Quarter 1 SOL Minor: Science

Unit Overview

• Biology: The study of life.

• Matter: Anything that takes up space (volume) and has mass. All things are made of matter.

• Living things: Must have water and carbon compounds. They are made up of chemical reactions.

Atoms and Elements

• Atoms: The basic building blocks of matter.

  • Subatomic Particles:

    • Protons: Positively charged (+), located in the nucleus.

    • Neutrons: No charge (0), located in the nucleus.

    • Electrons: Negatively charged (-), orbit the nucleus in a cloud, taking up most of the atom's volume.

  • Nucleus: Contains protons and neutrons, accounts for most of the atom's mass.

• Atomic Number: Number of protons in an atom. Defines the element.

• Mass Number: Sum of protons and neutrons in an atom.

• Neutral Atom: Number of electrons equals the number of protons, resulting in an overall charge of 0.

• Bohr Models: Represent atoms with a central nucleus and electrons in energy levels/shells.

  • Energy Levels:

    • Level 1: Max 2 electrons

    • Level 2: Max 8 electrons

    • Level 3: Max 18 electrons

    • Level 4: Max 32 electrons

  • Valence Electrons: Electrons in the outermost energy level. Determine an element's chemical properties. Maximum of 8 valence electrons.

• Elements: Pure substances consisting of atoms all having the same atomic number (same number of protons).

• Ions: Charged atoms.

  • Cation: Atom that has lost electrons, resulting in a positive charge.

  • Anion: Atom that has gained electrons, resulting in a negative charge.

• Isotopes: Atoms of the same element (same atomic number/protons) but with different mass numbers (different number of neutrons).

  • Identified by mass number (e.g., C-12, C-13, C-14).

  • Have the same chemical properties due to the same number of electrons.

  • Atomic Mass: Weighted average of the masses of an element's isotopes.

• Radioactive Isotopes: Isotopes with unstable nuclei that break down at a constant rate, giving off radiation.

  • Uses: Rock/fossil dating, cancer treatment, killing bacteria, biological tracers.

Periodic Table

• Organization: Elements classified based on chemical properties.

• Law of Periodicity: Properties of elements are a periodic function of their atomic number.

• Groups (Vertical Columns): Indicate the number of valence electrons.

• Periods (Horizontal Rows): Indicate the number of occupied energy levels.

• Trends:

  • Across a Period (Left to Right):

    • Atomic number increases.

    • Electronegativity increases (greater attraction between nucleus and valence electrons).

    • Atomic radius generally decreases.

  • Down a Group:

    • Atomic number increases.

    • Electronegativity decreases (increased distance between nucleus and valence electrons weakens attraction).

    • Atomic radius generally increases.

Chemical Bonds

• Valence electrons: Responsible for forming chemical bonds.

• Bonds between atoms (to form molecules):

  • Covalent Bonds: Electrons are shared between two atoms.

    • Strongest type of bond.

    • Orbitals overlap.

    • Single bond: Shares 2 electrons.

    • Double bond: Shares 4 electrons.

    • Triple bond: Shares 6 electrons.

    • Forms molecules: Smallest unit of compounds, multiple atoms chemically joined.

  • Ionic Bonds: Valence electrons are transferred between atoms.

    • Results in charged atoms (ions).

    • Oppositely charged ions attract each other (e.g., Na+ and Cl- form NaCl).

• Bonds between molecules:

  • Van der Waals Forces: Weak attractions between oppositely charged regions of nearby molecules. Not as strong as ionic or covalent bonds.

  • Hydrogen Bonds: Weak bonds formed between a partially positively charged hydrogen atom of one molecule and a partially negatively charged atom (like oxygen) of another molecule.

Water (H₂O)

• Abundance: Most abundant compound, 70% of Earth's surface, 60% of human body.

• Structure: One oxygen atom covalently bonded to two hydrogen atoms.

