final review

All organisms are composed of cells:
- Single-celled (unicellular) or multi-celled (multicellular).
Cells are the basic unit of life:
- Units of structure, physiology, and organization.
- All cells come from pre-existing cells.
Characteristics of life:
- Made of cells
- Use DNA for genetic information
- Possess metabolism (growth and development)
Scientific Method:
- Observations lead to hypotheses testing.
- Importance of experimental controls and repeatability.
- Self-correction based on evidence.
- Avoiding dogmatism.

Elements: About 20-25% of the 92 known elements are essential for life.
- Common Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N) make up 96% of living matter.
- Trace Elements: Required in minute quantities (e.g., Iron, Iodine, Copper).
Atoms:
- Smallest units of matter with distinct properties. Comprised of subatomic particles:
  - Neutrons: No charge
  - Protons: Positive charge
  - Electrons: Negative charge
- Atomic structures:
  - Atomic nucleus (protons + neutrons)
  - Atomic number: Number of protons
  - Mass number: Protons + neutrons
  - Atomic mass: Approximation by mass number.

Isotopes: Atoms of the same element with different neutron counts.
- Radioactive isotopes can be used in biological research, for example:
  - Tracing metabolic processes
  - Diagnosing diseases.
Chemical Bonds:
- Atoms form bonds to stabilize incomplete valence shells:
  - Covalent Bonds: Sharing of electron pairs between atoms.
  - Ionic Bonds: Transfer of electrons, creating ions.

Biological Medium: Water is essential for all living organisms.
- Cells are 70-95% water; survival of life forms depends on its properties.
Properties of Water:
- Cohesive Behavior: Water molecules stick to each other (cohesion).
- Adhesion: Water molecules stick to other substances.
- High Specific Heat: Requires substantial energy to change temperature, stabilizing climates.
- Expansion Upon Freezing: Ice is less dense than liquid water, allowing it to float, crucial for ecosystems.
- Versatile Solvent: Dissolves many ionic and polar substances (hydrophilic).

Solutions: Composed of solutes and solvents; water is the most versatile solvent.
pH and Biological Reactions:
- pH scale indicates acidity or basicity; neutral solutions have a pH of 7.
- Acids increase H+ concentration, while bases decrease it.
- Acidic solutions (<7) and basic solutions (>7).

Life’s Organic Molecules: Proteins, nucleic acids, carbohydrates, and lipids.
Macromolecules: Large polymers made from smaller building blocks (monomers).
Carbohydrates: Sugars (e.g., glucose) are energy sources and structural components.
- Monosaccharides, Disaccharides, Polysaccharides (such as starch, glycogen, cellulose).
Proteins: Essential for cellular functions, consisting of amino acids linked by peptide bonds.
Lipids: Comprised of fats, phospholipids, and steroids, essential for cell membranes and energy storage.

Enzymes: Biological catalysts that lower activation energy of reactions.
- Specificity for substrates and affected by environmental conditions (temperature/pH).
Types of Enzyme Inhibition:
- Competitive inhibitors bind to the active site.
- Noncompetitive inhibitors bind elsewhere, altering enzyme shape.

Metabolic Pathways: Cellular respiration converts biochemical energy from nutrients into ATP.
- Glycolysis, Citric Acid Cycle, and Oxidative Phosphorylation.
Energy Transfer: Electrons are transferred through a series of reactions, ultimately involving oxygen.
- Example reaction: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy.

Process of Photosynthesis: Converts solar energy into chemical energy stored in glucose.
- Light reactions and Calvin cycle.
Plants as Photoautotrophs: Produce organic compounds using sunlight.

Cell Division: Essential for growth, repair, and reproduction.
- Mitosis for somatic cells and Meiosis for gametes.
Cell Cycle: Includes interphase and mitotic phases, maintaining genetic continuity.