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Download Chapter 4: A Tour of the Cell 1. Cell Basics Limits to Cell Size
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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 Rough endoplasmic reticulum Nucleus Ribosomes Smooth endoplasmic reticulum Golgi apparatus Microtubule Intermediate Cytoskeleton filament Microfilament Central vacuole Not in animal Chloroplast cells Cell wall Mitochondrion Peroxisome Plasma membrane The Nucleus • enclosed by nuclear envelope (double membrane) • contains chromosomes (DNA + proteins) • nucleolus • ribosome production • nuclear pores • allow transport 4 The Endoplasmic Reticulum (ER) Convoluted membrane continuous with the nuclear env. • smooth ER (new lipid production) • rough ER (protein synthesis by ribosomes) 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 Discontinuous membrane stacks distal to the ER: • receive proteins, lipids from ER via vesicles • site of modification, packaging, sorting and distribution 5 Lysosome formation & function rough ER Lysosomes are membrane bound compartments derived from the Golgi apparatus 1 transport vesicle (containing inactive hydrolytic enzymes) Golgi apparatus plasma membrane engulfment of particle lysosome engulfing damaged organelle 2 “food” They are acidic and break down materials from inside & outside of the cell. lysosomes 3 food vacuole 4 5 digestion The Endomembrane System Newly made lipids & proteins in the ER travel to the Golgi apparatus and then to various destinations: transport vesicle Rough ER from ER to Golgi transport vesicle from Golgi to plasma membrane • plasma membrane Plasma membrane • cell exterior Nucleus • lysosomes Vacuole Lysosome Smooth ER Nuclear envelope • other organelles Golgi apparatus Mitochondria Main site of energy production (i.e., ATP, heat): • break down of food molecules (sugars and fatty acids) • the process of respiration (requires O2) 6 Chloroplasts Site of photosynthesis in plant cells: • 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 Internal network of protein fibers important for: • cell structure & shape • cell, organelle movement • cell division 7 Flagella & Cilia Cellular projections involved in movement. Found only on certain cell types • e.g., respiratory tract (cilia), sperm (flagellum) • move the cell itself, or material across its surface 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