Study Guide Biology Notes

What are Cells?
- Basic unit of structure and function of all living things.
- Cell Theory:
1. All organisms are composed of cells.
2. All cells come only from preexisting cells.
3. Cells are the smallest structural and functional unit of organisms.

Cell Size:
- Ranges from one millimeter down to one micrometer.
Surface Area to Volume Ratio:
- Cells need a large surface area of plasma membrane to adequately exchange materials.
- Surface area vs Volume:
- Surface-area-to-volume ratio requires cells to be small.
- As cells increase in size, volume increases faster than surface area, making exchange less efficient.
- Implications:
- Small cells are advantageous for exchanging nutrients, oxygen, and waste.

Definition:
- A thin flexible barrier that surrounds the cell, controlling what goes in and out.
Structure:
- Composed of a phospholipid bilayer made of amphipathic molecules:
- Phospholipid Structure:
  - Hydrophilic Heads:
  - Face outward, exposed to aqueous solutions on both sides.
  - Hydrophobic Tails:
  - Point inward, shielding from water.
- Embedded proteins can be channel proteins, carrier proteins, or pump proteins.
- Functionality:
- Proteins enable substances to pass through, facilitate movement, and utilize energy for transport.

Selectively Permeable Membranes:
- Certain substances pass easily; others require assistance.
What Can Pass Easily?
- Small & nonpolar molecules like:
- Oxygen (O₂)
- Carbon dioxide (CO₂)
What Needs Protein Help?
- Ions, large molecules, and polar molecules need proteins for transport.

Prokaryotic Cells:
- Lack a membrane-bound nucleus (Examples: Bacteria, Archaea).
- Smaller and simpler than eukaryotic cells.
- Key features:
- Plasma membrane.
- Cell wall (strengthened by peptidoglycan).
- Contains ribosomes.
Eukaryotic Cells:
- Contain membrane-bound nucleus and organelles.
- Larger and more complex.
- Examples include animals, plants, fungi, and protists.

Nucleus:
- Command center of the cell, typically centrally located.
- Produces RNA and contains chromatin (DNA bound with proteins).
- Nuclear envelope consists of double membranes with nuclear pores for exchange between nucleoplasm and cytoplasm.
Endoplasmic Reticulum (ER):
- A network of membranes (channels and saccules):
- Rough ER: Contains ribosomes; involved in protein synthesis.
- Smooth ER: Lacks ribosomes; synthesizes lipids and detoxifies harmful substances.
Ribosomes:
- Assemble proteins based on genetic instructions (traditionally: DNA → mRNA → protein).
- Composed of rRNA; can exist freely in cytoplasm or attached to Rough ER.
Golgi Apparatus:
- Processes and modifies proteins and lipids received from ER.
- Packages them into vesicles for transport.
Lysosomes:
- Membrane-bound vesicles with digestive enzymes (not found in plants).
- Involved in breaking down large molecules and recycling cellular components.
Peroxisomes:
- Similar to lysosomes; involved in metabolizing fatty acids and detoxifying substances.
Mitochondria:
- Produce ATP through cellular respiration (using oxygen, releasing carbon dioxide).
Chloroplasts:
- Found only in plants; involved in photosynthesis (converting sunlight to chemical energy).
- Produce glucose and release oxygen.

Functions:
- Maintains cell shape and assists in movement of organelles.
- Comprised of three types of protein fibers:
1. Microfilaments: Made of actin, aiding in movement and maintaining cell shape.
2. Intermediate Filaments: Various fibrous proteins; reinforce shape and provide support.
3. Microtubules: Form tracks for organelle movement and support cell structure.
Importance of Cytoskeleton:
- Enables vesicle movement and organization within the cell.
- Critical for cell division.
- Without it, cells could collapse and fail to transport materials properly.

Passive Transport:
- Movement of molecules from high to low concentration without energy input.
- Types include:
- Simple diffusion (e.g., small nonpolar molecules)
- Facilitated diffusion (e.g., ions, glucose).
Active Transport:
- Requires energy (ATP) to move substances against their concentration gradient.
- Includes transport pumps and mechanisms like exocytosis (export of materials) and endocytosis (import of materials).
Osmosis:
- Diffusion of water across a selectively permeable membrane.
- Water moves towards higher solute concentration to equilibrate solute levels.

Definition: The ability of a solution to cause a cell to gain or lose water.
- Isotonic: Equal solute concentration; no net movement of water.
- Hypotonic: Lower solute concentration outside the cell; water moves in, causing cells to swell or burst.
- Hypertonic: Higher solute concentration outside the cell; water moves out, leading to cell shrinkage.
Reactivity of Plant and Animal Cells:
- Plant cells are protected by a cell wall; thus, they don't burst in hypotonic solutions.
- Animal cells lack this protection and can burst.

Definition: Biological catalysts that speed up reactions without being consumed.
- Function by lowering activation energy, which is the energy required to start a reaction.
Active Site:
- The specific area on an enzyme where substrates bind, often changing shape slightly to facilitate the reaction (induced fit).
Types of Enzymes:
- Digestive Enzymes:
- Amylase (carbohydrates), Lipase (fats), Protease (proteins), Catalase (breaks down hydrogen peroxide), etc.
Factors Affecting Enzyme Action:
- Temperature, pH, enzyme concentration, and substrate concentration.
- Enzymes have optimal conditions; extremes can lead to denaturation (loss of shape).
Types of Inhibition:
- Competitive Inhibitors: Block substrate access to the active site.
- Non-competitive Inhibitors: Bind elsewhere and change enzyme shape.

Exergonic Reactions: Release energy (e.g., cellular respiration).
Endergonic Reactions: Require energy input (e.g., photosynthesis).
Energetic Coupling: An exergonic reaction provides energy for an endergonic reaction, usually mediated by ATP:
- ATP → ADP + energy
General Equation for Enzymatic Activity:
- Enzyme + Substrate → Enzyme-Substrate Complex → Enzyme + Product.

Objective Lenses:
- Different magnification powers typically found on teaching microscopes:
- Scanning lens (4X), Low Power lens (10X), High Dry lens (40X), Oil Immersion lens (100X).
Total Magnification:
- Calculated by multiplying objective lens magnification by ocular lens magnification (10 X 10 = 100X).

Understanding cell structure and function, transport mechanisms, enzymatic activity, and metabolism is essential for biology studies.