What type of macromolecule is lipase

Histamine plays a role in stimulating the parietal cells to secrete the gastric acid. Together, all these cells work together to produce gastric juice a mixture of HCl and enzymes that helps mechanically and chemically digest the food particles into smaller bits. The mixing of the gastric juice and the food produces a semi-fluid substance called chyme. The Small Intestine : The small intestine is an organ where most of the digestion and almost all of the absorption takes place.

It consists of three parts - the duodenum, the jejunum and the ileum. The duodenum is where the majority of the digestion occurs while the jejunum and ileum is where the absorption takes place. The small intestine contains a thick and thin layer of smooth muscle that creates a wave-like contraction called peristalsis, which allows the chyme to move along the small intestine. The inner layer of the small intestine contains epithelium along with projections called villi. Each villus consists of many enterocytes that each contain their own tiny hair-like projections called microvilli.

This fuzzy-looking border of the villi is called the brush border and this is where digestion of the dipeptides, disaccharides and triglycerides takes place. Together, the villi and the microvilli greatly increase the surface area on which the digestive enzymes can act on, which makes digestion a much more efficient process.

The small intestine can produce its own set of digestive enzymes that can break down the various macromolecules. In addition, accessory exocrine organs such as the pancreas produces its own set of pancreatic enzymes that help digestion in the small intestine.

The liver can produce bile, which is stored in the gall bladder until it is released into the small intestine. Bile consists of phospholipids, cholesterol, bile salts, water, among other things and it helps mechanically digest and emulsify fat into smaller pieces.

Emulsification greatly increases the efficiency and rate at which lipase breaks down the macromolecules. Besides digestion, absorption also takes place at the small intestine.

Fatty acids can be easily absorbed into the cells via simple diffusion because they are hydrophobic. The cells then transfer these fatty acids into the lacteal found in the villus, which connects to the lymph system. The amino acids and simple sugars i. Digestive Enzymes of Small Intestine and Pancreas : The small intestine and the pancreas both produce a variety of digestive enzymes that are responsible for breaking down the many macromolecules found in the small intestine.

At the brush border of the villi of the small intestine are many proteolytic enzymes, including disaccharidases maltase, sucrace and lactase and peptidases especially dipeptidases that break down dipeptides. Many of these enzymes are attached to the membrane of the cells and can digest disaccharides and dipeptides directly on the membrane. The small intestine contains exocrine glands called crypts of Lieberkuhn which can produce an enzyme called enterokinase.

Enterokinase is responsible for transforming the zymogen trypsinogen into trypsin. The small intestine can also produce several important hormones, including secretin, cholecystokinin CCK and enterogastrone. Secretin is a peptide hormone that stimulates the release of pancreatic juice, CCK is also a peptide hormone that stimulates the release the bile from the liver and enterogastrone slows down the movement of the chyme as to ensure that all the fat is digested.

The pancreas produces several important proteolytic enzymes of its own along with a mixture of bicarbonate. This mixture is called the pancreatic juice and when stimulated, it empties into the pancreatic duct, which connects to the common bile duct and eventually makes its way into the small intestine. The pancreas produces amylase, which breaks down alpha glycosidic linkages found in starch and glycogen. The pancreas also produces lipase, which breaks down the triglycerides into fatty acids and glycerol.

Finally, the pancreas also produces a set of peptidases which cleave peptide bonds. The three peptidases that you should be familiar with are trypsinogen, chymotrypsinogen and carboxytrypsinogen.

Trypsinogen must be activated by enterokinase into trypsin, which then goes on to activate other digestive enzyme. Chymotrypsinogen is actived by trypsin into chymotrypsin, which cleaves peptides at aromatic amino acids. Carboxypeptidase cleaves peptide bonds at the carboxyl end of the peptide. Emulsification of Fats : Fats are hydrophobic and as a result will not mix very well with the solution in the lumen of the small intestine nor with the chyme.

Instead the fat molecules such as triglycerides and cholesterol will aggregate together to form large spherical bundles called fat globules. Due to the large size of the fat globule, pancreatic lipase a water-soluble molecule will have no way of actually reaching the inside portion of the fat globule.

This means that the lipase can only cleave ester bonds of the triglycerides on the surface and it cannot access the inside portion, which makes the lipase very inefficient. To increase the efficiency and the rate at which lipase cleaves ester bonds, the liver produces and releases a fluid called bile.

Bile is composed of amphipathic molecules such as phospholipids and bile salts. When bile enters the small intestine, it will mix with the fat globules and will cause them to break down into smaller units called emulsion droplets. This process is called emulsification. Emulsification greatly increases the surface area of the fat on which the lipase can actually act on.

As a result, lipase is now in a position to begin digesting the ester bonds of the lipids efficiently. With the help of colipase, lipase binds onto the surface of these emulsion droplets and begins breaking them down. This is where digestion takes place. Eventually, the emulsion droplets are broken into fatty acids. Since fatty acids are hydrophobic, the bile phospholipids or bile salts can surround the fatty acids and form a tiny spherical structures called a micelles. The micelles are about two hundred times smaller than the emulsion droplets and can therefore easily cross the membrane of enterocytes and enter the cytoplasm of the cell.

