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Transcript
Cell Organelles Prokaryotic • Do not have structures surrounded by membranes • Few internal structures • One-celled organisms, Bacteria http://library.thinkquest.org/C004535/prokaryotic_cells.html Differences between Prokaryotic & Eukaryotic cells Feature Size Genetic material Organelles Prokaryote Eukaryote Small about 0.1 - 10.0 micrometres From 10 to 100 micrometres Circular DNA (in cytoplasm) and small rings of DNA called plasmids DNA in form of linear chromosomes (in nucleus) Few present, none membrane bound Many organelles: •Double membranes e.g.: nucleus, mitochondria & chloroplasts •Single membrane e.g.: GA, ER & lysosomes Cell walls Rigid formed from glycoproteins (mainly murein) •Fungi: rigid, formed from polysaccharide, chitin. •Plant: rigid, formed from polysaccharides. E.g.: cellulose. •Animals no cell wall Cystoskeleton Not present Present Cell Organelles • Organelle= “little organ” • Found only inside eukaryotic cells • All the stuff in between the organelles is cytosol (water and dissolved substances) • Everything in a cell except the nucleus is cytoplasm Cell Membrane • Boundary of the cell • Made of a phospholipid bilayer Nucleus • Control center of the cell • Contains DNA • Surrounded by a double membrane • Usually the easiest organelle to see under a microscope • Usually one per cell Cytoskeleton • Acts as skeleton and muscle • Provides shape and structure • Helps move organelles around the cell • Made of three types of filaments Endoplasmic Reticulum • A.k.a. “ER” • Connected to nuclear membrane • Highway of the cell • Rough ER: studded with ribosomes; it makes proteins • Smooth ER: no ribosomes; it makes lipids and it detoxifies substances within the cell Ribosome • Site of protein synthesis • Found attached to rough ER or floating free in cytosol • Produced in a part of the nucleus called the nucleolus That looks familiar…what is a polypeptide? Golgi Apparatus • Looks like a stack of plates • Stores, modifies and packages proteins • Molecules transported to and from the Golgi by means of vesicles (transport organelles) Lysosomes • Garbage recycling centre/disposal of the cell • Contain digestive enzymes that break down wastes, proteins and lipids Which organelles do lysosomes work with? Mitochondria • “Powerhouse of the cell” • Cellular respiration occurs here to release energy for the cell to use • Bound by a double membrane • Has its own strand of DNA Chloroplast • Found only in plant cells • Contains the green pigment chlorophyll • Site of food (glucose) production • Bound by a double membrane Cell Wall • Found in plant and bacterial cells • Rigid, protective barrier • Located outside of the cell membrane • Made of cellulose in plants • Extra protection for the cell and provides rigidity Vacuoles • Large central vacuole usually in plant cells • Many smaller vacuoles in animal cells • Storage container for water, food, enzymes, wastes, pigments, etc. Centrosome • "microtubule organising center” • Made of a pair of centrioles perpendicular to one another • Aids in cell division • Usually found only in animal cells • Made of microtubules Where else have we talked about microtubules? Cilia are thread-like projections of certain cells that beat in a regular fashion to create currents that sweep materials along; Flagella may extend to the rear of a cell and push it forward by snakelike wriggling, or stick out in front and draw it along. Each sperm cell is propelled by a trailing flagellum that accelerates the little torpedo forward in its quest to fertilise an egg. Quick Review • Which organelle is the control center of the cell? Nucleus • Which organelle holds the cell together? Cell membrane • Which organelles are not found in animal cells? Cell wall, central vacuole, chloroplasts • Which organelle helps plant cells make food? Chloroplasts • What does E.R. stand for? Endoplasmic reticulum