General Biology Study Guide: Foundations, Chemistry of Life, and Biomolecules

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Chapter 1 – Biology: Exploring Life

Biology: The Scientific Study of Life

Biology is the study of living organisms and their interactions with the environment. It encompasses various levels of organization, from molecules to the biosphere.

Levels of Biological Organization: The hierarchy includes molecules, organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and the biosphere.
Biosphere: The highest level of organization, encompassing all ecosystems on Earth.
Characteristics Differentiating Domains of Life: Organisms are classified into three domains: Bacteria, Archaea, and Eukarya. For example, extremophiles (Archaea) thrive in environments where other organisms perish.

Key Terms: biology, biosphere, cell, community, controlled experiment, data, dependent variable, domain, ecosystem, emergent properties, experiment, hypothesis, independent variable, molecule, organ, organ system, organelle, organism, population, science, theory, tissue

The Process of Science

Science seeks to understand the natural world through observation, hypothesis formation, experimentation, and analysis.

Hypothesis vs. Scientific Theory: A hypothesis is a testable explanation for an observation, while a scientific theory is a well-substantiated explanation based on a body of evidence.
Falsifiability: Scientific hypotheses must be falsifiable, meaning they can be disproven by evidence.
Controlled Experiment: Involves manipulating one variable (independent variable) while keeping others constant to determine cause and effect.
Tentativeness of Scientific Explanations: Scientific knowledge is subject to change as new evidence emerges.

Chapter 2 – The Chemical Basis of Life

Elements, Atoms, and Compounds

All matter is composed of elements, which are made of atoms. Compounds are substances formed from two or more elements chemically combined.

Element: A pure substance consisting of only one type of atom.
Compound: A substance formed when two or more elements are chemically bonded.
Trace Element: An element required by organisms in minute quantities (e.g., iron, iodine).
Essential Elements for Life: Carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur.

Atomic Structure

Atoms consist of protons, neutrons, and electrons. Their arrangement determines the atom's properties.

Proton: Positively charged particle in the nucleus.
Neutron: Neutral particle in the nucleus.
Electron: Negatively charged particle orbiting the nucleus.
Atomic Number: Number of protons in an atom ().
Mass Number: Sum of protons and neutrons ().
Isotope: Atoms of the same element with different numbers of neutrons.
Radioactive Isotope: An isotope with an unstable nucleus that decays, emitting radiation.

Chemical Bonds

Chemical bonds hold atoms together in molecules and compounds. The main types are covalent, ionic, and hydrogen bonds.

Covalent Bond: Atoms share electrons. Can be polar (unequal sharing) or nonpolar (equal sharing).
Ionic Bond: Atoms transfer electrons, resulting in oppositely charged ions that attract.
Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., oxygen, nitrogen).
Bond Strength: Covalent > Ionic > Hydrogen (hydrogen bonds are the weakest).

Chemical Reactions and Life

Chemical reactions rearrange atoms to form new substances, essential for biological processes.

Reactants: Substances that start a chemical reaction.
Products: Substances formed by a chemical reaction.
Cellular Respiration:
Photosynthesis:

Solutions, Acids, and Bases

Solutions are mixtures of solutes dissolved in solvents. Acids and bases affect the hydrogen ion concentration in solutions.

Solute: Substance dissolved in a solution.
Solvent: Substance that dissolves the solute (water is the universal solvent).
Acid: Increases hydrogen ion () concentration.
Base: Reduces hydrogen ion concentration.
pH Scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic).
Buffer: Substance that minimizes changes in pH.

pH Value	[H+] Concentration	Nature
0-6	High	Acidic
7	Neutral	Neutral
8-14	Low	Basic

Chapter 3 – The Molecules of Cells

Introduction to Organic Compounds

Organic compounds are carbon-based molecules essential for life. Carbon's ability to form four covalent bonds allows for diverse molecular structures.

Hydrocarbon: Molecule consisting only of carbon and hydrogen.
Isomer: Molecules with the same chemical formula but different structures.
Functional Groups: Groups of atoms that confer specific chemical properties (e.g., carboxyl, amino, phosphate).

Macromolecules

Macromolecules are large molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates: Provide energy and structural support. Monosaccharides (e.g., glucose), disaccharides (e.g., sucrose), polysaccharides (e.g., starch, cellulose).
Lipids: Energy storage, cell membrane structure. Includes fats, phospholipids, steroids.
Proteins: Enzymes, structural support, transport, signaling. Made of amino acids.
Nucleic Acids: Store and transmit genetic information (DNA, RNA).

Macromolecule	Monomer	Function
Carbohydrate	Monosaccharide	Energy, structure
Lipid	Fatty acid, glycerol	Energy storage, membranes
Protein	Amino acid	Enzymes, structure
Nucleic Acid	Nucleotide	Genetic information

Carbohydrates

Carbohydrates are sugars and polymers of sugars. They serve as energy sources and structural components.

Monosaccharide: Single sugar molecule (e.g., glucose).
Disaccharide: Two monosaccharides joined (e.g., lactose, sucrose).
Polysaccharide: Many monosaccharides joined (e.g., starch, cellulose, chitin).
Cellulose: Structural polysaccharide in plant cell walls.
Chitin: Structural polysaccharide in fungal cell walls and exoskeletons of arthropods.

Lipids

Lipids are hydrophobic molecules important for energy storage and membrane structure.

Fatty Acid: Long hydrocarbon chain with a carboxyl group.
Saturated vs. Unsaturated Fatty Acids: Saturated have no double bonds; unsaturated have one or more double bonds.
Phospholipid: Major component of cell membranes; has hydrophilic head and hydrophobic tails.

Type	Structure	Function
Saturated Fat	No double bonds	Energy storage
Unsaturated Fat	One/more double bonds	Energy storage
Phospholipid	Glycerol, 2 fatty acids, phosphate group	Membrane structure

Proteins

Proteins are polymers of amino acids and perform a wide range of functions in cells.

Amino Acid: Building block of proteins; contains amino group, carboxyl group, and side chain (R group).
Levels of Protein Structure:
1. Primary: Sequence of amino acids.
2. Secondary: Alpha helices and beta sheets formed by hydrogen bonding.
3. Tertiary: 3D folding due to side chain interactions.
4. Quaternary: Association of multiple polypeptide chains.
Enzyme: Protein that catalyzes biochemical reactions.
Denaturation: Loss of protein structure due to changes in pH, temperature, or chemicals.
Sickle Cell Anemia: Caused by a single amino acid change in hemoglobin.

Nucleic Acids

Nucleic acids store and transmit genetic information. DNA and RNA are the two main types.

DNA (Deoxyribonucleic Acid): Stores genetic information; double helix structure; sugar is deoxyribose.
RNA (Ribonucleic Acid): Involved in protein synthesis; single-stranded; sugar is ribose.
Nucleotide: Monomer of nucleic acids; consists of a sugar, phosphate group, and nitrogenous base.
ATP (Adenosine Triphosphate): Energy currency of the cell.

Feature	DNA	RNA
Sugar	Deoxyribose	Ribose
Strands	Double	Single
Bases	A, T, C, G	A, U, C, G
Function	Genetic storage	Protein synthesis

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