Large intestine absorbs the water from undigested food.

Small intestine is the site for complete digestion of fats by the action of bile juice

The various associated glands of digestive system and their role in digestion are as follows.
(i) Salivary gland digestion of starch in mouth.
(ii) Liver secretes bile juices which help in the digestion of fats.
(iii) Pancreas secretes pancreatic juices which act on carbohydrate, fats and proteins and change them into simpler compounds.

The various components of food and their simpler forms are

No, we connot survive only on raw, vegetables/grasses. This is due to the absence of cellulose degrading/digesting enzymes. Raw plants, vegetables and grasses, etc, contain chlorophyll, which is digested in ruminants by the action of microorganism but humans do not posses these microorganisms. Therefore, we would not be able to digest cellulose and meet our energy requirements.

Both Amoeba and humans require energy for the growth and maintenance of their bodies. This energy is derived from the food they eat. The food is in a complex form and is therefore broken down into simple forms by the process of digestion. Both these organisms are heterotrophs, i.e. they derive their food from other plants or animals.
Difference between nutrition in Amoeba and human beings are

Glucose is a simple sugar or carbohydrate which is broken down in the presence of oxygen into CO₂ and H₂O and releases instant energy. Glucose is easily absorbed by the blood, hence provides instant energy to the body.

Bile juice is produced by the liver and stored in gall bladder. It helps in digestion of fats present in food.

The shape of stomach is like flattened U-shaped.

The process by which absorbed food is taken by body cells and is used for energy, growth and repair is called assimilation.

The digestive juices from liver and pancreas is poured into small intestine which helps in complete digestion and absorption of food.

We should not eat hurriedly because if we ingest food in hurry or we talk or laugh while eating we experience hiccups, coughing or choking sensation.

Inspite of being blindfolded, one could identify two different drinks with the help of taste buds present in the tongue.

In an adult human, there are total 32 teeth.