Eukaryotic Cell Biology: The Nucleus PDF

Aled.Roberts @ Swansea.ac.uk EukaryoticCell Biology The Nucleus PM-132 1 Learning Objectives: Know the history of the nucleus, what lead to its discovery and the...

Aled.Roberts @ Swansea.ac.uk EukaryoticCell Biology The Nucleus PM-132 1 Learning Objectives: Know the history of the nucleus, what lead to its discovery and the various research leaps that led to our current understanding Explain the role of the nucleus and what it does within the cell. List the various components of the nucleus. Describe how these components relate to the overall function of the nucleus within the cell. 2 1  The Eukaryotic Cell:The Nucleus Each eukaryotic cell contains the crucially important membrane enclosed nucleus *basic visualisation 3 The Eukaryotic Cell:The Nucleus Contains most of the cell’s genetic information Each eukaryotic cell contains the crucially important membrane enclosed nucleus *basic visualisation 4 2  The Eukaryotic Cell:The Nucleus Contains most of the cell’s genetic information Each eukaryotic cell contains the crucially important membrane enclosed nucleus *basic visualisation Occupies ~10% of the cytoplasm 5 The Eukaryotic Cell:The Nucleus Each eukaryotic cell contains the crucially important membrane enclosed nucleus …however… *basic visualisation 6 3  The Eukaryotic Cell:The Nucleus Each eukaryotic cell contains the crucially important membrane enclosed nucleus …however… *basic visualisation it is nothing without the other organelles 7 The Nucleus: A (brief) History… Built an ”upgraded” Antonie Van Leeuwenhoek light microscope with increased magnification “Father of Optical Microscopy” 1719 Primarily worked on Prokaryotic cells, but observed the first organelle in Eukaryotic cells 8 4  The Nucleus: A (brief) History… Franz Baur Botanical Illustrator 1804 Observed the “nucleus” in orchid cells by highlighting its presence in drawings 9 The Nucleus: A (brief) History… Jan Purkyne Anatomist and Physiologist 1825 1839 Coined the term Identified the germinal vesicle “protoplasma” in chicken oocytes (nucleus) 10 5  The Nucleus: A (brief) History… Robert Brown Scottish Botanist 1831 Observed the “nucleus” in multiple plant species, coining the term nucleus for his observations 11 The Nucleus: A (brief) History… Collaborative approach Worldwide Effort 1870s and 1880s Scientists looking at both plant and animal cells believed the nucleus had a role in heredity 12 6  The Nucleus: A (brief) History… Modern Research Technological Advances 20 th Century Mendelian genetics and the chromosome theory of heredity, cleared up the function of the nucleus 13 The Nucleus: Structure 14 7  Structure: Size ~10% Average 6 μm Proportional Range 2-10 μm size Large cytoplasm > larger nucleus Small cytoplasm > small nucleus Nucleus Vol. Linear relationship between the volume of the cytoplasm and nucleus Cytoplasm Vol. *Size is also correlated with the number of chromosomes and the DNA content… 15 Structure: Shape proportional Shape? NO !!! In most cells, the nucleus is spherical regardless of cell shape… Onion Epidermal Liver Hepatocyte cells cells 16 8  Structure: Shape Proportional Shape? NO !!! In most cells, the nucleus is spherical regardless of cell shape… Onion Epidermal BUT… There are Liver Hepatocyte cells cells exceptions! 17 Structure: Shape Proportional Shape? NO !!! In most cells, the nucleus is spherical regardless of cell shape… BUT… Neutrophil There are cells exceptions! 18 9  Structure: Number Again… There are exceptions! Skeletal cells Liver cells Proportional White blood cells Number? Usually… In most cells, each cell will have a single nucleus Onion Epidermal Liver Hepatocyte cells cells 19 Structure: Overview nucleolus Nuclear Envelope Membrane barrier between Site of ribosome synthesis nucleus and cytoplasm nucleoplasm Viscous part of the nucleus Chromatin Condensed DNA Nuclear pore Complex Protein complex that allows chromosomes movement of materials Condensed DNA ready for cell division 20 10  Structure: Nuclear envelope The nuclear envelope defines the nucleus, separating the nucleoplasm from the cytoplasm 21 Structure: Nuclear envelope Two membrane structure Perinuclear space between The nuclear envelope defines the nucleus, separating the nucleoplasm from the cytoplasm 22 11  Structure: Nuclear envelope Outer Inner membrane has a protein membrane lining (Nuclear lamina) connects with the rough ER Two membrane structure Perinuclear space between The nuclear envelope defines the nucleus, separating the nucleoplasm from the cytoplasm *Ribosomes not shown 23 Structure: Nuclear envelope Outer Inner membrane has a protein membrane lining (Nuclear lamina) connects with the rough ER Binds chromatin and other nuclear components Two membrane structure Perinuclear