Chemical Level of Organization
Lesson focus - Describe how matter is organized, distinguish the types of chemical bonds, classify chemical reactions and energy forms, identify the building blocks and functions of the four macromolecules, and explain how ATP is produced through cellular respiration.
How Matter is Organized
- Element - a building block of matter that cannot be broken down into simpler forms
- Chemical symbol - one or two letters assigned to an element
Major Elements
The four major elements of the human body's mass are:
- Oxygen (O)
- Carbon (C)
- Hydrogen (H)
- Nitrogen (N)
Structure of an Atom
An atom is the smallest unit of matter that retains the properties and characteristics of the element.
| Particle | Location | Charge |
|---|
| Proton | Nucleus | Positive |
| Neutron | Nucleus | Uncharged |
| Electron | Orbits outside the nucleus | Negative |
| Term | Definition |
|---|
| Atomic number | The number of protons in the nucleus |
| Mass number (atomic weight / atomic mass) | The sum of protons and neutrons; the average mass of all occurring isotopes, measured in Daltons |
| Isotope | Atoms of an element with a different number of neutrons but the same number of protons |
| Dalton | The standard unit for measuring the mass of atoms and subatomic particles |
Ions, Molecules, and Compounds
| Term | Definition |
|---|
| Ion | A particle with a positive or negative charge because it has unequal numbers of protons and electrons |
| Cation | An ion with a positive charge |
| Anion | An ion with a negative charge |
| Ionization | The process of giving up or gaining electrons |
| Molecule | Two or more atoms sharing electrons |
| Molecular formula | Indicates the elements and the number of atoms of each element in a molecule |
| Compound | A substance that contains atoms of two or more different elements |
All compounds are molecules, but not all molecules are compounds.
Free Radicals
A free radical is an atom or group of atoms with an unpaired electron in the outermost shell.
- Causes instability
- Highly reactive
- Destructive to nearby molecules
- Causes: exposure to excessive UV radiation, x-rays, cigarettes, air pollutants, and superoxides
- Can contribute to cancers, atherosclerosis, and Alzheimer's
Antioxidants can slow the pace of damage from free radicals.
Chemical Bonds
Chemical bonds are the forces that hold together the atoms of a molecule.
Octet Rule
- Elements bind in an attempt to fill the valence shell (outer shell) for stability
- Chemicals come together to form bonds with one another
- This makes reactions predictable
Types of Bonds
| Bond | Description |
|---|
| Ionic | Positive and negative ions are attracted to each other; the ionic bond takes the electron |
| Covalent | Two or more atoms share electrons rather than gaining or losing them |
| Hydrogen | Forms when a partially positive hydrogen atom attracts a partially negative atom |
Ionic Bonds
- Formed between cations (+) and anions (−)
- An electrolyte is an ionic compound that breaks into positive and negative ions in a solution and is able to conduct an electric current
Covalent Bonds
| Type | Description |
|---|
| Polar covalent | Sharing of electrons is unequal, resulting in a partial charge |
| Nonpolar covalent | Sharing is 100% equal |
Hydrogen Bonds
- The cohesion of water molecules creates surface tension; water is more attracted to itself than to air
- Surface tension is a measure of the difficulty of stretching or breaking the surface of a liquid
- A thin watery fluid coats the air sacs of the lungs; each inhalation must have enough force to overcome the opposing effect of surface tension as the air sacs stretch and enlarge (compliance)
Chemical Reactions
Chemical reactions occur when new bonds form or old bonds break between atoms, based on the interactions of valence electrons.
| Term | Definition |
|---|
| Reactants | The starting substances |
| Products | The ending substances |
| Metabolism | All chemical reactions occurring in the body |
Types of Reactions
| Reaction | Description | Example |
|---|
| Decomposition | A large molecule breaks down into two or more smaller ones | H₂O → H + OH |
| Synthesis | Two or more molecules combine to form a larger one | H + OH → H₂O |
| Exchange | Two molecules exchange atoms or groups of atoms | HCl + NaOH → NaCl + H₂O |
| Reversible | Can proceed in either direction under different circumstances | — |
A reversible reaction is dictated by the law of mass action: if one side of the equation has a greater quantity of molecules, the reaction will proceed toward the other side.
