A2 Unit 3.1 &3.3: ATP & Respiration

Energy Transfer

Energy cannot be created or destroyed, only converted from one form to another. Food contains chemical energy.

Glucose & Fatty Acids are energy rich respiratory substances that are broken down during respiration.

C-C, C-H & C-OH bonds are the high energy bonds broken during respiration.

Lower energy bonds are formed and the difference is released. Energy from respiration is transferred to ATP & released as heat.

Define Endergonic & Exergonic

Endergonic - A reaction in which energy is absorbed and stored in the products.

Exergonic - A reaction in which energy is released from the products.

What is ATP & Synthesis of ATP?

ATP is referred to as the ‘Universal Energy Currency’ as ATP is present in all living organisms and used to provide energy for all cell reactions.

ATP Synthesis - Condensation reaction forms a bond between phosphate groups (Phosphorylation) when ADP reacts with inorganic phosphate during respiration - ADP + Pi (inorganic phosphate) —> ATP (Endergonic)

How is energy released from ATP?

ATP Breakdown - Hydrolysis reaction that breaks a bond between phosphate groups (Dephosphorylation) of ATP - ATP —> ADP + Pi + 30.6kJmol-1 (Exergonic - happens when energy is used, e.g during active transport)

• High energy bond broken between 2nd & 3rd Phosphate group by enzyme ATPase to release energy from ATP to provide energy for different chemical reactions.

Define Anabolism & Catabolism

Anabolism - Smaller molecules built up to form larger molecules.

Catabolism - Complex molecules broken down to form smaller molecules.

Advantages of ATP as an energy carrier

• 1 enzyme needed to break down ATP (ATPase)

• Single step reaction (only 1 bond broken)

• Releases small amounts of energy when and where needed

• Less energy wasted and energy release controlled

Respiration

Aerobic Respiration: Glucose + Oxygen —> Carbon Dioxide + Water & 38 ATP Molecules

Anaerobic Respiration: Glucose —> Lactic Acid

Enzymes such as ATPase catalyse the series of reactions in respiration.

Respiration is Catabolic.