AP Biology

Elements of Life
  - All living organisms are made of cells; all matter is made up of elements.
  - Definition of an element: A substance that cannot be broken down into other substances by chemical reactions.
  - Examples of elements:
    - Oxygen (O)
    - Hydrogen (H)
  - Elements exist as individual atoms or bonded together to form compounds.
  - Living organisms exchange basic elements and compounds with their environment for functioning.
  - Key elements involved in building biological molecules:
    - Carbon (C)
    - Hydrogen (H)
    - Oxygen (O)
  - Other essential elements:
    - Sulfur (S): Used in protein synthesis.
    - Phosphorus (P): Found in phospholipids and nucleic acids.
    - Nitrogen (N): Used in nucleic acids.
  - Essential elements play a crucial role in forming biological macromolecules, which are the building blocks of living organisms.

Water (H₂O) is a critical component of all life on Earth.
  - Water's primary components:
    - Two hydrogen atoms and one oxygen atom.
  - Types of bonds:
    - Covalent bonds between atoms.
    - Hydrogen bonds between water molecules due to polarity.
Properties of water:
  - Polarity: Water has polar covalent bonds, leading to hydrogen bonding.
  - Specific Heat Capacity: High capacity allows regulation of body temperature in living organisms.
  - Heat of Vaporization: Enables evaporative cooling, essential for maintaining body temperature.
Cohesion and Adhesion:
- Cohesion: Tendency for water molecules to stick to themselves.
- Adhesion: Attraction of water molecules to other polar substances, crucial for processes like water transport in plants.
Hydrolysis:
  - Chemical reaction that cleaves covalent bonds by adding water, breaking down larger molecules.
  - Example reaction:
    - Sucrose + Water → Glucose + Fructose (Hydrolysis reaction).
Dehydration Synthesis:
- Joins smaller molecules by removing a water molecule, forming covalent bonds.
- Example: Formation of polymers from monomers, known as polymerization.
Emergent Properties of Water:
- Water exhibits unique characteristics due to its molecular composition and interactions.

Structure: Range from simple sugars (monosaccharides) to complex polysaccharides.
Functions:
- Energy source, storage, and structural components within cells.
Monomer: Monosaccharides (simple sugars).
Polymers: Formed through glycosidic linkages.

Structure: Unique, not polymers like carbohydrates.
Categories: Fats, oils, steroids, phospholipids.
Functions: Energy storage, cellular membrane structure.
- Fatty acids: Saturated (no double bonds) vs. unsaturated (one or more double bonds).
Phospholipids: Form lipid bilayers in cell membranes.

Structure: Composed of amino acids linked by peptide bonds.
Levels of Structure:
  - Primary: Sequence of amino acids.
  - Secondary: Local folding (α-helices, β-pleated sheets).
  - Tertiary: Overall shape due to interactions among R groups.
  - Quaternary: Complex of multiple polypeptides.
Functions: Structural, transport, signaling, movement, and defense (antibodies).
Enzymes: Biological catalysts that lower activation energy.

Types: DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid).
Structure: Composed of nucleotides (sugar, phosphate group, nitrogenous base).
- Role in heredity and protein synthesis.
Genetic code: Encodes genetic information in the sequence of nucleotides.
DNA Replication: Semi-conservative; enzymes like helicase, DNA polymerase involved.

Cell Theory:
  - All organisms are made of cells.
  - Cells are the basic unit of life.
  - All cells arise from preexisting cells.
Differences in cell types:
- Prokaryotic and Eukaryotic cells differ in complexity and presence of organelles.

Fluid Mosaic Model: Cell membranes are dynamic structures composed of phospholipid bilayers and embedded proteins.

Types of Transport:
- Passive Transport: Movement without energy; includes simple diffusion and facilitated diffusion.
- Active Transport: Requires energy; moves substances against the concentration gradient.
Endocytosis and Exocytosis: Used for bulk transport of large molecules or particles across the membrane.
- Endocytosis: Engulfing of materials.
- Exocytosis: Expelling of materials.

Photosynthesis equation:
- $6CO_2 + 6H_2O + ext{Light Energy} ightarrow C_6H_{12}O_6 + 6O_2$
Stages:
- Light Reactions: Convert light energy into chemical energy (ATP and NADPH).
- Calvin Cycle: Uses ATP and NADPH to fix carbon into sugars.

Equation:
- $C_6H_{12}O_6 + 6O_2 ightarrow 6CO_2 + 6H_2O + ext{ATP}$
Stages of Cellular Respiration:
- Glycolysis, Kreb's Cycle, Electron Transport Chain.
- Processes release energy and produce ATP.

Energy moves through ecosystems; nutrients cycle between biotic and abiotic components.
Trophic levels:
- Producers → Primary consumers → Secondary consumers → Tertiary consumers.
Effects of human activity on ecosystems: pollution, habitat loss, and species extinction.

Population dynamics influenced by birth rates, death rates, and carrying capacity.
Model equations for population growth:
- Exponential Growth: $dN/dt = r_{max}N$
- Logistic Growth: $dN/dt = r_{max}N(K - N)/K$

Natural Selection: Mechanism of evolution; traits that provide survival advantage are more likely to be passed on.
Evidence for evolution: Fossils, comparative anatomy, and molecular biology.
Adaptation: Changes in traits that enhance survival and reproduction.

Understanding the chemistry, biology, and processes of life is essential in studying organisms. From cells and their functions to molecular pathways and evolutionary adaptations, this knowledge forms the foundation for the science of life.