Review of Basic Components of Life
Required Reading Additional Reading (2-3 Quiz questions from these sources)

Text, images and captions on this page


The purpose of this page is to provide a brief survey of fundamental components of life.

Study Questions

  1. Define “matter” and give examples.
  2. Is sunlight matter?
  3. Define “energy” and give examples.
  4. Is sunlight energy?
  5. Hydrogen bombs are an expression of which kind of energy?.
  6. Sunlight is an example of which kind of energy?
  7. Sugar is an example of the storage of which kind of energy?
  8. Striking a baseball with a bat is an example of which kind of energy?
  9. Boiling water is an example of which kind of energy?
  10. Practice the correct pronunciation of the word, “nuclear” three times. CAUTION: by pronouncing this word correctly, you could be labeled an intellectual elite and will never be elected to public office.
  11. Define “element.”
  12. How many unique kinds of atoms have we discovered?
  13. Apart from having different configurations of particles, what else is remarkable about the different elements?
  14. What is the difference between an element and an atom?
  15. What is the difference between an atom and a molecule?
  16. Proteins are biological molecules. What do proteins do?
  17. Carbohydrates are biological molecules. What do carbohydrates do?
  18. Fats are biological molecules. What do fats do?
  19. Nucleic acids are biological molecules. What do nucleic acids do?
  20. How does the DNA molecule behave like a digital information storage system?
  21. In a chemical reaction, what happens to the atoms of the reacting molecules?
  22. Photosynthesis is a biological chemical reaction / process. Why are biologists so interested in photosynthesis?
  23. Cellular respiration is a biological chemical reaction / process. Why are biologists so interested in cellular respiration?
  24. In living things, where does all the biochemistry (biological chemistry) take place?
  25. Biochemistry is a consumptive and productive process. For the cell, where do the raw materials come from, and where do the products go?
  26. What is a “gene?” What is an “allele?”
  27. What is the relationship between “gene” and “allele?”
  28. What types of living things perform photosynthesis?
  29. Animals include more than just mammals. What other kinds of animals are there?
  30. What happens to deer poop after it drops to the forest floor?
  31. Nitrogen fixation is an important biochemical process. What kinds of living things provide this rewarding service?
  32. Denitrification is an important biochemical process. What kinds of living things provide this rewarding service?



Matter is any object that takes up space and has Mass. In gravitational fields, objects that have mass also have weight.

Examples of objects composed of matter:
Atoms, molecules, books, human beings, trees, cars, rocks, water, dust, houses, stars, planets.

Examples of phenomena not composed of matter:
Expressed energy, radio waves, light waves, conscious thoughts.


Energy is any phenomenon that makes matter move.

Energy often is considered in the following forms:

Nuclear (pronounced: new -- klee --ar) – energy involving sub-atomic particles such as protons, neutrons, quarks and muons. Nuclear reactors slowly release nuclear energy to boil water. Atomic and hydrogen bombs rapidly release nuclear energy to produce explosive results. Stars are bright because of their continuous, rapid processing of fusion nuclear energy. The interiors of planets can be molten because of the continuous processing of fission nuclear energy.

Electromagnetic – radiating energy that travels as waves through space-time at the speed of light. Electromagnetic energy includes the following components of the electromagnetic spectrum: radio, radar, microwave, infrared, light, ultraviolet, x-rays, gamma rays and cosmic rays.

Chemical – energy based on the configurations of atoms in physical substances. Chemical energy is transferred when the physical configurations change. This can happen when atoms are added to or taken from a molecule. Chemical energy can be easily stored. Substances that store chemical energy include: sugar, fat, starch, cellulose, paper, wood, gasoline, coal, natural gas.

Electrical – energy made up of the flow of electrons through a conducting material, based on differences in electrical charge. Batteries have two connectors, each with an electrical charge opposite the other’s. Bridging these connectors causes electrons to flow from one to the other. Engineers capture this flow of electrons and use it to heat stove elements, light rooms, flip switches, fill up memory cards, and run computers.

