Chapter 3 biology 0.0 / 5 ? BiologyCellular processesA2/A-levelAQA Created by: Sam LoftCreated on: 08-12-20 19:03 What is the function of the nucleus ? • contains linear DNA (genetic info) wrapped up with proteins called histones (chromatin) • the nucleolus synthesises ribosomal RNA (rRNA) 1 of 22 What is the function of mitochondria ? to phosphorylate ADP to synthesise ATP by a condensation reaction 2 of 22 What is the function of chloroplasts ? to carry out photosynthesis 3 of 22 What is the function of the Golgi apparatus ? To process macromolecules from the endoplasmic reticula and package them into vesicles 4 of 22 What is the function of the rough endoplasmic reticulum (RER) ? • Provide a large surface area for the synthesis of proteins and glycoproteins • to provide a pathway for the transport of materials throughout the cell 5 of 22 What is the function of the smooth endoplasmic reticulum (SER) ? To synthesise, store and transport lipids and carbohydrates 6 of 22 What is the function of lysosomes ? vesicles containing digestive enzymes 7 of 22 What is the function of ribosomes ? to synthesise proteins 8 of 22 What is the function of the cell wall ? to prevent osmotic lysis 9 of 22 What is the function of the vacuole ? • Contains sap which helps with cell turgidity • sugars and amino acids may act as a temporary food store • pigments may colour petals to attract pollinating insects 10 of 22 2 disadvantages of using a scanning electron microscope (SEM) • Gives lower resolution images than TEMs • Can't be used on living specimens as it must be in a vacuum 11 of 22 3 advantages of using a scanning electron microscope (SEM)? • Can be used on thick specimens • shows the surface detail of the specimen • can show 3D images 12 of 22 3 disadvantages of using a transmission electron microscope (TEM)? • specimens must be very thin – one cell thick • can't be used on living specimens due to being viewed in a vacuum • very expensive 13 of 22 2 advantages of using a transmission electron microscope (TEM)? • much higher magnification can be achieved without losing resolution than an optical microscope and a SEM • Can show the internal structure of specimens 14 of 22 equation for magnification image size ______________ actual size 15 of 22 definition of resolution the ability to distinguish two objects as separate items (not blurred together) 16 of 22 What is the structure of the nucleus ? • Bound by nuclear envelope (membrane) that has nuclear pores that allow some molecules to enter the cytoplasm • Filled with nucleoplasm and chromatin 17 of 22 What is the structure of mitochondria ? • 2 membranes (inner and outer mitochondrial membrane) • Matrix contains proteins, lipids, 70s ribosomes and DNA (plasmids) • Cristae - extensions of the inner membrane that provide a large inner surface area 18 of 22 What is the maximum magnification and resolution of an optical microscope ? x 2000 0.2 micrometres 19 of 22 What has to happen before cell fractionation ? tissue is placed in a solution that is - • cold - to reduce enzyme activity • the same water potential as the tissue - prevents osmotic lysis • buffered - so the pH doesn't fluctuate 20 of 22 What is homogenation ? Homogenation is the lysis of cells into a mixture of organelles (homogenate) by a homogeniser (blender) 21 of 22 In what order are cell organelles removed from the homogenate in ultracentrifugation ? 1st - nuclei 2nd - chloroplasts 3rd - mitochondria 4th - ribosomes 22 of 22
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