General Biology Midterm 1 Review: Matter, Chemical Bonds, Water, Macromolecules, and Cell Types

Lecture 2: Intro to Matter & Interactions

Element vs. Atom

An atom is the smallest unit of matter, consisting of protons (+ charge), neutrons (no charge), and electrons (- charge). The element is a pure substance made up of only one type of atom. The number of protons in the nucleus determines the identity of the element.

• Valence electrons: Electrons in the outermost shell; determine bonding capacity and chemical behavior.

• Periodic Table: Organizes elements by atomic number and properties.

Electronegativity

Electronegativity is the ability of an atom to attract electrons in a chemical bond. Atoms with higher electronegativity (e.g., O, N) attract electrons more strongly than those with lower electronegativity (e.g., H).

• Electronegativity increases from left to right and bottom to top of the periodic table.

• Electronegativity differences determine the type of bond formed between atoms.

Practice Questions

• What particles determine the identity of an element? Proton

• Electronegativity trend: Increases from left to right and bottom to top of the table.

Lecture 3: Chemical Bonds & Water and Life

Valence Electrons

Valence electrons are crucial for chemical bonding. Atoms are most stable when their valence shell is full or when electrons are paired. Unpaired electrons can be shared, lost, or gained, leading to bond formation.

Bond Interactions

• Covalent Bonds: Form when two atoms share electrons in their valence shells.

  • Single covalent bond: two electrons shared.

  • Double covalent bond: four electrons shared.

• Ionic Bonds: Formed by electron transfer between atoms with large electronegativity differences. Results in charged ions (e.g., Na+ and Cl- forming NaCl).

• Hydrogen Bonds: Weak bonds formed when a hydrogen atom covalently bonded to an electronegative atom is attracted to another electronegative atom (usually O or N).

  • Requires a hydrogen with partial positive charge and a terminal atom with partial negative charge.

• Van der Waals Interactions: Weak attractions due to temporary charge differences when electrons are unevenly distributed.

Bond Type Comparison Table

Bond Type	Mechanism	Strength	Example
Covalent	Electron sharing	Strong	H2O, O2
Ionic	Electron transfer	Strong (in solid)	NaCl
Hydrogen	Electrostatic attraction	Weak	Between water molecules
Van der Waals	Temporary charge	Weak	Gecko's toe hairs

Lecture 4: Carbon, Water, Polarity and Solubility

Unique Properties of Water

• Polarity: Water is a polar molecule due to unequal sharing of electrons between O and H.

• Hydrogen bonding: Water molecules form hydrogen bonds, leading to high cohesion, adhesion, and surface tension.

• Universal solvent: Water dissolves many substances due to its polarity.

• Chemical reactivity: Water participates in many chemical reactions.

Water: The Solvent of Life

• Solvent: Dissolving agent in a solution.

• Solute: Substance dissolved in the solvent.

• Solution: Homogeneous mixture of solvent and solute.

• Aqueous solution: Water is the solvent.

Hydrophilic vs Hydrophobic

• Hydrophilic: Ionic and polar covalent compounds (e.g., salts, molecules with partial charges).

• Hydrophobic: Nonpolar covalent compounds (e.g., oils, fats).

• Hydration shell: Sphere of water molecules surrounding dissolved ions.

Hydrocarbons

• Molecules made only of carbon and hydrogen.

• Major component of organic molecules.

• Carbon forms four covalent bonds, allowing diverse structures (chains, rings, branched).

Lecture 5: DNA and RNA

Nucleic Acids

• Store, transmit, and express hereditary information.

• Two types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

DNA vs. RNA

Feature	DNA	RNA
Strands	Double	Single
Sugar	Deoxyribose	Ribose
Bases	A, T, C, G	A, U, C, G
Stability	More stable	Less stable

Nitrogenous Base Pairing

• DNA: Adenine (A) pairs with Thymine (T); Cytosine (C) pairs with Guanine (G).

• RNA: Adenine (A) pairs with Uracil (U); Cytosine (C) pairs with Guanine (G).

Lecture 6: Macromolecules: Proteins

Monomer vs. Polymer

• Monomer: Single molecule unit, building block of polymers.

• Polymer: Chain of monomers, formed by dehydration reaction (releases water), broken down by hydrolysis (uses water).

Amino Acids

• Building blocks of proteins.

• 20 common amino acids, categorized as polar, nonpolar, positive/negative charged.

Protein Structure

• Primary structure: Sequence of amino acids.

• Secondary structure: Hydrogen bonds form alpha helices and beta sheets.

• Tertiary structure: Side chain interactions, 3D folding.

• Quaternary structure: Interaction between multiple peptide chains.

Lecture 7: Carbohydrates & Lipids

Carbohydrates

• Made of carbon, hydrogen, and oxygen (C, H, O).

• Includes sugars, starches, cellulose.

• Structural polysaccharides (e.g., cellulose) enclose plant cells.

Types of Monomers and Polymers

Type	Structure	Example
Monosaccharide	Single sugar (CH2O)	Glucose, fructose
Disaccharide	Two sugars linked	Sucrose, maltose
Polysaccharide	Long chain of sugars	Starch, glycogen, cellulose, chitin

Lipids

• Composed of glycerol and fatty acids.

• Types of fats: Unsaturated, saturated, trans.

• Phospholipids: Major component of cell membranes; arrange in bilayers in water.

Lecture 8: Eukaryotic vs. Prokaryotic Cells, Organelles, Plant vs Animal

Eukaryotic Cells

• DNA inside nucleus.

• Multi-cellular, usually larger.

• Membrane-bound nucleus and organelles (e.g., endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, plasma membrane).

• Found in animals, plants, fungi, amoebas.

Prokaryotic Cells

• DNA in cytoplasm (no nucleus).

• Unicellular, usually smaller.

• No membrane-bound organelles; only ribosomes.

• Found in bacteria and archaea.

Comparison Table: Eukaryotic vs. Prokaryotic Cells

Feature	Eukaryotic	Prokaryotic
DNA Location	Nucleus	Cytoplasm
Organelles	Membrane-bound	None
Size	Larger	Smaller
Examples	Animals, plants, fungi	Bacteria, archaea

Practice and Application

• Identify atoms and elements by number of protons.

• Predict bond type based on electronegativity difference.

• Classify molecules as hydrophilic or hydrophobic.

• Distinguish DNA from RNA by base pairing and sugar type.

• Recognize protein structure levels and amino acid properties.

• Compare cell types and organelle presence.

Additional info: These notes cover foundational topics from General Biology, including atomic structure, chemical bonding, water properties, macromolecules, and cell biology, suitable for exam preparation.