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Transcript
Chapter 4: A Tour of the Cell 1. Cell Basics 2. Prokaryotic Cells 3. Eukaryotic Cells 1. Cell Basics Limits to Cell Size There are 2 main reasons why cells are so small: If cells get too large: 1) there’s not enough membrane surface area to facilitate the transfer of nutrients & wastes… 10 μm 30 μm 2) it would take too long for materials to diffuse within the the cell 30 μm 10 μm Surface area of one large cube = 5,400 μm2 Total surface area of 27 small cubes = 16,200 μm2 1 Prokaryotic vs Eukaryotic Prokaryotic cells (i.e, bacteria) are quite small and don’t have internal organelle structures. Prokaryotic cell Eukaryotic cells tend to be much larger and contain organelles such as a nucleus. Nucleus Eukaryotic cell Organelles 2. Prokaryotic Cells General Characteristics of Prokaryotic Cells Lack membrane-enclosed compartments • do not have a nucleus • prokaryotic means “before nucleus” • do not have any other organelles All prokaryotes are small, single-celled organisms • bacteria and archaea Have a single, circular chromosome 2 Typical Prokaryotic Cell Outside: • cell wall (protects cell) • capsule Prokaryotic flagella (outermost layer) • flagella (propels cell) Ribosomes Capsule Inside: Cell wall Plasma membrane • cytoplasm (liquid inside) • nucleoid (chromosome) Nucleoid region (DNA) • ribosomes (protein synthesis) 3. Eukaryotic Cells General Characteristics of Eukaryotic Cells Have a nucleus and internal organelles • eukaryotic means “true nucleus” Eukaryotes can be single-celled, or multi-cellular organisms • Protists, Fungi, Plants & Animals Much larger than prokaryotic cells • ~10-100 μm (vs ~1-10 μm for prokaryotes) Have multiple, linear chromosomes 3 A typical Animal Cell Rough endoplasmic reticulum Smooth endoplasmic reticulum Nucleus Flagellum Not in most Lysosome plant cells Ribosomes Centriole Golgi apparatus Peroxisome Microtubule Cytoskeleton Plasma membrane Intermediate filament Mitochondrion Microfilament A typical Plant Cell Nucleus Golgi apparatus Rough endoplasmic reticulum Ribosomes Smooth endoplasmic reticulum Microtubule Intermediate Cytoskeleton filament Microfilament Central vacuole Not in animal Chloroplast cells Cell wall Mitochondrion Peroxisome Plasma membrane The Nucleus • enclosed by nuclear envelope (a double membrane) Two membranes of nuclear envelope Nucleus Nucleolus Chromatin Nuclear pore Endoplasmic reticulum Ribosomes • contains chromosomes (DNA + proteins) • nucleolus (ribosomes assembled from RNA & proteins) 4 The Endoplasmic Reticulum (ER) Nuclear envelope Ribosomes • smooth ER (new lipid production) • rough ER (protein synthesis by ribosomes) Smooth ER Rough ER Synthesis and packaging of a protein by the rough ER transport vesicle buds off 4 ribosome secretory protein inside transport vesicle 3 sugar chain 1 2 glycoprotein polypeptide rough ER Proteins made in the RER are transported within membrane-enclosed vesicles to the Golgi apparatus… The Golgi Apparatus “Receiving” side of Golgi apparatus Golgi apparatus Golgi apparatus Transport vesicle from ER New vesicle forming “Shipping” side of Golgi apparatus Transport vesicle from the Golgi • protein modification, sorting and distribution 5 Lysosomes Lysosome Digestion Vesicle containing damaged mitochondrion Membrane bound compartments derived from the Golgi: • acidic and contain digestive enzymes • fuse with vesicles containing material to be broken down and digest the contents The Secretory Pathway Nucleus Nuclear membrane Rough ER Smooth ER Transport vesicle Transport vesicle Golgi apparatus Lysosome Vacuole Plasma membrane Mitochondria Mitochondrion Site of cellular respiration Outer membrane Intermembrane space • conversion of “food energy” to energy stored in ATP molecules Inner membrane Cristae Matrix 6 Chloroplasts site of photosynthesis in plant cells Chloroplast Stroma Inner and outer membranes Granum Intermembrane space • production of glucose from CO2 and H2O using sunlight • the basis of essentially all ecosystems Central Vacuole in Plants Storage of water, waste, & nutrients Source of “turgor pressure” that maintains rigidity of plant cells • swells when water is plentiful due to osmosis • cell wall provides support, prevents lysis The Cytoskeleton Nucleus Nucleus Actin subunit Fibrous subunits Microfilament Tubulin subunit 10 nm 7 nm 25 nm Intermediate filament Microtubule Internal network of protein fibers important for: • cell structure & shape • cell movement • internal transport • cell division 7 Flagella & Cilia Cellular projections involved in movement. flagellum cilia Tracheal Epithileum Sperm Cell Found only on certain cell types • cilia move material across cell surface or provide motility • flagella are used for cell motility Key Terms for Chapter 4 • prokaryotic, eukaryotic • cell wall, capsule, flagella, nucleoid, cytoplasm • nucleus, endoplasmic reticulum, ribosome • Golgi apparatus, lysosome • endomembrane system, central vacuole • mitochondria, chloroplasts • cytoskeleton, cilia Relevant Review Questions 1-3, 5-11, 13-15 8