IBDP Cell respiration

The goal of cell respiration is to produce something called ATP which is adenosine triphosphate It’s a nucleotide.

ATP is the energy of the energy currency of the cell. Breaking the Bond between the second and third phosphate releases energy (catabolic and it releases energy)#

ATP → ADP + Pi releases energy for cellular processes. ATP is soluble, stable, and cannot cross membranes—this helps keep energy compartmentalized within cells.

ATP is needed for anabolic reactions, active transport, and movement (e.g., mitosis, muscle contraction). ATP is regenerated by adding energy (from respiration, photosynthesis, etc.) back to ADP.

Cell respiration is a biochemical process that releases energy from carbon compounds to produce ATP. It’s not the same as breathing (ventilation), though related via gas exchange (O₂ in, CO₂ out).

Two types of respiration:

  • Aerobic (with oxygen): Glucose → CO₂ + H₂O + ATP

  • Anaerobic (without oxygen):

    • In yeast: Glucose → ethanol + CO₂

    • In humans: Glucose → lactate

Aerobic respiration (in mitochondria) yields up to 30 ATP/glucose, uses multiple substrates (carbs, fats, proteins).

Anaerobic (in cytoplasm) only produces 2 ATP/glucose and uses only carbohydrates.

Anaerobic respiration is temporary and inefficient. Lactate buildup causes fatigue and requires oxygen later to break down (called oxygen debt), but no further ATP is gained from this breakdown.

To measure respiration rate, observe:

  • ↓ in O₂ or glucose concentration

  • ↑ in CO₂ or pH changes
    Heat isn't a reliable measure due to variability in pressure/temperature.

Respirometers measure O₂ consumption. CO₂ is absorbed using a chemical (e.g., KOH), creating negative pressure, which pulls liquid in a connected tube—used to track respiration rate.

Experimental variables can include:

  • Type of organism (mouse vs. worm)

  • Temperature, substrate type, etc.
    Control variables (e.g., pressure, substrate) are essential for valid results.