• Polarity:

  • Oxygen has stronger electronegativity than hydrogen.

  • Electrons are shared unequally, spending more time around oxygen.

  • Oxygen side becomes partially negative (δ-).

  • Hydrogen sides become partially positive (δ+).

  • A polar molecule has unevenly distributed charges.

• Hydrogen Bonding:

  • Weak bonds between water molecules due to polarity.

  • Partially positive hydrogen of one water molecule attracts the partially negative oxygen of another.

  • Each water molecule can form hydrogen bonds with up to 4 other water molecules.

  • Contributes to water's unique properties.

• Properties of Water:

  • Cohesion: Water molecules sticking to each other (e.g., forming droplets, surface tension).

    • Surface Tension: Cohesion creates an "invisible skin" on water's surface, allowing insects to walk on it.

  • Adhesion: Water molecules sticking to other polar molecules (e.g., water sticking to glass, forming a meniscus).

  • Capillary Action: Cohesion and adhesion allow water to rise in narrow tubes against gravity (e.g., water transport in plants).

  • Expansion upon Freezing: Ice is less dense than liquid water, so it floats.

    • Prevents entire bodies of water from freezing solid, insulating aquatic life.

  • High Specific Heat: Water absorbs and releases large amounts of heat with only slight changes in its own temperature.

    • Takes a long time to heat up and cool down.

  • High Heat of Vaporization: A large amount of energy is required to change liquid water into water vapor.

    • Evaporation of sweat cools the body.

  • Universal Solvent: Dissolves many polar substances by forming hydration shells around them. Does not dissolve nonpolar substances.

Mixtures

• Mixture: Two or more substances physically mixed but not chemically combined.

  • Solution: Homogeneous mixture where one substance (solute) is dissolved evenly in another (solvent). Water is the greatest solvent.

  • Suspension: Mixture where particles are not dissolved but remain suspended (e.g., sand in water, blood).

Acids, Bases, and pH

• pH: Measure of the concentration of H+ ions in a solution.

• pH Scale: Ranges from 1 to 14.

  • Acids (1-6): Form H+ ions in solution, have more H+ ions and fewer OH- ions.

  • Neutral (7): Equal H+ and OH- ions.

  • Bases (8-14): Form OH- ions in solution, have fewer H+ ions and more OH- ions.

• Logarithmic Scale: Each unit change on the pH scale represents a 10-fold change in H+ ion concentration.

  • pH 4 has 10 times more H+ than pH 5.

  • pH 3 has 100 times more H+ than pH 5.

• Buffers: Weak acids or bases that help maintain homeostasis by resisting sharp, sudden changes in pH.

Organic Chemistry & Macromolecules

• Organic Molecules: Contain carbon, which can form four strong covalent bonds. Energy is often stored in these bonds.

• Macromolecules: Large organic molecules essential for life.

  • Monomers: Simple units that make up macromolecules.

  • Polymers: Large molecules made of many repeating monomer units.

  • Dehydration Synthesis: Process that joins monomers to form polymers, releasing water.

  • Hydrolysis: Process that breaks down polymers into monomers, consuming water.

Types of Macromolecules

1. Carbohydrates:

   • Monomer: Monosaccharide (simple sugars).

   • Functions:

     • Monosaccharides: Quick energy.

     • Polysaccharides: Energy storage or structural support.

   • Polysaccharides for Energy Storage: Starch (plants), Glycogen (animals).

   • Polysaccharides for Structure: Cellulose (plant cell walls), Chitin (fungi cell walls, insect exoskeletons).

   • Main source of energy for living things.

2. Lipids:

   • "Monomers": Glycerol and fatty acids (e.g., in triglycerides).

   • Functions: Long-term energy storage.

3. Nucleic Acids:

   • Monomer: Nucleotide.

   • Nucleotide Components: 5-carbon sugar, a base, and a phosphate group.

   • Functions: Genetics (hereditary information), instructions for making proteins.

