Blueprint for Life: DNA & Proteins
The basis of biotechnology is, well, biology. So in this blog post, we’re giving you a quick overview of the most important building blocks of the field. After reading this blog, you will have a general understanding of the scientific components that are VITAL to biotech products, biomedical engineers, and researchers.
Meet Your Inner Code: DNA and Proteins—The Ultimate Duo!
Do you ever wonder why you don’t have the gills of a fish? Or the black-and-white fur of a cuddly panda? Or the ferocious jaws of a T-Rex? Do you ever wonder what makes you, you? It's time to meet the duo running the show inside of you: DNA and proteins. Spoiler alert: they’re way cooler than they sound!
Cells are the building blocks of life. DNA and proteins are the building blocks of cells. Without these 2 components, cells wouldn’t be able to function properly. Our cells would die. They would undergo abysmal errors that may lead us to miss a thumb. Or, worst of all, our cells wouldn’t be able to replicate, causing species extinction! So, what are DNA and proteins and how do they contribute to the human genome? Are they as nightmarish as they sound, or could they be the sole reason for all of your quirky characteristics?
DNA - The Blueprint of Life
DNA stands for “Deoxyribonucleic Acid.” This may seem very complex at first, but it describes exactly what DNA is: a nucleic acid. Nucleic acids (in addition to proteins, which we’ll get into later) are one of the 4 main biomolecules. This means that without nucleic acids, life couldn’t even exist. Nucleic acids are made up of monomers (building blocks) called nucleotides joined together by phosphodiester bonds. Their main purpose in the living body is to store genetic material, which is exactly what DNA does. DNA stores all your genetic material inherited from both parents, and it’s located in the nucleus of EVERY SINGLE eukaryotic cell in the human body! These are literally TRILLIONS of cells that put your DNA to good use. Put simply, DNA is a nucleic acid that consists of long chains of nucleotides linked together by phosphodiester bonds.
DNA Structure
DNA is referred to as a double helix; it consists of 2 strands that loop around each other like a twisted ladder. Each strand is made up of a sugar-phosphate backbone, which, as stated previously, consists of chains of nucleotides linked together. But what makes up these nucleotides? Nucleotides consist of 3 main components: a 5-carbon sugar, a Phosphate group, and a Nitrogenous Base(1). The component you truly need to understand is the nitrogenous base.
The four nitrogenous bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G). The 2 strands of DNA connect at these nitrogenous bases through hydrogen bonds. However, they can’t just match up however they want because, remember, DNA is super specific. There are specific “base pairing rules” that the nitrogenous bases follow:
(A) pairs with (T): Two hydrogen bonds form between A and T, creating a stable connection.
(G) pairs with (C): Three hydrogen bonds form between G and C, making this pairing slightly stronger than the A-T pairing.
The pairing of nitrogenous bases in DNA is important because it allows DNA to accurately replicate itself, and it also ensures the safe transfer of information during transcription and replication. The consistent pairing of these nitrogenous bases contributes to the DNA’s double-helix structure, where the two strands wind around each other. The hydrogen bonds between the bases stabilize the DNA molecule, making it less prone to damage and ensuring that the genetic information remains secure within the cell.
DNA Purpose
Segments of DNA that contain specific sequences of nucleotides are called genes. Each gene contains the instructions for making a particular protein or set of proteins. Each set of three nucleotides, called a codon, corresponds to a specific amino acid (which are the building blocks of proteins, similar to how nucleotides are the building blocks of nucleic acids)(2). These amino acids join to form proteins which then go on to express specific characteristics of a species. For example, differences in genes are why some people have blue eyes and others have brown, or why fish have gills, pandas have black-and-white fur, and T-Rexs have HUGE jaws.
Proteins: The Workhorses of the Cell
Amino acids are the monomers of proteins. Each amino acid consists of three key components:
Amino Group(NH2): A functional group containing nitrogen and hydrogen, which gives amino acids their name(3).
Carboxyl Group (COOH): A functional group containing carbon, oxygen, and hydrogen, which makes the amino acid an acid.
R Group (Side Chain): A variable group that differs among amino acids and determines their unique properties. There are 20 different R groups, leading to 20 standard amino acids.
Similar to how nucleotides are connected by phosphodiester bonds, amino acids are connected by peptide bonds, formed between the amino group of one amino acid and the carboxyl group of another. This bonding creates a long chain of amino acids, known as a polypeptide, which then folds into a specific protein structure.
