[1] Biological Molecules

What is biological diversity?

The variety of life on Earth, including all the different plants, animals and microorganisms, the genes and molecules they contain, and the ecosystems they form on land and in water

What are the key molecules required to build structures that enable organisms to function?

Carbohydrates, proteins, lipids, nucleic acids and water

What are biological molecules?

Particular groups of chemicals found in all living organisms

What are the three main ways atoms combine with each other?

Covalent bonding, ionic bonding and hydrogen bonding

How does the strength of ionic bonds compare with covalent bonds?

Ionic bonds are weaker than covalent bonds

What is hydrogen bonding?

A weak electrostatic attraction formed between oppositely charged regions of polar molecules

What causes a molecule to be polar?

An uneven distribution of electrons creates regions with opposite charges

Why are hydrogen bonds important in biology?

Although individual hydrogen bonds are weak, collectively they produce important forces that affect physical properties, such as those of water

What are covalent bonds important for in biology?

They are key to the structure of carbon-based organic molecules such as DNA and proteins and are also found in smaller inorganic molecules such as H2O, CO2 and O2

How does the number of shared electrons affect covalent bond strength?

The more electrons shared between two atoms, the stronger the covalent bond

What two types can covalent bonds be?

Polar or non-polar

What is a cation?

A positive ion formed by losing electrons

What is an anion?

A negative ion formed by gaining electrons

What type of molecule is required for hydrogen bonding?

A polar molecule

Between what atoms can hydrogen bonds form?

Between a hydrogen atom and a highly electronegative atom such as oxygen or nitrogen

How are water molecules held together?

By hydrogen bonding

How is the secondary structure of proteins maintained?

By hydrogen bonding, including the alpha-helix and beta-sheet structures

How is the tertiary structure of proteins maintained?

Hydrogen bonding contributes to maintaining the tertiary structure of proteins

How is the DNA double helix held together?

By hydrogen bonding among the bases of its nucleotides

How does RNA form coils onto itself?

The coiling of an RNA chain onto itself takes place via hydrogen bonding

What is a monomer?

A small molecule that can be linked to other monomers to form a larger molecule called a polymer

What is a polymer?

A larger molecule formed by linking together monomers

What are monomers usually based on?

Carbon

What are examples of monomers?

Nucleic acids, amino acids, alpha and beta glucose, fructose, fatty acids and glycerol

What are isomers?

Molecules with the same molecular formula but a different molecular arrangement

What are examples of polymers?

Carbohydrates, proteins and nucleic acids

What is a condensation reaction?

A reaction in which monomers are joined to form a larger molecule and a molecule of water is produced

What happens when a new monomer is attached during polymer formation?

A molecule of water is formed

Why is it called a condensation reaction?

Because water is produced as monomers are joined together

How are two monomers joined in a condensation reaction?

An OH group is removed from one monomer and an H is removed from the other

Give an example of a condensation reaction in biology.

The formation of the polysaccharide starch from the monosaccharide glucose

What is a hydrolysis reaction?

A reaction in which polymers are broken down into monomers by the addition of water

What happens to water during hydrolysis?

Water is used to break the bonds linking the subunits of a polymer

What does hydrolysis mean?

Hydro means water and lysis means splitting

Give an example of hydrolysis.

The polysaccharide starch can be hydrolysed into the monosaccharide glucose

How does hydrolysis break a bond between monomers?

A water molecule is added

How many particles are in one mole?

6.022 × 10^23 particles

What is the relationship between condensation and polymer formation?

Condensation reactions join monomers together to form polymers while producing water

What is the relationship between hydrolysis and polymer breakdown?

Hydrolysis uses water to break polymers down into their monomers

Definition of a monosaccharide

A monomer from which large carbohydrates are made

describe the test for lipids (3)

• add ethanol and shake to dissolve

• add distilled water

• if lipid is present a white emulsion will form

describe the test for proteins (2)

• biuret test

• should turn from blue to lilac if proteins are present