Biology Unit 1 Notes: Metabolism, Energy & Homeostasis

1. Biology
Unit 1 Notes:
Metabolism, Energy
& Homeostasis

2. (1) Homeostasis
• Homeostasis:
Maintaining internal stability / balance.
• When/Why does this happen?
• Anytime there are changes inside your body, or directly around your body, away from
how it normally is.
• Helps keep you living and healthy, and keeps energy cycling through cells.
• Examples:
• Shivering when cold
• Bicarbonate in blood to neutralize acid
• Increasing respiratory rate when blood oxygen is low

3. (2) Energy Cycling & Transfer
• All living things need energy so that their cells can “do work” / stay alive.
• Organisms need to be able to:
• Release potential energy from the bonds of molecules.
• Store extra energy in newly formed bonds of molecules (for later).
• Metabolism = The breaking down, and building of molecules inside cells in
order to transfer energy and matter.

5. (3) Important Metabolic Reactions
• There are 2 very common and important metabolic reactions cells use:
• Hydrolysis
• Dehydration Synthesis
• These reactions are used to release or store energy as cells need to.
• Both reactions involve water.

6. (4) Hydrolysis
• What does it mean?
• Hydro = Water
• Lysis = Explode / Break Apart
• Hydrolysis = “To use water to break apart”.
• What is the purpose?
• Release energy from molecules so that cells can use it.
• What happens?
• Water is added to a larger polymer.
• The bonds holding the polymer together are broken.
• Energy is released.

8. (5) Dehydration Synthesis
• What does it mean?
• Dehydrate = Remove Water
• Synthesis = Put Together / Make
• Dehydration Synthesis = “To remove water to put together”.
• What is the purpose?
• Store energy for later, in newly formed bonds/molecules.
• What happens?
• Water is removed from individual monomers.
• New bonds are formed connecting the monomers together (to form a polymer).
• Energy is stored.

10. (6) ATP & ADP
• ATP = Adenosine Triphosphate = “Energy Storing Molecule”
• ADP = Adenosine Diphosphate
• Your cells use ATP to store energy for later, and break apart ATP when they
need energy to do work.

11. ATP
(“TRI-phosphate)
ADP
(“DI-phosphate)

12. (7) ATP & Metabolic Reactions
• Cells use Hydrolysis & Dehydration Synthesis with ATP.
• ATP  ADP
• Water is added to ATP.
• A phosphate is removed from ATP + the bond is broken.
• Energy is released + ADP is formed.
• ADP  ATP
• Water is removed from ADP.
• A phosphate is added to ADP + a new bond is formed.
• Energy is stored + ATP is formed.