Question

A ___________ is a portion of protein with a particular structure and function. a. peptide bond b. domain c. phospholipid d. wax e. monosaccharide

Short answer

The correct answer is b. Domain.

Step-by-step solution

Identify the context of the definition

The focus of this problem is protein structure. Proteins are composed of different parts that have distinct structures and functions.

Evaluate each option

By evaluating each option based on knowledge in biology, we can deduce the following: a. peptide bond – It's a bond that holds together amino acids to form proteins, but it's not a portion of protein. b. domain – A domain in proteins refers to a distinct functional and structural unit in a protein. c. phospholipid – This is a type of lipid and a primary component of cell membranes, not a part of proteins. d. wax – Waxes are lipids but not related to protein structure. e. monosaccharide – It's the simplest form of carbohydrates, not part of proteins.

Select the right option

From the insights gathered in step 2, it's clear that a 'domain' is a portion of protein with a specific structure and function. Hence, 'domain' is the correct answer.

Key concepts

Protein Domain

Understanding protein domains is essential for students studying biology and biochemistry. A protein domain is fundamentally a part of a protein's sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain typically performs a specific function, and proteins can have one or multiple domains that may appear in different combinations.

Domains are like the 'tools' in a multi-tool pocketknife. Just as each tool in a pocketknife, such as a blade or screwdriver, performs a specific function, each protein domain has a particular role in the protein's overall activity. Some domains bind DNA; others are responsible for enzymatic activities, while some may mediate interactions with other proteins.

For students: It is helpful to visualize protein domains as distinct 'building blocks' within the protein, which contribute to its three-dimensional structure and determine its interaction with other molecules.

Peptide Bond

The peptide bond is a chemical bond that is central to the structure of proteins. It's the bond that links amino acids together, forming the backbone of protein molecules. To imagine how a peptide bond works, picture a chain where each link is an amino acid, and the peptide bond is what holds these links together.

A peptide bond is formed through a dehydration synthesis reaction. This means that when two amino acids link to form a peptide bond, a water molecule is released. The bond itself is formed between the carboxyl group of one amino acid and the amino group of another, establishing a covalent bond that is both rigid and planar, leading to the stability of protein structures.

For students: Remember that without peptide bonds, amino acids couldn't connect to form proteins, so understanding this bond is fundamental to grasping how proteins are built at the molecular level.

Biological Macromolecules

Biological macromolecules are large molecules necessary for life that are built from smaller organic molecules. They are an important subject in biology because they play critical roles in cell structure and function. There are four main categories of biological macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

These macromolecules vary in structure and function. Carbohydrates provide energy and structure, as seen in sugars and starches; lipids serve as the key structural elements of cellular membranes and can be a source of energy; proteins perform a vast range of functions including catalyzing biochemical reactions as enzymes, providing structural support, and acting in defense mechanisms; and nucleic acids carry genetic information, which is crucial in heredity and guiding the synthesis of proteins.

For students: Visualize biological macromolecules as the 'hardware' of a cell, each type serving as a fundamental component necessary for the life-sustaining processes within all living organisms.