Chemical Basis of Life

What is chemistry?

The science of the structure and interactions of matter.

What is matter?

Anything that takes up space and has mass (touchable).

All forms of matter are composed of chemical elements.

What is mass?

The amount of matter in a substance.

The weight of an object is determined by its mass.

What is an important characteristic of elements?

Elements cannot be broken down

What is a compound?

The combination of 2 or more different elements.

Differing characteristics from their elements.

How many different elements are found in the body?

27 different elements.

Which essential elements make up 96% of living matter?

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Nitrogen (N)

What are some essential elements that make up 4% of living matter?

• Calcium (Ca)

• Phosphorus (P)

• Potassium (K)

What are trace elements?

Elements that are found in low amounts in the body but are still essential.

• Many act as cofactors for enzymes; responsible for enzyme function.

What are some essential trace elements?

• Iron (Fe)

• Magnesium (Mg)

• Iodine (I)

• Copper (Cu)

• Zinc (Zn)

What is iron needed for?

Binding site for oxygen in the RBCs.

What is iodine needed for?

Production of thyroid hormone (bind for formation).

What is an atom?

The smallest units of matter that retain the properties/characteristics of an element.

What are atoms composed of?

• Nucleus

  • Protons (positive charge)

  • Neutrons (no charge)

• Orbital

  • Electrons (negative charge)

What is the atomic number?

The number of protons in the nucleus of an atom.

What is the mass number?

The number of protons and neutrons in an atom

• Can change with isotopes (addition of a neutron)

What is the atomic mass?

The average mass of all naturally occurring isotopes in the atom.

What are radioactive isotopes?

Atoms with the same number of protons but a different number of neutrons

• Give off particles/energy

How can a molecule become stable?

Molecules are more stable if their electron shells are full

• First shell (inner) - 2e-

• Second shell (+) - 8e-

Electrons can be passed or shared between atoms

How are ions created?

Created by electron transfer between two atoms; an atom that has lost or gained an electron

• Anion (negative charge) - gains electrons

  • e.g. Cl - more likely to accept e- and become negative

• Cation (positive charge) - loses electrons

  • e.g. Na, K, Ca - more likely to donate e- and become positive

Anions and cations attract each other

What are some properties of ionic compounds?

• May form crystal-like structures (e.g. salts)

What are electrolytes?

Electrolyes (or ions) have a charge - positive or negative

• Important role in nerve/muscle physiology

  • Sodium (Na+)

  • Potassium (K+)

  • Calcium (Ca2+)

  • Hydrogen (H+)

  • Chloride (Cl-)

How are molecules formed?

Through the sharing of electrons between 2 or more atoms

e.g. O2, H2

What is a compound?

A substance that can be broken down into 2 or more different elements

e.g. NaCl

How does a chemical bond occur?

When atoms are held together by forces of attraction; vary depending on the strength of the attraction

• Based on the number of electrons in the valence shell - the e- number determines the likelihood that an atom will form a chemical bond with another atom

What is a covalent bond?

Occurs when atoms share their valence electrons- the strongest bond type

• Single, double, triple bonds

Compatible with many different elements; compatibility is dependent on the number of valence electrons

What are inorganic compounds?

Simple molecules that do not contain carbon atoms

• Water is the most important of the inorganic compounds

What are organic compounds?

In the body, organic compounds always contain hydrogen (H) and carbon (C); they usually contain oxygen (O)

• Always have covalent bonds

What are some characteristics of carbon in organic molecules?

• Has 4 valence electrons; can form 4 covalent bonds

• Forms a wide range of molecules in a variety of shapes

• Compounds do not dissolve easily in water; bonds don’t break down

• Compounds are a good source of energy

What is a carbon skeleton?

Carbon chains that form the basis of most organic molecules

• Vary in length and shape

What are hydrocarbons?

Molecules containing only carbon and hydrogen

What are isomers?

An isomer has the same molecular formula as another molecule, but has different structures and properties

e.g.

What are the functional groups of an organic molecule?

