Human Digestive System

Cheese production involves the coagulation of milk proteins (casein). Protease enzymes, specifically rennet (which contains chymosin), are used to break down proteins and curdle the milk.

The liver doesn't secrete any enzyme. The liver only secretes bile that it produced by the byproducts of haemoglobin breakdown. With the presence of bile, lipase, an enzyme will be able to break down the fat into smaller units. 

A. The functional unit of liver is called hepatic lobules. 

Bile is produced in the liver and then it's concentrated in the gallbladder. From gallbladder, it goes through the cystic duct. Cystic duct joins the pancreatic duct to form the hepato-pancreatic duct. Pancreatic juice and bile juice together is secreted through a common hepatic duct into the duodenum. During secretion from the hepato-pancreatic duct, pancreatic juice is present too making bile juice diluted. 

Steroids like cholesterol are crystallisable lipids having four hydrocarbon rings, consisting of three cyclohexane and one cyclopentane ring and a long hydrocarbon side chain. In animals,  liver is the major site of cholesterol production. Cholesterol is an important constituent of bile produced in liver.

The main centre of carbohydrate metabolism is liver. Following steps are related with carbohydrate metabolism-
(i) Glycogenesis- The conversion and storage of extra amount of glucose into glycogen. The main stored food in the liver is glycogen.
(ii) Glycogenolysis- The conversion of glycogen into glucose back when glucose level in blood falls down is called glycogenolysis.
(iii) Gluconeogenesis- At the time of need, liver converts non carbohydrate compounds (e.g., amino acids, fatty acids) into glucose. This conversion is called as gluconeogenesis. This is the neo-formative process of glucose. 

Stool that is pale or whitish grey colour may be caused by insufficient bile output. Bile salts from the liver give stool its brownish color. If there is decreased bile output, stool is much lighter in color. Thus whitish grey colour stool is due to malfunctioning of liver.

Jaundice is caused by a build-up of bilirubin in the blood and tissues of the body. Any condition that disrupts the movement of bilirubin from the blood to the liver and out of the body can cause jaundice. There are three types of jaundice, depending on what is affecting the movement of bilirubin out of the body. Pre-hepatic jaundice occurs when a condition or infection speeds up the breakdown of red blood cells. This causes bilirubin levels in the blood to increase, triggering jaundice. Intra-hepatic jaundice happens when a problem in the liver for example, damage due to infection or alcohol, disrupts the livers ability to process bilirubin. Post-hepatic jaundice is triggered when the bile duct system is damaged, inflamed or obstructed, which results in the gallbladder being unable to move bile into the digestive system.

The liver is the largest gland of the body weighing about 1.2 to 1.5 kg in an adult human. It is situated in the abdominal cavity, just below the diaphragm and has two lobes.  The bile secreted by the hepatic cells is released into the duodenum contains bile pigments (bilirubin and biliverdin), bile salts, cholesterol and phospholipids but no enzymes.  The bile secreted is a yellowish-green fluid that aids in the emulsification of fats. Bile is not an enzyme, but it does contain bile salts that emulsify large fat droplets. Hence, the liver does not produce digestive enzymes.

So, the correct answer is 'liver'.

Bile or gall is a dark green to yellowish brown fluid, produced by the liver of most vertebrates, that aids the digestion of lipids in the small intestine. In humans, bile is produced continuously by the liver (liver bile) and stored and concentrated in the gallbladder (gallbladder bile). After eating, this stored bile is discharged into the duodenum. Bile is not secreted by small intestine, large intestine or pancreas.

Angiotensin is a peptide hormone, that causes vasoconstriction and a subsequent increase in blood pressure. It is derived from the precursor molecule angiotensinogen, a serum globulin produced in the liver. It plays an important role in the renin-angiotensin system. 

The colour of the stool is determined by the liver. The liver imparts a brown colour to the stool by releasing bile juices which is the normal case. In the case of the colour change of stool. it means that the liver is not functioning properly. For example. the stool is whitish grey in colour when the liver produces less bile juice or the flow of bile from the liver is blocked.

When carbohydrate intake exceeds energy needs, the liver converts excess glucose into fatty acids through a process called lipogenesis, which are then stored as triglycerides.

Bile release is triggered by the presence of chyme in the duodenum, specifically the fat content which stimulates the release of the hormone cholecystokinin (CCK). CCK causes the gallbladder to contract, releasing bile to emulsify the fats.

The liver is the primary site for cholesterol biosynthesis in the human body. It regulates cholesterol levels by synthesizing it from acetyl-CoA.