Cell Structures 2023-24 PDF

3. Cell structures Inge Holsbeeks Biotechnology 1st stage bachelor engineering technology 2023-24  Cell structures 1. Cells under a microscope 2. Plasma membrane 3. The 2 main types of cells Prokaryotic cells Eukaryotic cells 4. Intracellu...

3. Cell structures Inge Holsbeeks Biotechnology 1st stage bachelor engineering technology 2023-24  Cell structures 1. Cells under a microscope 2. Plasma membrane 3. The 2 main types of cells Prokaryotic cells Eukaryotic cells 4. Intracellular structures Nucleus Ribosomes Endomembrane system Endoplasmic reticulm Golgi apparatus Lysosomes Vacuoles Energy related organels Mitochondria Chloroplasts Cytoskeleton Cilia and flagella 5. Extracellular structures Cell wall Extracellular matrix Junctions between cells 6. Cellular reproduction 7. What about viruses? 2 Cell structures  Summary: Cell structure and properties Cell theory All organisms are composed of cells. All cells come only from preexisting cells. All cells have: A plasma membrane to regulate movement of material Cytoplasm where chemical reactions occur Genetic material for growth and reproduction Metabolism Two main types of cells Based on organization of genetic material: Prokaryotic cells: lack membrane-bound nucleus Eukaryotic cells: have nucleus housing DNA 3 Cell structures  1. Cells under a microscope Cell Unit of life Are extremely diverse Cells can be specialized for a particular function Nearly all require a microscope to be seen Light microscope Invented in the 17th century Limited by properties of light Electron microscope Invented in 1930s Overcomes limitation resolution by using beam of electrons 4 Cell structures  1. Cells under a microscope Light microscope Classical - digital Digital LED microscope 5 Cell structures  1. Cells under a microscope Electron microscope TEM: transmission electron microscope SEM: scanning electron microscope 6 Cell structures  1. Cells under a microscope 7 Cell structures  1. Cells under a microscope The limit to cell size - Why are cells so small? Need surface areas large enough for entry and exit of materials Surface-area-to-volume ratio Small cells have relative more surface area for exchange compared to volume compared to large cells Adaptations to increase surface area Microvilli in the small intestine increase surface area for absorption of nutrients 8 Cell structures  Summary: Cell structure and properties Cell theory All organisms are composed of cells. All cells come only from preexisting cells. All cells have: A plasma membrane to regulate movement of material Cytoplasm where chemical reactions occur Genetic material for growth and reproduction Metabolism Two main types of cells Based on organization of genetic material: Prokaryotic cells—lack membrane-bounded nucleus Eukaryotic cells—have nucleus housing DNA 9 Cell structures  2. Plasma membrane Marks boundary between outside and inside of a cell Regulates passage in and out of a cell Phospholipid bilayer with embedded proteins Polar heads (hydrophilic) of phospholipids face into watery medium Nonpolar tails (hydrophobic) face each other Fluid-mosaic model—the structure of the plasma membrane 10 Cell structures  2. Plasma membrane cell membrane cell 11 Cell structures  2. Plasma membrane 12 Cell structures  2. Plasma membrane Organisms living in cold environment More unsaturated FA ~ fluidity of membrane ↑ Organisms living in hot springs More saturated FA ~ fluidity of membrane ↓ Extremely cold – Hotsprings – Yellowstone US Far Beneath an Antarctic Ice Shelf Extremely warm 13 Cell structures  2. Plasma membrane Fluid-mosaic model Illustration fluidity of the membrane: https://www.youtube.com/watch?v=jM_xePC70Yo 14 Cell structures  2. Plasma membrane: not only lipids Membrane proteins Essential in: Communication - signalling Nutrient uptake Waste removal 15 Cell structures  Membrane proteins Channel proteins Transport proteins Form tunnel for Involved in passage of specific molecules molecules through the membrane, sometimes requiring input of energy 16 Cell structures  Membrane proteins Cell recognition proteins Receptor proteins Enable our body to Allow signal distinguish between molecules to bind, our own cells and causing a cellular cells of other response organisms 17 Cell structures  Membrane proteins Enzymatic proteins Junction proteins Directly participate in Form junctions metabolic reactions between cells Cell-to-cell adhesion and communication 18 Cell structures  Cell structures 1. Cells under a microscope 2. Plasma membrane 3. The 2 main types of cells Prokaryotic cells Eukaryotic cells 4. Intracellular structures Nucleus Ribosomes Endomembrane system Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Energy related organels Mitochondria Chloroplasts Cytoskeleton Cilia and flagella 5. Extracellular structures Cell wall Extracellular matrix Junctions between cells 6. Cellular reproduction 7. What about viruses? 