Anatomy and Physiology_ An integrative approach, 4th edition

Cytology
- Definition: Study of cells.
Microscopy
- Objective: Using a microscope to view small-scale structures.
- Staining Techniques
- Purpose: Provide contrast to visualize cellular structures.
Types of Microscopes
- Light Microscope (LM)
- Produces a two-dimensional image by passing light through a specimen.
- Electron Microscope (EM)
- Definition: Uses a beam of electrons to illuminate specimen.
- Advantages: Greater magnification and resolution than light microscopes.
- Types of EM:
  - Transmission Electron Microscope (TEM):
  - Method: Directs an electron beam through thin-cut sections to produce 2-D images.
  - Scanning Electron Microscope (SEM):
  - Method: Directs an electron beam across the surface to produce 3-D images.

Size Variability: Cells vary greatly in size and shape.
- Example: Erythrocyte (red blood cell) measures between 7 to 8 μm.
- Example: Human oocyte (egg cell) has a diameter of 120 μm.
- Most cells are microscopic.
Common Shapes:
- Spherical, cubelike, columnlike, cylindrical, disc-shaped, or irregular.

Plasma Membrane
- Function: Forms the outer barrier, separating internal contents from the external environment.
- Modified extensions include cilia, flagellum, and microvilli.
Nucleus
- Description: Largest structure in a cell, enclosed by a nuclear envelope.
- Contains: Genetic material (DNA) and nucleolus.
- Nucleoplasm: Inner fluid of the nucleus.
Cytoplasm
- Definition: Contents between plasma membrane and nucleus.
- Includes: Cytosol, organelles, and inclusions.

Cytoplasmic Components
- Cytosol
- Definition: Viscous fluid of cytoplasm with high water content, containing dissolved macromolecules and ions.
- Organelles
- Definition: Complex, organized structures within cells, unique in shape and function.
- Two categories:
  - Membrane-Bound Organelles:
  - Definition: Enclosed by a membrane that separates contents from cytosol.
  - Examples: Endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, mitochondria.
  - Non-Membrane-Bound Organelles:
  - Definition: Not enclosed within membranes, composed mainly of proteins.
  - Examples: Ribosomes, cytoskeleton, centrosome, proteasomes.
- Inclusions
- Definition: Cytosol stores temporary molecules not considered organelles.
- Examples: Pigments, glycogen, triglycerides.

General Functions of Cells
- Maintain integrity and shape of a cell (dependent on plasma membrane and internal contents).
- Obtain nutrients and form chemical building blocks.
- Harvest energy for survival and dispose of waste to prevent disruption of cellular activities.
- Certain cells capable of division to replace dead cells.

What is the advantage of using a Transmission Electron Microscope (TEM) compared to a Light Microscope (LM) for intracellular structure study?
Which cell type is larger, an erythrocyte or a human oocyte? What are their respective sizes?
Diagram and label the three main components of the cell: the plasma membrane, nucleus, and cytoplasm.
Which cellular structure forms the boundary of a cell and maintains its integrity?

Plasma Membrane
- Composition: Fluid mixture with equal parts lipid and protein by weight.
- Function: Regulates movement of most substances in and out of the cell.
- Contains various lipid types:
- Phospholipids
  - Structure: Resembles a “balloon with two tails.”
  - Components: Polar hydrophilic head and two nonpolar hydrophobic tails.
  - Orientation: Forms two parallel sheets tail-to-tail.
  - Role: Ensures cytosol remains inside the cell and interstitial fluid remains outside.
- Cholesterol
  - Structure: Four-ring lipid scattered within phospholipid bilayer.
  - Function: Strengthens and stabilizes membrane against temperature changes.
- Glycolipids
  - Structure: Lipids with attached carbohydrate groups.
  - Location: Only on the outer phospholipid region.
  - Function: Helps form glycocalyx, which aids in protection and recognition of the cell.

Overview
- Membrane proteins account for about half of the plasma membrane by weight.
- General Function: Float and move within the fluid bilayer performing most of the membrane’s functions.
Two Structural Types:
- Integral Proteins
- Characteristics: Embedded within and extend across the phospholipid bilayer.
- Interactions: Hydrophobic regions interact with the hydrophobic interior while hydrophilic regions are exposed to aqueous environments.
- Some are glycoproteins with attached carbohydrate groups.
- Peripheral Proteins
- Characteristics: Not embedded in the lipid bilayer, loosely attached to the external or internal surfaces of the membrane.

Functional Categories of Proteins
- Transport Proteins: Regulate movement of substances across the membrane (e.g., channels, carrier proteins, pumps, symporters, antiporters).
- Cell Surface Receptors: Bind molecules called ligands (e.g., neurotransmitters from nerve cells attaching to muscle cells to initiate contraction).
- Identity Markers: Communicate to other cells that they belong to the body, distinguishing healthy cells from those that are harmful.
- Enzymes: Attached to either the internal or external surface of a cell, catalyzing chemical reactions.
- Anchoring Sites: Secure the cytoskeleton to the plasma membrane.
- Cell-Adhesion Proteins: Facilitate cell-to-cell attachment.

How do lipids maintain the basic physical barrier of the plasma membrane?
What type of plasma membrane protein facilitates movement of materials across the membrane? Name three subtypes.

Function of Plasma Membrane
- Serves as a physical barrier between the cell and surrounding interstitial fluid.
- Regulates movement into and out of a cell.
- Establishes and maintains an electrochemical gradient.
- Functions in cell communication.
Membrane Transport
- Definition: Process of obtaining and eliminating substances across the plasma membrane.
- Types of Processes:
- Passive Processes:
  - Do not