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1 DNA, RNA and Protein

This chapter will review the structure and function of DNA, RNA and proteins.

Learning Outcomes

By the end of this chapter, you will be able to

  • Identify the structure of DNA.
  • Differentiate DNA and RNA molecules.
  • Categorize the types of RNA molecules.
  • Identify the levels of a protein structure.
  • Categorize membrane proteins.

 

DNA

Zoomed-in AI-generated image of the double-DNA helix showing chemical groups.
Digital illustration of DNA. CC BY-ND 4.0 EN.

If you think of DNA, you are most likely reminded of its structure as a double helix molecule that acts as the cell’s genetic blueprint. But can you recall the specific components that make up this biomolecule?

Complete the following interactive to review your understanding of the structure of DNA.

Learning Tip! Try thinking about the differences before you click to see the answer!

Adapted from “Molecular Structure of DNA”, by BioRender.com (2024).

Great job! Now, you should be able to recall the structure of DNA, which will help you as we move on to assess the structure of RNA in comparison with DNA.

In Review

DNA is composed of a series of nucleotides. A single nucleotide comprises three components: a nitrogen-containing base, a five-carbon sugar, and a phosphate group. The nitrogenous base is either a purine or a pyrimidine.

Illustration of double-helix DNA strand. Showing the composition of sugar phosphate backbone and base pairing of nitrogenous bases.
Overall structure of DNA. Reprinted from “The Structure of DNA”, by BioRender.com (2024).

RNA

RNA, ribonucleic acid, is also a nucleic acid and is important in transmitting genetic information in living organisms.

Before we look at the possibilities of RNA in the cell, let’s begin with a review of DNA and RNA.

Comparison illustration of DNA and RNA nucleotide composition.
Simplified comparison of DNA and RNA strands. Adapted from “DNA Structure”, by BioRender.com (2020).

Complete the following interactive to review this comparison further. Click each title to reveal the comparison between DNA and RNA.

Learning Tip! Try thinking about the differences before you click the reveal button!

RNA’s main function is protein synthesis through translation, where genetic information is carried and translated into essential proteins by ribosomes.

The three main types of RNA that are involved in this process are

  • mRNA
  • rRNA
  • tRNA

RNA can also function as the genetic material for viruses and plays roles in RNA editing, gene regulation, and RNA interference. Small regulatory RNAs, such as small nuclear RNA, microRNA, and small interfering RNA (siRNA), are involved in these processes.

Complete the following interactive to test your understanding of the types of RNA.

Adapted from “Types of RNA Produced in Cells”, by BioRender.com (2024).

 

Proteins

 

Three-dimensional structure of a protein. Different domains are shown in a different rainbow colour.
Example protein – Spombe Pop2p protein structure rainbow. CC BY-ND 4.0 EN.

Now, we will review the structure and function of proteins. First, we will start by reviewing the levels of protein structure. Complete the following interactive to test your understanding.

Adapted from “Protein Structure”, by BioRender.com (2024).

 

As a result of the diverse structure that proteins can take on, they can perform and participate in various functions and roles in the eukaryotic cell. These roles can include some of the following.

 

Comparison of eight functions of proteins. Enzymatic proteins showing a ligand binding to a protein. Storage proteins showing the protein ovalbumin in an egg. Hormonal proteins showing the pituitary gland producing thyroid hormones. Motor proteins showing a skeletal muscle with actin and myosin assembled. Defensive proteins showing antibodies binding to a virus. Transport proteins showing the transportation of molecules being through the cell membrane by an ion channel. Receptor proteins showing a neuron releasing neurotransmitters into the synaptic cleft and binding to receptors on the opposing cell. Structural proteins showing connective tissue composed on collagen.
Protein functions. Functions include enzymatic proteins, storage proteins, hormonal proteins, motor proteins, defensive (immune) proteins, transport proteins, receptor proteins and structural proteins. Reprinted from “An Overview of Protein Functions”, by BioRender.com (2024).

Proteins can be broadly classified into three categories based on their structure:

  • fibrous proteins
  • globular proteins
  • membrane proteins

In our review, we will take a closer look at membrane proteins.

Membrane Proteins

Membrane proteins can consist of integral and peripheral membrane proteins.

Integral membrane proteins are transmembrane proteins that span the membrane more than once.

  • These can be further classified into lipid-linked and transmembrane membrane proteins.

Peripheral membrane proteins are associated either with the lipid bilayer or integral proteins by various interactions.

 

Here, we will review membrane proteins. Complete the following interactive activity to identify the types of membrane proteins.

Learning tip! Be sure to think about it before you click to see the answer!

 

Adapted from “Membrane Proteins”, by BioRender.com (2024).

 

 

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Advanced Cell Biology - Study Toolkit Copyright © by Marcia Chaudet is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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