* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Ribosomes - juan-roldan
Survey
Document related concepts
SNARE (protein) wikipedia , lookup
Cell culture wikipedia , lookup
Cell growth wikipedia , lookup
Cellular differentiation wikipedia , lookup
Cell encapsulation wikipedia , lookup
Cytoplasmic streaming wikipedia , lookup
Extracellular matrix wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Signal transduction wikipedia , lookup
Cytokinesis wikipedia , lookup
Cell membrane wikipedia , lookup
Cell nucleus wikipedia , lookup
Transcript
A Tour of the Cell Eukaryotic cells have internal membranes that compartmentalize their functions • Basic features of all cells: plasma membrane, cytosol, chromosomes, ribosomes • Prokaryotic vs Eukaryotic cells – – prokaryotic cells Bacteria and Archaea • No nucleus • DNA in an unbound region called the nucleoid • No membrane-bound organelles • Cytoplasm bound by the plasma membrane eukaryotic cells Protists, fungi, animals and plants • DNA in a nucleus bounded by nuclear envelope • Membrane-bound organelles • Cytoplasm in the region between the plasma membrane and nucleus Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 6-6 Prokaryotic cell Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial chromosome Cell wall Capsule 0.5 µm Flagella Eukaryotic Animal Cell Fig. 6-9a ENDOPLASMIC RETICULUM (ER) Flagellum*** (not in plants) Rough ER Nuclear envelope Nucleolus NUCLEUS Smooth ER Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome*** (not in plants/prokaryotes) Fig. 6-9b Eukaryotic Plant Cell NUCLEUS Nuclear envelope Nucleolus Chromatin Rough endoplasmic reticulum Smooth endoplasmic reticulum Ribosomes Central vacuole*** Golgi apparatus Microfilaments Intermediate filaments Microtubules CYTO-SKELETON Mitochondrion Peroxisome Plasma membrane Chloroplast*** Cell wall*** Plasmodesmata*** Wall of adjacent cell ***specific to plants Organelles to know • Nucleus – Genetic information • Ribosomes – protein factories • Endoplasmic Reticulum – protein trafficking and metabolic functions • Golgi Apparatus – shipping and receiving center • Lysosomes – digestive compartments • Vacuoles – maintenance compatments • Mitochondria – chemical energy conversion (site of cellular respiration) • Chloroplasts – light energy conversion (site of photosynthesis) • Peroxisomes - oxidation • Cytoskeleton – support, motility and regulation • Extracellular Matrix – support, adhesion, movement, regulation • Intercellular Junctions – facilitate contact between cells Nucleus: Information Central – nuclear envelope encloses the nucleus, separating it from the cytoplasm – nuclear membrane is a double membrane; each membrane consists of a lipid bilayer – Pores regulate the entry and exit of molecules from the nucleus – The shape of the nucleus is maintained by the nuclear lamina, which is composed of protein – In the nucleus, DNA and proteins form genetic material called chromatin – Chromatin condenses to form discrete chromosomes – The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 6-10 Nucleus 1 µm Nucleolus Chromatin Nuclear envelope Nuclear pore Pore complex Surface of nuclear envelope Ribosome 1 µm 0.25 µm Close-up of nuclear envelope Pore complexes Nuclear lamina Ribosomes: Protein factories – particles made of ribosomal RNA and protein – Protein synthesis occurs here • Free ribosomes are localized to the cytosol • Bound ribosomes are on the ER or the nuclear envelope Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Fig. 6-11 Small subunit Diagram of a ribosome Endoplasmic Reticulum (ER): Protein Trafficking – The ER membrane is attached to the nuclear envelope – There are two distinct regions of ER: • Smooth ER lacks ribosomes – Synthesizes lipids – Metabolizes carbohydrates – Detoxifies poison – Stores calcium • Rough ER with ribosomes – Secretes glycoproteins (proteins covalently bonded to carbohydrates) – Distributes transport vesicles, proteins surrounded by membranes – membrane factory for the cell Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 6-12 Smooth ER Rough ER Nuclear envelope Ribosomes Transport vesicle Rough ER Smooth ER Golgi apparatus: Shipping and Receiving Center – shipping and receiving center – consists of flattened membranous sacs called cisternae – Functions: • Modifies products of the ER • Manufactures certain macromolecules • Sorts and packages materials into transport vesicles Cisternae Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Lysosome: Digestive Compartment – a membranous sac of hydrolytic enzymes that can digest macromolecules – Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids • After phagocytosis (engulfing of another cell) lysosomes fuse with the food vacuole and digests the molecules • Autophagy uses enzymes to recycle the cell’s own organelles and macromolecules (a) Phagocytosis Lysosome (b) Autophagy Digestive enzymes Plasma membrane Lysosome Peroxisome Digestion Food vacuole Vesicle Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Mitochondrion Digestion Fig. 6-15 Vacuoles: Maintenance Compartment – – – – Diverse Maintenance Compartments Central vacuole Food vacuoles are formed by phagocytosis Contractile vacuoles pump excess water out of cells Cytosol Nucleus Cell wall Chloroplast Central vacuoles (in many mature plant cells) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings hold organic Central vacuole The Endomembrane System: A Review • The endomembrane system is a complex and dynamic player in the cell’s compartmental organization – Nuclear envelope – ER – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 6-16-3 Nucleus Rough ER Smooth ER Transport vessicle Golgi Transport vessicle Lysosome Plasma membrane •Nuclear envelope is connected to rough ER •Proteins produced by the ER flow in transport vessicles to the Golgi •Golgi pinches off vessicles that give rise to lysosomes, vessicles and vacuoles •Lysosomes can fuse with another vessicle for digestion •Transport vessicle carries proteins to plasma membrane for secretion •Plasma membrane expands by fusion of vessicles; proteins are secreted from the cell Mitochondria: Chemical Energy Conversion – sites of cellular respiration, a metabolic process that generates ATP – Have a double membrane – Contain their own DNA – Mitochondria are in nearly all eukaryotic cells – They have a smooth outer membrane and an inner membrane folded into cristae • Cristae present a large surface area for enzymes that synthesize ATP – The inner membrane creates two compartments: intermembrane space and mitochondrial matrix • Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 6-17 Intermembrane space Outer membrane Free ribosomes in the mitochondrial matrix Inner membrane Cristae Matrix 0.1 µm Chloroplasts: Light Energy Conversion – Capture light energy, are the sites of photosynthesis – found in plants and algae – Have a double membrane (similar to mitochondria) – Contain their own DNA (similar to mitochondria) – contain chlorophyll and other molecules that function in photosynthesis – found in leaves and other green organs of plants and in algae Ribosomes Stroma Inner and outer membranes Granum Thylakoid Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 1 µm Peroxisome: Oxidation – oxidative organelles – specialized metabolic compartments bounded by a single membrane Chloroplast Peroxisome Mitochondrion – produce hydrogen peroxide and convert it to water – Oxygen is used to break down different types of molecules Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 1 µm Cytoskeleton: Support, Motility and Regulation – a network of fibers extending throughout the cytoplasm – organizes the cell’s structures and activities, anchoring many organelles – composed of three types of molecular structures: • Microtubules are the thickest of the three components • Microfilaments, also called actin filaments, are the thinnest components • Intermediate filaments are fibers with diameters in a middle range – helps to support the cell and maintain its shape – interacts with motor proteins to produce motility Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microtubules • • • Functions – Shaping the cell – Guiding movement of organelles – Separating chromosomes during cell division Centrosomes – The centrosome is a “microtubule-organizing center” – microtubules grow out from a centrosome near the nucleus and attach to chromosomes during mitosis Cilia and Flagella – Microtubules control the beating of cilia and flagella – A core of microtubules sheathed by the plasma membrane Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microtubules separate chromosomes during mitosis Centrosome microtubules Microtubule centrosome Fig. 6-22 Microtubules assist in motility (a) EX: Motion of flagella in sperm Fig. 6-23 (b) EX: Motion of cilia in aquatic life Fig. 6-24 Microtubule structure in cilia Plasma membrane Microtubules Plasma membrane (b) Cross section of cilium Basal body (a) Longitudinal section of cilium (c) Cross section of basal body Microfilaments (Actin Filaments) • Microfilaments are solid rods built as a twisted double chain of actin subunits • The structural role: bear tension and resist pulling