BIOL 1406-lecture 2-Chemical Context of Life

The Chemical Context of Life - Chapter 2 Notes

Matter
- Definition: Any object or material that occupies space.
- Measurement: Quantity of matter is measured by its mass.
Element
- Definition: A substance comprised of a single type of atom.
- Characteristics: Cannot be broken down into simpler substances by any means.
Compound
- Definition: Formed from a combination of two or more elements in a fixed ratio.
- Examples: H2O (water), NaCl (sodium chloride).

Major Elements
- Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N) make up 96% of living matter.
- Life requires about 25 elements in total.
Minor Elements
- Calcium (Ca), Phosphorus (P), Potassium (K), Sulfur (S), Sodium (Na), Chlorine (Cl), and Magnesium (Mg) make up the remaining 4% of an organism’s weight.
Trace Elements
- Definition: Elements required by the body in minute quantities.
- Examples: Zinc (Zn), Iron (Fe), Copper (Cu), Iodine (I).
- Importance: Essential for life; iodine deficiency can lead to goiter, which is reversible with iodine administration.

Atoms
- Definition: The smallest unit of an element.
- Composition: Consists of three types of subatomic particles:
  - Neutrons (n) - uncharged
  - Protons (p) - positively charged
  - Electrons (e) - negatively charged

Structure
- Neutrons and protons form the atomic nucleus.
- Electrons form a cloud around the nucleus.
- Mass: Neutron mass and proton mass are almost identical.

Definition
- An ion is formed when an atom loses or gains electrons, resulting in a net electrical charge.
Types of Ions
- Cation: Positively charged ion.
- Anion: Negatively charged ion.

Definition
- Isotopes are atoms of the same element that differ in the number of neutrons.
Radioactive Isotopes
- Characteristics: Decay spontaneously, giving off particles and energy.

Uses in Biological Research
- Dating fossils.
- Tracing atoms through metabolic processes.
- Diagnosing medical disorders, such as cancerous tissue.

Definition
- Valence electrons are those in the outermost shell (valence shell).
Chemical Behavior
- The chemical behavior of an atom is primarily determined by its valence electrons.
- Elements with a full valence shell are chemically inert.

Formation and Function
- Molecules depend on chemical bonding between atoms.
- Atoms with incomplete valence shells can share or transfer valence electrons, resulting in chemical bonds.

Definition
- A covalent bond is formed by the sharing of a pair of valence electrons between two atoms.

Molecule Definition
- A molecule consists of two or more atoms held together by covalent bonds.
Types of Covalent Bonds
- Single covalent bond: Sharing of one pair of valence electrons.
- Double covalent bond: Sharing of two pairs of valence electrons.

Definition
- Electronegativity is an atom’s attraction for the electrons in a covalent bond.
Behavior
- More electronegative atoms pull shared electrons more strongly.

Nonpolar Covalent Bond
- Atoms share electrons equally.
Polar Covalent Bond
- One atom is more electronegative, leading to unequal sharing and partial charges.

Definition
- Ionic bonds form when atoms strip electrons from their bonding partners, resulting in charged ions.

Definition
- A hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is attracted to another electronegative atom.

Importance of Shape
- A molecule’s shape is crucial to its function.
- Biological molecules interact based on molecular shape.

Definition
- Chemical reactions involve the making and breaking of chemical bonds.
Components
- Reactants: Starting molecules.
- Products: Final molecules.

Chemical Reaction
- Sunlight powers the conversion of carbon dioxide and water into glucose and oxygen.
- Reaction: 6 CO2 + 6 H2O → C6H12O6 + 6