A Tour of the Cell Figures 4.4 – 4.7 CHAPTER 4 A Tour of the Cell Figures 4.4 – 4.7

The Two Major Categories of Cells The countless cells on earth fall into two categories Prokaryotic cells Eukaryotic cells

Prokaryotic and eukaryotic cells differ in several respects Prokaryotic cell Nucleoid region Eukaryotic cell Nucleus Organelles Figure 4.4

Prokaryotic cells Are smaller than eukaryotic cells Lack internal structures surrounded by membranes Lack a nucleus

Prokaryotic flagella Nucleoid region (DNA) Plasma Ribosomes membrane Cell wall Capsule Pili Figure 4.5

A Panoramic View of Eukaryotic Cells An idealized animal cell Centriole Ribosomes Lysosome Not in most plant cells Flagellum Cytoskeleton Plasma membrane Mitochondrion Nucleus Rough endoplasmic reticulum (ER) Smooth endoplasmic reticulum (ER) Golgi apparatus Figure 4.6A

An idealized plant cell Not in animal cells Cytoskeleton Mitochondrion Central vacuole Nucleus Cell wall Rough endoplamsic reticulum (ER) Chloroplast Ribosomes Plasma membrane Smooth endoplasmic reticulum (ER) Plasmodesmata Golgi apparatus Figure 4.6B

MEMBRANE STRUCTURE AND FUNCTION The plasma membrane separates the living cell from its nonliving surroundings

A Fluid Mosaic of Lipids and Proteins The membranes of cells are composed of Lipids Proteins

The lipids belong to a special category called phospholipids Phospholipids form a two-layered membrane, the phospholipid bilayer Outside cell Hydrophilic head Hydrophobic tail Cytoplasm (inside cell) (a) Phospholipid bilayer of membrane Figure 4.7A

Most membranes have specific proteins embedded in the phospholipid bilayer Hydrophilic region of protein Phospholipid bilayer Hydrophobic region of protein (b) Fluid mosaic model of membrane Figure 4.7B