Absorption of Carbohydrates by Small Intestine : Carbohydrates begin digestion in the mouth, where salivary amylase begins to break down the carbohydrates into smaller polysaccharides. These polysaccharides eventually end up in the small intestine. In the small intestine, pancreatic amylase begins to break down the polysaccharides into disaccharides. The three most common disaccharides in the human are maltose combination of two glucose molecules , sucrose combination of glucose and fructose and lactose combination of glucose and galactose.

These disaccharides travel to the cell membrane also known as the brush border of enterocytes, where membrane-bound digestive enzymes act on the disaccharides and break them down into monomeric sugars. Fructose is transported across the cell membrane of enterocytes via passive transport, in which a membrane protein helps move the fructose without using any ATP molecules. However, both galactose and glucose are transported into the cell by using a sodium-linked secondary active transport system.

This means that the cell uses a sodium-potassium ATPase to create an electrochemical gradient in which there is a lower concentration of sodium inside the cell than on the outside.

Most of the fructose in the cell is transformed into glucose, and these three sugars are transported across the basolateral membrane by using either a cotransport system or passive transport. They travel into the blood stream, which takes them to the liver. Digestion of carbohydrates is temporarily suspended in the stomach but continues in the small intestine with enzymes secreted from the pancreas such as pancreatic amylase and other enzymes attached to the membrane of cells lining the small intestine such as maltase as well as sucrase and lactase.

Maltase breaks maltose into two glucose molecules which are then absorbed into the blood stream and taken to the liver. Digestion Macromomolecules. There are three class of macromolecules that we will consider, proteins, complex carbohydrates and lipids. Their formation is through reactions known as condensation reactions. During such reactions covalent bonds are formed between smaller molecules and a small molecule, mainly water, is expelled. Digestion of large molecules such as starch, lipids and proteins involves enzyme catalysed hydrolysis reactions.

Hydrolysis involves the breaking of bonds by the insertion of a water molecule. Consider the animation below, it shows the digestion of a dipeptide by a protease enzyme.

What bond is broken by a protease? What type of bond holds amino acids together in a protein. What is involved in hydrolysis? What is the general name for an enzyme that breaks covalent bonds in a protein chain to release amino acids? The chemical breakdown of proteins starts in the mouth, small intestine stomach, large intestine.

What is the role of stomach acid in the digestion of protein? The group of atoms shown on the right represent an: glycosidic bond joining two amino acids together glycosidic bond joining two sugars together.

Another name for a protein chain is a polyprotein polyamino polypeptide polyamine. The animation below shows the hydrolysis of a triglyceride. Digestion of fats takes place in the mouth, small intestine stomach, large intestine.

Bile acts to lubricate food as it moves along the digestive tract. This creates very large granules of multi-branched starch. Both the parotid and pancreatic amylases hydrolyse the link, but not the terminal links or the links.

This breaks amylose down into mainly disaccharides, and glycogen with its linkages into polysaccharides. The net result of these actions are numerous disaccharides and polysaccharides.

Enzymes attached to the enterocycytes of the small intestine break these down to monosaccharides. Hydrolysis by amylase : Both the parotid and pancreatic amylases hydrolyse the link, but not the terminal links or the links.

Proteins and polypeptides are digested by hydrolysis of the carbon—nitrogen C—N bond. The proteolytic enzymes are all secreted in an inactive form, to prevent auto-digestion, and are activated in the lumen of the gut.

Activation is caused by HCl in the case of the stomach enzyme pepsinogen, and by enteropeptidase and trypsin in the case of the pancreatic enzymes. Final digestion takes place by small intestine enzymes that are embedded in the brush border of the small intestine.

The enzymes are divided into endo- and exo-peptidases. Stomach pepsin cleaves the interior bonds of the amino acids, and is particularly important for its ability to digest collagen. This is a major constituent of the connective tissue of meat. In the absence of stomach pepsin, digestion in the small intestine proceeds with difficulty. Hydrolysis of peptide bond : Proteins and polypeptides are digested by hydrolysis of the C—N bond. Fats are digested by lipases that hydrolyze the glycerol fatty acid bonds.

Of particular importance in fat digestion and absorption are the bile salts, which emulsify the fats to allow for their solution as micelles in the chyme, and increase the surface area for the pancreatic lipases to operate. Lipases are found in the mouth, the stomach, and the pancreas. Because the lingual lipase is inactivated by stomach acid, it is formally believed to be mainly present for oral hygiene and for its anti-bacterial effect in the mouth.

Gastric lipase is of little importance in humans. Pancreatic lipase accounts for the majority of fat digestion and operates in conjunction with the bile salts. RNA and DNA are hydrolized by the pancreatic enzymes ribonucleases, deoxyribonucleases into nucleic acids, which are further broken down to purine and pyrimidine bases and pentoses, by enzymes in the intestinal mucosa nucleases.

The chemical breakdown of the macromolecules contained in food is completed by various enzymes produced in the digestive system. Protein digestion occurs in the stomach and the duodenum through the action of three primary enzymes:.