Scientists Say

Scientists Say: Respiration

This can refer to breathing or how cells produce energy

a photo of a Black woman running

Respiration can refer to the cycle of our breathing — in and out, in and out. Exercising might increase your respiration rate — meaning you’ll breathe faster.

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By Bethany Brookshire

Respiration (noun, “RES-per-a-shun”)

Respiration has different meanings, depending on where it takes place. In our lungs, respiration can refer to the act of breathing. If you breathe in and out 20 times per minute, you have 20 respirations per minute.

It also refers to what happens when we breathe in and out. Respiration describes how oxygen moves into our cells and carbon dioxide moves out. This transfer of oxygen and carbon dioxide occurs when we breathe.

But within cells, respiration means something else. Cellular respiration is a chemical process that takes place inside cells and produces energy. The process breaks bonds in sugars. Breaking those bonds releases the energy they contain. That energy gets stored in molecules called ATP. That stands for adenosine triphosphate. These ATP molecules act as tiny chemical batteries, carrying the energy to places in the cell that need it.

Cellular respiration is often aerobic. That means it requires oxygen and makes carbon dioxide as a waste product. But cells can also perform anaerobic respiration, or making energy without oxygen, if they have to. Some kinds of bacteria are so good at anaerobic respiration that they don’t bother with oxygen at all.

In a sentence

With a combination of aerobic and anaerobic respiration, Cuvier’s beaked whales can stay underwater for up to four hours.

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aerobic: Occurring in the presence of oxygen. Aerobic reactions take place in locations with access to oxygen.

anaerobic: Occurring in the absence of oxygen. Anaerobic reactions take place in oxygen-free locations.

ATP: Short for adenosine triphosphate. Cells make this molecule to power almost all of their activities. Cells use oxygen and simple sugars to create this molecule, the main source of their energy. The small structures in cells that carry out this energy-storing process are known as mitochondria. Like a battery, ATP stores a bit of usable energy. Once the cell uses it up, mitochondria must recharge the cell by making more ATP using energy harvested from the cell’s nutrients.

bacteria: (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals). Bacteria are one of the three domains of life on Earth.

bond: (in chemistry) A semi-permanent attachment between atoms — or groups of atoms — in a molecule. It’s formed by an attractive force between the participating atoms. Once bonded, the atoms will work as a unit. To separate the component atoms, energy must be supplied to the molecule as heat or some other type of radiation.

carbon: The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules. (in climate studies) The term carbon sometimes will be used almost interchangeably with carbon dioxide to connote the potential impacts that some action, product, policy or process may have on long-term atmospheric warming.

carbon dioxide: (or CO2) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas). Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.

cell: The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

chemical: A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

lactic acid: A chemical compound commonly found in milk and in exercising muscles.

molecule: An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

oxygen: A gas that makes up about 21 percent of Earth's atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).

respiration: (in cells) The process by which organisms produce energy from sugars, usually by taking in oxygen and releasing carbon dioxide. (in physiology) One complete inhalation and exhalation cycle, which transfers oxygen from outside the body to inside cells, and the release of carbon dioxide from inside those cells to the outside world.  

waste: Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.

whale: A common, but fairly imprecise, term for a class of large mammals that lives in the ocean. This group includes dolphins and porpoises.

About Bethany Brookshire

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.