• The process of digestion begins from the mouth itself and gets completed in small intestine.
• Stomach plays a key role in the digestion of food. It has gastric glands which secrete gastric juices needed to break down food to simple nutrients and thereby contributing to digestion.
• There are different hormones in our body that has different functions. For example, there could be pH changes associated with different types of food. This pH change stimulates the secretion of a hormone called gastrin which induces the production of digestive juices. But it is not directly connected to the digestion process.
• Water is present in cell, organs and tissues to help regulating temperature and maintaining body functions.
• Absorbed food enters the blood stream and is taken to different parts of the body.

• William Beaumont revealed the functioning of human stomach in a living person. In 1833, He published his findings in the book, 'The Experiments and Observation of the Gastric juice and Physiology of Digestion'. After 10 years from there, he listed many conclusions about the chemical nature of digestion.
• He primarily discovered that gastric juice is responsible for the breakdown of food into simple nutrients and he also described the movement of stomach during digestion. 
• So, the correct option is B.
  

Digestion is completed in the Ileum because it is the last part of small intestine where all the digestive secretions end. From the large intestine, the process of absorption occurs predominantly.

The saliva contains an enzyme called salivary amylase which hydrolyses starch into maltose. The complete digestion of starch occurs only in the small intestine by the action of pancreatic amylase. The activity of enzymes is strongly affected by several factors, such as temperature and pH.

Cellulose falls into the category of indigestible carbohydrates known as dietary fibre. Humans don't have an enzyme to digest cellulose. 

• The digestion process depends upon hydrolysis to provide the biochemical reactions that break down food.
•  The digestive tract secretes enzymes, such as proteases, carbohydrases, nucleases and lipases that, along with water, catalyze the hydrolysis that releases various nutrients. Hence, the Digestion of food occurs as a result of hydrolysis.

Enteropeptidase is an enzyme produced by the cells of the duodenum and is involved in the digestion in humans and other animals. Enteropeptidase converts trypsinogen (a zymogen) into its active form trypsin, resulting in the subsequent activation of pancreatic digestive enzymes

The digestive system plays an important role in the absorption of nutrients into the body. It takes the food we ingest, breaks it down mechanically and chemically in the mouth and stomach. It then absorbs nutrients, fats, proteins, and water in the intestines before eliminating the waste through the rectum

1. The stomach produces gastrin, hydrochloric acid and pepsinogen.
2. G-cells in the stomach releases gastrin in response to distension of the antrum. This, in turn, causes an increase in the secretion of HCl from the parietal cells or oxyntic cells, which kills or inhibits bacteria and provides the acidic pH for the proteases to work and pepsinogen is released from chief cells in the stomach called zymogenic cells or peptic cells. 
3. Pepsinogen, inactive form of the enzyme in presence of hydrochloric acid activates into the active form, pepsin. Pepsin breaks down proteins into polypeptides. Hence, sodium hydrogen carbonate is not produced in the stomach.
   

All of these choices are a part of your digestive system. Your digestive system has many other associated organs including the small intestine, large intestine, and liver. The stomach is an area of food digestion. The pancreas releases hormones that affect the digestive process. The rectum is the last place you store you food before the process of elimination (pooping).

Cyclosis is the movement in the fluid in the cytoplasm where the proteins and nutrient in the cytoplasm get digested.

(A)Pepsin is not a nitrogenous base.

• The alimentary canal includes the mouth, pharynx, oesophagus, stomach, small intestine, large intestine, and anus.
• The longest part of the alimentary canal is small intestine because it is the main organ of absorption and digestion of food. 
  
• The surface area of the small intestine gets increased because of the presence of villi which gives food plenty of time to break down properly. Hence, the longest part of the alimentary canal is a small intestine.  

• Bile  is a dark green to yellowish brown fluid, produced by the liver of most vertebrates, that helps in the digestion of lipids in the small intestine.
•  In humans, bile is produced continuously by the liver, and stored and concentrated in the gallbladder. Hence, Bile is secreted by the liver.

• The stomach is made of  4 layers. They are serosa, muscularis, submucosa, mucosa. These layers of smooth muscle consist of the outer longitudinal, the middle circular, and the inner oblique muscles.
• The innermost layer or lining (mucosa) contains the glands that release digestive juices which includes pepsin, chymotrypsin, hydrochloric acid etc. Hence, The inner layer of the stomach releases digestive juices.

A pyramid-shaped diagram represents quantity wise numbers of organisms, energy relationships, and biomass of an ecosystem; In lower trophic levels number of organisms are high(plants) and at the highest trophic level, lesser number as some energy is lost as heat, in each transformation. This relationship is sometimes called an ecological pyramid.  The ecological pyramids represent the trophic structure and also trophic function of the ecosystem. In many ecological pyramids, the producer form the base and the successive trophic levels make up the apex. The ecological pyramids may be of following three kinds-

Answer C: Hepatic Caecae

The phenotype of an organism is the composite of the organisms observable characters, A has 2 observable characters, B shows 4 characters, while C shows 3.

Archenteron is the primary cavity which is formed at the initial stage of gastrulation. This cavity begins at the dorsal lip of blastopore which is at the one side of the dividing zygote and then this cavity moves through the zygote to the other side which gives rise to the anus. 

The brush borders of the intestinal lining are the site of terminal carbohydrate digestions. The microvilli that constitute the brush border have enzymes for this final part of digestion anchored into their apical plasma membrane as integral membrane proteins. Maltase, lactase, erepsin, nucleosidase are the brush border enzymes.

So, the correct option is 'four'.

In step two, an enzyme called aconitase converts citrate into isocitrate. Next, an isocitrate dehydrogenase enzyme oxidizes isocitrate, a six-carbon molecule, to a five-carbon α-ketoglutarate. The carbon that was lost is released as carbon dioxide and one NADH is also formed.

Starvation is defined as a severe deficiency in calorie energy intake needed to maintain human life.

The digestive juices consist of saliva, gastric juice, pancreatic juice, intestinal juice and bile. They help in break down of complex food into simpler building block components that can easily be absorbed by the body. These reactions occur outside the cells lining the gut.

Pepsin is the chief digestive enzyme in the stomach that stomach that breaks down proteins. Cells produce pepsinogen that is produced to act on mucus by epithelial cells of the stomach that helps to protect the lining of the stomach from corrosive hydrochloric acid and pepsin. And the absorption is done in small intestine.

The mouth leads to the buccal cavity or oral cavity. The oral cavity has a number of teeth and a muscular tongue. Teeth help in mastication of food when tongue helps in mixing of food with saliva.

• Ingestion is the consumption of a substance by an organism.
•  In animals, it normally accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking. 
• In single-celled organisms, ingestion can take place by taking the substance through the cell membrane. Hence, The process of taking in food from the environment is called ingestion.

The tongue is a muscular structure that cannot break down food. The food is broken down by the teeth of the upper jaw and lower jaw. Teeth is a hard part of the mouth that has a hard chewing surface covering made up of an enamel which helps in the mastication of food.

Saliva is present in the buccal cavity. It helps in lubricating and adhering the masticated food particles into a bolus.(mass of food) has salivary amylase that hydrolyzed 30% of starch into maltose. Hence, it helps in particle digestion of food.

A bolus is a mass of crushed food moistened with saliva.