19 Cell structures  Summary: Cell structure and properties Cell theory All organisms are composed of cells. All cells come only from preexisting cells. All cells have: A plasma membrane to regulate movement of material Cytoplasm where chemical reactions occur Genetic material for growth and reproduction Metabolism Two main types of cells Based on organization of genetic material: Prokaryotic cells—lack membrane-bounded nucleus Eukaryotic cells—have nucleus housing DNA 20 Cell structures  4. The two main cell types Prokaryotic cells Eukaryotic cells 21 Cell structures  Prokaryotic cells Unicellular Organisms from the domains Bacteria and Archaea Generally smaller and simpler in structure than eukaryotic cells Allows them to reproduce very quickly and effectively Extremely diverse group of organisms Bacteria Well known because some cause disease Others have roles in the environment Some are used to manufacture chemicals, food, drugs, etc. 22 Cell structures  Prokaryotic cells Bacterial structure Cytoplasm surrounded by plasma membrane* and cell wall Exceptional no cell wall Sometimes extra capsule - protective layer Plasma membrane is the same as eukaryotes Cell wall maintains the shape of a cell DNA - single circular dsDNA**, coiled chromosome located in nucleoid (region - not membrane enclosed) Ribosomes - site of protein synthesis Appendages Flagella - propulsion Fimbriae - attachment to surfaces Conjugation pili - DNA transfer ü Cell membrane – cytoplasm with ribosomes, genetic material ü Cell wall - mostly 23 *Plasma membrane – syn. cell membrane Cell structures **dsDNA: double stranded DNA  Prokaryotic cells see cases e.g. ‘Construction biotechnology’ 24 Cell structures  Eukaryotic cells Animal cells à multicellular organisms Plant cells à multicellular organisms Microorganisms – multicellular - unicellular E.g. yeast, parasites Algae Microscopic Macroscopic ØSee case e.g. ‘Marine biotechnology’ 25 Cell structures  Microorganisms Microorganisms – ‘microbes’ Microscopic size Prokaryotic microorganisms E.g. Lactic acid bacteria Eukayotic microorganisms E.g. baker’s yeast 26 Cell structures  Eukaryotic cells Animal cell ü Cell membrane – cytoplasm, ribosomes, membrane bound organelles 27 Cell structures  Eukaryotic cells Animal cell Huge diversity of cells types – illustration See case: ‘Red biotechnology’ 28 Cell structures  Eukaryotic cells Plant cells ü Cell wall, cell membrane – cytoplasm, ribosomes, membrane bound organelles 29 Cell structures  Cell structures 1. Cells under a microscope 2. Plasma membrane 3. The 2 main types of cells Prokaryotic cells Eukaryotic cells 4. Intracellular structures Nucleus Ribosomes Endomembrane system Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Energy related organels Mitochondria Chloroplasts Cytoskeleton Cilia and flagella 5. Extracellular structures Cell wall Extracellular matrix Junctions between cells 6. Cellular reproduction 7. What about viruses? 30 Cell structures  4. Intracellular structures Nucleus Ribosomes Endomembrane system Endoplasmic reticulm Golgi apparatus Lysosomes Vacuoles Energy related organels Mitochondria Chloroplasts Cytoskeleton Cilia and flagella 31 Cell structures  Nucleus Nuclear envelope - double membrane Nuclear pores permit passage in and out Stores genetic information Chromatin diffuse DNA, protein, some RNA Prior to cell division: DNA compacts into linear chromosomes DNA organized into genes à transcription into mRNA Outside nucleus / in cytoplasm à via ribosomes translated in polypeptide Nucleolus - region where ribosomal RNA (rRNA) is made 32 Cell structures  Nucleus 33 Cell structures  Ribosomes Carry out protein synthesis in the cytoplasm Found in both prokaryotes and eukaryotes Composed of 2 subunits Mix of proteins and ribosomal RNA (rRNA) Receive mRNA as instructions à sequence of amino acids in a polypeptide In eukaryotes: Some ribosomes free in cytoplasm Many attached to endoplasmic reticulum 34 Cell structures  Ribosomes 35 Ø Details function: see chapter DNA biology Cell structures  Endomembrane System Endomembrane system Consists of nuclear envelope, membranes of endoplasmic reticulum, Golgi apparatus, and numerous vesicles Helps compartmentalize cell Restricts certain reactions to specific regions Transport vesicles carry molecules from one part of the system to another. 