Dehydration Synthesis and Hydrolysis
| Process | Description |
|---|
| Dehydration synthesis | Removes a hydroxyl group and an H⁺, which releases H₂O (water comes out) |
| Hydration synthesis (hydrolysis) | A water molecule ionizes into OH⁻ and H⁺, which connect to the individual monomers, splitting the bond apart (water goes in) |
Rate of Reactions
- Concentration of reactants
- Temperature
- Catalysts (enzymes)
Forms of Energy
| Term | Definition |
|---|
| Exergonic reaction | Releases energy (e.g., glucose) |
| Endergonic reaction | Absorbs energy |
| Catalysts | Compounds that speed up chemical reactions by lowering the activation energy required (e.g., enzymes) |
Macromolecules
Carbon serves as the building block for several nutrients useful to the human body.
| Term | Definition |
|---|
| Monomer | Small "building blocks" or functional groups |
| Polymer | Two or more monomers |
| Isomer | Molecules that have the same molecular formula but different structures |
| Macromolecule | Generally a polymer (e.g., carbohydrates, lipids, proteins, nucleic acids) |
Carbohydrates
- The primary source of chemical/cellular energy
- Include sugars, glycogen, starches, and cellulose
- Glycolysis is the splitting of sugars
Lipids / Fatty Acids
- A secondary source of energy; not as readily broken down as carbohydrates; used in times of stress
- Lipolysis is the process of reversing lipid structures back to fatty acids and glycerol to form glucose
- Hydrophobic - insoluble in water
| Lipid | Description |
|---|
| Fatty acids | The simplest of all lipids; used to synthesize triglycerides and phospholipids |
| Triglycerides | Three fatty acid chains bonded to glycerol |
| Fat | The solid (room temperature) form of triglycerides |
| Oils | The liquid (room temperature) form of triglycerides |
Other Lipids
| Lipid | Role |
|---|
| Eicosanoids | Signaling molecules especially involved in the inflammatory response (e.g., prostaglandins and leukotrienes) |
| Steroids | Can be used to block the effects of inflammatory responses |
Proteins
- Responsible for the structure of body tissues and composed of amino acids
| Term | Definition |
|---|
| Enzymes | Proteins that speed up biochemical reactions (catalysts) |
| Substrate | The reactant molecules on which the enzyme acts |
| Active site | The area of the enzyme that catalyzes the reaction |
| Model | Description |
|---|
| Lock and key | A specific substrate fits with a specific active site |
| Induced fit | The active site fits around the substrate |
Nucleic Acids
DNA (Deoxyribonucleic Acid)
- Forms inherited information (the genetic code) inside human cells
- Double stranded (a double helix)
- Replicates by splitting and transcribing the corresponding nucleotide
| Term | Definition |
|---|
| Mutation | Any change in the base sequence of a DNA strand; can lead to death of the cell, cancer, or genetic defects in future generations |
| Chromosome | Thin, threadlike structures made of protein and DNA that carry hereditary information from cell to cell (contains genes) |
| Genes | The basic units of heredity |
RNA (Ribonucleic Acid)
- Single-stranded genetic information
- Examples: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA)
Adenosine Triphosphate (ATP)
ATP is the energy currency of living organisms. Cellular respiration is the oxidation of glucose to produce ATP.
Phase 1: Glycolysis
- One glucose molecule is oxidized and two molecules of pyruvic acid are produced
- Occurs within the cytoplasm
- Anaerobic - glucose is broken down in the absence of O₂, producing 4 ATP
Phase 2: Krebs Cycle
- The second stage of cellular respiration
- Acetyl-CoA breaks pyruvic acid into NADH⁺, H⁺, and FADH₂
- Other byproducts are CO₂ and H₂O
- Aerobic - in the presence of O₂, producing 36–38 ATP
- Occurs in the cristae of the mitochondria
Review
- How matter is organized
- Chemical bonds
- Chemical reactions
- Carbohydrates
- Lipids
- Proteins
- Nucleic acids
- Adenosine triphosphate