Biological Molecules

Lecture 3

how many bonds can carbon form?

4

Hydrocarbons

organic compounds only made up of Carbon and Hydrogen

nonpolar, uncharged —> Hydrophobic (unless modified with functional groups)

Functional Groups

specific clusters of atoms within a molecule that give that molecule its distinct chemical properties and behaviors (molecules’ personality traits)

The 6 Key Functional Groups

Hydroxyl, Carbonyl, Carboxyl, Amino, Phosphate, Methyl

Hydroxyl Group

(-OH) An oxygen bonded to a hydrogen

Highly polar and hydrophilic
Turning a hydrocarbon into an alcohol makes it easily dissolvable in water
Ex: ethanol

Carbonyl Group

(=O) A carbon double-bonded to an oxygen

Polar and hydrophilic
Found in sugars, it creates polar regions that allow sugars to interact with water and dissolve
Ex: Acetone, Propanal

Carboxyl Group

(-COOH) A carbon double-bonded to an oxygen and single-bonded to a hydroxyl group.

Polar and hydrophilic
This group can easily drop its hydrogen ion (𝐻+), making it act as an acid (e.g., Vinegar / Acetic acid)

Amino Group

(-NH₂) A nitrogen bonded to two hydrogens.

Polar and hydrophilic
It acts as a base because it can pick up an extra hydrogen ion (𝐻+) from its surroundings, taking on a positive charge.
Ex: Glycine

Phosphate Group

(-OPO₃^2-) A phosphorus atom surrounded by four oxygen atoms.

Acidic and hydrophilic
It carries a heavy negative charge and transfers massive amounts of chemical energy (the key driver behind ATP, your cells' battery)
Ex: Glycerol phosphate

Methyl Group

(-CH₃) one carbon atom bonded to three hydrogen atoms

Non-polar and hydrophobic
In DNA, affects gene expression
Ex: 5-Methyl cytosine

Macromolecules

massive molecules made up of thousands of covalently bonded atoms

polymers

Giant, chain-like molecules made up of hundreds or thousands of repeating monomer units (a lot of atoms), all locked together by strong covalent bonds

monomers

Small, relatively simple molecules with specific functional groups that allow them to bind chemically to other molecules

ALL polymers are macromolecules but…

NOT ALL macromolecules are polymers!

Dehydration Reaction

Synthesizing/making a polymer

To join two monomers together, a cell removes a hydrogen atom from one monomer and a hydroxyl group from another. This forms a molecule of water (𝐻₂𝑂) as a byproduct and leaves a clean slot for the two monomers to snap together with a strong covalent bond

Enzyme doing this: dehydrogenases

Hydrolysis

water breaking down a polymer

During this process, a water molecule (𝐻₂𝑂) is consumed: one part of the split molecule gains a hydrogen ion (𝐻+), and the other part collects a hydroxyl group (𝑂𝐻−)

Enzyme doing this: hydrolases

The 4 classes of biological molecules

Carbohydrates, Lipids (NOT POLYMERS), Proteins, Nucleic Acids

Carbohydrates

𝐶𝐻₂𝑂 organic macromolecules made entirely of carbon (C), hydrogen (H), and oxygen (O)

primary jobs are providing fast electrical and metabolic energy to cells and building structural support walls in plants and insects

Hydrophilic

Monosaccharides

simplest form of carbohydrates. They are the single-unit monomers that link together to build all complex sugars, starches, and fibers

Ex: Glucose C₆H₁₂O₆

Polysaccharides

massive carbohydrate polymers made of hundreds or thousands of monosaccharide rings linked together by glycosidic linkage

2 main functions: Energy Storage and Structure

Lipids

a diverse group of organic, hydrophobic biomolecules that include fats, oils, waxes, and certain hormones; NOT POLYMERS

They don’t dissolve in water BUT dissolve in nonpolar solvents

3 important lipid families

Fats, phospholipids, steroids

Fats

large and abundant lipid molecules made of one glycerol backbone attached to three fatty acid chains

Serve as a dense energy source, insulate the body, cushion vital organs, and form cell structures

Phospholipids

a type of amphipathic lipid molecule that forms the primary building block of cellular membranes

Glycerol + 2 fatty acids (hydrophobic tail + hydrophilic head) + phosphate group

Steroids

a class of lipids defined by a core chemical structure of four fused carbon rings (3 6-C Rings, 1 5-C Ring), hydrophobic

Ex: cholesterol, sex hormones

Proteins

large, complex macromolecules made of one or more long chains of amino acids linked together by peptide bonds

Amino Acids (AA)

an organic molecule that serves as the fundamental building block of proteins (protein’s monomers)

Amino Acids can either be…

1. Nonpolar - hydrocarbon side chains

1. Polar - hydroxyl groups

2. Charged - acidic or basic

Peptide Bonds

a strong covalent chemical bond that links amino acids together to form proteins and peptides via dehydration reaction

Polypeptides

a continuous, unbranched chain of amino acids linked together by peptide bonds (Not a protein yet; requires correct shape)

Protein Structure

1. Central (alpha) carbon

2. Hydrogen atom

3. Amino group (basic)

4. Carboxyl group (acidic)

5. R group - side chain - variable

Denature

process where a protein or DNA loses its natural three-dimensional shape and stops working —> protein unfolds

Caused by pH, salt concentration, high temperature

Protein Functions

1. Structure

2. Signaling

3. Enzymes

4. Defense

5. Transport