Study Notes
Nutrition in humans involves the processes of ingestion, digestion, absorption, assimilation, and egestion. Humans, as heterotrophs, obtain energy from the food they consume, which is broken down and absorbed through the digestive system.
- Ingestion — the process by which food is taken in through the mouth. Example: Food is chewed by teeth and mixed with saliva to form a bolus.
- Digestion — the breakdown of large, insoluble food molecules into smaller, soluble molecules. Example: Starch is broken down into maltose by salivary amylase.
- Absorption — the process by which digested food molecules are absorbed into the bloodstream. Example: Glucose and amino acids are absorbed through the villi in the small intestine.
- Assimilation — the process by which absorbed nutrients are used by the body. Example: Glucose is used in cellular respiration to release energy.
- Egestion — the removal of undigested or unabsorbed food substances from the body. Example: Faeces are expelled through the anus.
Exam Tips
Key Definitions to Remember
- Ingestion: The process of taking food into the mouth.
- Digestion: The breakdown of food into smaller, absorbable components.
- Absorption: The uptake of nutrients by the cells of the small intestine.
- Assimilation: The use of absorbed nutrients by the body.
- Egestion: The expulsion of undigested food from the body.
Common Confusions
- Confusing digestion with absorption.
- Misunderstanding the role of enzymes in chemical digestion.
Typical Exam Questions
- What is the role of the epiglottis during swallowing? It prevents food from entering the trachea.
- Why is digestion necessary? To break down food into molecules small enough to be absorbed.
- How does bile aid in digestion? Bile emulsifies fats, increasing their surface area for enzyme action.
What Examiners Usually Test
- Understanding of the digestive process and the role of enzymes.
- The structure and function of the alimentary canal.
- The adaptations of the small intestine for absorption.