Cell Theory • Cells : – Most basic unit of living system – Arise by cell division from existing cell – Make up all living organisms • All living things composed of one or more cells & cell products
Cell membrane Separates cell from environment and regulates passage in/out of cell Cell Structure and Function
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How tiny are cells, anyway?
Cell Structure and Function
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How tiny are cells, anyway? Very, very tiny
Cell Structure and Function
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Resolution of lenses
Cell Structure and Function
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Electron Microscope • Used to see things smaller than 0.1 mm (= 100 μm) • Uses beam of electrons to “see” structures • Scanning EM used to study surface of object • Transmission EM used to internal structure Cell Structure and Function
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Light microscope
SEM
Cell Structure and Function
TEM
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Categories of Cells • Based on how they feed – Autotrophs vs. Heterotrophs
• Based on cell structure – Prokaryotes vs. Eukaryotes
Cell Structure and Function
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Categories of Cells Autotrophs make their own food
Heterotrophs eat another organism
Cell Structure and Function
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Categories of Cells Prokaryotes lack organelles
Eukaryotes have organelles
Cell Structure and Function
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• Organelles – Internal membrane-bound structures • For example, nucleus & chloroplasts
Cell Structure and Function
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• Organelles – Internal membrane-bound structures • For example, nucleus & chloroplasts
– Perform specific functions • Nucleus contains DNA, transcribes genetic code into messages that control cell activities • Chloroplasts site of photosynthesis
Cell Structure and Function
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Prokaryote--no organelles
Cell Structure and Function
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Eukaryote--organelles
Cell Structure and Function
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Eukaryotic Cell Structure • Variety of organelles present • Cell structure related to cell function – Not all organelles present in all cells – Abundance of organelles differs between cells
Cell Structure and Function
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Plant vs. Animal Cells • Plant cells
• Animal cells
Cell Structure and Function
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Plant vs. Animal Cells • Plant cells – Cell wall
• Animal cells – None
Cell Structure and Function
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Plant vs. Animal Cells • Plant cells – Cell wall – Chloroplasts for P/S
• Animal cells – None – None
Cell Structure and Function
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Plant vs. Animal Cells • Plant cells – Cell wall – Chloroplasts for P/S – Central vacuole
• Animal cells – None – None – None
Cell Structure and Function
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Plant vs. Animal Cells • Plant cells – – – –
Cell wall Chloroplasts for P/S Central vacuole None
• Animal cells – – – –
Cell Structure and Function
None None None Lysosomes
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Plant vs. Animal Cells • Plant cells – – – – –
Cell wall Chloroplasts for P/S Central vacuole None None
• Animal cells – – – – –
Cell Structure and Function
None None None Lysosomes Centrioles to assist with cell division
Nucleus Nuclear Envelope: • 2-layered membrane • Pores allow chemical communication Inside Nucleus: • Chromatin = DNA + protein • Nucleolus – makes ribosomal RNA (rRNA) Cell Structure and Function
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Nucleus Ribosomes: • Made of rRNA • Not organelles • Present in cytoplasm & on membrane outside nucleus • Function in making proteins
Cell Structure and Function
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Nucleus Inside nucleus: • DNA messenger RNA Outside nucleus: • Ribosomes use mRNA to make proteins to be used in cell functions
Cell Structure and Function
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Ribosomes
Cell Structure and Function
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Endomembrane System • Membrane made around nucleus
Cell Structure and Function
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Endomembrane System • Membrane made around nucleus • Membrane moves from nucleus to outer plasma membrane – Moves through various organelles on the way – Different function with each new organelle
Cell Structure and Function
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Endomembrane System
Cell Structure and Function
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Endomembrane System
Cell Structure and Function
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Endomembrane System
Cell Structure and Function
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Endomembrane System
Cell Structure and Function
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Endomembrane System
Cell Structure and Function
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Endomembrane System
Cell Structure and Function
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Endomembrane System
Cell Structure and Function
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Organelles of Endomembrane System
Cell Structure and Function
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Organelles of Endomembrane System: Nuclear Envelope • Membrane made around the nucleus • Moves into Endoplasmic Reticulum
Cell Structure and Function
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Organelles of Endomembrane System: Endoplasmic Reticulum Rough ER: • Has ribosomes • Surface area • Makes proteins
Cell Structure and Function
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Organelles of Endomembrane System: Endoplasmic Reticulum Rough ER: • Has ribosomes • Surface area • Makes proteins
Smooth ER: • • • •
No ribosomes, has enzymes Surface area Makes lipids Breaks down drugs, etc.
