Ch 04 H

Chapter 04: Anatomy & Physiology Overview

4.1 How Cells Are Studied

• Cytology: Study of cells.

• Microscopy: Techniques using microscopes to view small-scale structures.

  • Staining Techniques: Used to provide contrast for better visibility.

4.1a Microscopic Techniques

• Light Microscope (LM):

  • Produces 2D images by passing light through a specimen.

• Electron Microscope (EM):

  • Uses electron beams for greater magnification and resolution.

  • Transmission Electron Microscope (TEM):

    • Directs electrons through thin sections; produces 2D images.

  • Scanning Electron Microscope (SEM):

    • Scans surface of specimen; produces 3D images.

4.1b Cell Size and Shape

• Variation: Cells vary significantly in size (e.g., erythrocytes: 7-8 μm; human oocyte: 120 μm) and shape (spherical, cubelike, etc.).

• Most Cells: Are generally microscopic.

4.1c Common Features and General Functions

• Plasma Membrane:

  • Outer limiting barrier that separates internal and external environments.

• Nucleus:

  • Largest structure, contains genetic material (DNA).

  • Enclosed by nuclear envelope, contains nucleolus.

• Cytoplasm:

  • Contents between plasma membrane and nucleus consisting of cytosol and organelles.

Cytoplasmic Components

• Cytosol: Intracellular fluid with dissolved macromolecules and ions.

• Organelles: Complex structures with unique shapes and functions.

  • Membrane-bound: Enclosed by a membrane (e.g., mitochondria, Golgi apparatus).

  • Non-membrane-bound: Composed of proteins (e.g., ribosomes, cytoskeleton).

• Inclusions: Temporarily stored materials in cytosol (pigments, glycogen).

4.1c Functions of Cells

• Cell Integrity: Maintained by plasma membrane.

• Nutrient Acquisition: Cells obtain nutrients and form chemical building blocks.

• Waste Disposal: Dispose of unwanted materials to maintain functionality.

• Cell Division: Some cells are capable of dividing to replace dead cells and maintain tissues.

4.2 Plasma Membrane Components

• Composition: Fluid mixture of lipids and proteins (mostly phospholipids).

• Function: Regulates movement in and out of cells.

• Types of Lipids:

  • Phospholipids: Bilayer formation with hydrophilic heads and hydrophobic tails.

  • Cholesterol: Strengthens and stabilizes membrane.

  • Glycolipids: Lipids with carbohydrate groups aiding in cell recognition.

4.2b Membrane Proteins

• Integral Proteins: Embedded within and traverse the bilayer interface.

• Peripheral Proteins: Attached to the exterior or interior surfaces of the membrane.

• Functional Categories:

  • Transport Proteins: Enable movement across the membrane.

  • Receptor Proteins: Bind signaling molecules (ligands).

  • Enzymes: Catalyze reactions locally.

4.3 Membrane Transport

• Processes:

  • Passive Processes (No energy): Include diffusion and osmosis.

  • Active Processes (Require energy): Active transport and vesicular transport.

Passive Processes: Diffusion

• Definition: Movement from high to low concentration.

  • Types: Simple diffusion, facilitated diffusion (channel or carrier-mediated).

• Factors Affecting Rate: Temperature, concentration gradient steepness.

Passive Processes: Osmosis

• Definition: Movement of water across a semipermeable membrane.

• Mechanism: Water crosses through phospholipids or aquaporins.

• Concentration Gradient Influence: Water moves down the gradient until equilibrium.

4.5 Cell Communication

• Importance: Facilitated by structures like glycolipids and glycoproteins.

• Types of Signaling:

  • Direct Contact: Important for immune cells, and during fertilization.

  • Ligand-Receptor Signaling: Involves neurotransmitters and hormones affecting growth and function.

4.6 Structures of the Nucleus

• Nuclear Envelope: Double membrane with pores for molecule transport.

• Nucleolus: Produces ribosome subunits from RNA and proteins.

• DNA Structure: Composed of nucleotides in a double helix, forming chromatin and chromosomes depending on cell division status.

4.9 Cell Division

• Types:

  • Mitosis: Divides somatic cells, producing two identical cells.

  • Meiosis: Reductive division for sex cells.

• Phases of Cell Cycle:

  • Interphase: Preparation for division (G1, S, G2 phases).

  • Mitotic Phase: Includes mitosis and cytokinesis.

4.10 Cell Aging and Death

• Aging: Characterized by reduced ability to maintain homeostasis and functional decline.

• Cell Death: Can occur from damage or be programmed (apoptosis), which serves to remove unnecessary or harmful cells.