Tag: nutrition and diet

Digestion is the breakdown of food into smaller components that can be more easily absorbed and assimilated by the body. These smaller substances are absorbed through the small intestine into the blood stream.

• The starch, proteins and fats in food get digested by digestive enzymes and get converted into simpler components and this type of digestion is called extracellular digestion.
• The starches and some glycogen in food get hydrolysed inside the mouth while the food is swallowed by ptyalin or salivary amylase enzyme in the saliva.
  
• So, the correct answer is 'All of the above'.

In Planaria, digestion involves both the modes, ie, extracellular as well as intracellular. Fats are normally digested extracellularly, while other food components are digested intracellularly.
The intracellular digestion is done by amoeboid cells lining the intestine. Digested food diffuses to the surrounding mesenchyme. 

None of the options is correct. However, in some cases toxic level of Nickel is approached well above the concentration of $1$mg/g as that of macronutrients.

The digestion in sponges is intracellular. It takes place in coenocytic oral cells. The movement of water initiated by the coenocyteS. It helps in the digestion and respiratory system of sponges because along with the water they also transport oxygen. They then push out carbon dioxide which is a waste material out of the sponge body.