36 Ø Details function: see chapter DNA biology Cell structures  Endoplasmic reticulum (ER) Complicated system of membranous channels and saccules Physically continuous with outer membrane of nuclear envelope Rough ER Studded with ribosomes Modifies proteins in lumen Forms transport vesicles going to Golgi apparatus Smooth ER Continuous with rough ER No ribosomes Synthesizes lipids like phospholipids and steroids Function depends on cell Produces testosterone, detoxifies drugs 37 Cell structures  Endoplasmic reticulum (ER) 38 Cell structures  Golgi apparatus Stack of flattened saccules/vesicles Transfer of molecules ER ↔ other vesicles Modifies molecules within the vesicles Sorts and repackages à transport to other vesicles or outside the cell Some vesicles cut off from Golgi apparatus are lysosomes 39 Cell structures  Lysosomes Vesicles that digest molecules or portions of the cell Intracellular digestive enzymes 40 Cell structures  Vacuoles Membranous sacs Larger than vesicles Examples of functions Rid a cell of excess water plant cell Digestion Storage Plant pigments Animal adipocytes 41 Cell structures protist  Energy-related organelles Mitochondria Chloroplasts 42 Cell structures  Mitochondria Found in BOTH plants and animals Usually only visible under an electron microscope Bounded by double membrane Inner membrane folds called cristae Increase surface area Inner membrane encloses matrix Mixture of enzymes assisting in carbohydrate breakdown Reactions permit ATP synthesis Matrix also contains its own DNA and ribosomes Break down carbohydrates to produce adenosine triphosphate (ATP) Chapter Cellular respiration energy - needs cells CO2 O2, produces 43 Cell structures  Mitochondria 44 Cell structures  Chloroplasts Use solar energy to synthesize carbohydrates through the process of photosynthesis Plants and algae Three-membrane system Double membrane enclosing stroma Thylakoids formed from third membrane Thylakoid membrane contains pigments that capture solar energy Chloroplasts have their own DNA and ribosomes. 45 Cell structures  Endosymbiosis Origin of mitochondria and chloroplasts 46 Cell structures  Endosymbiosis Evolution of eukaryotic cells 47 Cell structures  Cytoskeleton Proteins Network of interconnected protein filaments Extends from the nucleus to the plasma membrane Only in eukaryotes A schematic of the typical organisation of the cytoskeletal filaments inside an eukaryotic cell. Maintains cell shape 48 Cell structures  Cytoskeleton Microtubules Small, hollow cylinders Assembly controlled by centrosome Help maintain cell shape and act as track for organelles and other materials to move dynamic Intermediate filaments Intermediate in size Run from nuclear envelope to plasma membrane Actin filaments Two chains twisted in a helix Forms a dense web to support the cell dynamic 49 Cell structures  Cytoskeleton Data courtesy of ReGenesys Time lapse recording 50 Cell structures  Cytoskeleton 51 Cell structures  Cilia and flagella Eukaryotes For movement of the cell or fluids past the cell Similar construction in both 9+2 pattern of microtubules Cilia shorter and more numerous than flagella ØDifferent structure compared to prokaryotes 52 Cell structures  Cell structures 1. Cells under a microscope 2. Plasma membrane 3. The 2 main types of cells Prokaryotic cells Eukaryotic cells 4. Intracellular structures Nucleus Ribosomes Endomembrane system Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Energy related organels Mitochondria Chloroplasts Cytoskeleton Cilia and flagella 5. Extracellular structures Cell wall Extracellular matrix Junctions between cells 6. Cellular reproduction 7. What about viruses? 53 Cell structures  5. Extracellular structures Cell walls Extracellular matrix Junction between cells 54 Cell structures  Cell wall Cell wall provides support and strength to cell in many nonanimal cells plant fungi protists ØAlso cell wall in bacteria, but different structure 55 Cell structures  Cell walls Plant cell walls Primary cell walls Cellulose fibrils and noncellulose substances Wall stretches when cell is growing Secondary cell walls (some plant cells) Forms inside primary cell wall Woody plants Lignin adds strength Plasmodesmata Plant cells connected by numerous channels that pass through cell walls For exchange of water and small solutes between cell 56 Cell structures  Cell walls Architecture of plant cells walls 57 Cell structures  Extracellular matrix (ECM) In animal cells : no cell wall but ECM Meshwork of fibrous proteins and polysaccharides E.g. Collagen and elastin Matrix varies - flexible in cartilage, hard in bone 58 Cell structures  Junctions between cells Adhesion junctions Internal cytoplasmic plaques joined by intercellular filaments Sturdy but flexible sheet of cells Tight junctions Impermeable barrier Adjacent plasma membraned joined Gap junctions Allow communication between two cells Adjacent plasma membrane channels joined 59 Cell structures  Summary Ch. DNA biology Ch. Dynamic cell/Energy for cells 60 Cell structures  Cell structures 1. Cells under a microscope 2. Plasma membrane 3. The 2 main types of cells Prokaryotic cells Eukaryotic cells 4. Intracellular structures Nucleus Ribosomes Endomembrane system Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Energy related organels Mitochondria Chloroplasts Cytoskeleton Cilia and flagella 5. Extracellular structures Cell wall Extracellular matrix Junctions between cells 6. Cellular reproduction 7. What about viruses? 