Mechanical – energy in moving objects, often associated with mechanisms  such as mechanical clocks, cars, bicycles, and aircraft. Human skeletons are mechanisms. When a foot strikes a soccer ball, mechanical energy is transferred from the foot to the ball.

Heat – energy associated with the motion of small particles like atoms and molecules. Heat energy causes small particles to move around quickly. For example, in reduced heat conditions, water molecules stop moving around and transform from a liquid substance into a solid substance (ice).


An atom is the smallest particle of an element that maintains the chemical properties of the element. An atom’s structure consists of a nucleus and an electron cloud, or shell. Protons and neutrons occupy the nucleus and electrons occupy the electron cloud. Under normal conditions, atoms can interact with each other. These atom-to-atom interactions are chemical interactions (as opposed to nuclear interactions).

atom bohr model
bohr model of an atom
image source:


The “Elements” is a term that refers to the names for all of the different kinds of atoms in nature. As of 2010, scientists have observed 118 unique kinds of atoms. Each kind of atom is given a name and is referred to by name. Differences in atoms is based on variations in the number of the atom’s protons, neutrons and electrons. For example, all atoms with a single proton and a single electron are chemically identical, and are called “hydrogen” atoms. Carbon atoms have six protons, six neutrons and six electrons and behave identically to each other, but differently from hydrogen atoms.

periodic table
Periodic table of elements.
Image source:


large biological molecule
A molecule is a discrete construct of atoms. A molecule’s chemical properties are influenced by its atomic makeup. The above molecule is constructed out of different kinds of atoms including: carbon, hydrogen, oxygen, nitrogen and sulfur. A molecule of two atoms of oxygen (molecular oxygen – O2) behaves much differently from a molecule of one carbon plus two atoms of oxygen (carbon dioxide – CO2).

The biological world contains hundreds of thousands (if not millions) of unique molecular formulations. Biologists recognize that molecules, rather than being random lumps of matter, perform rewarding services for their biological unit. The nature of a molecule's activity is determined by the specific placement of different kinds of atoms, and the shape of the final construction.

Biological molecules are constructed out of many different kinds of atoms including: carbon, hydrogen, oxygen, nitrogen and sulfur atoms.

There are several main categories of biological molecules including:

  • proteins - structural materials, connective materials (muscles, tendons) and enzymes (action molecules that do work)
  • carbohydrates - energy storage, include sugars and starches, structural materials (cellulose)
  • fats - energy storage, thermal insulation, electrical insulation, lubrication and other uses
  • nucleic acids - information management, including DNA and RNA

Above is a diagram of a chlorophyll molecule. Chlorophyll is a "specialty" molecule. Notice the presence of several different kinds of atoms: carbon, hydrogen, oxygen, nitrogen and magnesium. The specific order and arrangement of these atoms results in specific behavioral properties such that this molecule provides rewarding energy-capturing services.


Above is a model of a DNA molecule. It takes a great deal of resources to construct a DNA molecule -- specifically atoms of carbon, hydrogen, oxygen, nitrogen and phosphorous.

DNA is a particularly interesting and powerful molecule because of its ability to hold discrete bits of data in an orderly manner.

DNA splitting

The data bits of a DNA molecule are in the form of a small set of different "base" molecules. As the base molecules are unique, they act as discrete data bits like letters in an alphabet or numbers in a counting system. The base molecules form the cross-members of the double helix, holding the two strands together. By varying the sequence of base molecules in a section, its data arrangement changes.

Some data sequences provide useful code sequences for the fabrication of proteins (especially enzymes). In other words, the data sequence in DNA informs the cell about how to construct useful molecules. As a result, it is reasonable to consider DNA as an information storage medium. And because the bits of information storage are discrete, DNA's information storage system has the attributes of a digital information system.

