Biology Notes

Chemistry Fundamentals

Key Definitions

• Element: A substance that cannot be broken down into simpler substances by chemical reactions.

• Atom: The smallest unit of matter that retains the properties of an element.

• Molecule: Composed of multiple atoms connected by covalent bonds.

• Compound: A substance consisting of two or more elements formed through chemical reactions.

Essential Elements for Life

• Out of 92 naturally occurring elements, 25 are essential for life, with 4 comprising 96% of living matter:

  • Carbon (C)

  • Oxygen (O)

  • Hydrogen (H)

  • Nitrogen (N)

• Example of a compound: Sodium chloride (NaCl) formed by ionic bonds.

Atomic Structure

• Atoms consist of:

  • Protons: Positively charged particles.

  • Neutrons: Neutral particles.

  • Electrons: Negatively charged particles.

• In neutral atoms, the number of protons equals the number of electrons.

Atomic Concepts

• Atomic Number: The number of protons in an atom (e.g., Carbon has 6 protons).

• Isotopes: Variations of elements with the same number of protons but different numbers of neutrons (e.g., Carbon-12: 6 protons, 6 neutrons; Carbon-14: 6 protons, 8 neutrons).

Atomic Mass and Energy

Key Measurements

• Mass Number: The sum of protons and neutrons in the nucleus.

• Atomic Mass: The actual mass of an atom, accounted for by the presence of isotopes. Measured in Daltons.

• Dalton: Unit for atomic mass; approximately equal to the mass of one proton or neutron.

Electron Configuration

• Electrons possess varying levels of potential energy based on their distance from the nucleus.

• Potential Energy: Energy due to position or structure (e.g., a ball at the top of stairs).

• Energy Levels: Represented by electron shells; identified as least energetic closest to the nucleus.

Periodic Table and Chemical Bonds

Arrangement and Reactivity

• The periodic table is arranged by electron distribution.

• Elements in the same column have similar chemical reactivity due to the same number of valence electrons.

• Valence Electrons: Higher energy level electrons that dictate an atom's chemical behavior.

Types of Chemical Bonds

• Covalent Bonds: Formed when electrons are shared between atoms.

• Ionic Bonds: Formed when electrons are transferred from one atom to another, resulting in ions.

• Types of Covalent Bonds:

  • Single Bond: Sharing one pair of electrons.

  • Double Bond: Sharing two pairs of electrons.

• Hydrogen Bonds and Van der Waals Interactions: Weaker interactions that play essential roles in biological structures.

Water's Unique Properties

Water as a Solvent

• Hydrophilic: Substances that interact well with water due to polarity; water forms hydration shells around polar molecules, including proteins.

• Hydrophobic: Non-polar substances that do not interact with water effectively (e.g., lipids).

Special Properties of Water

• Cohesion: Water molecules stick to each other, contributing to surface tension.

• Adhesion: Water's ability to stick to other molecules, facilitating capillary action.

Biological Molecules and Structure

Macromolecules Overview

• Macromolecules: Large, complex molecules typically built from smaller organic molecules.

• Types:

  • Polymers: Chains of monomers (e.g., carbohydrates, proteins, nucleic acids, lipids).

Specific Substances

• Carbohydrates: Composed of monosaccharides (e.g., glucose).

• Proteins: Polypeptides formed from amino acids through dehydration reactions.

• Lipids: Not true polymers, but large molecules (e.g., fats, phospholipids).

Protein Structure and Function

Levels of Protein Structure

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Folding patterns (alpha-helix and beta-pleated sheet).

• Tertiary Structure: Overall 3D shape influenced by interactions among R-groups.

• Quaternary Structure: Complex of multiple polypeptides forming a functional unit.

Function and Importance

• The specific structure of proteins determines their function, with interactions such as hydrogen bonds, ionic bonds, and hydrophobic interactions being crucial.

Nucleic Acids: DNA and RNA

Structure and Function

• Nucleotides: Monomers of nucleic acids consisting of a phosphate group, pentose sugar, and nitrogenous base.

• DNA: A double-stranded helical structure formed by two antiparallel strands with complementary base pairing (A-T and G-C).

• RNA: Single-stranded and plays various roles including mRNA in transcription and tRNA in translation.

Central Dogma of Molecular Biology

• Gene Expression: Flow of genetic information from DNA to RNA to protein.

Genetics and Inheritance Principles

Mendelian Genetics

• Heredity: Traits passed from parents to offspring.

• Punnett Squares: Helpful tool for predicting genetic outcomes based on observed and expected ratios.

• Dihybrid Crosses: Examines two traits simultaneously, showing principles of independent assortment.

Key Genetic Concepts

• Alleles: Different versions of genes.

• Genotypes and Phenotypes: The genetic composition (genotype) regulates observable traits (phenotype).

Cell Division

Mitosis vs. Meiosis

• Mitosis: Produces two identical daughter cells; essential for growth and repair.

• Meiosis: Produces haploid gametes through two divisions; critical for sexual reproduction.

Stages of Cell Division

• Prophase, Metaphase, Anaphase, Telophase: Sequential phases of the cell cycle.

• Cytokinesis: Division of cytoplasm resulting in two separate cells.