Proteins have four levels of structure, each contributing to the protein's overall shape and function(4):
Primary Structure
Definition: The primary structure is the linear sequence of amino acids in a polypeptide chain, determined by the gene encoding the protein.
Importance: The sequence of amino acids dictates how the protein will fold and its final shape. Any change in the sequence (mutation) can alter the protein's function, which might lead to diseases or other functional changes.
Secondary Structure
Definition: The secondary structure refers to the local folding of the polypeptide chain into specific patterns, stabilized by hydrogen bonds between the backbone atoms (not the side chains).
Common Forms:
Alpha Helix: A coiled, spring-like structure where hydrogen bonds form between every fourth amino acid, stabilizing the helix.
Beta Pleated Sheet: A sheet-like structure formed when two or more segments of the polypeptide chain lie side by side and are connected by hydrogen bonds.
Importance: Secondary structures contribute to the overall stability of the protein and create specific shapes that are critical for the protein’s function.
Tertiary Structure
Definition: The tertiary structure is the overall three-dimensional shape of a single polypeptide chain, formed by the interactions between the R groups (side chains) of the amino acids.
Types of Bonds:
Hydrogen Bonds: Form between polar side chains.
Ionic Bonds: Form between oppositely charged side chains.
Disulfide Bridges: Strong covalent bonds that form between sulfur atoms in the side chains of cysteine amino acids.
Importance: The tertiary structure determines the protein's overall shape, which is essential for its function.
Quaternary Structure
Definition: The quaternary structure arises when two or more polypeptide chains come together to form a functional protein.
Examples:
Hemoglobin: Consists of four polypeptide subunits that work together to transport oxygen in the blood.
Collagen: A protein that forms strong, fibrous structures, composed of three intertwined polypeptide chains.
Importance: Quaternary structures are crucial for proteins that function as complexes, where the arrangement of multiple subunits allows for cooperativity and regulation of the protein’s activity.
Key Proteins
DNA is found in nearly all cells in the body, and if unraveled and stretched end-to-end, the DNA in a SINGULAR cell could span OVER 6.5 FEET! Long pieces of DNA are tightly looped, coiled, and folded to fit inside the cell. In eukaryotes, this is accomplished by wrapping the DNA around proteins called histones(5)
DNA Replication: The replication process is when the DNA strands split in two to synthesize two brand new strands for each of the original strands. We’ll save this process for another day because there’s a LOT to cover. Several proteins, or more specifically, enzymes, are involved in this process, such as DNA Polymerase, RNA Polymerase, Helicase, Single-Stranded Binding proteins, Topoisomerase, and more! Without these vital proteins, genetic information wouldn’t be preserved across generations and cellular replication couldn’t occur.
Summary
This blog post covers the basics of DNA and proteins, highlighting their structures and functions. DNA stores genetic instructions and directs protein synthesis. Proteins, made from amino acids, have complex structures that determine their diverse roles in the cell, including acting as enzymes, which catalyze reactions.
In future posts, we will explore the importance of understanding these molecules in fields like gene therapy, drug development, and biotechnology, emphasizing their crucial roles in medicine and technological innovation.
So stay tuned!
Bibliography
National Cancer Institute. “Definition of Nucleotide - NCI Dictionary of Cancer Terms.” National Cancer Institute, Cancer.gov, 2019, www.cancer.gov/publications/dictionaries/genetics-dictionary/def/nucleotide.
Alberts, Bruce, et al. “DNA and Chromosomes.” Nih.gov, Garland Science, 2024, www.ncbi.nlm.nih.gov/books/NBK21074/#:~:text=Life%20depends%20on%20the%20ability. Accessed 20 Aug. 2024.
Nature Education. “Protein Structure | Learn Science at Scitable.” Www.nature.com, 2014, www.nature.com/scitable/topicpage/protein-structure-14122136/#:~:text=The%20building%20blocks%20of%20proteins.
Sun PD, Foster CE, Boyington JC. Overview of protein structural and functional folds. Curr Protoc Protein Sci. 2004 May;Chapter 17(1):Unit 17.1. doi: 10.1002/0471140864.ps1701s35. PMID: 18429251; PMCID: PMC7162418.
“DNA Is a Structure That Encodes Biological Information | Learn Science at Scitable.” Www.nature.com, www.nature.com/scitable/topicpage/dna-is-a-structure-that-encodes-biological-6493050/#:~:text=During%20DNA%20packaging%2C%20long%20pieces.
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