Ch4 Cell INK

Chapter 4: Cell Biology

Key Cell Components

  • Plasma Membrane: Structures that serve as the barrier for cells, consisting of a phospholipid bilayer, cholesterol, and proteins.

  • Cytoplasm: Jelly-like substance inside the cell, which contains organelles and is the site for many metabolic processes.

  • Nucleus: Control center of the cell containing chromatin and a nucleolus.

    • Nuclear Envelope: Double membrane that surrounds the nucleus.

    • Nuclear Pores: Openings that control the entry and exit of molecules from the nucleus.

  • Organelles: Specialized structures within the cell that perform specific functions, such as ribosomes, mitochondria, Golgi apparatus, lysosomes, and endoplasmic reticulum.

Definitions of Key Terms

  • Cytology: Study of cells.

  • Microscopy: Techniques used to view cellular structures.

  • Phospholipid Bilayer: Major component of the plasma membrane, consisting of hydrophilic heads and hydrophobic tails.

  • ATP (Adenosine Triphosphate): The primary energy currency of the cell.

  • Diffusion: Passive movement of molecules from areas of high concentration to areas of low concentration.

  • Osmosis: Diffusion of water across a selectively permeable membrane.

Cell Theory

  • Principles:

    • All living things are composed of cells.

    • The cell is the basic unit of life.

    • All cells arise from pre-existing cells.

Functions of the Plasma Membrane

  • Selectively Permeable: Controls the movement of substances in and out of the cell.

  • Functionality Features:

    • Encloses and supports cell contents.

    • Facilitates communication between cells.

    • Maintains homeostasis.

    • Contributes to cell recognition.

Plasma Membrane Composition

  • Composed of:

    • 45-50% Lipids (primarily phospholipids)

    • 45-50% Proteins

    • 4-8% Carbohydrates

Membrane Lipids and Proteins

  • Cholesterol: Increases membrane fluidity.

  • Proteins: Function as channels, receptors, and enzymes that help in cell signaling and substance transport.

  • Membrane Potential: Difference in charge across the plasma membrane critical for action potentials in neurons and muscle cells.

Transport Mechanisms

  • Passive Transport:

    • Simple Diffusion: Movement of molecules without energy across the membrane.

    • Facilitated Diffusion: Requires channels or carrier proteins.

    • Osmosis: The specific case of water movement via selective permeability.

  • Active Transport:

    • Requires ATP to move substances against their concentration gradient.

    • Examples include the Sodium-Potassium Pump.

Osmosis and Tonicity

  • Tonicity refers to the ability of a solution to affect cell volume.

  • Hypotonic: Causes cells to swell; water enters.

  • Hypertonic: Causes cells to shrink; water exits.

  • Isotonic: No net movement of water; cells remain normal.

Cellular Transport Processes

  • Endocytosis: Process of taking substances into the cell via vesicle formation.

  • Exocytosis: Process of exporting substances out of the cell using vesicles.

Secondary Active Transport

  • Co-transport mechanism:

    • Uses the energy from the movement of one ion (e.g., Na+) down its concentration gradient to facilitate the movement of another molecule (e.g., glucose) against its gradient.

Overview of Organelles

  • Small structures within the cell that have specific functions:

    • Mitochondria: Powerhouse of the cell, ATP production.

    • Ribosomes: Synthesize proteins.

    • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

    • Lysosomes: Digestive enzymes that break down waste.

    • Endoplasmic Reticulum: Rough (with ribosomes) and smooth (lipid synthesis).

Cytoplasm

  • Fluid inside the cell excluding the nucleus.

  • Cytosol: Fluid part of the cytoplasm.

  • Cytoskeleton: Network providing structural support and shape.