IB Biology SL Topic C1.2

State the full name and type of molecule of ATP.

• Full Name: Adenosine triphosphate

• Type of Molecule: Nucleic acid derivative / Phosphorylated nucleotide

State three reasons for ATP being a good energy currency in cells.

• Soluble: It easily dissolves in the aqueous cytoplasm and nucleoplasm, allowing quick diffusion to where energy is needed.

• Stable at Cellular pH: It does not break down spontaneously at normal cell pH levels, making it reliable for energy transfer.

• Yields manageable amounts of energy: Hydrolysis releases a precise, usable quantity of energy, minimizing waste as heat compared to burning a large molecule like glucose all at once.

What does “energy currency” mean?

It refers to a molecule that can be synthesized to store energy in small, standard units and continuously hydrolyzed to release energy immediately for cellular work (much like cash is used for transactions rather than bartering large goods).

State the partial equation for how energy is released from ATP.

ATP + H₂O → ADP + P_i + Energy

State the partial equation for how energy is stored in ATP.

ADP + P_i + Energy → ATP + H₂O

Name the principal substrates of cell respiration.

• Carbohydrates (specifically glucose; lipids and amino acids can also be used).

State the difference between cell respiration and gas exchange in animals.

• Cell Respiration: A microscopic, biochemical process occurring inside cells that breaks down organic molecules (like glucose) to produce ATP.

• Gas Exchange: A macroscopic, physical process (like breathing or diffusion across membranes) where oxygen is absorbed into the organism/blood and carbon dioxide is removed.

State the word equation for aerobic respiration.

Glucose + Oxygen → Carbon Dioxide + Water + ATP (Energy)

State the word equation for anaerobic respiration.

• In animals / humans: Glucose → Lactate (Lactic Acid) + ATP (Energy)

• In yeast / plants: Glucose → Ethanol + Carbon Dioxide + ATP (Energy)

State the difference between aerobic and anaerobic respiration in terms of ATP produced.

• Aerobic: Produces a large yield of ATP per glucose molecule (approx. 30–32 ATP).

• Anaerobic: Produces a small yield of ATP per glucose molecule (net yield of 2 ATP).

State the difference between aerobic and anaerobic respiration in terms of where it occurs

• Aerobic Respiration: Begins in the cytoplasm (glycolysis) and is completed inside the mitochondria (link reaction, Krebs cycle, electron transport chain).

• Anaerobic Respiration: Occurs entirely within the cytoplasm.

Life Processes that Need ATP

BAM

Biosynthesis of Macromolecules

Active transport across membrane

Movement of Whole Cell or Cell Components