What Are the Basic Units of Protein Macromolecules

What Are the Basic Units of Protein Macromolecules.

two.1: Introduction to Biomolecules and Cell Components

  • Page ID
  • Learning Objectives
    • ane: Ascertain the basic construction of biomolecules, such as: amino acids and proteins, carbohydrates, fatty acids, triacylglycerol, phospholipids, steroids and nucleic acids.
    • ii: Ascertain the meaning and significance of essential and non-essential amino acids.
    • 3: Understand the function of enzymes.
    • 4: Define the basic structure of ribonucleic acid (RNA) and deoxyribonucleic acid (Dna).


    Amino Acids and Proteins

    Amino acids are the basic units of proteins. All amino acids nowadays in proteins behave a carboxyl- and an amino group, hydrogen and variable side chains (R) at a single α – carbon atom.

    Amino Acid Basic Structure:

    Every amino acid has four components linked together with a primal carbon atom α – carbon:

    • Amino grouping (NH2)
    • Carboxylic acrid grouping (COOH)
    • Hydrogen cantlet (H)
    • R-group, which varies with each amino acid (R)
    Effigy \(\PageIndex{1}\): Bones structure of an amino acid. Credit: Aline de Conti

    R groups may be:

    • Hydrophobic
    • Hydrophilic
    • Charged R-groups:

      positive or negative charged
    • Special R-groups:

      conjugated with other molecules

    Amino Acids are classified into two groups.


    Humans cannot synthesize them and must be obtained directly from food (phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, histidine, cysteine, and arginine).

    The homo torso is able to produce them (glycine, alanine, serine, asparagine, glutanine, tyrosine, aspartic acid, glutanic acid, and proline).

    Below, you can see unlike structures of the most mutual amino acids in humans. Amino acids link together, in a reaction known as

    , to form proteins.

    Chemical structures of 22 standard amino acids, including the recently discovered amino acids Pyl and Sec

    Peptide bond. Credit: Aline de Conti
    Figure \(\PageIndex{2}\): Peptide bail. Credit: Aline de Conti

    Levels of Protein Structure

    Primary (1°) Structure

    The sequence of amino acids in a protein is named as


    The amino acids are linked via peptide bonds formed with the carboxylic acid group of one amino acid and the amino grouping of a other amino acid.

    Secondary (two°) Structure

    The secondary structure is the way a polypeptide folds to form

    β-strand, or

    Third (3°) Structure

    The tertiary structure is the way the polypeptide chain coils and turns to form a circuitous molecular shape. Additionally, third structure starts to develop an agile sites of proteins where critical actions and interactions will take place.

    Quaternary (4°) Construction

    The quaternary structure is the combination of the multiple protein subunits that interact to course a unmarried, larger, biologically active protein.

    Poly peptide Functions

    Proteins take several functions in the human being trunk including hormonal, enzymes, structural proteins in cell membranes, proteins also receive signals from exterior the cell and mobilize intracellular response, and they are part of the immune organisation.

    Enzymes are specialized proteins that accelerate a chemical reaction by serving every bit a biological catalyst. Past catalyzing these reactions, enzymes cause them to have place 1 million or more than times faster than in their absence. Several biochemical reactions of import for cellular maintenance occur due to enzymes activity. For example: environmental response and metabolic pathways.

    Enzymes and Activation Energy - © 2010 Nature Education
    Figure \(\PageIndex{3}\): Enzymes and Activation Free energy – © 2010 Nature Education



    Disaccharide structure Carbohydrates are made of molecules of carbon (C), Hydrogen (H) and Oxygen (O), and are composed of recurring monomers called monosaccharides (which typically form ring structures). A common name of monomers and dimers is ‘sugar’.

    Read:   Which of the Following Statements is True of John Brown

    Carbohydrates are classified into iii subtypes.


    i. Monosaccharides:
    ane unit of measurement of monomer. Examples: fructose, glucose, galactose.

    Nowadays in fruits, etc.

    2. Disaccharides:
    2 units of monosaccharides. Examples: lactose, maltose, sucrose.

    Present in milk, etc.

    3. Polysaccharides:
    Many monosaccharide units. Examples: cellulose, glycogen, starch.

    Present in breads, grass, etc.

    Carbohydrates are a group of macromolecules that are important energy source required for diverse metabolic activities. Carbohydrates may demark to proteins and lipids that play important roles in cell interactions e.yard. receptor molecules and immune system e.m. antigens.