Digital information systems include written language (using an alphabet of characters), numbering systems, digital computers, music CDs, and DVDs. Digital systems are superior to analog systems in that information can be copied endlessly with no loss in fidelity. This is why CDs sound so much better than vinyl LPs and cassette tapes.

This system of information management is extremely robust, given that the DNA you inherit from your parents must be copied trillions and trillions of times throughout your life.


Chemical reaction

A chemical reaction is a phenomenon when two or more chemical substances interact in such a way that one or more of the participants is chemically transformed as a result. Chemical transformation usually involves the loss or gain of atoms. For example, when molecular hydrogen (H2) reacts with molecular oxygen (O2), both are transformed and result in a completely new chemical substance, water (H2O).

H2 + O2 ----------> H2O

Note that chemical reactions involve simply the rearrangement of existing atoms. Atoms are neither created nor destroyed in chemical reactions.

Fixed Carbon

Fixed carbon is carbon that has been converted from a gaseous form (like CO2) to a solid form (initially, short chains of carbon atoms). Photosynthesis is the main biochemical process on Earth that "fixes" carbon. Fixed carbon from photosynthesis is fed to many different biosynthetic pipelines that assemble much larger molecules like sugars, proteins, fats, nucleic acids and specialty molecules like vitamins.

The organic body of any living thing is composed of fixed carbon.


Photosynthesis is a biochemical process (system of many different chemical reactions) that consumes CO2, H2O and light energy to build short chains of carbon (fixed carbon). Water is used as a source of hydrogen atoms to stabilize the chains, and resultant oxygen atoms are released as waste O2.

The carbon chains then can be passed to other biochemical synthetic pipelines inside the cell for the assembly of carbohydrates, proteins, fats, nucleic acids and other kinds of biological molecules. Apart from other functional properties, all molecules of fixed carbon store sizeable amounts of chemical energy.

The general chemical expression for photosynthesis is:

CO2 + H2O + light --> carbon chains (fixed carbon) + O2

Cellular Respiration

Cellular respiration disassembles molecules of fixed carbon, releasing the chemical energy stored in them. The disassembly process produces large amounts of unescorted hydrogen atoms that, if allowed to accumulate, could clog up the system. Molecular oxygen (O2 ) is brought in to clear out these hydrogen atoms by combining with them to make water (H2O). The disassembled carbon is released as CO2.

The general expression for cellular respiration is:

Fixed carbon + O2 --> CO2 + H2O + biological energy

Living Cells

living cell
Above is a false color image of a living cell. The cell is the fundamental living unit in living things. It is composed of complex, biochemical operating systems that are self maintaining. Cells exploit their surroundings for resources in support of the self-maintenance component. The combined activities of living cells in all living things churn the planetary surface environment -- with remarkable results.

Living things grow by the addition of cells much in the same way that a wall grows by the addition of bricks. So, in order to support the growth and maintenance of new cells, living things constantly consume resources from their surrounding environment.

And as the cells in living things do their work, they are constantly producing wastes that are released to the  surrounding environment.


geneIn the simplest terms, a gene is a section of a DNA molecule that codes for a particular trait. We can think of a gene as the fundamental unit of information related to a given trait.

Specifically, genes hold information for the construction of protein molecules inside the cell. Enzymes are special kinds of protein molecules that are the "action" molecules. By varying the types and quantities of enzymes in the cell, the overall cell operation can be controlled.

Depending upon the genes available, there will be qualitative and quantitative differences in cell operations, trait operations and functioning of the whole organism.

Individual living things do not synthesize their own genes. Rather, they inherit them from parent, or parents. The inherited genes are then copied over-and-over as the individual adds new cells in its development. Generally, each living cell of an individual contains identical copies of the original genes inherited from parents. As a result, individuals are genetically constrained by the genetic makeup of their parents. Individuals have no choice in the matter.

Genes are packaged together in large molecular structures called chromosomes. Chromosomes make for more efficient physical management of genes, especially during cell division. And chromosomes often engage in gene-swapping during sex cell (eggs and sperm) formation.


