Amino acid

Definition

An amino acid is a small organic molecule that serves as a building block for proteins, which are essential for various biological functions. Each amino acid contains a central carbon atom, an amino group, a carboxyl group, and a unique side chain (R group) that determines its properties. Understanding amino acids is crucial because they play a key role in the structure and function of proteins, which can be compared through methods like pairwise sequence alignment to identify similarities and differences between protein sequences.

5 Must Know Facts For Your Next Test

1. There are 20 standard amino acids that combine in various sequences to form proteins, with each sequence determining the specific function of the protein.
2. Amino acids can be categorized as essential (must be obtained from the diet) and non-essential (can be synthesized by the body).
3. The unique properties of an amino acid's side chain influence how proteins fold and function, which can be crucial for their interactions with other molecules.
4. In pairwise sequence alignment, the similarities between sequences of amino acids are assessed to identify evolutionary relationships or functional similarities between proteins.
5. Amino acids are not only involved in protein synthesis but also play roles in metabolism, cell signaling, and neurotransmission.

Review Questions

• How do the properties of different amino acids influence protein structure and function?
  • The properties of different amino acids are dictated by their side chains (R groups), which can be polar, non-polar, charged, or neutral. These properties affect how amino acids interact with each other during protein folding, influencing the final three-dimensional structure of the protein. For instance, hydrophobic amino acids tend to be buried within the core of proteins, while polar or charged amino acids are often found on the surface, where they can interact with water or other molecules.
• Discuss the significance of pairwise sequence alignment in understanding evolutionary relationships between proteins based on their amino acid sequences.
  • Pairwise sequence alignment is vital for comparing two protein sequences to find regions of similarity that may indicate shared evolutionary origins or functional roles. By aligning sequences based on their amino acid composition, scientists can infer how closely related different proteins are and even predict functions for unknown proteins. The alignment helps identify conserved regions critical for function and can highlight evolutionary changes over time.
• Evaluate how variations in amino acid sequences might impact protein functionality and lead to diseases.
  • Variations in amino acid sequences can significantly impact protein functionality by altering the protein's structure and stability. For example, a single mutation in a sequence can disrupt a protein's active site or its ability to interact with other molecules, potentially leading to loss of function or malfunction. Such changes can result in diseases; for instance, sickle cell disease is caused by a single amino acid substitution in hemoglobin, leading to severe health consequences. This illustrates how critical precise amino acid sequences are for proper biological function.

Related terms

Peptide bond: A covalent bond formed between two amino acids during protein synthesis, linking the carboxyl group of one amino acid to the amino group of another.

Protein structure: The three-dimensional arrangement of amino acids in a protein, which is determined by the sequence of amino acids and affects the protein's function.

Homologous sequences: Similar sequences found in different proteins or genes that have evolved from a common ancestor, often analyzed through pairwise sequence alignment.