exam practice 1

📘 Study Guide – Cellular Level of Organization

🔹 Cell Theory

    1.    The cell is the basic unit of life.

    2.    All living things are made of cells.

    3.    New cells arise only from pre-existing cells .

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🔹 Microscopy

    •    Compound Light Microscope – Uses light and lenses; up to ~1000x; can view live specimens .

    •    Transmission Electron Microscope (TEM) – 2D image of thin slices; very high magnification; no live specimens .

    •    Scanning Electron Microscope (SEM) – 3D surface images; very high magnification; no live specimens .

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🔹 Cell Components

    •    Plasma (cell) membrane / Plasmalemma – Flexible barrier separating intracellular from extracellular fluid; made of phospholipid bilayer with proteins .

    •    Integral (transmembrane) proteins – Span across membrane; transport, receptors, enzymes.

    •    Peripheral proteins – Attached to surface inside or outside.

    •    Phospholipids – Amphipathic (hydrophilic heads, hydrophobic tails).

    •    Cholesterol – Stabilizes membrane fluidity .

    •    Cytoplasm – Material between plasma membrane and nucleus.

    •    Cytosol – Gel-like fluid with water, proteins, salts, sugars.

    •    Organelles – Specialized metabolic machinery .

    •    Nucleus – Control center; contains nucleolus, DNA (chromatin/chromosomes), and genes .

    •    Organelles & Functions:

    •    Rough ER – Produces proteins.

    •    Smooth ER – Produces lipids, steroids, detox.

    •    Golgi Apparatus – Processes and ships proteins/lipids.

    •    Mitochondria – Powerhouse; ATP production via respiration.

    •    Lysosomes – Digest and recycle waste.

    •    Centrioles – Organize cell division; form cilia/flagella .

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🔹 Cell Division

    •    Mitosis – Produces 2 genetically identical diploid cells (somatic).

    •    Interphase – Cell grows, replicates DNA & organelles (G1, S, G2).

    •    Prophase – Chromatin → chromosomes; nuclear membrane dissolves; spindle forms .

    •    Metaphase – Chromosomes align at equator .

    •    Anaphase – Centromeres split; chromatids pulled apart; cytokinesis begins .

    •    Telophase – Spindle dissolves; new nuclei form; cytokinesis completes .

    •    Meiosis – Produces 4 genetically unique haploid gametes (sperm/egg) from one diploid parent; reduces chromosome number by half .