06_Eukaryotic_Cellular organelles .pdf

1 Chapter 4: Inside the Cell 2 Outline Eukaryotic Cells Organelles and their functions Outside the Eukaryotic Cell Objectives Identify the general function of the organelles in a eukaryotic cell. State the components of the endomembrane system, and list their functions. Relate the specific component...

1 Chapter 4: Inside the Cell 2 Outline Eukaryotic Cells Organelles and their functions Outside the Eukaryotic Cell Objectives Identify the general function of the organelles in a eukaryotic cell. State the components of the endomembrane system, and list their functions. Relate the specific components of the cytoskeleton to their diverse roles within the cell. 3 Cells Under the Microscope Cells are extremely diverse Each type in our body is specialized for a particular function. Nearly, all require a microscope to be seen. Light microscope Invented in the seventeenth century Limited by properties of light Electron microscope Invented in 1930s Overcomes limitation by using beam of electrons 4 Tour of the Eukaryotic Cell 5 Structure of a Typical Animal Cell 6 Structure of a Typical Plant Cell ku.ac.ae Structure of a Typical Plant Cell 7 ku.ac.ae Nucleus Stores genetic information DNA organized into genes, which specify a polypeptide Relayed to ribosome using messenger RNA (mRNA) Nucleolus—region where RNA and ribosomal RNA (rRNA) are made Nuclear envelope has double membrane It permit passage in and out of the nucleus through the nuclear pores 8 The Nucleus: Information Central In the nucleus, DNA is organized into discrete units called chromosomes Each chromosome contains one DNA molecule associated with proteins, called chromatin Chromatin condenses to form discrete chromosomes as a cell prepares to divide 10 Ribosomes: Protein Factories Carry out protein synthesis in the cytoplasm Found in both prokaryotes and eukaryotes Ribosomes are composed of two subunits Receive mRNA as instructions sequence of amino acids in a polypeptide ku.ac.ae Ribosomes In eukaryotes ribosomes build proteins in two locations: In the cytosol (free ribosomes) On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes) 12 The Nucleus, Ribosomes, and Endoplasmic Reticulum (ER) 13 Endomembrane System Consists of nuclear envelope, membranes of endoplasmic reticulum, Golgi apparatus, and numerous vesicles Helps compartmentalize cell Restricts certain reactions to specific regions Transport vesicles: carry molecules from one part of the system to another. 14 Endomembrane System 15 Endoplasmic Reticulum Accounts for more than half of the total membrane in many eukaryotic cells. Physically continuous with outer membrane of nuclear envelope There are two distinct regions of ER: Rough ER Studded with ribosomes Modifies proteins Forms transport vesicles to Golgi apparatus Smooth ER Continuous with rough ER No ribosomes Synthesizes lipids (phospholipids and steroids Function depends on cell Produces testosterone, detoxifies drugs Endomembrane System: Golgi apparatus Stack of flattened saccules Transfer station Receives vesicles from ER Modifies molecules within the vesicles Sorts and repackages for new destination Some are lysosomes. Lysosomes Vesicles that digest molecules or portions of the cell Digestive enzymes 16 Lysosomes: Digestive Compartments A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules or portions of the cell Lysosomal enzymes work best in the acidic environment inside the lysosome Hydrolytic enzymes and lysosomal membranes are made by rough ER and then transferred to the Golgi apparatus for further processing Tay-Sachs disease: lysosomes in nerve cells are missing an enzyme for a particular lipid molecule 18 Vacuoles Membranous sacs that are larger than vesicles Vacuoles perform a variety of functions in different kinds of cells: In plants: store nutrients, plant pigment and maintain water balance In Animal: They are very small in animal cells and store and keep away waste products 19 Energy-Related Organelles: Mitochondria Found in both plants and animals Usually only visible under an electron microscope Break down carbohydrates to produce adenosine triphosphate (ATP) Location of Cellular respiration—needs oxygen, produces carbon dioxide. ku.ac.ae Mitochondrion Structure Bounded by double membrane Inner membrane folds called cristae Increase surface area Inner membrane encloses matrix Mixture of enzymes assisting in carbohydrate breakdown Matrix also contains its own DNA and ribosomes.?? Access the text alternative for slide images. 