Question

Living organisms are composed mainly of which atoms? a. calcium, hydrogen, nitrogen, and oxygen b. carbon, hydrogen, nitrogen, and oxygen c. hydrogen, nitrogen, oxygen, and helium d. carbon, helium, nitrogen, and oxygen e. carbon, calcium, hydrogen, and oxygen

Short answer

The correct answer is b. carbon, hydrogen, nitrogen, and oxygen.

Step-by-step solution

Identify significant components of organic molecules

In biochemistry, it's well known that the major organic molecules that comprise living organisms are proteins, nucleic acids (DNA and RNA), carbohydrates, and lipids. These are all primarily made up of the atoms carbon (C), hydrogen (H), nitrogen (N), and oxygen (O). Therefore, these atoms should also be the most common in living organisms.

Compare options

After recognizing the importance of carbon, hydrogen, nitrogen, and oxygen, the student then needs to compare the provided answers to find the one that contains all of these elements. Answer (b) carbon, hydrogen, nitrogen, and oxygen is the only one that fits.

Choose the correct answer

Considering the major biochemical components of living organisms and comparing the given options, the appropriate answer to this exercise is 'carbon, hydrogen, nitrogen, and oxygen'.

Key concepts

Biochemical Components

When we refer to the biochemical components of living organisms, we are discussing the building blocks that make up the structures and carry out the functions necessary for life. These components include a vast array of molecules, but the most fundamental are proteins, nucleic acids (including DNA and RNA), carbohydrates, and lipids. Each of these complex molecules is built from simpler units: amino acids for proteins, nucleotides for nucleic acids, and simple sugars or monosaccharides for carbohydrates.

All of these molecules, despite their complexity, are predominantly composed of just a few elements: carbon (C), hydrogen (H), nitrogen (N), and oxygen (O). These elements form a variety of chemical bonds with one another to produce the diversity of structures and functions seen in living organisms. Understanding the significance of these elements is not just a matter of memorizing a list; it is about recognizing their roles in the macromolecules that facilitate life's processes.

Organic Molecules in Biology

The term organic molecules might evoke thoughts of health food stores, but in biology, it refers to a vast category of molecules that all contain carbon and are found in living organisms. The 'organic' label dates back to a time when scientists believed these molecules could only be produced by living beings — a belief long since proven incorrect. Nevertheless, the term stuck.

Organic molecules in biology perform countless functions and come in diverse forms, such as the enzymes that catalyze reactions, the hormones that signal between cells, and the cellulose that gives plants their structure. They are also involved in energy storage (like fats and oils, or lipids) and carry genetic information (DNA and RNA).

Central to All Organic Molecules: Carbon

Carbon's unique ability to form four covalent bonds allows it to act as a backbone for complex molecular structures. It's essential in biology because of the versatility and stability of the molecules it can compose. For example, the carbon chains in fatty acids can vary in length and in the presence of double bonds, affecting how they are stored and used as energy.

Atomic Composition in Living Organisms

While there are 118 known elements, living organisms are primarily made up of a select few: carbon (C), hydrogen (H), nitrogen (N), and oxygen (O). This atomic composition is not a random assemblage but a reflection of the stability and chemical reactivity that these elements offer. They are versatile and can form an incredible variety of compounds necessary for life.

These elements are the stars of the periodic table when it comes to life. Carbon is central to organic chemistry; oxygen is critical for respiration and energy production; nitrogen is vital in the form of amino and nucleic acids; hydrogen bonds with carbon and also has a role in energy production and in maintaining the structure of molecules like DNA. It's fascinating to consider that such a minute subset of the periodic table has given rise to the incredible diversity and complexity of life on Earth.

It's important for students to understand that the reason why these particular elements are common in living organisms has to do with their abilities to create a diverse range of functional structures and to participate in a wide variety of biochemical reactions, making them indispensable to life's molecular dance.