Adenosine triphosphate, or ATP, is like the energy money that cells use. It plays an important part in how cells get their energy to work. ATP is mostly made during a process called cellular respiration, which is a series of steps that changes food into ATP while also getting rid of waste.

How ATP is Made During Cellular Respiration

Cellular respiration has three main steps:

1. Glycolysis:

   • This happens in the cytoplasm, which is a jelly-like part of the cell.
   • It changes one glucose molecule into two pyruvate molecules.
   • This process gives us 2 ATP and 2 NADH.

2. Citric Acid Cycle (Krebs Cycle):

   • This step takes place in the mitochondria, which are like powerhouses for the cell.
   • Each time the cycle runs, it processes one acetyl-CoA, which comes from pyruvate.
   • Each turn produces 3 NADH, 1 FADH2, and 1 GTP (or ATP).
   • Overall, from one glucose, this step makes 6 NADH, 2 FADH2, and 2 ATP (or GTP).

3. Oxidative Phosphorylation:

   • This involves two parts: the electron transport chain (ETC) and chemiosmosis.
   • NADH and FADH2 give away their electrons to the ETC, helping move protons (H+) into a space between membranes. This creates a buildup of protons.
   • ATP is then made when protons flow back into the mitochondrial matrix through a special protein called ATP synthase. Each NADH can create about 2.5 ATP, and each FADH2 can create about 1.5 ATP.

Total ATP Production

From one glucose molecule used in cellular respiration, we can get around 30-32 ATP. Here’s how it breaks down:

• Glycolysis: 2 ATP
• Krebs Cycle: 2 ATP
• Oxidative Phosphorylation: 26-28 ATP (depending on how NADH and FADH2 donate electrons)

What Affects ATP Production

Several things can change how well ATP is made:

1. Proton Motive Force (PMF):

   • If there's a strong PMF, more ATP can be produced.
   • If the cell's membrane isn’t working well, ATP production goes down.

2. Nutrient Availability:

   • If there aren't enough nutrients, glycolysis and the Krebs cycle can slow down, reducing ATP production.

3. Mitochondrial Function:

   • If mitochondria aren’t working properly, ATP production decreases, and harmful substances called reactive oxygen species (ROS) can increase, which can damage the mitochondria.

4. Inhibition or Uncoupling:

   • Some chemicals, like oligomycin, stop ATP synthase from working. Others, like 2,4-dinitrophenol, let protons return without making ATP, which affects how efficiently the cell gets energy.

Summary

In short, making ATP during cellular respiration is a complicated but essential process. It includes glycolysis, the citric acid cycle, and oxidative phosphorylation. The efficiency and amount of ATP made depend on factors like proton gradients, nutrient levels, mitochondrial health, and whether there are chemicals that inhibit or uncouple ATP production. Understanding how this all works helps us appreciate how cells use energy, which is important in medical studies.