20 21 Energy-Related Organelles: Chloroplasts Use solar energy to synthesize carbohydrates through the process of photosynthesis Found in plants and algae Chloroplasts have their own DNA and ribosomes?? Three-membrane system Double membrane enclosing stroma Thylakoids formed from third membrane stacked to form a granum Thylakoid membrane contains pigments that capture solar energy The Evolutionary Origins of Mitochondria and Chloroplasts Mitochondria and chloroplasts have similarities with bacteria Enveloped by a double membrane Contain free ribosomes and circular DNA molecules Grow and reproduce somewhat independently in cells These similarities led to the endosymbiont theory It suggests that an early ancestor of eukaryotes engulfed an oxygen-using nonphotosynthetic prokaryotic cell 24 The Cytoskeleton The Cytoskeleton is a network of interconnected protein filaments and tubules Extends from the nucleus to the plasma membrane extending throughout the cytoplasm It is only found in eukaryotes Maintains cell shape: It organizes the cellʼs structures and activities, anchoring many organelles 25 Components of the Cytoskeleton 1. Microtubules are : Hollow cylinders thickest of the three components of the cytoskeleton Help maintain cell shape and act as track for organelles and other materials to move 2. Intermediate filaments are: Ropelike assembly that run from nuclear envelope to plasma membrane (Intermediate in size) 26 Components of the Cytoskeleton 3. Microfilaments (Actin filaments): Two chains of monomers twisted in a helix Forms a dense web to support the cell are the thinnest components 27 The Cytoskeleton and Motor Proteins Motor proteins allow cell and organelles to move along tracks provided by the cytoskeleton. Myosin, kinesin, and dynein Instrumental in allowing cellular movements Myosin Interacts with actin Muscle contraction Kinesin and dynein Move along microtubules Transport vesicles from Golgi apparatus to final destination 28 Components of the Cytoskeleton- Centrioles The centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring Only found in animal cells; not present in plant cells In cell division, microtubules grow out from a centrosome near the nucleus 29 Cilia and Flagella For movement of the cell or fluids past the cell Similar construction in both Cilia shorter and more numerous than flagella 30 Outside the Eukaryotic Cell: Extracellular components Cell wall provides support in plants, Fungi and Protists cells Plant cell walls has: Primary cell walls Cellulose fibrils and noncellulose substances Wall stretches when cell is growing Secondary cell walls (some plant cells) Forms inside primary cell wall e,g Woody plants Lignin: complex organic polymers adds strength Plasmodesmata Plant cells connected by numerous channels that pass through cell walls For exchange of water and small solutes between cells 31 Exterior Cell Surfaces in Animals No cell wall Extracellular matrix (ECM) Is made up of glycoproteins such as collagen, proteoglycans, and fibronectin Matrix varies—flexible in cartilage, hard in bone 32 Cell Junctions: Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact Intercellular junctions help integrate cells into higher levels of structure and function. Junctions Between Cells of the Intestinal Wall 33 Adhesion Junctions Adhesion junctions between cells fasten cells together into strong sheets Internal cytoplasmic plaques joined by intercellular filaments Sturdy but flexible sheet of cells 34 Tight Junctions Tight junctions (anchoring junctions) Adjacent plasma proteins joined Impermeable barrier: preventing leakage of extracellular fluid 35 Gap Junctions Allow communication between two cells Adjacent plasma membrane channels joined provide cytoplasmic channels between adjacent cells Revision Questions Which structure is common to all three domains of life? a) b) c) d) e) nucleus endoplasmic reticulum mitochondria phospholipid bilayer cell membrane endocytotic vesicles Where are enzymes responsible for biosynthesis of membrane lipids located? a) b) c) d) e) endoplasmic reticulum nucleus lysosomes Golgi apparatus plasma membrane What is the correct order of the exocytosis or secretion pathway? a) b) c) d) e) rough ER, endosome, Golgi apparatus, smooth ER rough ER, Golgi apparatus, smooth ER, plasma membrane smooth ER, rough ER, exocytosis, Golgi apparatus rough ER, Golgi apparatus, transport vesicle, plasma membrane rough ER, Golgi apparatus, endosome, plasma membrane, transport vesicle Which image shows the best resolution? d) e) Which of the following correctly lists the objects in order from largest to smallest? a) b) c) d) human body, mitochondrion, lipid, frog egg frog egg, mitochondrion, lipid, human body human body, frog egg, mitochondrion, lipid mitochondrion, frog egg, lipid, human body What kind of cell would you be examining if you identified fimbriae? a) b) c) d) e) plant animal fungal bacterial All of the above are possible. If you were studying mutant cells and found that many proteins are going to the wrong compartments in these cells, where is the mutation having the greatest effect? a) b) c) d) e) nuclear envelope endoplasmic reticulum Golgi apparatus peroxisome mitochondrion 44 Thank You ku.ac.ae