General Biology: Foundations of Life and Cell Structure

Foundations of Life

Levels of Biological Organization

Living organisms exhibit a hierarchy of complexity, from the simplest to the most complex structures.

• Subatomic: Particles smaller than atoms (protons, neutrons, electrons)

• Atomic: Basic units of matter (elements)

• Molecular: Groups of atoms bonded together (e.g., H2O, CO2)

• Organelle: Specialized structures within cells (e.g., mitochondria)

• Cellular: The basic unit of life

• Tissue: Groups of similar cells performing a function

• Organ: Structures composed of different tissues

• Organ System: Groups of organs working together

• Organism: An individual living entity

• Population: Group of organisms of the same species

• Community: Different populations living together

• Ecosystem: Community plus the physical environment

• Biosphere: All ecosystems on Earth

Cell: The Unit of Life

Cells are the fundamental units of structure and function in living organisms.

Sun: Primary Energy Source

• All life ultimately depends on energy from the sun.

Domains of Life

• Bacteria

• Archaea

• Eukarya

Scientific Method

The scientific method is a systematic approach to understanding the natural world.

• Observation

• Question

• Hypothesis

• Prediction

• Experiment

• Conclusion

Discovery of Penicillin

• Led to the foundation of antibiotics.

• Helped find treatment for bacterial diseases.

Inductive and Deductive Reasoning

• Inductive Reasoning: Uses specific observations to form general conclusions.

• Deductive Reasoning: Uses generalizations to reach a specific conclusion about an instance.

Elements in Humans

• Most common: Carbon, Hydrogen, Oxygen, Nitrogen

Subatomic Particles

• Proton: Positive charge

• Neutron: Neutral

• Electron: Negative charge

Hydrogen Bonds

• Weak bonds between a slightly positive hydrogen atom and a slightly negative electronegative atom.

Chemical Bonds and Water

Types of Chemical Bonds

• Covalent Bonds: Atoms share electrons (e.g., H2O, O2).

• Ionic Bonds: Atoms transfer electrons, forming charged ions (e.g., NaCl).

• Hydrogen Bonds: Weak attractions between polar molecules.

Redox Reactions

• Oxidation: Loss of electrons.

• Reduction: Gain of electrons.

Properties of Water

• Cohesion: Attraction between molecules of the same substance (surface tension).

• Adhesion: Attraction between different substances.

• pH Scale: Measures hydrogen ion concentration.

$\text{pH} = -\log_{10}[\text{H}^+]$

• Below 7: Acidic (more H+)

• Above 7: Basic (more OH-)

Biological Molecules

Organic Molecules

• Small organic molecules (monomers) join to form polymers.

• Dehydration synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers by adding water.

Carbohydrates

• Made of C, H, and O.

• Energy source and storage.

• Monomer: Monosaccharides (e.g., glucose).

• Polysaccharides: Starch, glycogen, cellulose, chitin.

Lipids

• Saturated: Single bonds, solid at room temperature.

• Unsaturated: At least one double bond, liquid at room temperature.

• Phospholipids: Main component of cell membranes.

Proteins

• Polymers of amino acids joined by peptide bonds.

• Levels of structure: Primary, secondary, tertiary, quaternary.

• Denaturation: Loss of structure due to heat, pH, or chemicals.

• Disulfide bridges: Covalent bonds between sulfur atoms of cysteine residues.

Nucleic Acids

• DNA and RNA: Polymers of nucleotides.

• Nucleotide: Phosphate group, sugar, nitrogenous base (A, T, C, G, U).

• ATP: Energy currency of the cell.

Cell Structure and Function

Cell Walls

• Present in plants, fungi, and some bacteria.

• Gram staining differentiates bacteria by cell wall type.

Cytoskeleton

• Microfilaments: Smallest, actin subunits, 7 nm diameter.

• Intermediate Filaments: Twisted protein strands, structural support.

• Microtubules: Largest, tubulin subunits, 25 nm diameter.

Cilia and Flagella

• Cilia: Short, numerous, move fluid past cells.

• Flagella: Longer, fewer, move cells (e.g., sperm).

Nucleus

• Contains DNA, nucleolus, and chromatin.

• Chromosomes: Condensed DNA during cell division.

Ribosomes

• Site of protein synthesis (translation of mRNA).

Endoplasmic Reticulum (ER)

• Rough ER: Studded with ribosomes, synthesizes and modifies proteins.

• Smooth ER: Lacks ribosomes, synthesizes lipids, detoxifies chemicals.

Golgi Apparatus

• Modifies, sorts, and packages proteins and lipids for transport.

Endomembrane System

• Includes ER, Golgi apparatus, lysosomes, and vesicles.

• Coordinates synthesis and transport of cellular products.

Additional info:

• Some context and definitions have been expanded for clarity and completeness.