Biology - Human Nutrition

A balanced diet contains all essential nutrients in the correct proportions: $Carbohydrates$, $Fats$, $Proteins$, $Vitamins$, $Minerals$, $Water$, and $Fiber$.

Energy requirements vary based on age, gender, and activity levels. Energy is measured in $kilojoules$ ($kJ$).

The chemical digestion of starch begins in the mouth: $Starch + H_2O \xrightarrow{Amylase} Maltose$.

Proteins are polymers of amino acids containing elements $C$, $H$, $O$, and $N$. They are digested as: $Proteins \xrightarrow{Protease} Amino\ Acids$.

Lipids (fats and oils) are broken down into $Glycerol$ and $Fatty\ Acids$ by the enzyme $Lipase$.

Bile is alkaline and serves two main functions: neutralizing the $HCl$ (hydrochloric acid) from the stomach and emulsifying fats to increase the surface area for $Lipase$ action.

The villi in the small intestine increase the surface area for absorption. $Glucose$ and $Amino\ Acids$ are absorbed into the blood capillaries, while $Fatty\ Acids$ and $Glycerol$ are absorbed into the $Lacteal$.

Vitamin deficiencies: Lack of $Vitamin\ C$ leads to Scurvy, and lack of $Vitamin\ D$ or $Calcium$ ($Ca^{2+}$) leads to Rickets.

The alimentary canal involves five main stages: Ingestion, Digestion (Mechanical and Chemical), Absorption, Assimilation, and Egestion.