The chemically reactive group of atoms in an organic molecule; give it its distinctive chemical properties

What are 6 important functional groups of organic compounds?

• Hydroxyl - OH

• Carbonyl - C=O

• Carboxyl - O=C-OH

• Amino - H-N-H

• Sulfhydryl - SH

• Phosphate - O-, OH- P =O, -OH

What are free radicals?

An unstable atom with an unpaired electron; looking to take an electron from another molecule (oxidation)

• Causes that molecule to destabilize, leading to cell injury/disease

e.g. Waste products from metabolism, UV light, nicotine, alcohol, fried foods

What is the free radical theory of aging?

Free radicals build up and damage cell membranes, leading to disease and cell death

• Apoptosis (intentional cell death by the body) is a cause of aging

How can we combat free radical aging?

With antioxidants

• Can donate electrons without destabilizing themselves

• Able to remove free radicals

e.g. Vitamin E, Vitamin C, Beta-carotene (found in berries, carrots)

What are polar covalent bonds?

Occurs when electrons are shared unequally

• One atom pulls the shared electrons closer to itself than the other atom

  • The more electronegative atom attracts the shared electrons

• This leads to one side having a small positive charge and the other side having a small negative charge (partial charges)

What is a hydrogen bond?

When a partially positive hydrogen atom bonds with a strongly electronegative atom

• Only occurs with oxygen, nitrogen, fluorine

What is a dipole bond?

When the positive partial charge of an atom on one molecule attracts the partial negative charge of a lone pair of electrons on another molecule

How does a chemical reaction occur?

When new bonds are formed, or old bonds are broken

• Reactants - starting substances

• Products - ending substances

e.g. Metabolism

What are chemical reactions like in the body?

Many body reactions are reversible

• If more reactants, the reaction moves forward

• If more products, the reaction reverses

What is energy, and what are the kinds of energy?

The capacity to do work

• Potential energy - stored energy

• Kinetic energy - energy of movement

• Chemical energy - bond energy

What is the law of conservation of energy?

Energy and mass can neither be created nor destroyed during a reaction

What are the types of energy transfer?

• Exergonic reaction - gives off energy

  • Net release of free energy; spontaneous

• Endergonic reaction - takes in energy

  • Absorbs free energy from surroundings; non-spontaneous

• Activation energy - the minimum amount of energy needed to start a chemical reaction

What is the purpose of catalysts?

Responsible for lowering the activation energy, making reactions more likely to occur

What are enzymes?

Protein catalysts, needed for most bodily reactions

What is the law of mass action?

• If we have more reactants than products - reaction goes forward

• If we have more products than reactants - reaction can go backwards

What is hydrolysis?

Example of a chemical reaction where water breaks 1 or more chemical bonds in a compound

What is synthesis (anabolism)?

The formation of a molecule

e.g. Glycogen

What is decomposition (catabolic reaction)?

The break down of a molecule into smaller fragments

e.g. Glucose metabolism

What is an exchange chemical reaction?

When part of the reactant becomes part of the product

What is a reversible chemical reaction?

Reactions that occur in both directions

What is an oxidation-reduction reaction?

Occurs with the removal or addition of electrons

What is an anabolic pathway?

Occurs when molecules are built from simpler ones

• Consumes energy

What is a catabolic pathway?

The breakdown of complex molecules

• Releases energy

What is oxidation and reduction?

• Oxidation - loss of electrons

• Reduction - gain of electrons

Reducing agents cause reduction in another substance; the reducing agent itself gets oxidized (and vice versa)

What are the 3 types of work a cell performs?

• Mechanical work

  • e.g. Movement

• Transport

  • e.g. Moving ions and particles

• Chemical (reactions)

All powered by ATP

What is ATP hydrolysis?

Removes the energy from ATP

• Can be coupled with other reactions that require energy

What is the regeneration of ATP?

Occurs on a catabolic pathway; drives the regeneration of ATP from ADP and phosphate

What are some characteristics of a living cell?

• Thousands of reactions occurring

• Can convert energy in many ways (e.g. bioluminescence)