4. Proteins:

   • Monomer: Amino acid.

   • Functions: Catalysts (enzymes), structural support (hair), immunity (antibodies), transport, signaling.

   • Structure is crucial for function.

   • Levels of Protein Structure:

     • Primary Structure: Linear chain of amino acids in a specific order, linked by peptide bonds.

     • Secondary Structure: Local folding patterns (alpha-helix or beta-pleated sheet), stabilized by hydrogen bonds in the backbone.

     • Tertiary Structure: Overall three-dimensional globular shape, stabilized by various bonds (hydrogen, ionic, covalent/disulfide bridges, van der Waals). Polar amino acids are typically on the outside (near water), nonpolar on the inside.

     • Quaternary Structure: Two or more polypeptide chains (subunits) interacting to form a functional protein.

Enzymes

• Definition: Biological catalysts, almost always proteins.

• Function: Increase the rate of chemical reactions by decreasing the activation energy needed to start the reaction.

• Active Site: Region on the enzyme where reactants (called substrates) bind.

• Enzyme Specificity: Enzymes are specific to their substrates.

• Factors Affecting Enzyme Function:

  • pH: Optimal pH range for each enzyme. Deviations (too high or too low) interfere with ionic bonds in the tertiary structure, causing the enzyme to unfold or denature, losing function.

  • Temperature:

    • Above optimal temperature: Increased molecular motion disrupts hydrogen bonds in the tertiary structure, causing denaturation and loss of function.

    • Below optimal temperature: Decreased molecular motion slows down the reaction rate, but usually does not denature the enzyme.

  • Concentration of substrate and product: Also affect reaction rate.

• Naming Convention: Enzymes often end in "-ase" (e.g., protease breaks down proteins).

Chemical Reactions

• Reactants: Starting materials in a chemical reaction.

• Products: Substances formed as a result of a chemical reaction.

• Activation Energy: Energy needed to get a reaction started.

• Exergonic Reaction: Releases energy. Products have less energy than reactants. May start on its own.

• Endergonic Reaction: Absorbs energy. Products have more energy than reactants. Requires energy input to start.

Important Facts to Memorize

• Biology is the study of life.

• Matter takes up space and has mass.

• Protons (+), Neutrons (0), Electrons (-).

• Atomic Number = # Protons.

• Mass Number = # Protons + # Neutrons.

• Neutral Atom: # Protons = # Electrons.

• Valence electrons determine chemical properties.

• Ions are charged atoms (Cation: lost e-, Anion: gained e-).

• Isotopes: Same protons, different neutrons.

• Covalent bonds share electrons (strongest).

• Ionic bonds transfer electrons.

• Hydrogen bonds are weak intermolecular attractions.

• Water is a polar molecule.

• Water's properties: Cohesion, Adhesion, Capillary Action, High Specific Heat, High Heat of Vaporization, Ice floats.

• pH scale: 1-6 Acid, 7 Neutral, 8-14 Base.

• Buffers maintain pH.

• Organic molecules contain Carbon.

• Monomers build Polymers (Dehydration Synthesis builds, Hydrolysis breaks).

• Carbohydrate monomer: Monosaccharide (quick energy, storage, structure).

• Lipid "monomers": Glycerol + Fatty Acids (long-term energy).

• Nucleic Acid monomer: Nucleotide (genetics, protein instructions).

• Protein monomer: Amino Acid (enzymes, structure, immunity).

• Enzymes are proteins that lower activation energy.

• Enzyme function depends on shape (active site).

• pH and temperature affect enzyme activity (denaturation).

• Primary protein structure: Amino acid sequence (peptide bonds).

• Secondary protein structure: Alpha-helix/Beta-pleated sheet (hydrogen bonds).

• Tertiary protein structure: 3D shape (various bonds).

• Quaternary protein structure: Multiple polypeptide chains.

• Exergonic reactions release energy; Endergonic reactions absorb energy.