61 Cell structures  Summary: Cell structure and properties Cell theory All organisms are composed of cells. All cells come only from preexisting cells. All cells have: A plasma membrane to regulate movement of material Cytoplasm where chemical reactions occur Genetic material for growth and reproduction Metabolism Two main types of cells Based on organization of genetic material: Prokaryotic cells—lack membrane-bounded nucleus Eukaryotic cells—have nucleus housing DNA 62 Cell structures  6. Cellular reproduction Prokaryotes Eukaryotes Mitosis Binary fission Cell cycle 1 cellà 2 cells à 4à … Cellà ‘identical’ cell If conditions are optimal – When new cells needed exponential growth E.g. growth, wound healing, renewal, … E.g. nutrient availability, Control >< loss of control: temperature, … cancer Meiosis Sexual reproduction Production of gametes, cells for reproduction Number chromosomes/2 63 Cell structures  6. Cellular reproduction Prokaryotes Eukaryotes Binary fission Cell cycle - Mitosis 64 Cell structures  6. Cellular reproduction Prokaryotes Eukaryotes E.g. binary fission Mitosis 65 Cell structures  6. Cellular reproduction Eukaryotes Mitosis 66 Cell structures  7. What about viruses? Viruses are not included in the classification of organisms. Noncellular Obligate intracellular parasites Very specific host cells Spikes Capsid Hijack host to make new viral particles Alive or not? Two parts to every virus: Gen. mat Outer capsid - composed of protein subunits Inner core - either DNA or RNA Viral genome very small Some viruses have: Spikes for attachment to host cell Envelope Outer envelope Size: virus < prokaryotic cell< eukaryotic cell 67 Cell structures  Summary: Cell structure and properties Viruses do NOT have a lot of these properties Cell theory👎 All organisms are composed of cells. 👎 All cells come only from preexisting cells. 👎 All cells have: A plasma membrane to regulate movement of material 👎 Cytoplasm where chemical reactions occur 👎 Genetic material for growth and reproduction Metabolism 👎 Two main types of cells 👎 Based on organization of genetic material: Prokaryotic cells—lack membrane-bounded nucleus Eukaryotic cells—have nucleus housing DNA 68 Cell structures  7. What about viruses? Good animation on amplification of virus and immune response: Flu virus: https://www.youtube.com/watch?v=Rpj0emEGShQ 69 Cell structures  Summary: Cell structure and properties Cell theory All organisms are composed of cells. All cells come only from preexisting cells. All cells have: A plasma membrane to regulate movement of material Cytoplasm where chemical reactions occur C5: Dynamic cell Genetic material for growth and reproduction C6: Energy for cells Metabolism Two main types of cells Based on organization of genetic material: Prokaryotic cells: lack membrane-bound nucleus Eukaryotic cells: have nucleus housing DNA 70 Cell structures  What did you learn? You now know the key elements – organelles in a cell and their function You know the main differences between a prokaryotic and eukaryotic cell You know that cells can have different shapes and functions You know that cells can form new cells but do this in a different way in prokaryotes and eukaryotes You know that viruses are not cells 71 Cell structures  But also… You are ready to move to the case of Red biotechnology The proces of copying DNA and also on transcription and translation of genes is incluced in a later chapter. 72 Cell structures  Review: ‘fluid mosaic model’ Flexible character of the cell membrane Why do proteins migrate in the cell membrane? https://youtu.be/jM_xePC70Yo 73 Cell structures  Mobility of cells and molecules Cells in a tissue 74 Cell structures  Review: ‘case: intestinal cell’ Illustration of: Surface increase – organ level – cell level Cell renewal – speed Tight junctions Importance cytoskeleton 75 Cell structures  Open questions What are the main functions of the cell membrane? What are the main functions of a cell wall? You have to manipulate a cell (in this case having cell wall and membrane) and for this or cell wall or cell membrane has to be removed. After the removal, you need to maintain the viability of the cell. What would you remove and why? 76 Cell structures  8. References Chapter “Lipids and their function in biological systems” of Biotechnology (2021) Chapter “Inside the cell’” of Biotechnology (2021) + references in notes of slides for figures 77 Cell structures  Paragraphs discussed from handbook Chapter 4: inside the cell 4.1 Cells under a microscope 4.2 The plasma membrane 4.3 The two main cell types 4.4 A tour in the eukaryotic cell Motor proteins, centrioles: not 4.5 Outside the eukaryotic cell Chapter 17: Lipids and their function in biochemical systems 17.6 The structure of biological membranes Medical perspective: not Extra: Cell replication à see slides and lecture Viruses à see slides and lecture 78 Cell structures 79 Cell structures