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
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
