Chapter 4: Cells Overview

Introduction to Cells

Cells are the smallest unit of life.
All living things are made of one or more cells.
Types of Organisms:
- Unicellular: Single-celled organisms.
- Multicellular: Organisms like humans made of multiple cells.
Cells with common functions form tissues, which combine to form organs, and organs make up organ systems.

Microscopes: Used to view cells too small for the naked eye.
Magnification & Resolution:
- Magnification depends on the types of lenses.
- Resolution distinguishes two adjacent structures as separate.
Types of Microscopes:
- Light Microscopes: Use visible light.
- Electron Microscopes: Use electrons for higher resolution.
Staining: Used to view transparent cells, but usually kills them.
Phase Contrast Microscopy: Allows viewing of live, unstained specimens.

Tenets:
1. Cells are the basic units of life.
2. All living things are made of cells.
3. All cells come from pre-existing cells.
Cytotechnologists: Study cells to detect abnormalities, such as HPV infections.

Common to All Cells:
- Plasma membrane.
- Cytoplasm (includes cytosol and structures).
- DNA.
- Ribosomes.

Characteristics:
- No nucleus or membrane-bound organelles.
- DNA is in the nucleoid.
- Often have cell walls made of peptidoglycan.
- Domains: Bacteria and Archaea.
Structures:
- Ribosomes, cell membrane, and cell wall.
- May have flagella, pili, and capsules.
Size: Prokaryotes are 10-100 times smaller than eukaryotic cells.

Importance of Efficient Transport:
- Smaller cells are more efficient due to a higher surface area to volume ratio.
- Large cells have more difficulty transporting materials.
Adaptations in Large Cells:
- Increase surface area through invaginations or becoming flat.
Prokaryotic vs. Eukaryotic Cells:
- Prokaryotic cells lack complex structures that aid in transport.