The Structure of Cells

3A The Structure of Cells

Monday, September 30, 2013

• Cytology ○ Cyto = cell ○ Logos = study of • Background ○ 1665 Robert Hook's Micrographia § Was studying cork cells ○ 1833 R. Brown § Discovered nucleus ○ 1838 M. Schleiden § Said that all plants consist of cells ○ 1839 T. Schwann § All animals consist of cells ○ 1855 Virchow § Cells come only from preexisting cells • The Cell Theory ○ Cells are the structural units of all living things ○ Cells are the functional units of living things ○ Cells come from preexisting cells • Processes of the cell ○ Absorption ○ Digestion ○ Synthesis ○ Respiration ○ Movement ○ Irritability ○ Excretion ○ Egestion ○ Secretion ○ Homeostasis ○ Reproduction • Cellular Organization ○ Unicellular § Consists of only one cell § Examples include □ Bacteria □ Protozoans □ Some algae □ Some fungi ○ multicellular § Organisms made of many cells § Colonial □ A group of similar cells living together that could exist separately □ Examples include ® Algae ® Fungi § Multicellular levels □ Tissues ® Groups of similar cells □ Organs ® Groups of tissues □ Systems ® Groups of organs • Structures of the Cell § Boundaries § Cytoplasm § Nucleus ○ Organelles § A structure inside the cell that performs a specific function • Types of cells ○ Prokaryotic § Lack of true nucleus § Have only non-membrane-bound organelles ○ Eukaryotic § ''True nucleus'' § Have membrane-bound and non-membrane-bound organelles • Cell boundaries ○ Cell membrane § Outermost boundary § Surrounds every cell § Composed of lipids and proteins □ Lipid bilayer (phospholipids) □ Hydrophilic and hydrophobic ends § Fluid mosaic model □ Cell membrane flows like a liquid ○ Cell wall § Primarily composed of cellulose § Examples include □ Plants □ Algae □ Fungi □ Many protozoans □ Bacteria ○ Capsule or sheath § Many unicellular and colonial organisms § Extra protection ○ Cytoplasm □ All of the materiel within the cell membrane except the nucleus □ Cytoplasmic organelles § Mitochondria □ Powerhouse of the cell □ Center of cellular respiration □ Cristae ® Folds of the inner membrane ® Contain enzymes for cellular respiration § Ribosomes □ Non-membrane-bound organelles functioning as "protein factories" § Endoplasmic Reticulum □ Often called "ER" □ Folds of membranes running throughout the cytoplasm □ Rough and smooth □ Channel and synthesis § Golgi Apparatus □ Composed of flat, curved membrane-covered sacs □ Synthesis and secretion § Lysosomes □ Contain enzymes for digestion □ Destroy old or useless cell structures § Cytoskeleton □ The system of fibers within the cell that provides structure for the cell □ Microtubules □ Centrosome □ Microfilaments § Flagella and Cilia □ Flagellum ® Long whip-like structure ® Motility □ Cilia ® Short, hair-like structures ® Motility § Plastids □ Found in the cells of plants and algae but not in animal cells □ Leucoplasts ® "leuco" - clear ® Storehouse for plant products □ Chromoplasts ® "chromo" - color ® Contain pigments □ Chloroplast ® Important in photosynthesis ® Thylakoids ◊ Flattened sacs inside the chloroplast ◊ Organized into stacks called grana (granum, sing.) □ Vacuoles ® Membrane bound sacks for storage ® Vesicle - a small vacuole Vauole Function Food Ingestion Waste Egestion central Maintain turgor pressure in plant cells Contractile Removes extra water from unicellular organisms Secretion Secretes § Nucleus □ Control center □ Nuclear envelope □ Chromatin material □ Nucleolus ® Concentrated RNA ® Ribosome synthesis