    Examples of carbohydrates



    Lipid molecules are mainly hydrophobic molecules i.due east. found in areas abroad from water molecules, only also present smaller hydrophilic parts that are important for its biological function. The major roles of lipid molecules are to serve as storage of biological energy (Example:
    triacylglycerols) and provide the building blocks for biological membranes (Example:
    cholesterol). Although there are other types of lipids, in this topic we will discuss the structure and function of these main groups of lipids.


    Triacylglycerols are composed of fatty acids and glycerol.

    • Glycerol
      is a elementary three-carbon molecule with hydroxyl groups at each carbon.
    • Fatty acids
      are chains of carbon molecules with a carboxylic acid (COOH) in the outset carbon and a CH3 (methyl) group at the end of the chain.


    Fatty acids can be…

    Fat acids contain only single carbon-carbon bonds, and all of the carbon molecules are bonded to the maximum number of hydrogen molecules.

    Fatty acids have at least one double carbon-carbon bail with the potential for additional hydrogen atom bonding still existing for some of the carbon atoms in the backbone concatenation. If more than than one double bond is present, the term polyunsaturated is used.

    Essential Fatty Acids

    Examples of ii essential fatty acids, linoleic acrid (known as
    omega-6;ω-6) and linolenic acid (known as
    omega-3; ω-iii). These fatty acids nowadays double bonds at the sixth and third carbon atoms, respectively, counting from the methyl finish of their chains. They are considered essential considering humans practise not take the ability to produce double bonds at these locations and, therefore, must obtain these two fatty acid from vegetable oils.

    Figure 8. Examples of essential fatty acids


    Phospholipids are the major component of jail cell membranes. They form lipid bilayers because of their amphiphilic characteristic.

    The structure of the
    molecule mostly consists of 2 hydrophobic fatty acid “tails” and a hydrophilic “head” consisting of a phosphate group (PO4−3) attached to the third glycerol carbon. This head group is usually charged, creating a role of the lipid that is hydrophilic, and wants to be near water, a quality that is essential for the formation of biological membranes and many lipid functions.

    Figure 9. Structure of phospholipid - © 2010 Nature Education


    Cholesterol is an important molecule institute only in eukaryotic organisms with a variety of functions. Cholesterol is also a component of biological membranes and its main function is to control the fluidity of membranes. Cholesterol does non like to be exposed to water environments, preferring to exist shielded by other hydrophobic molecules such as lipids or hydrophobic parts of proteins.

    Cholesterol also serves as the main source for the production of steroid hormones, bile salts, and vitamin D.

    Figure 10. Structure of cholesterol


    Nucleosides and nucleotides are involved in the preservation and transmission of the genetic information of all living creatures. In improver, they play roles in biological energy storage and transmission, signaling and regulation of diverse aspects of metabolism.

    These molecules tin be divided into two major families.

    They are two-ring structures: adenine and guanine.

    They are 1-ring structures: thymine, cytosine, and uracil.

    The unique structure and interaction of these molecules serve equally the cardinal building block of RNA and DNA molecules and allow cardinal processes of Dna replication and poly peptide synthesis to occur.

    Components of Nucleotides

    • Nitrogenous base:
      The nitrogenous base of a nucleoside or nucleotide may be either a purine or a pyrimidine.
    • Saccharide:
      The carbohydrate component of nucleosides and nucleotides is usually the sugar ribose for RNA molecules and deoxyribose for Dna molecule
    • Phosphate Group:
      One or more phosphate groups (PO4−iii) may exist fastened to the carbon 5 of the carbohydrate molecule.

    Example of structure of nucleotide: Adenosine triphosphate



    DNA stands for deoxyribonucleic acid.

    It is an extremely long molecule that forms a double-helix.

    Basic structure of DNA

    Deoxyribonucleic acid components:

    – Sugars – Deoxyribose

    – Phosphates – (PO4−3)

    – Base – cytosine (C), guanine (G), adenine (A) and thymine (T).

    The DNA consists of ii strands attached to each other by hydrogen bond created by nucleotide pairing (A-T and C-G).

    structure of Deoxyribonucleic acid is of import for its function because these 2 bonded strands can temporarily separate to allow for DNA replication.

