Chemical Basis of Life

Elements vs. Compounds

Elements → cannot be broken down, e.g. Na, Cl

Compounds → two or more elements (e.g. NaCl), differing characteristics (depends on what elements are bound together)

Essential Elements of Life (what are they)

Essential elements → carbon, hydrogen, oxygen, and nitrogen

• make up 96% of living matter

Other elements make up the remaining 4% → Ca, P, K

Trace Elements (what they are and their characteristics)

• minute amounts of elements but are essential (e.g. Fe, Mg, I, Cu, Zn)

• Many act as cofactors for enzymes (“on-off” switches)

Atoms (what they are and what they’re composed of)

The smallest unit of matter that retain properties and characteristics of an element

• are composed of protons, neutrons, and electrons

What is the atomic #, the mass #, and the atomic mass?

Atomic # → number of protons in the nucleus of an atom

Mass # → number of protons and neutrons in an atom (changes with isotopes → adding neutrons)

Atomic mass → average mass of all its naturally occurring isotopes

Isotopes

Have the same # of protons but a different number fo neutrons

Radioactive isotopes → give off particles and energy

• can be used to identify cancerous cells

Ions

Created by electron transfer between two atoms

• anion → negatively charged (extra electrons)

• Cation → positively charged (fewer electrons)

  • Anions and cations attract each other and form ionic compounds

Electrolytes

Ions

Play an important role in nerve and muscle physiology

• sodium → Na+

• Potassium → K+

• Calcium → Ca2+

• Hydrogen → H+

• Chloride → Cl-

Molecule

2 or more atoms sharing electrons (has to be the same element → e.g. O2)

Chemical bonds (what it is and what determines the bond)

Occurs when atoms are held together by forces of attraction

• the # of electrons in the outer/valence shell determines the likelihood that an atom will form a chemical bond with another atom

  • Atom is more stable with full shells

Covalent Bonds

Sharing of a pair of valence electrons → e.g. molecules

Strongest bond

Can have single, double, or triple bonds

Inorganic vs organic compounds

Inorganic → usually lack carbon and are simple molecules

• water is the most important and abundant inorganic compound in all living things

Organic → always contain H and C, usually have O, and always have covalent bonds

Organic Molecules Characteristics

• always contain carbon

• Many carbons can combine in a variety of shapes

• Carbon compounds do not dissolve easily in water (dont break down their bonds)

• Carbon compounds are a good source of energy

Carbon chains

• basis of most organic molecules

• Vary in length and shape

Hydrocarbons

Molecules of only carbon and hydrogen

Isomers

Have the same molecular formula but different structures and properties

Functional groups characteristics

Chemically reactive group of atoms within an organic molecule

• gives molecule its distinctive chemical properties

Functional groups seen with alcohols, ketones, and amino acids

Alcohols → OH

Ketones → double bonded CO

Amino Acids → NH2

Ionic bonds

• weaker than covalent

• Donation of electrons

• Still have attraction to each other

Free Radicals

An atom with an unpaired electron

• unstable

• Looking to “steal” an electron from another molecule

  • Causes that molecule to destabilize

  • Causes cell injury and cell disease

Anti-Oxidants

Reduce free radicals

• can donate an electron without destabilizing

• Can “remove free radicals”

  • E.g. Vitamin E, C, Beta-carotene

Polar Covalent Bond

Share the electron unequally

• creates a positive force on one side and a negative force on the other

Hydrogen Bonds

2 other atoms associate with a hydrogen atom

Very weak bond

Chemical Reactions

Occur when new bonds are formed or old bonds are broken

Reactants → starting substances

Products → ending substances

(Metabolism is a chemical reaction)

Forms of Energy

Energy is the capacity to do work:

• Potential energy → stored energy (energy used for work)

• Kinetic energy → energy of movement

• Chemical energy → bond energy (e.g. energy released after breaking a bond)

Energies transfer into each other → potential into chemical into kinetic

Exergonic vs Endergonic reactions

Exergonic → has a net release of free energy and is spontaneous

Endergonic → absorbs free energy from its surroundings and is non spontaneous

Catalysts

Lower the required activation energy → makes reactions more likely to occur

• enzymes are protein catalysts → needed for most body reactions

Law of Mass Action

If reactants > products → reaction goes forward

If reactants < products → reaction can go backwards

Synthesis

Aka anabolism → usually Endergonic

Chemical reaction

Formation of a molecule (e.g. glucose)

Decomposition

Aka catabolic

Exergonic

Chemical reaction

Breaks a molecule into smaller fragments (e.g. glucose metabolism)

Exchange, Reversible, and Oxidation-Reduction Chemical Reactions

Exchange → part of reactant becomes part of product

Reversible → reactions occur in both directions (depends on amount of reactants and products)

Oxidation-Reduction → removal or addition of electrons

Anabolic vs Catabolic pathways

Anabolic → build molecules from simpler ones, consume energy

Catabolic → break down complex molecules, release energy

Kinds of work in a cell

Mechanical → movement

Transport → moving ions and particles

Chemical → reactions

(All powered by ATP)