Science 101

Science 101 Glossary

Learn the scientific terms that can help you understand the science of aging.

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Scientific terms are shrouded in dense language, named using Latin root words, chemical nomenclature, or the scientist who made the discovery. Sometimes the names even suggest the role a molecule plays in nature. It can get confusing, but with a glossary handy and a bit of hard work anyone can navigate papers and articles about the science of aging — even if you haven’t cracked a biology or chemistry textbook since high school. You’ll find many of the terms below on the Elysium Health website, in Endpoints (our science publication), and elsewhere as you read about biology and human health. Want to go deeper? Check out our Science 101 page for more information about the science of aging.


NAD+: Nicotinamide adenine dinucleotide (NAD+) is a coenzyme found in all living cells that is vital to metabolism and hundreds of other biological processes. Levels of NAD+ decline with age.

Acetyl Groups: In the human body, acetyl groups are chemical tags on molecules that can be added (acetylating) or removed (deacetylating) from other molecules, causing different reactions.

Age-Related Diseases: Illnesses, diseases, and conditions that occur with more frequency as people age, such as Alzheimer’s disease, cardiovascular disease, and diabetes.

Calorie Restriction: Also called caloric restriction, this is the process of drastically restricting calories and has been shown to increase longevity and delay the onset of age-related diseases in mice, worms, and monkeys. Scientists have studied how caloric restriction, and related dietary interventions like time-restricted feeding and periodic fasting can promote health and longevity.

Chromatin: A highly condensed combination of DNA and proteins that makes up chromosomes.

Circadian Rhythm: The 24-hour physiological patterns that most organisms, including humans, follow each day; from Latin circa ("about") and diem ("day").

Coenzyme: Colloquially referred to as “helper molecules” because they’re required for the function of enzymes  —  large molecules (usually proteins) made of amino acids that carry out important biological work in the body.

De novo Pathway: The process by which complex biological molecules are synthesized from simple molecules such as amino acids. The de novo pathway for NAD+ synthesis describes how NAD+ is formed from the amino acid tryptophan.

DNA: Deoxyribonucleic acid, or DNA, is a hereditary nucleic acid present in almost all organisms that carries all genetic information. DNA damage can happen over time, making DNA repair a key function of the body.  

Enzyme: Proteins (with a few exceptions), made of amino acids, that bring about chemical reactions with other molecules to complete important biological work in the body.

Gene Editing: Biotechnology that alters specific sequences of DNA.

Ketogenic Diet: A high-fat, low-carb diet meant to put the body in a state of ketosis, causing the body to rely on fat instead of carbohydrates for energy.

Krebs Cycle: Also called the citric acid cycle, the Krebs cycle is a central metabolic pathway found in aerobic organisms, which generates ATP, or energy, through a sequence of reactions.

Metabolism: All of the life-sustaining chemical reactions in an organism. The fires of life.

Mitochondria: Organelles within each cell, and a site where respiration occurs. The majority of the cell’s ATP, or energy, is made here. The term “mitochondrial function” describes how well the mitochondria functions within the cell.

Nicotinamide: Nam, or nicotinamide, is an NAD+ precursor and variation of vitamin B3.

Nicotinamide riboside: NR, or nicotinamide riboside, is an NAD+ precursor and a variation of vitamin B3. Of the three forms of B3, NR has been shown to raise NAD+ levels more efficiently compared to nicotinic acid and nicotinamide.

Nicotinic Acid: NA, called nicotinic acid or niacin, is an NAD+ precursor and a variation of vitamin B3.

Oxidative Stress: An imbalance between unstable molecules, called free radicals, and antioxidant defense mechanisms.

PARPs: Stands for poly (ADP-ribose) polymerase. PARPs are a family of 17 proteins that require NAD+ to function, and they are mostly understood to play a role in cellular stress response — for instance, in repairing damaged DNA.

Pellagra: A fatal disease that plagued the American south in the 1900s and was eradicated when scientists discovered a way to alleviate symptoms, with foods rich in vitamin B3.

Precursor: Molecules that go through chemical transformations to become a variant or more mature form.

Preiss-Handler Pathway: The process through which nicotinic acid is converted into NAD+, named for the scientists Jack Preiss and Philip Handler.

Protein: Large, complex molecules made up of amino acids and needed for the body’s biological functions.

Pterostilbene: A polyphenol that can be synthetic or found in nature and is well-known as the primary antioxidant in blueberries. It can activate sirtuins and has a very similar structure to resveratrol (a polyphenol in red wine), but has better bioavailability in humans.

RNA: Ribonucleic acid, or RNA, is a nucleic acid similar to DNA but containing ribose rather than deoxyribose. The primary role of RNA is to convert information from DNA into proteins.

Salvage Pathway: The process through which nicotinamide and nicotinamide riboside are converted into NAD+, which also includes a recycling element for the nicotinamide byproduct made by NAD+-consuming enzymes like sirtuins.

Sirtuins: A family of seven proteins that help maintain homeostasis in the cell and also play a role in aging. Sirtuins require NAD+ to function.

Tryptophan: An amino acid and NAD+ precursor obtained from the diet.

Science 101

What is NAD+ and Why Is it Important for Aging and Health?

You can’t live without the coenzyme NAD+, nicotinamide adenine dinucleotide. Here’s why it’s so important, how it was discovered, and how you can get more of it.