A Tour of the Cell

 Every living organism is composed of one or more cells  A cell is the smallest unit having the properties of life  The continuity of life directly arises from the growth and division of single cells

 Plasma membrane  Phospholipid bilayer  Regulates transport in/out of cell  Genetic material (DNA)  Nucleus—eukaryotic  Nucleoid—prokaryotic  Cytoplasm  Fills cell  Contains organelles or cell structures

 Metabolic activity related to cell volume and surface area  Volume increases faster than surface area  The speed and amount of “stuff” (waste & nutrients) across a cell membrane is determined by the surface area  Larger cell volume needs more nutrients and produces more waste  Eventually the cell becomes big enough that the membrane can’t transport “stuff” fast enough

 Prokaryotes  “Before the nucleus”—no nucleus or membrane- covered structures (organelles)  Bacteria  Very small  Simplest cells  Eukaryotes  Nucleus and other complex organelles  Organelle—internal membrane-bound compartment that serves specialized functions. “Little organs”

 Nucleoid region  DNA (single loop)  Cell membrane  Cell wall (in some)  Capsule (in some)  Cytoplasm  Ribosomes  Pili  Flagellum

 Most kinds of living organisms  Protozoans  Algae  Fungi  Plants  Animals  Organelles allow compartmentalizing  Different areas of the cell can carry on reactions without affecting the rest of the cell

 Complex systems

 Nucleus  Control center  Nucleolus Constructs ribosomes  Chromatin All DNA in cell Organized into chromosomes 6 Feet of DNA in one nucleus!!!

 Nucleus (cont.)  Nuclear envelope/membrane Regulates transport of molecules Receptors for signaling  Nuclear pores Allow communication with cytoplasm

 Endoplasmic Reticulum (ER)  Rough Ribosomes attach Protein synthesis  Smooth No ribosomes Lipid synthesis Carbohydrate synthesis

 Ribosomes  Synthesize proteins  On rough ER

 Golgi Body/Apparatus  Package and process proteins & lipids  “Warehouse & finishing factory”  Receives vesicles from ER  Produces vesicles for finished products

 Endomembrane system  Interconnecting membrane system  Nuclear membrane  Rough ER  Smooth ER  Golgi apparatus  lysosomes/vacuoles  plasma membrane

 Vesicles—sacs containing enzymes  Lysosomes Intracellular digestion Destroy bacteria in white blood cells Breaks down damaged organelles  Peroxisomes Break down fatty acids & proteins Detoxify alcohol & other toxic substances  Vacuoles—large vesicles for storing food & water  Only some eukaryotes

 Mitochondria  Forms ATP (energy) from carbohydrates  Requires oxygen  Site of cellular respiration  Similar to bacteria: have their own DNA & ribosomes May be artifact of ancient symbiotic relationship between prokaryotes & eukaryotes

 Plastids  Chlorloplasts Photosynthesis (energy from light) Only in plant cells  Amyloplasts Store starches Specialized chloroplast  Like mitochondria, may be artifact of ancient symbiotic relationship between prokaryotes & eukaryotes

 Central Vacuole  Storage (amino acids, sugars, ions, wastes)

 Centrioles—produce microfilaments during cell division.

 Protein filaments between nucleus & plasma membrane  Internal shape & organization  Can be permanent or temporary

 Microtubules  Keep organelles & cell structures in place or move them  Centrioles  Compose cilia & flagellae  Intermediate filaments  Ropelike structure  Reinforce cell shape  Anchor some organelles  More permanent than other cytoskeleton  Microfilaments  Thin filaments  Help in cell division (contracts midsection)  Anchor membrane proteins  Help support cell shape  Muscle contraction (actin filaments)

 Motor proteins move things within cells  Flagella—long outer structures for movement  Usually only a few  Cilia—short outer structures for movement  Usually many  Pseudopod  “False foot”

 Structures outside of the plasma membrane  Holds cells together in tissues  Protects & supports plasma membrane  Collagen  Glycoproteins  Strong fibers

 Plasma (cell) membrane  Regulates movement of “stuff” in and out of cell  Phospholipid bilayer

 Animal Cell Junctions  Tight junctions Tight seal, prevents leakage of fluids  Anchoring junctions Rivets Fasten cells together  Gap junctions Channels, pores Allow small molecules to travel between neighboring cells Cell-to-cell communication Nutrient & waste transfer

 Cell wall  Strong, gives permanent shape to cell  Bacteria, protists, fungi, plants  Not found in animals  Plasmodesmata  Junctions between plant cell walls  Circulation and communication between cells