Molecules of life biomolecules
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Molecules of Life – Biomolecules

What Do These Pictures Have in Common?

Brain Tissue

Protein Structure – the correct protein structure is important for normal function


Dr. Stanley Prusiner.

Why Is Carbon So Important?Organic/Inorganic Molecules

  • Organic vs. Inorganic in Chemistry

    • Organic refers to molecules containing a carbon skeleton

    • Inorganic refers to carbon dioxide and all molecules without carbon

Carbon’s Versatility

  • Carbon atoms are versatile and can form up to four bonds (single, double, or triple) and rings

  • Functional Groups in organic molecules confer chemical reactivity and other characteristics

    • Determines how that molecule will function (For ex. whether it is polar [charged] or nonpolar [uncharged])

Common Elements Found in Living Organisms

  • Carbon (C)

  • Hydrogen (H)

  • Nitrogen (N)

  • Oxygen (O)

  • Phosphorous (P)

Organic Molecule Synthesis

  • Biomolecules are polymers (chains) of subunits called monomers

Dehydration Synthesis

  • Monomers are joined together through dehydration synthesis

    • An H and an OH are removed, resulting in the loss of a water molecule (H2O)


  • Polymers are broken apart through hydrolysis (“water cutting”)

    • Water is broken into H and OH and used to break the bond between monomers

Biological Molecules

  • All biological molecules fall into one of four categories

    • Carbohydrates

    • Lipids

    • Proteins

    • Nucleic Acids

1. Carbohydrates

  • Carbohydrate composition

    • Made of C, H, and O in the ratio of 1:2:1

  • Construction

    • Simple or single sugars are monosaccharides

    • Two linked monosaccharides are disaccharides

    • Long chains of monosaccharides are polysaccharides


  • Carbohydrates are important energy sources for most organisms


  • Basic monosaccharide structure

    • Backbone of 3-7 carbon atoms

    • Many –OH and –H functional groups

    • Usually found in a ring form in cells

  • Example monosaccharides

    • Glucose (C6H12O6): the most common


  • Fate of monosaccharides inside a cell

    • Some broken down to free their chemical energy

    • Some are linked together by dehydration synthesis for storage


  • Disaccharides are two-part sugars

    • Sucrose (table sugar) = glucose + fructose

    • Lactose (milk sugar) = glucose + galactose

    • Maltose (malt sugar)= glucose + glucose

Polysaccharides Used For Energy Storage

  • Monosaccharides are linked together to form chains (polysaccharides)

  • Storage polysaccharides

    • Starch (polymer of glucose)

      • Formed in roots and seeds as a form of glucose storage

    • Glycogen (polymer of glucose)

      • Found in liver and muscles

Polysaccharides Used For Structural Support

  • Structural polysaccharides

    • Cellulose (polymer of glucose)

    • Found in the cell walls of plants

      • Indigestible for most animals due to orientation of bonds between glucoses

Polysaccharides Used For Structural Support

  • Structural polysaccharides continued

    • Chitin (polymer of modified glucose units)

      • Found in the outer coverings of insects, crabs, and spiders

      • Found in the cell walls of many fungi

2. Lipids

  • All lipids contain large chains of nonpolarhydrocarbons (a chain of carbon atoms w/hydrogen atoms attached)

  • Most lipids are hydrophobic (don’t like water) and water insoluble (don’t dissolve in water)

  • Lipids are diverse in structure and serve in a variety of functions

    • Energy storage

    • Waterproofing

    • Membranes in cells

    • Hormones

3 Groups of Lipids

  • 1. Oils, fats, and waxes

  • 2. Phospholipids

  • 3. Steroids

Oils, Fats, and Waxes

  • Made of only C, H, and O

  • Made of one or more fatty acid subunits

    • Long chains of C and H with a carboxylic acid group (-COOH) at one end

  • Fats and oils

    • Formed by dehydration synthesis

Oils and Fats

  • Fats and oils used for long-term energy storage

    • Fats and oils possess a high density of stored chemical energy

Oils and Fats

  • Fat solidity is due to single or double carbon bonds

    • Fats that are solid at room temperature are saturated (carbon chain has as many hydrogen atoms as possible, and mostly or all C-C single bonds), e.g. beef fat

Oils and Fats

  • Fat solidity is due to single or double carbon bonds (continued)

    • Fats that are liquid at room temperature are unsaturated(fewer hydrogen atoms, many C=C double bonds), e.g. corn oil


  • Composed of long hydrocarbon chains and are strongly hydrophobic

  • Highly saturated and solid at room temperature

  • Form waterproof coatings

  • Used to build honeycomb structures


  • Form plasma membranes around all cells

  • Phospholipids have hydrophobic and hydrophilic portions

    • Polar functional groups are water soluble

    • Nonpolar fatty acid “tails” are water insoluble


  • Steroids are composed of four carbon rings fused together

  • Examples of steroids

    • Cholesterol

      • Found in membranes of animal cells

    • Male and female sex hormones

3. Proteins

  • Proteins have a variety of functions

    • Enzymes catalyze (speed up) reactions

    • Structural proteins (e.g. collagen) provide support

Amino Acids

  • Proteins are formed from chains of amino acids (monomers)

    • There are 20 amino acids that make up proteins of living things.

Amino Acids

  • All amino acids have similar structure

    • Central carbon atom bonded to four different functional groups

      • 1. An amino group (-NH2)

      • 2. A carboxylic acid group (-COOH)

      • 3. A hydrogen (H)

      • 4. All have a variable “R” group

        • Some R groups are hydrophobic

        • Some are hydrophilic

        • Cysteine R groups can form disulfide bridges

Amino Acids

  • The sequence of amino acids in a protein dictates its function

Dehydration Synthesis

  • Amino acids are joined to form chains by dehydration synthesis

    • An amino group reacts with a carboxyl group, and water is lost

Dehydration Synthesis

  • Resultant covalent bond is a peptide bond

  • A chain of two amino acids or a short amino acid chain is called a peptide

  • Long chains of amino acids are known as polypeptides or just proteins

Three Dimensional Structures

  • The type, position, and number of amino acids determine the structure and function of a protein

    • Precise positioning of amino acid R groups leads to bonds that determine structure

    • Disruption of these bonds leads to denatured proteins and loss of function

      • For ex. If you expose a protein to high temperatures, it will cause the protein to unfold, in other words, to denature.

4.Nucleic Acids

  • Nucleotides are the monomers of nucleic acid chains

  • All nucleotides are made of three parts

    • Phosphate group

    • Five-carbon sugar

    • Nitrogen-containing base

Molecules of Heredity

  • Two types of nucleotides

    • Ribonucleotides (A, G, C, and U) found in RNA

      • A = adenine

      • G = guanine

      • C = cytosine

      • U = uracil

    • Deoxyribonucleotides (A, G, C, and T) found in DNA

      • A = adenine

      • G = guanine

      • C = cytosine

      • T = thymine

Molecules of Heredity

  • Two types of polymers (chains) of nucleic acids

    • DNA (deoxyribonucleic acid) found in chromosomes

      • Carries genetic information needed for protein construction

    • RNA (ribonucleic acid)

      • Copies of DNA used directly in protein construction

One nucleotide

Molecules of Heredity

  • Each DNA molecule consists of two chains of nucleotides that form a double helix

  • The nucleotides on opposing strands form hydrogen bonds, linking the two strands

  • RNA is copied from DNA in the nucleus

    • That information is used to synthesize proteins in the cell’s cytoplasm

The End

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