Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Nutrition is a complex process involving five steps: Ingestion, Digestion, Absorption, Assimilation, and Egestion.
The Alimentary Canal is a long continuous tube consisting of the buccal cavity, oesophagus, stomach, small intestine, large intestine, rectum, and anus.
The buccal cavity contains salivary glands that secrete saliva; saliva contains the enzyme amylase which breaks down starch into sugars.
The stomach wall secretes mucous to protect its lining, hydrochloric acid () to kill bacteria and provide an acidic medium, and digestive juices to break down proteins.
The liver is the largest gland in the body and secretes bile juice, which is stored in the gall bladder and helps in the digestion of fats.
The pancreas secretes pancreatic juice that acts on carbohydrates, fats, and proteins, converting them into simpler forms.
The small intestine is the site of complete digestion. Its inner walls have finger-like outgrowths called villi, which increase the surface area for the absorption of digested food.
The large intestine is wider and shorter than the small intestine; its function is to absorb water and some salts from the undigested food material.
📐Formulae
💡Examples
Problem 1:
Explain why boiled rice gives a blue-black color with iodine, but chewed rice does not.
Solution:
Boiled rice contains starch, which reacts with iodine to produce a blue-black color. When rice is chewed, salivary amylase breaks down the into . Since sugar does not react with iodine, the chewed rice does not change color.
Explanation:
The chemical reaction involved is the enzymatic hydrolysis of into simpler sugars like maltose.
Problem 2:
What is the role of in the human stomach?
Solution:
(Hydrochloric acid) creates an acidic medium in the stomach with a low . This environment is necessary for the protein-digesting enzyme pepsin to become active. Additionally, kills many bacteria that enter the stomach along with food.
Explanation:
Acidity is a prerequisite for gastric proteolysis where proteins are converted into peptones and proteoses.
Problem 3:
How does the small intestine facilitate the absorption of nutrients?
Solution:
The inner wall of the small intestine has millions of finger-like projections called villi. Each villus has a network of thin and small blood vessels close to its surface.
Explanation:
The villi increase the effective surface area for absorption, allowing nutrients to pass into the blood capillaries via diffusion and active transport.