Fundamental Concepts in Anatomy & Physiology: Gross Anatomy, Development, and Body Organisation

1. METABOLISM
Definition

Metabolism is the total sum of all chemical reactions occurring inside an organism’s cells
and internal environment.
It includes reactions that:

 Use energy
 Release energy
 Build molecules (anabolism)
 Break molecules down (catabolism)

Together, these reactions allow the organism to:

 Stay alive
 Maintain internal balance
 Grow and develop
 Respond to the environment
 Reproduce




1.1 Two Major Divisions of Metabolism
A. Catabolism (breaking down)

 Larger molecules → smaller molecules
 Releases energy
 Example: digestive enzymes breaking down food
o Proteins → amino acids
o Carbohydrates → glucose
o Lipids → fatty acids
 Energy released is used for:
o Movement
o Heat production
o Cellular reactions




. Anabolism (building up)

 Smaller molecules → larger molecules
 Requires energy
 Examples:
o Building muscle proteins
o Synthesising hormones
o Repairing tissues

, o Forming new cell membranes




1.2 Importance of Molecular Shape
The passage emphasises a key concept in anatomy & physiology:

“The shape of a molecule determines its function.”

 Enzyme shape → determines what reactions it can catalyse
 Receptor shape → determines what signals it detects
 Antibody shape → determines what pathogens it binds

Changes in shape = changes in function.




1.3 Example: Immune Cell Shape-Changing
Some white blood cells (e.g., phagocytes) can:

 Change their shape
 Extend pseudopods
 Surround and engulf bacteria

This shape-changing ability is powered by metabolic energy.




2. RESPONSIVENESS
Definition

Responsiveness is an organism’s ability to:

 Detect changes (stimuli)
 Process them
 Respond appropriately

This includes both external and internal changes.




2.1 Examples of Responsiveness
External stimuli