How does the energy get to muscles of a human body?

The energy required by the muscles of the human body comes from the breakdown of glucose molecules through a process called cellular respiration. Glucose is a type of sugar that is obtained from the foods we eat and transported to the cells via the bloodstream.

The process of cellular respiration occurs within the mitochondria of cells. It involves three main stages: glycolysis, the Krebs cycle (also known as the citric acid cycle), and oxidative phosphorylation. Here's an overview of each stage:

1. Glycolysis:

- Occurs in the cytoplasm of the cell.

- Glucose is broken down into two molecules of pyruvate.

- Generates a small amount of ATP (adenosine triphosphate), which is the energy currency of the cell.

2. Krebs Cycle (Citric Acid Cycle):

- Takes place in the mitochondria.

- Each pyruvate molecule is further broken down into carbon dioxide, releasing energy in the form of ATP.

- Generates ATP, NADH (nicotinamide adenine dinucleotide), and FADH2 (flavin adenine dinucleotide), which carry high-energy electrons.

3. Oxidative Phosphorylation:

- Occurs in the inner mitochondrial membrane.

- NADH and FADH2 produced in the previous stages pass their high-energy electrons to the electron transport chain.

- As electrons move through the electron transport chain, their energy is used to pump hydrogen ions across the membrane, creating a concentration gradient.

- The flow of hydrogen ions back through ATP synthase, an enzyme, drives the synthesis of ATP.

Ultimately, the breakdown of glucose through cellular respiration generates ATP, which serves as the primary energy source for cells and muscles. These reactions provide the cells with the energy needed to perform various functions, including muscle contraction, nerve impulse transmission, and other essential cellular processes.