Advanced BiologyAdvanced BiologyCell StructureCell Structure

Chapter 5Chapter 5

All organisms are All organisms are composed of cellscomposed of cells

Prokaryotes have a single circular Prokaryotes have a single circular molecule of DNA, while eukaryotic molecule of DNA, while eukaryotic cells have a nucleus, bounded by a cells have a nucleus, bounded by a nuclear membrane and containing nuclear membrane and containing DNA.DNA.

All organisms are All organisms are composed of cellscomposed of cells

Cytoplasm fills the interior of the cell, Cytoplasm fills the interior of the cell, exclusive of the nucleus, and a plasma exclusive of the nucleus, and a plasma membrane encloses the cell and membrane encloses the cell and separates it from its surroundings. The separates it from its surroundings. The plasma membrane contains several plasma membrane contains several types of proteins that allow the cell to types of proteins that allow the cell to interact with its environment. interact with its environment.

All organisms are All organisms are composed of cellscomposed of cells

Early cell theory included three Early cell theory included three principles: (1) All organisms are principles: (1) All organisms are composed of one or more cells; (2) composed of one or more cells; (2) cells are the smallest living things; and cells are the smallest living things; and (3) cells arise only by division of (3) cells arise only by division of previously existing cells.previously existing cells.

All organisms are All organisms are composed of cellscomposed of cells

Smaller cells are more advantageous Smaller cells are more advantageous than larger cells due to the limitations than larger cells due to the limitations of communication in relation to of communication in relation to surface area-to-volume ratios. surface area-to-volume ratios.

Eukaryotic cells are more Eukaryotic cells are more structurally complex than structurally complex than

prokaryotic cells.prokaryotic cells. Most prokaryotic cells are encased by Most prokaryotic cells are encased by

a strong cell wall and can be classified a strong cell wall and can be classified using the Gram staining procedure. using the Gram staining procedure.

Gram Positive – thicker cell wall Gram Positive – thicker cell wall retains the violet stainretains the violet stain

Gram Negative – thinner wall, does not Gram Negative – thinner wall, does not retain violet stain, but will appear pink retain violet stain, but will appear pink due to the second stain applied.due to the second stain applied.

Eukaryotic cells are more Eukaryotic cells are more structurally complex than structurally complex than

prokaryotic cells.prokaryotic cells. Some prokaryotes use a flagellum for Some prokaryotes use a flagellum for

locomotion. locomotion. Because prokaryotic cells lack Because prokaryotic cells lack

membrane-bounded organelles, all membrane-bounded organelles, all cytoplasmic constituents have access cytoplasmic constituents have access to all areas of the cell. to all areas of the cell.

Eukaryotes: Cells with Complex Eukaryotes: Cells with Complex InteriorsInteriors

Eukaryotic cells have extensive Eukaryotic cells have extensive internal compartmentalization, with internal compartmentalization, with multiple membrane-bounded multiple membrane-bounded organelles carrying out specific organelles carrying out specific functions. functions.

The Nucleus: Information Center for The Nucleus: Information Center for the Cellthe Cell

The nucleus is the repository for the The nucleus is the repository for the genetic information that directs cell genetic information that directs cell activities. activities.

The surface of the nucleus is bounded The surface of the nucleus is bounded by two phospholipid bilayer by two phospholipid bilayer membranes that form the nuclear membranes that form the nuclear envelope. envelope.

The Nucleus: Information Center for The Nucleus: Information Center for the Cellthe Cell

DNA is organized into chromosomes DNA is organized into chromosomes located in the nucleus. located in the nucleus.

The Endomembrane SystemThe Endomembrane System

The endoplasmic reticulum is an The endoplasmic reticulum is an extensive system of folded extensive system of folded membranes that compartmentalizes membranes that compartmentalizes the cell's interior. the cell's interior.

The Golgi apparatus collects, The Golgi apparatus collects, packages, modifies, and distributes packages, modifies, and distributes molecules throughout the cell. molecules throughout the cell.

The Endomembrane SystemThe Endomembrane System

Lysosomes contain digestive enzymes Lysosomes contain digestive enzymes that catalyze the rapid breakdown of that catalyze the rapid breakdown of proteins, nucleic acids, and proteins, nucleic acids, and carbohydrates. carbohydrates.

Ribosomes: Sites of Protein Ribosomes: Sites of Protein SynthesisSynthesis

Two ribosomal subunits join to form a Two ribosomal subunits join to form a ribosome when they attach to ribosome when they attach to messenger RNA to direct protein messenger RNA to direct protein synthesis. synthesis.

The Cytoskeleton: Interior The Cytoskeleton: Interior Framework of the CellFramework of the Cell

The cytoplasm of all eukaryotic cells is The cytoplasm of all eukaryotic cells is meshed by a network of protein fibers meshed by a network of protein fibers called the cytoskeleton, which called the cytoskeleton, which supports the shape of the cell and supports the shape of the cell and anchors its organelles. anchors its organelles.

The Cytoskeleton: Interior The Cytoskeleton: Interior Framework of the CellFramework of the Cell

Eukaryotic cells may contain three Eukaryotic cells may contain three types of cytoskeletal fibers: actin types of cytoskeletal fibers: actin filaments, microtubules, and filaments, microtubules, and intermediate filaments. intermediate filaments.

Not all eukaryotic cells are the Not all eukaryotic cells are the same.same.

Vacuoles and Cell WallsVacuoles and Cell WallsPlant cells usually contain a large Plant cells usually contain a large central vacuole for storage, and are central vacuole for storage, and are encased by thick cell walls and often encased by thick cell walls and often even by strong secondary walls. even by strong secondary walls.

Not all eukaryotic cells are the Not all eukaryotic cells are the same.same.

The Extracellular MatrixThe Extracellular MatrixAnimal cells lack the thick cell walls of Animal cells lack the thick cell walls of plants, but secrete a mixture of plants, but secrete a mixture of glycoproteins to form an extracellular glycoproteins to form an extracellular matrix, which helps coordinate the matrix, which helps coordinate the behavior of all the cells in a particular behavior of all the cells in a particular tissue. tissue.