Instruct: Given a question, retrieve relevant documents that answer the question.
Query: How do enzymes help digest food?
Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption by the body. Digestive enzymes are found in the digestive tracts of animals (including humans) and in the traps of carnivorous plants, where they aid in the digestion of food, as well as inside cells, especially in their lysosomes, where they function to maintain cellular survival. Digestive enzymes of diverse specificities are found in the saliva secreted by the salivary glands, in the secretions of cells lining
The act of reproduction, regarding the female, leads to an increase of digestive enzymes. This allows her to eat more prey and to stock more nutrients. The digestive enzymes then start to digest the inside of the organism itself, except for the heart, guts, and mostly the ovaries. Once the offspring are born, and until the mother dies, the mother regurgitates for two weeks the fluids stocked inside as highly nutritive food for the progeny. Ninety-five per cent of the mother's mass is digested by the offspring. They will grow to three times their original size between their birth and dispersion. During the period when female spiders are caring for their hatched offspring, the mothers do not eat, and their offspring only eat the food that the mother regurgitates along with the mother's body at the end of this time.
Most grasshoppers are polyphagous, eating vegetation from multiple plant sources,[18] but some are omnivorous and also eat animal tissue and animal faeces. In general their preference is for grasses, including many cereals grown as crops.[19] The digestive system is typical of insects, with Malpighian tubules discharging into the midgut. Carbohydrates are digested mainly in the crop, while proteins are digested in the ceca of the midgut. Saliva is abundant but largely free of enzymes, helping to move food and Malpighian secretions along the gut. Some grasshoppers possess cellulase, which by softening plant cell walls makes plant cell contents accessible to other digestive enzymes.[20]
Single-celled organisms as well as sponges digest their food intracellularly. Other multi-cellular organisms digest their food extracellularly, within a digestive cavity. In this case the digestive enzymes are released into a cavity that is continuous with the animal's external environment. In cnidarians and in flatworms such as planarians, the digestive cavity, called a gastrovascular cavity, has only one opening that serves as both mouth and anus. There is no specialization within this type of digestive system because every cell is exposed to all stages of food digestion.
The digestive functions of saliva include moistening food and helping to create a food bolus. the lubricative function of saliva allows the food bolus to be passed easily from the mouth into the esophagus. Saliva contains the enzyme amylase, also called ptyalin, which is capable of breaking down starch into simpler sugars such as maltose and dextrin that can be further broken down in the small intestine. About 30% starch digestion takes place in the mouth cavity. Salivary glands also secrete salivary lipase (a more potent form of lipase) to begin fat digestion. Salivary lipase plays a large role in fat digestion in newborn infants as their pancreatic lipase still needs some time to develop.
Teeth are complex structures made of materials specific to them. They are made of a bone-like material called dentin, which is covered by the hardest tissue in the body—enamel. Teeth have different shapes to deal with different aspects of mastication employed in tearing and chewing pieces of food into smaller and smaller pieces. This results in a much larger surface area for the action of digestive enzymes.
The teeth are named after their particular roles in the process of mastication—incisors are used for cutting or biting off pieces of food; canines, are used for tearing, premolars and molars are used for chewing and grinding. Mastication of the food with the help of saliva and mucus results in the formation of a soft bolus which can then be swallowed to make its way down the upper gastrointestinal tract to the stomach. 
The digestive enzymes in saliva also help in keeping the teeth clean by breaking down any lodged food particles.
Chewing, in which food is mixed with saliva, begins the mechanical process of digestion. This produces a bolus which can be swallowed down the esophagus to enter the stomach. Here it is mixed with gastric acid until it passes into the duodenum where it is mixed with a number of enzymes produced by the pancreas. Saliva also contains a catalytic enzyme called amylase which starts to act on food in the mouth. Another digestive enzyme called lingual lipase is secreted by some of the lingual papillae on the tongue and also from serous glands in the main salivary glands. Digestion is helped by the chewing of food carried out by the muscles of mastication, by the teeth, and also by the contractions of peristalsis, and segmentation. Gastric acid, and the production of mucus in the stomach, are essential for the continuation of digestion.
