General Biology I: Foundational Concepts and Biological Molecules

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Biological Organization and Characteristics of Life

Levels of Biological Organization

The biological world is organized into hierarchical levels, each representing increasing complexity. Understanding these levels helps in studying how life is structured and functions.

Atom: The smallest unit of matter, composed of protons, neutrons, and electrons.
Molecule: A group of atoms bonded together, representing the next level of organization.
Cell: The basic unit of life, made up of molecules and organelles.
Tissue: A group of similar cells performing a specific function.
Organism: An individual living entity.
Population: A group of organisms of the same species living in a specific area.
Community: Different populations living together in a defined area.
Ecosystem: A community and its non-living environment.
Biosphere: All ecosystems on Earth.

Example: The correct order from largest to smallest: Biosphere > Ecosystem > Community > Population > Organism.

Characteristics of Life

Living organisms share several key characteristics that distinguish them from non-living matter.

Homeostasis: The ability to maintain stable internal conditions (e.g., regulation of blood sugar by insulin).
Metabolism: The sum of all chemical reactions in an organism.
Reproduction: The ability to produce new individuals.

Example: When blood sugar rises, the pancreas secretes insulin to restore normal levels, demonstrating homeostasis.

Atomic Structure and Chemical Bonds

Structure of the Atom

Atoms are the fundamental units of matter, consisting of subatomic particles.

Proton: Positively charged particle found in the nucleus.
Neutron: Neutral particle found in the nucleus.
Electron: Negatively charged particle orbiting the nucleus.
Valence Shell: The outermost electron shell, important in chemical bonding.

Example: Carbon atom: 6 protons, 6 neutrons, atomic mass 12.011.

Ions and Ionic Bonds

Ions are atoms or molecules with a net electric charge due to the loss or gain of electrons.

Cation: Positively charged ion (loss of electrons).
Anion: Negatively charged ion (gain of electrons).
Ionic Bond: Electrostatic attraction between cations and anions.

Equation:

Covalent and Hydrogen Bonds

Covalent bonds involve the sharing of electrons between atoms. Hydrogen bonds are weak attractions between polar molecules.

Polar Covalent Bond: Unequal sharing of electrons, creating partial charges.
Nonpolar Covalent Bond: Equal sharing of electrons.
Hydrogen Bond: Attraction between a hydrogen atom in one molecule and a negative region in another molecule.

Example: Water molecules form hydrogen bonds, leading to properties like cohesion and adhesion.

Bond Interactions

Ionic Bonds: Electrostatic interactions between anions and cations.
Covalent Bonds: Sharing of electrons between atoms.
Hydrogen Bonds: Attraction between polar molecules.

Properties of Water

Cohesion and Adhesion

Water exhibits unique properties due to hydrogen bonding.

Cohesion: Water molecules stick to each other.
Adhesion: Water molecules stick to other surfaces.
Polarity: Water is a polar molecule, leading to its solvent abilities.

Example: Water's ability to "stick" to glass is called adhesion.

pH and Acidity

pH measures the concentration of hydrogen ions in a solution.

Lower pH: More acidic (higher concentration of H+ ions).
Higher pH: Less acidic.

Example: A substance with pH 3 is more acidic than one with pH 5.

Macromolecules and Their Functions

Types of Biological Macromolecules

Cells contain four major types of macromolecules, each with distinct functions and building blocks.

Molecule	Examples	Functions	Building Blocks
Protein	Keratin, myosin	Enzymes, mobility, immune defense, structure	Amino acid
Lipid	Oils, waxes, phospholipids, steroids	Energy storage, insulation, cushioning	Fatty acids + glycerol
Carbohydrate	Glucose, cellulose	Energy storage, structure	Monosaccharide
Nucleic Acid	DNA, RNA	Encode genetic info	Nucleic acid

Monomers and Polymers

Macromolecules are formed by joining smaller units called monomers.

Protein: Monomer is amino acid.
Carbohydrate: Monomer is monosaccharide; two monosaccharides form a disaccharide.
Lipid: Composed of fatty acids and glycerol; triglyceride is a common lipid.
Nucleic Acid: Monomer is nucleotide.

Example: Water is used to break polymers into monomers (hydrolysis reaction).

Saturated vs. Unsaturated Fatty Acids

Saturated Fatty Acids: No double bonds between carbon atoms; solid at room temperature.
Unsaturated Fatty Acids: One or more double bonds; liquid at room temperature.

Example: Triglyceride with saturated fatty acids contains no double bonds.

Cell Structure and Organelles

Major Organelles and Their Functions

Cells contain specialized structures called organelles, each with specific roles.

Nucleus: Holds genetic information (DNA).
Rough Endoplasmic Reticulum (ER): Makes glycoproteins and vesicles.
Smooth ER: Detoxifies, makes lipids, stores calcium.
Golgi Apparatus: Accepts, sorts, packs, and sends proteins in vesicles.
Vesicles: Hold cell products for transport.
Vacuole: Stores ions, food, pumps out water.
Chloroplast: Site of photosynthesis.
Mitochondrion: Site of cell respiration, makes cell energy.
Peroxisome: Detoxifies, breaks down hydrogen peroxide.
Lysosome: Contains enzymes that digest food or old organelles (low pH).

Scientific Method

Steps of the Scientific Method

The scientific method is a systematic approach to investigation.

Observation
Question
Hypothesis
Experiment
Analysis
Conclusion

Data Interpretation

Graph Analysis

Graphs are used to visualize data trends in biology.

Example: A graph showing the number of bubbles produced per minute by a plant at various water depths demonstrates that bubble production decreases at depths greater than 10 meters.
At 33 meters, approximately 8 bubbles are produced per minute.

Domains of Life

Classification of Life

All living organisms are classified into three domains based on genetic and cellular characteristics.

Bacteria: Prokaryotic, single-celled organisms.
Archaea: Prokaryotic, often found in extreme environments.
Eukarya: Eukaryotic, includes plants, animals, fungi, and protists.

Example: Plants (trees, flowers), animals (birds, reptiles, mammals), fungi (mushrooms), protists (Paramecium, amoeba).

DNA Structure and Bases

Nucleic Acids and DNA Bases

DNA is composed of nucleotides, each containing a nitrogenous base.

Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Uracil (U): Found in RNA, not DNA.

Example: Uracil is not found in DNA.

Summary Table: Biological Macromolecules

Molecule	Examples	Functions	Building Blocks
Protein	Keratin, myosin	Enzymes, mobility, immune defense, structure	Amino acid
Lipid	Oils, waxes, phospholipids, steroids	Energy storage, insulation, cushioning	Fatty acids + glycerol
Carbohydrate	Glucose, cellulose	Energy storage, structure	Monosaccharide
Nucleic Acid	DNA, RNA	Encode genetic info	Nucleic acid

Additional info: Some explanations and examples were expanded for clarity and completeness, including definitions and context for scientific method, macromolecule structure, and atomic properties.