General Biology I: Comprehensive Study Guide by Topic

Study Guide - Smart Notes

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Intro to Biology

Characteristics of Living Things

Biology is the study of living organisms and their interactions with the environment. To be considered living, an entity must exhibit several key characteristics.

Organization: Living things are composed of one or more cells, which are the basic units of life.
Metabolism: They carry out chemical reactions to obtain and use energy.
Homeostasis: The ability to maintain stable internal conditions.
Growth and Development: Living things grow and develop according to specific instructions coded in their DNA.
Reproduction: The ability to produce new organisms.
Response to Stimuli: Reacting to environmental changes.
Evolution: Populations of living things evolve over generations.

Examples: Use of natural selection, homeostasis, and DNA as defining features.

Chemistry for Biology Students

Atoms, Isotopes, Ions, and Chemical Bonds

Understanding atomic structure and chemical bonding is essential for studying biological molecules.

Isotopes: Atoms of the same element with different numbers of neutrons.
Ions: Atoms or molecules that have gained or lost electrons, resulting in a charge.
Atomic Number: Number of protons in the nucleus.
Electron Configuration: Distribution of electrons in atomic orbitals.
Covalent Bonds: Sharing of electron pairs between atoms.
Ionic Bonds: Transfer of electrons from one atom to another.
Polar vs. Nonpolar Bonds: Polar bonds have unequal sharing of electrons; nonpolar bonds share electrons equally.

Example: Water (H2O) is a polar molecule due to unequal sharing of electrons between hydrogen and oxygen.

Properties of Water

Water is vital for life due to its unique chemical and physical properties.

Hydrogen Bonding: Weak bonds between the hydrogen atom of one water molecule and the oxygen atom of another.
High Specific Heat: Water can absorb a lot of heat before changing temperature.
Cohesion and Adhesion: Water molecules stick to each other and to other surfaces.
Solvent Properties: Water dissolves many substances, facilitating chemical reactions.
States of Water: Solid (ice), liquid, and gas (vapor); water expands upon freezing.

Example: Ice floats on water because it is less dense than liquid water.

Water and Life (Essential Water)

Water in Biological Systems

Water is essential for all known forms of life and plays a critical role in biological processes.

Search for Life: Scientists look for water when searching for life in extreme environments.
Thermal Energy: Water moderates temperature due to its high specific heat.
Surface Tension: Water molecules at the surface are attracted to each other, creating a 'skin'.
pH and Concentration: Solutions with high concentrations of H+ are acidic; those with high OH- are basic.

Formula:

Carbon and the Molecular Diversity of Life

Organic Chemistry and Carbon Compounds

Carbon is the backbone of organic molecules due to its ability to form four covalent bonds.

Versatility: Carbon can form chains, rings, and complex structures.
Isomers: Molecules with the same chemical formula but different structures.
Enantiomers: Isomers that are mirror images of each other.
Functional Groups: Specific groups of atoms that confer particular properties to molecules (e.g., hydroxyl, carboxyl, amino).

Example: Glucose and fructose are structural isomers.

Biological Molecules

Monomers and Polymers

Biological macromolecules are formed by joining smaller units called monomers into polymers.

Monomers: Simple molecules that can join to form polymers (e.g., amino acids, nucleotides).
Polymers: Large molecules made by linking monomers (e.g., proteins, DNA).
Dehydration Synthesis: Formation of polymers by removing water.
Hydrolysis: Breaking polymers into monomers by adding water.

Example: Starch is a polymer of glucose monomers.

Types of Biological Molecules

There are four major classes of biological macromolecules.

Carbohydrates: Energy storage and structural support (e.g., glucose, cellulose).
Lipids: Energy storage, membrane structure (e.g., fats, phospholipids).
Proteins: Catalysis, structure, transport (e.g., enzymes, hemoglobin).
Nucleic Acids: Information storage and transfer (e.g., DNA, RNA).

Example: Cellulose is a structural carbohydrate found in plant cell walls.

Structure and Function of Nucleic Acids

Nucleic acids store and transmit genetic information.

Nucleotide: The monomer of nucleic acids, consisting of a sugar, phosphate, and nitrogenous base.
DNA vs. RNA: DNA contains deoxyribose sugar; RNA contains ribose. DNA is double-stranded, RNA is single-stranded.
Base Pairing: In DNA, adenine pairs with thymine, cytosine with guanine.

Example: The double helix structure of DNA allows for complementary base pairing.

Tour of the Cell

Cell Structure and Function

Cells are the basic units of life, and their structure is closely related to their function.

Microscopy: Electron microscopes provide detailed images of cell structures.
Cell Size: Cells are typically small to maximize surface area to volume ratio.
Organelles: Specialized structures within cells (e.g., nucleus, mitochondria, lysosomes).
Endomembrane System: Includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, and vesicles.
Cytoskeleton: Network of protein filaments for support and movement (microtubules, microfilaments, intermediate filaments).

Example: Mitochondria are the site of cellular respiration.

Cell Membrane Structure and Function

The cell membrane controls the movement of substances in and out of the cell.

Phospholipid Bilayer: Provides a semi-permeable barrier.
Selective Permeability: Only certain molecules can pass through.
Fluid Mosaic Model: Membrane is composed of lipids, proteins, and carbohydrates.
Transport Mechanisms: Includes passive (diffusion, osmosis) and active (pumps, co-transport) transport.

Example: The sodium-potassium pump maintains ion gradients across the membrane.

Membrane Transport and pH

Cells regulate their internal environment through transport and pH control.

Osmosis: Movement of water across a membrane from low to high solute concentration.
Tonicity: Refers to the relative concentration of solutes (hypotonic, hypertonic, isotonic).
pH Scale: Measures acidity/alkalinity; affects enzyme activity and cellular processes.
Active Transport: Requires energy to move substances against their concentration gradient.
Co-transport: Coupled transport of two substances across a membrane.

Formula:

Table: Comparison of Cell Transport Mechanisms

Transport Type	Energy Required?	Direction	Example
Diffusion	No	High to Low	Oxygen entering cells
Osmosis	No	High to Low (water)	Water absorption in roots
Active Transport	Yes	Low to High	Sodium-potassium pump
Co-transport	Yes	Coupled (varies)	Glucose transport with Na+

Flow of Information in the Cell

Central Dogma of Molecular Biology

Genetic information flows from DNA to RNA to protein.

Transcription: DNA is used as a template to make RNA.
Translation: RNA directs the synthesis of proteins.
Gene Expression: The process by which information from a gene is used to synthesize a functional gene product.

Example: The sequence of bases in DNA determines the sequence of amino acids in a protein.

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard General Biology curriculum.