Joint intracellular and extracellular digestion In hydra and other cnidarians, the food is caught by the tentacles and ingested through the mouth into the single large digestive cavity, the gastrovascular cavity. Enzymes are secreted from the cells bordering this cavity and poured on the food for extracellular digestion. Small particles of the partially digested food are engulfed into the vacuoles of the digestive cells for intracellular digestion. Any undigested and un-absorbed food is finally thrown out of the mouth.
Salivary glands plays primary role in the anatomical and physiological adaptations of the digestive system of predatory gastropods. Ducts from large salivary glands lead into the buccal cavity, and the oesophagus also supplies the digestive enzymes that help to break down the food. Salivary secretions lubricate the food and they also contain bioactive compounds.
An exocrine pancreas cell is a pancreatic cell that produces enzymes that are secreted into the small intestine. These enzymes help digest food by releasing enzymes as it passes through the gastrointestinal tract.
Digestion begins in the mouth with the secretion of saliva and its digestive enzymes. Food is formed into a bolus by the mechanical mastication and swallowed into the esophagus from where it enters the stomach through the action of peristalsis. Gastric juice contains hydrochloric acid and pepsin which would damage the walls of the stomach and mucus is secreted for protection. In the stomach further release of enzymes break down the food further and this is combined with the churning action of the stomach. The partially digested food enters the duodenum as a thick semi-liquid chyme. In the small intestine, the larger part of digestion takes place and this is helped by the secretions of bile, pancreatic juice and intestinal juice. The intestinal walls are lined with villi, and their epithelial cells is covered with numerous microvilli to improve the absorption of nutrients by increasing the surface area of the intestine.
The enzymes that are secreted in the stomach are gastric enzymes. The stomach plays a major role in digestion, both in a mechanical sense by mixing and crushing the food, and also in an enzymatic sense, by digesting it. The following are enzymes produced by the stomach and their respective function:
Food enters the mouth where the first stage in the digestive process takes place, with the action of the tongue and the secretion of saliva. The tongue is a fleshy and muscular sensory organ, and the very first sensory information is received via the taste buds in the papillae on its surface. If the taste is agreeable, the tongue will go into action, manipulating the food in the mouth which stimulates the secretion of saliva from the salivary glands. The liquid quality of the saliva will help in the softening of the food and its enzyme content will start to break down the food whilst it is still in the mouth. The first part of the food to be broken down is the starch of carbohydrates (by the enzyme amylase in the saliva).
Extracellular digestion is a process in which saprobionts feed by secreting enzymes through the cell membrane onto the food. The enzymes catalyze the digestion of the food into molecules small enough to be taken up by passive diffusion, transport, or phagocytosis. Since digestion occurs outside the cell, it is said to be extracellular. It takes place either in the lumen of the digestive system, in a gastric cavity or other digestive organ, or completely outside the body.
Exocrine pancreatic insufficiency (EPI) is the inability to properly digest food due to a lack of digestive enzymes made by the pancreas. EPI is found in humans afflicted with cystic fibrosis and Shwachman–Diamond syndrome, and is common in dogs. EPI is caused by a progressive loss of the pancreatic cells that make digestive enzymes; loss of digestive enzymes leads to maldigestion and malabsorption of nutrients from normal digestive processes. 
Two diverticular glands open into the stomach, and secrete enzymes that help to break down the food. In the more primitive species, these glands may also absorb the food particles directly and digest them intracellularly.
The prefix "extra" means "outside", and indicates that extracellular digestion must occur outside the cell. During extracellular digestion, food is broken down outside the cell either mechanically or with acid by special molecules called enzymes. Then the newly broken down nutrients can be absorbed by the cells nearby. Humans use extracellular digestion when they eat. Their teeth grind the food, enzymes and acid in the stomach liquefy it, and additional enzymes in the small intestine break the food down into parts their cells can use.
