Amino acids, the building blocks of proteins, are made up of which basic chemical elements?

Introduction / Context:
Amino acids are the fundamental building blocks of proteins, which are essential macromolecules in all living cells. Knowing what elements are present in amino acids is an important step in understanding biochemistry, nutrition, and molecular biology. While many biomolecules contain carbon, hydrogen, and oxygen, amino acids have an additional element that gives them unique properties and allows them to form peptide bonds and complex protein structures. This question asks you to identify the set of basic chemical elements that make up amino acids.

Given Data / Assumptions:

• The options list carbon, nitrogen, hydrogen, and oxygen in different combinations.
• We focus on the general structure of standard amino acids found in proteins.
• We ignore special cases such as sulfur containing amino acids when thinking about the basic framework.
• We assume standard textbook representations of amino acid structure.

Concept / Approach:
Each amino acid has a central carbon atom, called the alpha carbon, to which four groups are attached: an amino group, a carboxyl group, a hydrogen atom, and a variable side chain. The amino group contains nitrogen and hydrogen, while the carboxyl group contains carbon and oxygen. The side chain may also contain additional carbon, hydrogen, oxygen, and often nitrogen, and some amino acids include sulfur. However, the core definition of amino acids emphasises that they contain carbon, hydrogen, oxygen, and nitrogen. The correct approach is to choose the option that includes all four of these basic elements rather than any single subset.

Step-by-Step Solution:
Step 1: Recall that the central framework of an amino acid is built around a carbon atom, so carbon must be included. Step 2: Remember that amino acids have an amino group (NH2 or a related form), which always contains nitrogen and hydrogen. Step 3: Recognise that amino acids also have a carboxyl group (COOH), which contains carbon and oxygen as well as hydrogen. Step 4: Understand that the side chains or R groups vary, but in nearly all standard amino acids they still contain some combination of carbon, hydrogen, and often oxygen and nitrogen. Step 5: Compare the options and identify the one that lists all four core elements: carbon, hydrogen, oxygen, and nitrogen. Step 6: Conclude that the correct answer is the option representing this complete set of elements, acknowledging that some amino acids also include sulfur in addition to these basics.

Verification / Alternative check:
Chemical formulas of common amino acids confirm this reasoning. For example, glycine has the formula C2H5NO2, alanine is C3H7NO2, and lysine is C6H14N2O2. Each of these contains carbon (C), hydrogen (H), nitrogen (N), and oxygen (O). Some amino acids, such as cysteine, add sulfur (S), but they still include the core CHNO elements. Laboratory analysis of proteins shows that these four elements are present in all amino acids, while sulfur appears only in some. This consistent pattern supports selecting the option that lists all four core elements together.

Why Other Options Are Wrong:
Carbon atoms only is incorrect because amino acids also contain hydrogen, oxygen, and nitrogen; carbon alone cannot form the amino and carboxyl groups characteristic of amino acids.
Nitrogen atoms only is wrong because while nitrogen is essential for the amino group, amino acids would not exist without carbon, hydrogen, and oxygen in their structure.
Hydrogen and oxygen atoms only are far too limited to describe amino acids, which also require carbon to form the backbone and nitrogen to form the amino group, so this option is incomplete.

Common Pitfalls:
A common mistake is to focus only on one element, such as nitrogen, because amino acids are often introduced as nitrogen containing compounds. Another pitfall is to think that because many biomolecules contain carbon, hydrogen, and oxygen, this trio must be sufficient to define amino acids. To avoid these errors, remember the structural formula of amino acids and the presence of an amino group and a carboxyl group, which together require carbon, hydrogen, oxygen, and nitrogen.

Final Answer:
Amino acids, the building blocks of proteins, are made up of carbon, hydrogen, oxygen, and nitrogen atoms as their basic chemical elements.