3  •  Cells 85

The smallest part of you

What is a cell? 86

3.1

All organisms are made of cells. 86

3.2

Prokaryotic cells are structurally simple but extremely diverse. 89

3.3

Eukaryotic cells have compartments with specialized functions. 90

Cell membranes are gatekeepers. 94

3.4

Every cell is bordered by a plasma membrane. 94

3.5

Molecules embedded in the plasma membrane help it perform its functions. 96

3.6

Faulty membranes can cause diseases. 98

3.7

Membrane surfaces have a “fingerprint” that identifies the cell. 100

Molecules move across membranes in several ways. 102

3.8

Passive transport is the spontaneous diffusion of molecules across a membrane. 102

3.9

Osmosis is the passive diffusion of water across a membrane. 104

3.10

In active transport, cells use energy to move small molecules into and out of the cell. 106

3.11

Endocytosis and exocytosis are used for bulk transport of particles. 107

Cells are connected and communicate with each other. 110

3.12

Connections between cells hold them in place and enable them to communicate with each other. 110

Nine important landmarks distinguish eukaryotic cells. 112

3.13

The nucleus is the cell’s genetic control center. 112

3.14

Cytoplasm and the cytoskeleton form the cell’s internal environment, provide its physical support, and can generate movement. 114

3.15

Mitochondria are the cell’s energy converters. 115

3.16

This is how we do it: Can cells change their composition to adapt to their environment? 117

3.17

Lysosomes are the cell’s garbage disposals. 118

3.18

In the endoplasmic reticulum, cells build proteins and lipids and disarm toxins. 120

3.19

The Golgi apparatus processes products for delivery throughout the body. 122

3.20

The cell wall provides additional protection and support for plant cells. 124

3.21

Vacuoles are multipurpose storage sacs for cells. 125

3.22

Chloroplasts are the plant cell’s solar power plant. 126

StreetBIO: KNOWLEDGE YOU CAN USE

Drinking too much water can be dangerous! 128