The Chemistry of Metabolism


In all of us, our cells need to stay very active in order for the main functions of the body to run properly and efficiently. Functions like contracting muscles, moving ions across a plasma membrane, or building up new molecules. To activate these functions, energy is needed. Now, the thing is, our cells can not produce this energy on its own unless we gain this energy from an outside source. We gain this energy from the foods we eat. This is the definition of metabolism, through a series of chemical reactions that break down are foods to form energy. That energy can power chemical reactions that help maintain life.

I chose to do metabolism because I find biological processes the most interesting thing in the world. Before doing this project, I have tried to comprehend this topic, but some of the aspects still were not clear to me. I wanted to clear some things up for myself, while at the same time, maybe enlightening others. Metabolism is a very important part of my life. Well, everyone's life. It's one of the main characteristics of life

Composition of ...

  • The components of Metabolism are built with the six most abundant elements of life.

    • Carbon

    • Hydrogen

    • Nitrogen

    • Oxygen

    • Phosphorus

    • Sulfur

  • These Elements build the more complex organic compounds which are the main macromolecules in life

    • Carbohydrates: made of monosaccharides

      • Glucose

      • Fructose

      • Galactose

    • lipids

      • Fatty acids

      • glycerol

      • cholesterol

    • proteins: made of amino acids

      • enzymes

    • nucleic acids

    • cofactors

      • ATP

      • NAD+

      • FAD

Main Chemicals, Compounds, Components

  • All these molecules play different parts in the main components of metabolism, which are the two main metabolic pathways

    • Carbohydrate metabolism-the breaking down or building up of sugars

      • glycolysis-the oxidation of glucose to form two pyruvate molecules, yielding an NADH

      • gluconeogenesis-the building up of glucose from noncarbohydrate molecules

      • glycogenolysis- the breaking down of glycogen to glucose-6-phosphate

      • glycogenesis-the synthesis of glycogen

    • Aerobic respiration

      • citric acid cycle-the two pyruvates from the oxidation of glucose are oxidized further to form CO2 while yielding 2 ATP, 3 NADH, and 1 FADH2

      • oxidative phosphorylation- the use of energy from the oxidation of nutrients to synthesis ATP

Chemistry's Role

  • How metabolism creates energy for the body

    • When nutrients are catabolized, they undergo a set of oxidation-reduction reactions(redox-reactions). Redox-reactions are reactions that change the oxidation state of two species by the transfer of electrons   

    • the species that loses the electrons is being oxidized or lowering its oxidation state

    • the species that gains the electrons is being reduced or raising its oxidation state

    • The swapping of electrons between atoms creates energy, just like how the flow of electrons in a wire creates a current of energy

  • How the body uses redox-reactions to create energy

    • redox-reactions take energy from the catabolism of food by oxidizing them, while at the same time reducing electron carrying molecules like NAD+ and FAD.

    • The energy inside the reduced coenzymes is used to oxidize ADP into ATP.

    • ATP is now energy rich and can help do work in a cell like contracting a muscle, aiding in reactions, or moving ions across a membrane.

  • How is ATP energy rich

    • ATP itself is not in itself energy rich. It’s how the cell uses it that makes it a molecule that can do a lot of work. Thermodynamically speaking, when ATP is used to do work in the cell, the reactions are spontaneous, which means that it is favorable. Two main factors play a role in why this is. They are Enthalpy and Entropy.

      • Enthalpy is the total amount of energy in a system

      • Entropy the measurement of disorder in a system  

    • looking at how these factors interact in a system we can understand how much free energy a system can have that is capable of doing work during a reaction. This interaction is commonly known as Gibbs Free Energy.

    • The equation for Gibbs Free Energy is G=H-TS

      • G is the amount of free energy

      • H is Enthalpy

      • S is Entropy


  • For a reaction to be spontaneous, like when ATP is used to do work, the amount of free energy in the system has to be negative. This means that the reaction is exothermic and that energy is released to do work, and that the reaction can happen on its own without using an outside source of energy. In order for this to happen Enthalpy has to decrease and Entropy has to increase. When Enthalpy is decreased, it means that energy is being released. When Entropy is increased, it basically means that molecules are being broken down and thus there's more disorder. In summary, when ATP reacts to do work, the reactions are spontaneous because ATP gives off  a ton of energy as it is broken down

Background Research

How digestion breaks down carbohydrates, lipids, and proteins into smaller molecules

Overview of metabolism

catabolism and anabolism

What enzymes are and how do they work

Overview of metabolism

catabolism and anabolism

metabolic pathways

what ATP, NAD+, and FAD are

Overview of cellular respiration


citric acid cycle,

oxidative phosphorylation

what ATP is

How redox reaction work and how metabolic reactions use them

How redox reactions work

Basic thermodynamics

what is gibbs free energy

how to calculate it

enthalpy and entropy

How ATP hydrolysis is a spontaneous reaction and what that means

About the Author
Chris Fite is a Junior at Billings Senior High School. Chris likes going to youth group to hang with his friends and playing in the worship band. When he is not at youth group he spends most of his time studying his favorite topic, human anatomy and physiology. Ever since chris was in the 6th grade he has taken much pleasure in learning about the body. If Chris is not doing that, than he is usually practicing piano for the worship band. After highschool, he plans on going to college to become a doctor, yet Chris does not know which college he will be attending.