Cell Structure and Function
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Organelles of Endomembrane System: Endoplasmic Reticulum
Cell Structure and Function
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Organelles of Endomembrane System: Transport Vesicles • Membrane sacs pinched off ER or other organelles • Transport – to Golgi apparatus – to other areas of cell – to outside of cell
Cell Structure and Function
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Organelles of Endomembrane System: Transport Vesicles • Membrane sacs pinched off ER or other organelles • Transport – to Golgi apparatus – to other areas of cell – to outside of cell
Cell Structure and Function
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Organelles of Endomembrane System: Golgi Apparatus • Flattened sacs pinched off Rough ER • Receives proteins from rough ER via transport vesicles • Modifies proteins • Packages proteins for transport to other area of cell or plasma membrane Cell Structure and Function
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Organelles of Endomembrane System: Golgi Apparatus
Cell Structure and Function
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Organelles of Endomembrane System: Transport Vesicles • Membrane sacs pinched off ER or other organelles • Transport – to Golgi apparatus – to other areas of cell – to outside of cell • Fuse with plasma membrane
Cell Structure and Function
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Organelles of Endomembrane System: Lysosomes • Sacs pinched off from Golgi membrane • Contain digestive enzymes • Intracellular digestion – Food vacuoles to digest food – Damaged organelles – Cell destruction after death Cell Structure and Function
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Organelles of Endomembrane System: Lysosomes
Cell Structure and Function
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Organelles of Endomembrane System: Vacuoles • Sacs pinched off from internal membrane or plasma membrane • Variety of types with different functions – Contractile vacuoles in Protista – Central vacuole in plants
Cell Structure and Function
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Organelles of Endomembrane System: Vacuoles Contractile vacuole • Absorbs excess water in cytoplasm • Contracts to expel excess water
Cell Structure and Function
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Organelles of Endomembrane System: Vacuoles Central vacuole • Storage – – – – –
Cell Structure and Function
Water Nutrients Wastes Toxins Pigments
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Other Organelles & Structures Not Associated with Endomembrane System
Cell Structure and Function
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Organelles associated with energy • Chloroplasts and mitochondria – Provide cellular energy – Contain their own DNA • • • •
Feature not found in other organelles Encodes some of their proteins Still require nuclear DNA for full function Considered evidence that these organelles evolved from free-living prokaryotes
Cell Structure and Function
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Organelles associated with energy Chloroplasts • Found in photosynthetic cells – plants and some protistans
• Site of P/S
Cell Structure and Function
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Chloroplasts • Grana – Surface area to trap light – Contains chlorophyll
• Stroma – fluid – Site of sugar production
Cell Structure and Function
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Organelles associated with energy Mitochondria • Found in all eukaryotes • Site of ATP production
Cell Structure and Function
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Mitochondrion • Cristae – Surface area for ATP production
• Matrix – Fluid – Site of sugar breakdown
Cell Structure and Function
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Non-membrane bound structures • Found in prokaryotes or eukaryotes • May or may not be found in all cells
Cell Structure and Function
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Non-membrane bound structures Cytoskeleton • Network of fibers – Microtubules • Associated with cell movement
– Intermediate filaments – Microfilaments
• Function – Support – Movement Cell Structure and Function
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Non-membrane bound structures Cytoskeleton • Support – Maintains cell shape – Holds organelles in place
Cell Structure and Function
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Non-membrane bound structures Cytoskeleton • Movement – Network of fibers constantly dissolving and reforming in new arrangements • Allows cell to change shapes • Allows chromosomes to move apart during cell division
• Core of microtubules • Occur in pairs • Act as anchor to pull chromosomes apart during cell division • Not found in plant cells
Cell Structure and Function
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Non-membrane bound structures Flagella & Cilia • Hair-like structures that aid in movement • Core of microtubules creates beating motion • Move cells through liquid • Create currents past non-moving cells Cell Structure and Function
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Non-membrane bound structures Flagella • • • •
Long whipping “tails” Usually 1-3 per cell Propel cell forward Found in many protists • Found in human sperm
Cell Structure and Function
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Non-membrane bound structures Cilia • Short hair-like structures • Usually many on cell surface • Beat in synchrony • Found in many protists • Found in human tissues Cell Structure and Function
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Non-membrane bound structures
Cell Structure and Function
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Non-membrane bound structures Cell Wall • Found in variety of cells – – – –
Bacteria Protistans Plants Fungus
• Protective structure outside plasma membrane • Porous to water, salts Cell Structure and Function
Cell wall 69
Cell Junctions • Connections between cells – Proteins tie cells together
Cell Structure and Function
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Cell Junctions • Types – Tight junctions • Seal cells together so molecules cannot slip between cells – i.e., cells lining intestine
