Life Processes - Explain nutrition in plants and animals including photosynthesis and digestion

Nutrition is the process of intake of nutrients like $Carbohydrates$, $Proteins$, and $Fats$ and their utilization by the body.

Autotrophic Nutrition: Organisms like green plants synthesize their own food using $CO_2$ and $H_2O$ in the presence of $Sunlight$ and $Chlorophyll$.

Photosynthesis involves three steps: Absorption of light energy by $Chlorophyll$, conversion of light energy to chemical energy and splitting of $H_2O$ molecules, and reduction of $CO_2$ to $C_6H_{12}O_6$.

Heterotrophic Nutrition: Organisms depend on others for food. Types include Holozoic (Amoeba, Humans), Saprophytic (Fungi), and Parasitic (Cuscuta, Ticks).

Holozoic Nutrition in Amoeba involves $Phagocytosis$ where food is engulfed using $Pseudopodia$ and digested in a food vacuole.

Human Digestive System: Involves the Alimentary Canal starting from the $Mouth$ to the $Anus$.

Saliva contains $Salivary Amylase$ which breaks down complex $Starch$ into simple sugar ($Maltose$).

The Stomach releases $HCl$, $Mucus$, and $Pepsin$. $HCl$ creates an acidic medium ($pH \approx 1.5 - 3.5$) for $Pepsin$ to act.

Small Intestine: Site of complete digestion. It receives secretions from the $Liver$ (Bile) and $Pancreas$ (Trypsin, Lipase).

Villi: Finger-like projections in the small intestine that increase the surface area for the absorption of digested food.