    The sequences of nucleotides (A, C, T, G) in the Deoxyribonucleic acid molecule will make up the
    and, subsequently, proteins are referred to as “expressed sequences” or “exons.” Sequences that practice non lawmaking for a poly peptide are called “intervening sequences” or “introns.”

    Human karyotype

    Human Genome

    The genome of humans is estimated to incorporate approximately 20,000–25,000 different genes arranged on multiple chromosomes.

    Twenty three

    pairs of chromosomes:
    Xx ii pairs (autosomes).

    One pair (sexual practice chromosome) (twenty) (female person) or (xy) (male).

    Humans have 23 pairs of chromosome in every cell (except mature ruby blood cells); Gametes or sexual practice cells (sperm and eggs) have half the normal complement of chromosomes.


    Basic structure of RNA

    RNA stands for ribonucleic acrid.

    RNA molecules are single strands.

    Read:   Is Food a Limiting Factor for Plants

    RNA components:

    • Sugars – Ribose
    • Phosphates – (PO4−3)
    • Base of operations: cytosine (C), guanine (Thou), adenine (A) and uracil (U)

    RNA molecules often class secondary (2°) structures and may interact with DNA, other RNA molecules, and proteins. These interactions help to ascertain the particular office of each type of RNA.

    Types of RNA molecules and functions:


    RNA (mRNA):

    Molecules which role as the transmitter of genetic information from the DNA genetic code to the resulting protein.

    Transfer RNA (tRNA)

    Molecules that carry amino acids and lucifer them with a specific mRNA sequence during protein synthesis.

    Ribosomal RNA (rRNA)

    Molecules associated with proteins and are responsible for the synthesis of protein molecules.

    Regulatory RNA

    Molecules involved in regulation of Deoxyribonucleic acid expression, posttranscriptional mRNA processing, and the action of the transcribed mRNA message.

    The bones structure of DNA and RNA are similar, however with iii main differences:

    Nitrogenous Bases:
    Three of the nitrogenous bases are the aforementioned in the Deoxyribonucleic acid and RNA: adenine, cytosine, and guanine. The fourth base for DNA is thymine while for RNA it is uracil. Thymine and uracil both bind to adenine.

    Number of Strands:
    The DNA molecule is usually double-stranded and most cellular RNA molecules are single-stranded.

    Type of Sugar:
    In the Deoxyribonucleic acid molecule the sugar is
    and in the RNA molecule the saccharide is

    Topic one: Primal Points

    In this section, we explored the following principal points:

    • 1: Amino acids link together, in a reaction known every bit peptide bond, to form proteins.
    • 2: One important function of protein is to deed as enzymes to advance chemical reactions.
    • 3: Carbohydrates are important free energy source required for various metabolic activities and may demark to proteins and lipids that play important roles in prison cell interactions
    • 4: Lipid molecules serve as storage of biological energy and provide the edifice blocks for biological membranes
    • 5: Deoxyribonucleic acid and RNA structures take 3 primary differences .The nitrogenous bases (DNA has thymine and RNA has uracil). The Deoxyribonucleic acid molecule is ordinarily double stranded and most of the RNA molecules are unmarried stranded. In the DNA molecule the saccharide is deoxyribose and in the RNA molecule the saccharide is ribose.
    Cognition Check

    1. What type of nucleic acid does thymine belong to?


    Deoxyribonucleic acid

    2. Uracil?



    iii. Enzymes are…

    specialized proteins that accelerate a chemical reaction past serving as a biological goad.

    specialized proteins that stops a chemical reaction.


    specialized proteins that advance a chemic reaction past serving as a biological catalyst.

    A nucleotide consists of…

    Cheque all that apply.

    • A sugar (either deoxyribose or ribose )
    • Uracil every bit the nitrogen base
    • A phosphate grouping
    • One of the four nitrogen bases

    A sugar, A phosphate group, and 1 of the four nitrogen bases

    Lipid molecules are mainly hydrophilic molecules.

    True or False?



    What Are the Basic Units of Protein Macromolecules

    Source: https://chem.libretexts.org/Bookshelves/Environmental_Chemistry/Toxicology_MSDT/02:_Biochemistry_and_Molecular_Genetics/2.01:_New_Page

    Check Also

    According to the Seventeenth Amendment Who Could Elect Senators

    1913 amendment establishing the straight election of senators The Seventeenth Amendment (Amendment XVII) to the …