4BBY1030 L2 .pdf

FoLSM/IoPPN Dr Clemens Kiecker 4BBY1030 Cell Biology & Neuroscience Lecture 2 Neuroscience Education Cell types and subcellular structures Learning outcomes By the end of this lecture you should be able to: Explain the concept of ‘the cell’ Classify different types of cells: prokaryotes, eukaryotes,...

FoLSM/IoPPN Dr Clemens Kiecker 4BBY1030 Cell Biology & Neuroscience Lecture 2 Neuroscience Education Cell types and subcellular structures Learning outcomes By the end of this lecture you should be able to: Explain the concept of ‘the cell’ Classify different types of cells: prokaryotes, eukaryotes, bacteria, archaea, fungi, plants, animals Outline the basic organisation of eukaryotic cells and give a brief description of the major features and organelles, and the specialised cellular processes that take place in them: plasma membrane, nucleus, rough and smooth endoplasmic reticulum, Golgi apparatus, lysosomes and peroxisomes, mitochondria and chloroplasts, cytosol, cytoskeleton Dr Clemens Kiecker Topic title: Cell types and subcellular structures Chapter 1 The concept of the cell Dr Clemens Kiecker Topic title: Cell types and subcellular structures 3 The cell theory Our bodies are made up of approx. 37 trillion cells Robert Hooke (1635-1703): microscope Matthias Jakob Schleiden (1804-1881), Theodor Schwann (1810-82), Rudolf Virchow (1821-1902): Cell theory 1. 2. 3. Dr Clemens Kiecker All living organisms are made up of one or more cells The cell is the basic unit of life Cells arise from existing cells by division Topic title: Cell types and subcellular structures 4 True or false? Ø All cells are surrounded by a plasma membrane ✓ Ø All cells are surrounded by a cell wall ✗ Ø All cells contain genetic material in the form of DNA ✓✗ Ø All cells contain DNA in a nucleus ✗ Ø All cells perform metabolism ✓ Ø All cells can move ✗ Dr Clemens Kiecker Topic title: Cell types and subcellular structures 5 Chapter 2 Types of cells Dr Clemens Kiecker Topic title: Cell types and subcellular structures 6 Prokaryotes versus eukaryotes Prokaryotes: no nucleus (Greek pro- karyon = ‘before nucleus’), always single-cellular a) Bacteria (formerly eubacteria) including cyanobacteria (photosynthetic, formerly known as blue-green algae) b) Archaea (formerly archaebacteria): many species live in extreme environments (halophiles = high salt concentrations, thermoacidophiles = hot sulfur springs etc.) Eurkaryotes: nucleus (Greek eu- = ‘true’), single or multi-cellular Plants (including algae) Animals Fungi (molds, yeasts, mushrooms) Protozoans Dr Clemens Kiecker Topic title: Cell types and subcellular structures 7 Evolution of cells Dr Clemens Kiecker Topic title: Cell types and subcellular structures 8 Chapter 3 Cellular organisation, organelles and subcellular structures Dr Clemens Kiecker Topic title: Cell types and subcellular structures 9 The cell (plasma) membrane Bilayer (double layer) of phospholipids, cholesterol and embedded transmembrane proteins Phospholipids = amphipathic = hydrophilic phosphate group + hydrophobic lipid tails Dynamic, lipid rafts Four main roles: 1. 2. 3. 4. Barrier Communication Import and export Electrical capacitor More on this in Lectures 6-8 and on 4BBY1013 Dr Clemens Kiecker Topic title: Cell types and subcellular structures 10 The cytoskeleton Network of protein fibres: 1. 2. 3. Actin filaments Intermediate filaments Microtubules Main roles: Maintenance of shape, stability Adaptation of shape Cell division Motility Movement of particles within cells More on this in Lecture 4 Dr Clemens Kiecker Topic title: Cell types and subcellular structures 11 The cytoplasm (cytosol) Aequeous solution of defined pH (approx. 7.2) and ion composition, but also contains: A high concentration of proteins (20-30% metabolic enzymes, intracellular messengers etc.) tRNAs Free ribosomes Inclusion bodies (e.g. glycogen granules) Dr Clemens Kiecker Topic title: Cell types and subcellular structures 12 The nucleus Surrounded by two layers of membrane (two lipid double layers) à nuclear envelope Contains nucleoplasm Contains chromosomal DNA + packaging proteins (histones) + gene regulatory proteins Site of RNA synthesis and processing (RNA splicing) Nucleolus: site of ribosome synthesis (and signal recognition particle), can capture gene regulatory proteins (nucleolar detention) More on this on 4BBY1013 and 4BBY1070 Dr Clemens Kiecker Topic title: Cell types and subcellular structures 13 Endoplasmic reticulum (ER) rER Network of interconnected membrane vesicles (cisternae), continuous with the outer nuclear membrane Rough ER (rER): synthesis of secreted and transmembrane proteins More on this in Lecture 16 and on 4BBY1013 Smooth ER (sER): synthesis of lipids and steroid hormones, detoxification (liver), release of glucose from the liver sER Dr Clemens Kiecker Topic title: Cell types and subcellular structures 14 Golgi apparatus/complex Stack of flattened membrane vesicles Modification of proteins destined for secretion and transmembrane proteins rER à cis Golgi à trans Golgi à secretory vesicles More on this in Lecture 14 Dr Clemens Kiecker Topic title: Cell types and subcellular structures 15 Mitochondria Often oval or sausage-shaped, 0.5-1 x 1-2 µm Can make up to 25% of the cytoplasm Double membrane: inner membrane folded into cristae (high transmembrane protein content) Contains circular DNA (mtDNA) and ribosomes in matrix Alternative genetic code Functions: 1. Respiration/oxidative phosphorylation (electron transport chain) 2. Citric acid (Krebs) cycle 3. Heat production 4. Ca2+ storage 5. Programmed cell death (apoptosis) Dr Clemens Kiecker Mitochondrial disorders: mutations in mtDNA (e.g. Kearns-Sayre syndrome), defects in nuclear genes that encode mitochondrial proteins (e.g. hereditary spastic paraplegia) Topic title: Cell types and subcellular structures 16 Lysosomes Membrane-bound organelles found in animal cells Degrade unwanted proteins and particles taken up by the cell, and membranes and organelles that are no longer needed Acidic pH = 4.5-5 à optimal environment for degradative enzymes Degradation of pathogens by macrophages More on this in Lecture 17 Dr Clemens Kiecker Topic title: Cell types and subcellular structures 17 Peroxisomes Degrade fatty acids and toxic compounds Fatty acid oxidation produces precursors for biosynthetic pathways Oxidation produces H2O2 (corrosive) The enzyme catalase neutralizes H2O2: 2 H 2 O2 à 2 H 2 O + O 2 Detoxification of ethanol in the liver: C2H5OH + H2O2 à CH3CHO + 2 H2O Dr Clemens Kiecker Topic title: Cell types and subcellular structures 18 Recommended reading Pollard, Earnshaw, Lippincott-Schwartz, Johnson, Pollard (2017) Cell Biology. 3rd ed. Elsevier, PA. Please note that the content of this book is broader than the learning outcomes of this module. Thus, do not panic – we do not expect you to study this book from the first to the last page. You should rather use it to supplement your learning and as a resource if you have a question or if you find a particular topic interesting and would like to learn a little bit more about it. Dr Clemens Kiecker Topic title: Cell types and subcellular structures 19 Thank you for your attention [email protected] © King’s College London. All rights reserved