Answer: Option A. -> Liver
:
A
Kupffer cells, also known as stellate macrophages are specialized macrophages located in the liver, lining the walls of the sinusoids that form part of the mononuclear phagocyte system.

Answer: Option A. -> Slightly acidic medium
:
A
Ptyalin of saliva acts in acts in a neutral or faintly acidic medium (optimally at pH 6.5)

Answer: Option D. -> Small Intestine
:
D
Protein and all other nutrients get absorbed in the small intestine. The digestion process starts in the stomach and continues in the duodenum. The digested protein and other nutrients then gets absorbed.

Answer: Option A. -> Rennin
:
A
Chymosin, known also as rennin, is a proteolytic enzyme synthesized by chief cells in the stomach. Its role in digestion is to curdle or coagulate milk in the stomach, a process of considerable importance in the very young animal. If milk were not coagulated, it would rapidly flow through the stomach and miss the opportunity for initial digestion of its proteins.

Answer: Option C. -> rennin – casein
:
C
Rennin is the enzyme that acts on casein which is a milk protein. It is secreted by the gastric glands in an inactive form prorennin which is activated by HCI. Rennin converts caesinogen into calcium paracaesinate in the presence of calcium ions. This ensures that milk remains in the stomach as long as possible. The largest amounts of rennin are present in the stomach of young mammals. Carbohydrate, maltose and protein are acted upon by carbohydrase, maltase and protease respectively.

Answer: Option D. -> Different cells
:
D
The pancreas is a gland organ in the digestive and endocrine systems of vertebrates.It is both exocrine; (secreting pancreatic juice containing digestive enzymes) and endocrine (producing several important hormones, including insulin, glucagon, and somatostatin). The beta cells produce insulin, alpha cells produce glucagon and delta cells produce somatostatin. There are two main types of exocrine pancreatic cells, responsible for two main classes of secretions. The centroacinar cells produce bicarbonate ions and basophilic cells secrete digestive enzymes.

Answer: Option C. -> Cellulase
:
C
Human digestive juices lack cellulase which digests cellulose. Cellulose thus acts as dietary fibers that help is the easy egestion of the food from the large intestine.

Answer: Option C. -> Crypts of Leiberkuhn
:
C
These enzymes include peptidase, sucrase, maltase, lactase and intestinal lipase.

Answer: Option B. -> Protein digestion begins in the stomach
:
B
Dietary proteins are first denatured by the hydrochloric acid secreted by the parietal cells of gastric glands (the weak non-covalent interactions that hold proteins in their specific 3-D configuration are disrupted exposing many peptide bonds that were initially shielded inside the protein). The cells of the stomach epithelium secrete pepsinogen (stimulated by the hormone gastrin) which is activated to pepsin initially by the hydrochloric acid, then by autocatalysis by pepsin itself. Pepsin then begins the specific partial hydrolysis of the denatured proteins in the stomach where the pH of the environment is 1-2 (optimum pH of pepsin). Pepsin is an endopeptidase that only hydrolyses those peptide bonds in which an aromatic amino acid supplies the NH of the peptide bond.
Trypsin is synthesised in the pancreas as trypsinogen (together with other proenzymes) and released into the small intestine. It is not present in the stomach.

Answer: Option B. -> Enteropeptidase
:
B
The inactive precursor of trypsin, produced by the pancreas and converted to trypsin in the small intestine by enteropeptidase.