chapter 3

• Cells are the smallest unit of life that can function independently
• Being composed of cells is one of the most basic characteristics of life
• All organisms are made of one or more cells
• The cell is the fundamental unit of life
• All cells come from preexisting cells
• All cells have the same basic chemical composition
• All cells use energy
• All cells contain DNA that is duplicated and passed on as each cell divides
• Light microscopes are used to view the entire cell
• Electron microscopes are used to view the parts of cells, and viruses, which are smaller and require higher magnification
• A transmission electron microscope (TEM) is a very powerful tool for seeing internal cell structures
• A scanning electron microscope (SEM) is also very powerful and reveals details on cell surfaces
• All cells have genetic material, ribosomes, cytoplasm, and a cell membrane
• Prokaryotes are small, simple in structure, and lack a nucleus
• Bacteria and archaea are two different domains of prokaryotes
• Eukaryotes are larger and more complex, with many internal parts including a nucleus and other membranous organelles
• Protists, fungi, plants, and animals are eukaryotic
• Some features are common to all three domains (cell membrane), while others are unique to each domain
• Bacteria lack membrane-bounded organelles, with ribosomes and DNA free in the cytoplasm
• Plant cells have most of the same membrane-bounded organelles as animal cells, with additional structures like a large central vacuole, cell wall, and chloroplasts
• Cell membranes form a barrier between the cell and the outside world, regulating passage of substances and maintaining homeostasis
• Cell membranes are composed of phospholipids, which are amphipathic molecules with polar and nonpolar regions
• Phospholipids are made of a molecule of glycerol, a phosphate group, and 2 fatty acids
• Phospholipids spontaneously form bilayers in water, creating a selectively permeable membrane to lipids and small, nonpolar molecules
• Phospholipids make up the cell membrane
• The nucleus controls protein production
• Proteins are synthesized on ribosomes
• Lysosomes contain digestive enzymes
• The cytoskeleton has three major components: Actin molecules microfilaments, intermediate filaments, and microtubules
• Plant cells are surrounded by a cell wall
• Plant cells communicate through plasmodesmata
• Different membrane proteins carry out different functions
• Cell membranes are fluid mosaics
• The membrane is neither a solid nor a liquid; it is more like Jell-O
• The combination of phospholipids and proteins forms a fluid mosaic
• The nucleus controls protein production
• The nucleus contains DNA, which specifies the “recipe” for the proteins
• The nucleus also contains the nucleolus, which synthesizes ribosomes
• RNA moves from the nucleus out to a ribosome, where the protein is synthesized
• Proteins are synthesized on ribosomes