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Transcript
Endomembrane System • Endoplasmic Reticulum (ER) o Rough ER (RER) • Ribosomes are attached to the cytoplasmic surface o Studded appearance • Ribosomes on the surface RER surface synthesize proteins o New polypeptides enter the lumen of the RER (inside compartment) o Polypeptides are chemically modified and folded in the lumen o Modified proteins are packaged in vesicles and transported from the RER by budding Endomembrane System • Endoplasmic Reticulum (ER) o Smooth ER (SER) • • • • • Continuous with the RER, but no ribosomes Synthesis of lipids and steroid hormones Detoxification of medications and poisons Alcohol metabolism Storage of calcium ions Rough ER Smooth ER Fig. 4.14, p. 63 Endomembrane System • Golgi Apparatus o Compartment of flattened membrane sacs o Proteins and lipids from the ER (transported by vesicles) are sorted, packaged, and tagged so that they end up in the right place Endomembrane System • Golgi Apparatus o Vesicles containing proteins or lipids from the ER bud off and join the Golgi on the cis side (near the ER) • Vesicles fuse with the Golgi membrane • Contents of the vesicle empty into the Golgi lumen • Contents are sorted and modified o Vesicles bud off the trans side (side away from the ER) to exit the Golgi • Contain modified and sorted proteins or lipids • Have a “signal” that tells the cell where the product needs to be delivered ROUGH ER Golgi SMOOTH ER GOLGI BODY Cis side Lumen Trans side budding vesicle Endomembrane System • Lysosomes • Cell’s “garbage disposal” containing very reactive enzymes Lysosome Endomembrane System • Lysosomes • Cell’s “garbage disposal” containing very reactive enzymes • Used to break down waste material and cellular debris Endomembrane System • Lysosomes • Cell’s “garbage disposal” containing very reactive enzymes • Used by uni-cellular organisms for digestion of food Endomembrane System • Lysosomes • Cell’s “garbage disposal” containing very reactive enzymes • Used by immune system cells (macrophages) to capture and process pathogens Endomembrane System • Vesicles o Membrane-bound sacs functioning in storage and transport • ER Golgi cell membrane o Form when patches of membrane bulge and break away (or bud) • Vesicles can fuse with membranes and empty their contents to the other side Endomembrane System • Vesicles o Endocytosis • Bulk movement of materials across the plasma membrane into the cell • Pinocytosis o Nonspecific uptake of small droplets of extracellular fluid Endomembrane System • Vesicles o Endocytosis • Phagocytosis o Cell takes in solid material rather than liquid o The vesicle fuses with a lysosome to digest the particles • Receptor-mediated endocytosis o A specific receptor protein grabs hold of the specific solid material to bring it in Endomembrane System • Vesicles o Exocytosis • Secretory vesicles fuse with the plasma membrane releasing the molecules to the outside of the cell Animation of exocytosis and endocytosis Endomembrane System • Vacuoles o Small vesicles fuse together into larger sacs o Central Vacuole in plants • Very large structure • Contain amino acids, sugars, toxins and ions • Fluid pressure keeps plant cells firm Central Vacuole Endomembrane System • Vacuoles o Contractile vacuole • Collects and expels excess water • Used by single-celled protists Endomembrane System • Vacuoles o Food vacuole • Cell membrane is used to engulf bacteria or other small food • Used by some single-celled protists lysosome Ribosomes • Assemble amino acids into polypeptides (protein synthesis) • Found in the cytoplasm or on the rough ER • Not bound by membranes • Composed of two subunits Ribosomes o Proteins, enzymes, and RNA make up the subunits Mitochondria • Produce energy using aerobic respiration o Oxygen-requiring metabolic pathway that breaks down organic molecules (food) • Surrounded by two lipid bilayers • Envelope o Outer membrane is smooth o Inner membrane is highly folded • More surface area for energy production • All eukaryotic cells have mitochondria (a few exceptions in Kingdom Protista) • Referred to as “powerhouse” or “energy factories” of the cell Plastids • Plastids function in production or storage of organic molecules o Chromoplasts • Make and store pigments o Responsible for the color in many flowers, leaves, fruits, and roots o Amyloplasts • Store starch grains • Found in potatoes and other starch-storing plant parts Plastids • Chloroplasts • Make chlorophylls and function in photosynthesis • Produce energy using photosynthesis • Pigments capture the sun’s energy which is converted into chemical energy and organic molecules • Surrounded by two phospholipid bilayers (envelope) • Outer membranes are smooth • Enclose the stroma (semifluid interior) • Thylakoid membrane is a third inner membrane • Continuous compartment folded into disks • Only found in Plant and Algae cells Peroxisomes • Small, round organelles enclosed by a single membrane • Functions o Break down fatty acids and amino acids o Detoxify some poisons • Alcohol is detoxified by peroxisomes in liver cells • These chemical reactions produce H2O2 o Which is broken down to water and oxygen o Reactions are contained in peroxisomes Cell Surface Specialization • Cell Wall o o o o Surrounds the cell membrane on some cells Porous structure that protects, supports, and gives shape to the cell Plants, Fungus, and some Protista have cell walls Animals do not have cell walls Cell Surface Specialization • Extracellular matrix o Non-living mixture secreted by cells • Fibrous proteins and polysaccharides o Supports, anchors, separates, etc. o Plant cuticle o Exoskeleton of arthropods o Bone Cell Surface Specialization • Cell junctions o Connect a cell to other cells and the environment • Plasmodesma o Channel between cell walls of two adjacent plant cells o Some send or receive signals Match the following Nucleus Powerhouse Rough ER Sort and package Smooth ER Chromosomes Golgi Organize lipid synthesis Vesicle Photosynthesis Chloroplasts Cytoskeleton Mitochondria Organize polypeptide synthesis Microtubules Transport Summary • How Cells are Studied • Comparing Prokaryotic and Eukaryotic Cells • Eukaryotic Cells o Plasma membrane, cytoplasm, cytoskeleton, endomembrane system, ribosomes, mitochondria, chloroplasts, cell surface NUCLEUS nuclear envelope nucleolus DNA in nucleoplasm CYTOSKELETON microtubules microfilaments intermediate filaments RIBOSOMES ROUGH ER MITOCHONDRION SMOOTH ER CENTRIOLES GOLGI BODY PLASMA MEMBRANE b Typical animal cell components. LYSOSOME Stepped Art Fig. 4-19, p. 64 plasma membrane nucleus mitochondria Fig. 4-14, p. 60 CELL WALL CHLOROPLAST CENTRAL VACUOLE NUCLEUS nuclear envelope nucleolus DNA in nucleoplasm CYTOSKELETON microtubules microfilaments intermediate filaments (not shown) RIBOSOMES ROUGH ER MITOCHONDRION SMOOTH ER PLASMODESMA GOLGI BODY a Typical plant cell components. PLASMA MEMBRANE LYSOSOMELIKE VESICLE cell wall plasma membrane central vacuole nucleus chloroplast Fig. 4-14, p. 60