Lecture 9-10 Slides.pdf

The Endomembrane System Concept: The endomembrane systemregulates protein traffic and performs metabolic functions The endomembrane system consists of: –Nuclear envelope –Endoplasmic reticulum –Golgi apparatus –Lysosomes –Vacuoles –Plasma membrane These components are either continuous or connected...

The Endomembrane System Concept: The endomembrane systemregulates protein traffic and performs metabolic functions The endomembrane system consists of: –Nuclear envelope –Endoplasmic reticulum –Golgi apparatus –Lysosomes –Vacuoles –Plasma membrane These components are either continuous or connected via transfer by vesicles The Endoplasmic Reticulum: Biosynthetic Factory The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells The ER membrane is continuous with the nuclear envelope There are two distinct regions of ER: –Smooth ER, which lacks ribosomes.. Synthesizes lipids. Detoxifies drugs and poisons. Stores calcium ions. Metabolizes carbohydrates. –Rough ER, whose surface is studded with ribosomes. –Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates). –Distributes transport vesicles, secretory proteins surrounded by membranes. –Is a protein and membrane factory for the cell. The Golgi Apparatus: Shipping and Receiving Center The Golgi apparatus consists of flattened membranous sacs called cisternae The Golgi apparatus –Modifies products of the ER (mostly sugars) –Manufactures certain macromolecules (polysaccharides) –Sorts and packages materials into transport vesicles Transport vesicles At Plasma membrane: exocytosis and endocytosis (bulk transportation) Two main pathways (inside > outside) –ER > Golgi Apparatus >Plasma membrane –ER > Golgi Apparatus >lysosomes One pathway (outside > inside) Plasma membrane > endosomes > lysosomes Protein synthesis/trafficking ER Golgi Apparatus ER Golgi Apparatus Mediated by transport vesicles Plasma Membrane Lysosomes Vacuoles: Diverse Maintenance Compartments Vacuoles are large vesicles derived from the ER and Golgi apparatus Vacuoles perform a variety of functions in different kinds of cells ‫محذوفة‬ 1) In ER: Carbohydrates are added to proteins = glycoprotein 2) Golgi apparatus: glycoproteins undergo further carbohydrate modification & lipids acquire carbohydrates becoming glycolipids 3) Glycolipids, glycoproteins and secretory proteins are transported in vesicles to PM 4) Fusion, exocytosis and carbohydrate portions of tran-membrane proteins are positioned to the outside Concept: Bulk transport across the plasma membrane occurs by exocytosis and endocytosis Small molecules and water enter or leave the cell through the lipid bilayer or via transport proteins. Large molecules, such as polysaccharides and protein, cross the membrane in bulk inside vesicles. In exocytosis, transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell. Many secretory cells use exocytosis to export their products –For example, cells in the pancreas secrete insulin by exocytosis In endocytosis, macromolecules are taken into the cell in vesicles The membrane forms a pocket that deepens and pinches off forming a vesicle around the material for transport There are three types of endocytosis: –Phagocytosis (“cellular eating”) –Pinocytosis (“cellular drinking”) –Receptor-mediated endocytosis types of endocytosis phagocytosis In phagocytosis,a cell engulfs a particle by extending pseudopodia around it and packing it in a membranous sac called a food vacuole such as WBCs engulfing bacteria The vacuole fuses with a lysosome to digest the particle pinocytosis In pinocytosis, molecules are taken up when extracellular fluid is “gulped” into tiny vesicles Pinocytosis is nonspecific for the substances it transports; any and all solutes are taken into the cell Parts of the plasma membrane that form vesicles are lined on the inner side with coat proteins, forming coated vesicles receptor-mediated endocytosis In receptor-mediated endocytosis, binding of ligands to receptors triggers vesicle formation A ligand is any molecule that binds specifically to a receptor site of another molecule Human cells use receptor-mediated endocytosis to take in cholesterol, which is carried in particles called low-density lipoproteins (LDLs) Individuals with familial hypercholesterolemia have missing or defective LDL receptor proteins Cholesterol accumulates in the blood, building up lipids and narrowing the space in the blood vessels, resulting in potential heart damage or stroke Quiz 1-Which of the following cellular organelles is not a component of endomembrane system: A- Cell membrane B- Golgi apparatus C-Lysosome D- Mitochondria Answer: D 2- which of the following organelles synthesize lipid?? A- Rough ribosome B- Smooth ribosome C- Golgi apparatus D- Nucleus Answer: B 3- which of the following terms refer to "cellular eating": A- phagocytosis B- pinocytosis