<< Chapter < Page Chapter >> Page >
By the end of this section, you will be able to:
  • Describe the ways in which carbon is critical to life
  • Explain the impact of slight changes in amino acids on organisms
  • Describe the four major types of biological molecules
  • Understand the functions of the four major types of molecules

The large molecules necessary for life that are built from smaller organic molecules are called biological macromolecules . There are four major classes of biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids), and each is an important component of the cell and performs a wide array of functions. Combined, these molecules make up the majority of a cell’s mass. Biological macromolecules are organic, meaning that they contain carbon. In addition, they may contain hydrogen, oxygen, nitrogen, phosphorus, sulfur, and additional minor elements.


It is often said that life is “carbon-based.” This means that carbon atoms, bonded to other carbon atoms or other elements, form the fundamental components of many, if not most, of the molecules found uniquely in living things. Other elements play important roles in biological molecules, but carbon certainly qualifies as the “foundation” element for molecules in living things. It is the bonding properties of carbon atoms that are responsible for its important role.

Carbon bonding

Carbon contains four electrons in its outer shell. Therefore, it can form four covalent bonds with other atoms or molecules. The simplest organic carbon molecule is methane (CH 4 ), in which four hydrogen atoms bind to a carbon atom ( [link] ).

Diagram of a methane molecule.
Carbon can form four covalent bonds to create an organic molecule. The simplest carbon molecule is methane (CH 4 ), depicted here.

However, structures that are more complex are made using carbon. Any of the hydrogen atoms can be replaced with another carbon atom covalently bonded to the first carbon atom. In this way, long and branching chains of carbon compounds can be made ( [link] a ). The carbon atoms may bond with atoms of other elements, such as nitrogen, oxygen, and phosphorus ( [link] b ). The molecules may also form rings, which themselves can link with other rings ( [link] c ). This diversity of molecular forms accounts for the diversity of functions of the biological macromolecules and is based to a large degree on the ability of carbon to form multiple bonds with itself and other atoms.

Examples of three different carbon-containing molecules.
These examples show three molecules (found in living organisms) that contain carbon atoms bonded in various ways to other carbon atoms and the atoms of other elements. (a) This molecule of stearic acid has a long chain of carbon atoms. (b) Glycine, a component of proteins, contains carbon, nitrogen, oxygen, and hydrogen atoms. (c) Glucose, a sugar, has a ring of carbon atoms and one oxygen atom.


Carbohydrates are macromolecules with which most consumers are somewhat familiar. To lose weight, some individuals adhere to “low-carb” diets. Athletes, in contrast, often “carb-load” before important competitions to ensure that they have sufficient energy to compete at a high level. Carbohydrates are, in fact, an essential part of our diet; grains, fruits, and vegetables are all natural sources of carbohydrates. Carbohydrates provide energy to the body, particularly through glucose, a simple sugar. Carbohydrates also have other important functions in humans, animals, and plants.

Questions & Answers

difference between DNA and RNA
Eyitayo Reply
what determines the aeration level in the soil
Shola Reply
what is homeostasis?
Sarita Reply
What is biology
Don Reply
Biology z the study of life
what's biology
biology is the study of living nd none living organism
Biology is the study of life
yes Sir
what's cell biology
biology is the study of life
what is asexual reproduction,?
Awoi Reply
A type of reproduction which does not involve the fusion of gametes or a change in the number of chromosomes
Reproduction without sex... In which form a single organism or cell makes a copy of itself.
Please explain the concept of mitosis and meiosis
I guess you could use it for study buddies and brushing up on what you need to
what is mitosis
Asexual reproduction?
why pepsin and trypsin released in active form?
mitosis is the type cell division in which two daughter cells have same no. of chormosomes
chromosome number remains the same in mitosis
Yrr help me.
Physical chemistry..... Koi h jo mujhe physical chem ki notes send kr ske
what is asexual reproduction
what makes golgi body in plants
Abdulkareem Reply
name the membrane of the plants
how can turners syndrome be corrected before birth
which animal survive from being preyed just because of being humble, slow, and not aggressive
During organs transplantation, the organs cannot be taken from just anybody since the graft would be rejected sooner or later due to
Liter Reply
Non-MHC compatibility on the organ and an attack from the patient's immune system.
what makes golgi body in plants
why trypsin and pepsin released in active form
what is integument system
Joy Reply
Cellular respiration
Lucy Reply
what are the characteristics of living things
Ruth Reply
Movement Respiration Nutrition/Feeding Irritability/Sensitivity Growth Excretion Reproduction Deat/Life span
What makes children from the same father and mother sometimes don't look alike?
identification of problems
Nana Reply
what happens in the process of raising the human arms
what is biology
Brandi Reply
first step in scientific method
In an investigation the pancreatic duct of a mammal was blocked.It was found that the blood sugar regulation remained normal while food digestion was impaired.Explain
Mac Reply
To begin with, obstruction of pancreatic duct will alter the blood sugar level as the juices responsible for glucose regulation will be rendered inconsequential. This will in turn affect the rate of digestion and absorbtion of digested food substances by the Villus .
characteristics of algae
Algae are eukaryotic organisms. Algae do not have roots and stems. Algae have chlorophyll and helps in carrying out photosynthesis.
Cell wall is the rigid layer enclosed by membranes of plants and prokayortic cell, it maintains the shape of the cell and serve as a protective barrier.
chizoba Reply
ECOLOGY: is a branch of biology that studies the interactions among organisms and their biophysical environment, which includes both biotic and abiotic components. 
via nutrient cycles and energy flows. For instance, the energy from the sun is captured by plants through photosynthesis. Photosynthesis is a biological process through which plants manufacture their own food with the aid of light from the sun and frc sources (e.g. cabon dioxide and water)

Get the best Concepts of biology course in your pocket!

Source:  OpenStax, Concepts of biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11487/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Concepts of biology' conversation and receive update notifications?