Topic 1:Chemicals of life

1. Molecules and Atoms2. Water3. Carbon and other elements

1. Atoms and Molecules

1.1 Elements and Compounds1.2 Elements of Life 1.3 Chemical and Physical Bonds1.4 Importance of Carbon, Nitrogen, and

Water

Organisms are composed of matter.

Matter is made up of elements.

Elements combine to form compounds.

anything that has mass and takes up space

cannot be broken down to other substances by chemical reactions

1.1 Elements and Compounds

Sodium Chloride Sodium Chloride

+

compounds have characteristics different from those of their elements

Emergent Properties

Essential Elements(elements required by living organisms)

macroelements• C, H, O, N• 96% of living matter

microelements• Na, K, Ca, Mg, P, S, Cl• 4% of living matter

trace elements• Fe, I, Cu, Mn, etc.• required in minute (tiny) amounts

1.2 Elements of Life

the properties of elements depend on the chemical characteristics of their atoms

chemical characteristics of atoms depend on the arrangement of electrons in electron shells (electron configuration)

Electronegativity• the attraction of an atom for electrons from other atoms• important property of elements of life

Bonds

Chemical Bonds

Physical Bonds

form between elements form between molecules

Covalent Ionic Dipole Interactions Van der Waals

1.3 Chemical and Physical Bonds

Chemical Bonds

Covalent BondsIonic

Bondselements of similar electronegativity share pairs of electrons

elements of very different electronegativity transfer electrons, creating ions (anions and cations)

The properties of a compound (solubility, melting point, etc.) depend on the type of bonding involved.

Covalent bonds are the most important in biological molecules because they allow for a variety of properties

they can be single, double, or triple bonds

H Hsingle covalent bond

O Odouble covalent bond

N Ntriple covalent bond

Covalent bonds can be classified as non-polar or polar

create dipoles - molecules with partial negative ( -) and positive ( +) charges at 𝛿 𝛿opposite ends

non-polar covalent bonds(elements of the same or almost the

same electronegativity)

ethane

polar covalent bonds(elements of slightly different

electronegativity)

water

weak attractions between molecules (not the result of chemical reactions)

Physical Bonds

There are two major types of Physical Bonds

Dipole InteractionsAttraction between opposite poles

of polar molecules (dipoles)

Van der Waals Interactions

(aka London Dispersion Forces) Caused by momentary asymmetric

distribution of moving electrons in large non-polar molecules.

– +

+

Water(H2O)

Ammonia(NH3)

OH

H

+

–

N

HH H

+ d+

Hydrogen Bonds

• the most important dipole interaction in biology

• forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom from a different molecule

bonds determine the shape of the molecule

Shape of a Molecule

• determines the biological function• Differently-shaped molecules have different functions• similar shape molecules can mimic the function of another

molecule (morphine/endorphins)

• Carbon is the element most widely used in biomolecules due to its special properties.

• Organisms can obtain carbon in two ways:

inorganic carbon (CO2)autotrophs

organic carbon (glucose)heterotrophs

1.4 Importance of C, N, and H2O

• Nitrogen is also essential to living organisms, making part of proteins and nucleic acids.

• Organisms can obtain nitrogen in two ways:

inorganic nitrogen (N2)atmosphere – microorganisms, fungi

minerals – nitrates for plants

organic nitrogen from other organisms

Water

• fundamental to life• organisms are composed mostly of water (65% in humans, 99% in

jellyfish)• most chemical reactions in organisms take place in water (wet

chemistry)