C- Exocytosis D- receptor-mediated endocytosis Answer: A Extra Practice Which part of the cell is most crucial for getting membrane proteins to their proper location? plasma membrane mitochondrion chloroplast Golgi apparatus lysosome Answer: D 1- One of the endomembrane systems that controls the packaging? A- Nucleus B- Mitochondria C- Golgi Apparatus D- ER Answer: C 2-Which of the following is responsible for the synthesis of lipids and steroids? A- Rough Endoplasmic reticulum B- Golgi Apparatus C- Smooth Endoplasmic reticulum D- Nucleus Answer: C Extra Practice 3- what mediate between endoplasmic reticulum and Golgi apparatus A-cytoplasm B-proteins C- ribosomes D- vesicles Answer: D 4- The cell can swallow droplets of extracellular fluids in small vesicles by: a- Pinocytosis b- Phagocytosis c- Exocytosis d- Osmosis Answer: A 5- Which of the following is NOT a component of the endomembrane system: a- Mitochondrion b- Nuclear envelope c- Golgi apparatus d- Vacuole Answer: a Extra Practice 6- Which of the following describes the describes the process that can bring large particles into the eukaryotic cell: a- Endocytosis b- Exocytosis c- Diffusion d- Trafficking Answer: A 7-Which of the following describes the process that can bring large particles into the eukaryotic cell: A endocytosis C diffusion B exocytosis D trafficking Answer: A 8- Which of the following organelles plays a primary role in the digestion of bacteria engulfed by white blood cells: A Lysosomes B Vacuoles C Golgi vesicles D secretory vesicles Answer:A Extra Practice 9-The plasma membrane receives transport vesicles carrying modified proteins and lipids from the? A-Rough ER B- Cis-face of Golgi Apparatus C- Smooth ER D-Trans-face of Golgi Apparatus Answer: D 10- Detoxification of poisons and drugs happens mostly in the liver. Which of the following endomembrane structures would likely be abundant in liver cells so they adopt to this function? A-Smooth ER B-Golgi Apparatus C-Rough ER D-Nuclear envelope Answer: A 11-Which of the following processes best describes the process wherewhite blood cells engulf and destroy pathogens such as bacteria? A- Exocytosis B- Pinocytosis C-Phagocytosis D-Receptor-mediated endocytosis Answer: C Extra Practice 12- Glycoproteins are synthesized in: A lysosomes C Smooth ER B Ribosome D Rough ER Answer: D 13-Which of the following describe the process of exocytosis A Rough ER > Smooth ER> Golgi apparatus> plasma membrane B Smooth ER> Golgi apparatus> vesicles> plasma membrane C Plasma membrane> lysosomes> mitochondria D Rough ER> Golgi apparatus> vesicles> plasma membrane Answer: D 14- If you were studying mutant cells and found that many proteins are going to the wrong compartments, where is the mutation having the greatest effect? A Nuclear envelope B Peroxisome C Golgi apparatus D Mitochondrion Answer: C Extra Practice 15- Which organelle is storge site for calcium ions? A Smooth ER B Golgi apparatus C Rough ER D Lysosomes Answer: A 16- Which of the following process is used by white blood cells when engulfing bacteria? A Phagocytosis B Osmosis C Pinocytosis D Receptor-mediated exocytosis Answer: A 17- What is the correct path for endocytosis? A. Plasma membrane → Endosomes → Lysosomes B. Endoplasmic reticulum → Golgi apparatus → Plasma membrane C. Endoplasmic reticulum → Lysosomes → Plasma membrane D. Plasma membrane → Golgi apparatus → Mitochondria Answer: A 18- When a cell takes up specific molecules into it, this process is known as: A. Exocytosis B. Receptor-mediated endocytosis C. cell signaling D. Phagocytosis Answer: B Extra Practice 19- Glycoproteins are secreted by which of the following endomembrane system? A- Plasma membrane B- Golgi apparatus C- Smooth ER D- Rough ER 22- The process by which the white blood cells engulf bacteria A- Exocytosis B- Pinocytosis C- Phagocytosis D- Diffusion Answer: D Answer: C 20- What is the transportation that enables polysaccharides to cross the plasma membrane? A- Active transport B- Facilitated diffusion C- Bulk transportation D- Passive diffusion 23- Which of the following processes known as cellular drinking ? A- Exocytosis B- Pinocytosis C- Phagocytosis D- Diffusion Answer: C Answer: B 21- Which one of the following is NOT a component of the endomembrane A- Plasma membrane B- Golgi apparatus C- Nuclear envelope D- Mitochondria Answer: D 24- In the context of protein trafficking. What is the sequence of locations a protein might through A- Plasma membrane > ER > Golgi apparatus B- ER > Golgi apparatus > Plasma membrane C-ER > Plasma membrane > Golgi apparatus D- Plasma membrane > ER > Golgi apparatus Answer: B Extra Practice 25- Which of the following accurately describes receptor-mediated endocytosis? A- It is non specific form of endocytosis B- It uptakes specific molecules depends on their cell's protein C- It is unglup D- It exports Answer: B