Alleles are genes that code for the same trait but in different ways. For example, let's consider the trait for "eye color" in a population of rabbits. In this population, there are four different genes for eye color red, green, blue, brown). That is, there are four different alleles for eye color. Alleles are alternative forms of a gene for a given trait. The more alleles for a given trait, the greater variety in the population.


Genetics is a science interested in the dynamics of genetic information in living things. Genetic information plays a variety of interesting roles in biology, particularly in reproduction, and the development, operation and maintenance of traits.

In the field of genomics, geneticists map out the location of genes on different chromosomes that influence a given trait. Recently, geneticists have mapped the entire collection of genes for many species, including humans.

Knowledge of genetics has helped physicians to understand the cause of genetic disorders.

Population genetics is the branch of genetics that tracks the frequencies of alleles from generation-to-generation in a population. Population geneticists identify the ebbs and flows of allele frequencies. Combined with the science of ecology, population genetics can help biologists identify environmental causes for a population's genetic changes. This effort is the basis for modern evolution theory.

Different Kinds of Living Things

Photosynthetic types

Photosynthetic organisms usually require simple resources from their surroundings. These resources come in material form, such as carbon dioxide, molecular oxygen, nitrate salts (and other mineral salts) and water. Additional resources come in the form of energy, mainly sunlight.

Photosynthetic types also release materials back into their surroundings. Released chemicals include, carbon dioxide, molecular oxygen, water, nitrogen oxides and dimethyl sulfide.

Cyanobacteria are microscopic aquatic organisms that are responsible for the overwhelming majority of photosynthesis in the world's oceans, lakes and rivers. Cyanobacteria occur mostly in marine and freshwater environments (lakes rivers).

Diatoms. Photosynthetic, single-celled plankton that float in the oceans, especially in cold waters.

oak tree
Plants. Mostly terrestrial (on land). Plants are the main photosynthesizers on the continents.

Non-photosynthetic: animals

Animals require a mix of simple and complex materials from their surroundings. Simple materials include molecular oxygen, water and mineral salts. More complex materials includes the bodies, products or remains of other living things -- otherwise referred to as food.

Animals return simple materials to their surroundings such as carbon dioxide, water and nitrogen salts. They also return complex materials including digestive wastes and their own bodies after death.

Beetle -- an insect

sea star
Sea star

Barracuda -- a fish

tree frog
Tree frog -- an amphibian

Desert iguana -- a reptile

Baby chicken -- a bird

Deer -- a mammal

Non-photosynthetic: decomposers

Decomposers consume and process the remains and wastes of all living things. Decomposition converts biological molecules into their basic components. For example, decomposers would convert a dead leaf into: carbon dioxide, nitrate salts, magnesium salts, sulfur salts, phosphorous salts and water. The results of decomposition are released into the surrounding environment.

As decomposers break down the complex mass of remains of once-living things (and their wastes), they return the most basic buidling blocks of life (collectively referred to as "mineral nutrients") to the environment.


Bacteria. Many bacteria species behave as decomposers. When you have a bacterial infection, bacteria are trying to decompose you.

Nitrogen fixing types

Cyanobacteria also fix nitrogen in addition to being photosynthetic.
Cyanobacteria occur mostly in marine and freshwater environments (lakes rivers).

Root nodules containing symbiotic nitrogen-fixing bacteria.
Certain types of plants, especially legumes like beans, peas and alfalfa, have these root nodules. This symbiotic arrangement is good for the bacteria (which get sugar from the plant) and the plant (which gets fixed nitrogen from the bacteria).

Denitrifying types

denitrifying bacteria
Denitrifying bacterium. Denitrification converts nitrate salts to molecular nitrogen.
Denitrifying bacteria live only in oxygen-free environments like the deep mud of a marsh, pond or ocean bottom.


Copyright© 2009 by Tom E. Morris. All rights reserved.

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