Although fungi do not have a digestive tract like humans, they still use extracellular digestion. Fungi and other decomposers utilize nutrients derived from breaking down the substrate they grow on. Another example of extracellular digestion being used is in the hydra, or sea anemone. A large cavity, called the gastrovascular cavity, fills the center of the animal, with one opening for both food and waste. When unsuspecting prey swim into the opening, stinging cells paralyze the prey. The hydra uses its tentacles to push the prey further into the cavity, where enzymes are secreted to break down the food. Once the food is broken down extracellularly into nutrients, the cells of the hydra can absorb it for energy.
The digestive system can respond to external stimuli, such as the sight or smell of food, and cause physiological changes before the food ever enters the body. This reflex is known as the cephalic phase of digestion. The sight and smell of food are strong enough stimuli to cause salivation, gastric and pancreatic enzyme secretion, and endocrine secretion in preparation for the incoming nutrients; by starting the digestive process before food reaches the stomach, the body is able to more effectively and efficiently metabolize food into necessary nutrients. Once food hits the mouth, taste and information from receptors in the mouth add to the digestive response. Chemoreceptors and mechanorceptors, activated by chewing and swallowing, further increase the enzyme release in the stomach and intestine.
Exocrine pancreatic insufficiency (EPI) is the inability to properly digest food due to a lack of digestive enzymes made by the pancreas. EPI is found in humans afflicted with cystic fibrosis and Shwachman–Diamond syndrome. It is caused by a progressive loss of the pancreatic cells that make digestive enzymes. Chronic pancreatitis is the most common cause of EPI in humans. Loss of digestive enzymes leads to maldigestion and malabsorption of nutrients.
Jaws allow fish to eat a wide variety of food, including plants and other organisms. Fish ingest food through the mouth and break it down in the esophagus. In the stomach, food is further digested and, in many fish, processed in finger-shaped pouches called pyloric caeca, which secrete digestive enzymes and absorb nutrients. Organs such as the liver and pancreas add enzymes and various chemicals as the food moves through the digestive tract. The intestine completes the process of digestion and nutrient absorption.
The partially digested and pulverized gizzard contents, now called a bolus, are passed into the intestine, where pancreatic and intestinal enzymes complete the digestion of the digestible food. The digestion products are then absorbed through the intestinal mucosa into the blood. The intestine ends via the large intestine in the vent or cloaca which serves as the common exit for renal and intestinal excrements as well as for the laying of eggs. However, unlike mammals, many birds do not excrete the bulky portions (roughage) of their undigested food (e.g. feathers, fur, bone fragments, and seed husks) via the cloaca, but regurgitate them as food pellets.
Some carnivorous plants, like the Heliamphora do not use digestive enzymes, but use bacteria to break down the food. These plants do not have digestive juices, but use the rot of the prey.[8]
Jaws allow fish to eat a wide variety of food, including plants and other organisms. Fish ingest food through the mouth and break it down in the esophagus. In the stomach, food is further digested and, in many fish, processed in finger-shaped pouches called pyloric caeca, which secrete digestive enzymes and absorb nutrients. Organs such as the liver and pancreas add enzymes and various chemicals as the food moves through the digestive tract. The intestine completes the process of digestion and nutrient absorption.
The exocrine pancreas is a portion of this organ that contains clusters of ducts (acini) producing bicarbonate anion, a mild alkali, as well as an array of digestive enzymes that together empty by way of the interlobular and main pancreatic ducts into the duodenum (upper small intestine). The hormones cholecystokinin and secretin secreted by the stomach and duodenum in response to distension and the presence of food in turn stimulate the production of digestive enzymes by the exocrine pancreas. The alkalization of the duodenum neutralizes the acidic chyme produced by the stomach that is passing into it; the digestive enzymes serve to catalyze the breakdown of complex foodstuffs into smaller molecules for absorption and integration into metabolic pathways. The enzymes include proteases (trypsinogen and chymotrypsinogen), hydrolytic enzymes that cleave lipids (the lipases phospholipase A2 and lysophospholipase, and cholesterol esterase), and amylase to digest starches. EPI results from progressive failure in the exocrine function of the pancreas to provide its digestive enzymes, often in response to a genetic condition or other disease state, resulting in the inability of the animal involved to properly digest food.