	Site of digestion/absorption
Amylase
Lipase

Answer 1

DIGESTION OF CARBOHYDRATE:

1. The mouth

You begin to digest carbohydrates the minute the food hits your mouth. The saliva secreted from your salivary glands moistens food as it’s chewed.

Saliva releases an enzyme called amylase, which begins the breakdown process of the sugars in the carbohydrates you’re eating.

2. The stomach

From there, you swallow the food now that it’s chewed into smaller pieces. The carbohydrates travel through your esophagus to your stomach. At this stage, the food is referred to as chyme.

Stomach makes acid to kill bacteria in the chyme before it makes its next step in the digestion journey.

3. The small intestine, pancreas, and liver

The chyme then goes from the stomach into the first part of the small intestine, called the duodenum. This causes the pancreas to release pancreatic amylase. This enzyme breaks down the chyme into dextrin and maltose.

From there, the wall of the small intestine begins to make lactase, sucrase, and maltase. These enzymes break down the sugars even further into monosaccharides or single sugars.

These sugars are the ones that are finally absorbed into the small intestine. Once they’re absorbed, they’re processed even more by the liver and stored as glycogen. Other glucose is moved through the body by the bloodstream.

The hormone insulin is released from the pancreas and allows the glucose to be used as energy.

4. Colon

Anything that’s left over after these digestive processes goes to the colon. It’s then broken down by intestinal bacteria. Fiber is contained in many carbohydrates and cannot be digested by the body. It reaches the colon and is then eliminated with your stools.

ABSORPTION OF CARBOHYDRATES:

Glucose, fructose, and galactose are absorbed across the membrane of the small intestine (jejunum)and transported to the liver where they are either used by the liver, or further distributed to the rest of the body

DIGESTION OF PROTEINS:

Protein digestion begins when you first start chewing. There are two enzymes in your saliva called amylase and lipase. They mostly break down carbohydrates and fats.

Once a protein source reaches your stomach, hydrochloric acid and enzymes called proteases break it down into smaller chains of amino acids. Amino acids are joined together by peptides, which are broken by proteases.

From your stomach, these smaller chains of amino acids move into your small intestine. As this happens, your pancreas releases enzymes and a bicarbonate buffer that reduces the acidity of digested food. This reduction allows more enzymes to work on further breaking down amino acid chains into individual amino acids.

Some common enzymes involved in this phase include:

• trypsin:In the duodenum, trypsin catalyzes the hydrolysis of peptide bonds, breaking down proteins into smaller peptides. ... Tryptic digestion is a necessary step in protein absorption, as proteins are generally too large to be absorbed through the lining of the small intestine.
• chymotrypsin:Chymotrypsin is an enzyme that is used in the small intestine to break down proteins into individual amino acids. It specifically targets the aromatic amino acids, tyrosine, phenylalanine, and tryptophan.
• carboxypeptidase:Carboxypeptidase is an enzyme synthesized in the pancreas and secreted into the small intestine. This enzyme hydrolyzes the first peptide or amide bond at the carboxyl or C-terminal end of proteins and peptides. It has a stronger preference for those amino acids that have aromatic or branched hydrocarbon chains.
• Pepsin:Pepsin is an endopeptidase that breaks down proteins into smaller amino acids. It is produced in the chief cells of the stomach lining and is one of the main digestive enzymes in the digestive systems of humans and many other animals, where it helps digest the proteins in food.

ABSORPTION OF PROTEIN:

In adults, essentially all protein is absorbed as tripeptides, dipeptides or amino acids and this process occurs in the duodenum or proximal jejunum of the small intestine. The peptides and/or amino acids pass through the interstitial brush border by facilitative diffusion or active transport.

DIGESTION OF FATS:

4. Small intestine

The majority of fat digestion happens once it reaches the small intestine. This is also where the majority of nutrients are absorbed.

Your pancreas produces enzymes that break down fats, carbohydrates, and proteins.

Your liver produces bile that helps you digest fats and certain vitamins. This bile is stored in the gallbladder. These digestive juices are delivered to your small intestine through ducts where it all works together to complete the fat breakdown.

During this process, fat and cholesterol are packaged into tiny particles called chylomicrons.

Lipase:Lipase is an enzyme that breaks down dietary fats into smaller molecules called fatty acids and glycerol. Pancreatic lipase, also called steapsin, acts on these fat globules, converting them into fatty acids and glycerol, which are small, energy-dense molecules used by all your cells.

ABSORPTION OF FAT:

Absorption of fats occurs only in the small intestines. Once the triglycerides are broken down into individual fatty acids and glycerols, along with cholesterol, they will aggregate into structures called micelles