space between The nuclear envelope defines the nucleus, separating the nucleoplasm from the cytoplasm 24 12  Structure: Nuclear envelope Ribosome Nuclear Pore Complex Endoplasmic Reticulum Cytoplasm Outer Membrane Inner Membrane Perinuclear space Nucleoplasm 25 Structure: Nuclear Lamina Ribosome Nuclear Pore Complex Endoplasmic Reticulum Cytoplasm Outer Membrane Inner Membrane Perinuclear space Membrane Associated Proteins Proteins Intermediate Filaments Chromatin Nucleoplasm Fibrillar mesh network 26 13  Function: Nuclear Lamina Ribosome NuclearPore Complex Endoplasmic Reticulum Cytoplasm OuterMembrane InnerMembrane Perinuclearspace MembraneAssociatedProteins Proteins Intermediate Filaments Chromatin Nucleoplasm 1. Mechanical Support - maintains shape of nucleus 2. Regulation - regulates DNA replication and cell division 3. Organisation - helps organise chromatin 4. Anchor - stabilises pores in the nuclear envelope 27 Structure: Nuclear Pore Complex Cytoplasm Cytosolic Filaments ~30 unique proteins (contains scaffold nuclear porins) Cytosolic Ring ~500 Total proteins Pore Ring Nuclear Ring (contains scaffold nuclear porins) Nuclear Basket (aids gene tethering and membrane curvature) Nucleoplasm 28 14  Function: Nuclear Pore Complex Cytoplasm Translation TRANSCRIPTION Nucleoplasm 29 Structure: Nucleolus 30 15  Structure: Chromatin 2 nm 31 Structure: Chromatin 11 nm 32 16  Structure: Chromatin 30 nm 33 Structure: Chromatin 30 nm 34 17  Structure: Nucleolus rRNA molecules being packaged with cytoplasmic proteins Granules nucleolus 1-4 Nucleoli Condensed area of chromatin Relatively large… Number can alter between species (but fixed within a species) Chromatin Condensed DNA Fibrils DNA that is being actively transcribed into rRNA 35 Structure: Chromatin Loops 300 nm 36 18  Structure: Chromatin Loops 700 nm 37 Structure: Chromosomes Storing… transmitting… heredity characteristics from one generation to the next 1400 nm 1 gene = 1 characteristic 38 19  Structure: Chromosomes Storing… transmitting… heredity characteristics from one generation to the next 1400 nm multiple genes = 1 characteristic 39 Function: The nucleus separates translation from transcription allowing Eukaryotes levels of gene regulation not available to Prokaryotes 40 20  Function: The nucleus separates translation from transcription allowing Eukaryotes levels of gene regulation not available to Prokaryotes The nucleus controls the replication of DNA during the cell division process 41 Function: The nucleus separates translation from transcription allowing Eukaryotes levels of gene regulation not available to Prokaryotes Compartmentalisation Pre-mRNA processing Gene expression Nuclear Transport The nucleus mediates the replication of DNA during the cell division process 42 21  Function: Compartmentalisation The nuclear envelope creates a clear separation of nucleus from cytoplasm Pre-mRNA processing Gene expression Nuclear Transport 43 Function: Compartmentalisation The nuclear envelope creates a clear separation of nucleus from cytoplasm Removal of key participants from one area allows processes to be controlled Pre-mRNA processing Gene expression Nuclear Transport 44 22  Function: Compartmentalisation Gene expression Transcription factor separation until the time is right… Pre-mRNA processing Nuclear Transport 45 Function: Compartmentalisation Gene expression Transcription factor separation until the time is right… Activation by other signalling pathways Pre-mRNA processing Nuclear Transport 46 23  Function: Compartmentalisation Pre-mRNA processing Gene expression Eukaryotic mRNA contains introns that must be removed before being translated to produce functional proteins Nuclear Transport 47 Function: Compartmentalisation Pre-mRNA processing Gene expression Splicing Eukaryotic mRNA contains introns that must be removed before being translated to produce functional proteins Nuclear Transport 48 24  Function: Compartmentalisation Pre-mRNA processing Gene expression Nuclear Transport 49 Function: NuclearTransport Replication Proteins Protein Transcription Proteins Protein synthesis Chromosome TRNA replication Transcription mRNA RNA Processing DNA Ribosome subunits RRNA 50 25  NuclearTransport: Passive vs. Active Allows free diffusion of Guanine triphosphate small molecular weight molecules through the Nuclear Pore Complex Energy Importins and exportins transport proteins Passive Small molecules Active Nucleoside triphosphates Selective movement of large SmallHistones proteins ions molecular weight proteins and RNA through the Nuclear Pore Complex. 100 per minute per pore!!! 51 Active: Import 52 26  Active: Import 53 Active: Export 54 27  Active: Import 55 Aled.Roberts @ Swansea.ac.uk EukaryoticCell Biology The Nucleus PM-132 56 28