forces within the cell • Cellular function: cellular motility – • Microvillus Microfilaments (actin filaments) Myosin and actin contribute to this Examples – Muscle contraction – Ameoboid movement occurs through Pseudopodia – Cytoplasmic streaming Intermediate filaments Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Intermediate Filaments • They support cell shape and fix organelles in place • more permanent cytoskeleton fixtures than the other two classes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cell Walls of Plants • Prokaryotes, fungi, and some protists also have cell walls • Functions: protects the plant cell, maintains its shape, prevents excessive uptake of water • made of cellulose fibers • Plant cell walls may have multiple layers: – Primary cell wall: relatively thin and flexible – Middle lamella: thin layer between primary walls of adjacent cells – Secondary cell wall (in some cells): added between the plasma membrane and the primary cell wall Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 6-28 Secondary cell wall Primary cell wall Middle lamella 1 µm Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata The Extracellular Matrix (ECM) of Animal Cells • Functions – – – – • • Support Adhesion Movement Regulation made up of glycoproteins (collagen, proteoglycans, and fibronectin) Collagen EXTRACELLULAR MATRIX Proteoglycan complex Fibronectin ECM proteins bind to receptor proteins in the plasma membrane called integrins Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Integrins Microfilaments CYTOPLASM Intercellular Junctions • Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact • Intercellular junctions facilitate this contact • There are several types of intercellular junctions – Plasmodesmata – channels that perforate cell walls – Tight junctions - membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid – Desmosomes (anchoring junctions) fasten cells together into strong sheets – Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 6-32 Tight junction Tight junctions prevent fluid from moving across a layer of cells 0.5 µm Desmosomes fasten cells together in sheets Tight junction Intermediate filaments Desmosome Desmosome Gap junctions Space between cells Plasma membranes of adjacent cells Extracellular matrix Gap junctions all cells to communicate with one another via cytoplasmic channels Gap junction 0.1 µm Fig. 6-UN1 Cell Component Concept 6.3 The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes Structure Surrounded by nuclear envelope (double membrane) perforated by nuclear pores. The nuclear envelope is continuous with the endoplasmic reticulum (ER). Nucleus Function Houses chromosomes, made of chromatin (DNA, the genetic material, and proteins); contains nucleoli, where ribosomal subunits are made. Pores regulate entry and exit of materials. (ER) Two subunits made of riboProtein synthesis somal RNA and proteins; can be free in cytosol or bound to ER Ribosome Concept 6.4 The endomembrane system regulates protein traffic and performs metabolic functions in the cell Concept 6.5 Mitochondria and chloroplasts change energy from one form to another Extensive network of membrane-bound tubules and sacs; membrane separates lumen from cytosol; continuous with the nuclear envelope. Smooth ER: synthesis of lipids, metabolism of carbohydrates, Ca2+ storage, detoxification of drugs and poisons Golgi apparatus Stacks of flattened membranous sacs; has polarity (cis and trans faces) Modification of proteins, carbohydrates on proteins, and phospholipids; synthesis of many polysaccharides; sorting of Golgi products, which are then released in vesicles. Lysosome Membranous sac of hydrolytic enzymes (in animal cells) Vacuole Large membrane-bounded vesicle in plants Digestion, storage, waste disposal, water balance, cell growth, and protection Mitochondrion Bounded by double membrane; inner membrane has infoldings (cristae) Cellular respiration Endoplasmic reticulum (Nuclear envelope) Chloroplast Peroxisome Rough ER: Aids in synthesis of secretory and other proteins from bound ribosomes; adds carbohydrates to glycoproteins; produces new membrane Breakdown of ingested substances, cell macromolecules, and damaged organelles for recycling Typically two membranes Photosynthesis around fluid stroma, which contains membranous thylakoids stacked into grana (in plants) Specialized metabolic compartment bounded by a single membrane Contains enzymes that transfer hydrogen to water, producing hydrogen peroxide (H2O2) as a by-product, which is converted to water by other enzymes in the peroxisome