Cell Structure & Function - Week 3 PPT PDF

DNA, Chromosomes, and Cell Division Vienna Jamaica Cari-cari, RMT Lesson Objectives: 1. Differentiate cell organelles according to their functions 2. Describe the structures of human chromosomes 3. Organize human chromosomes according to its characteristics The Cell Cells are the basic, living,...

DNA, Chromosomes, and Cell Division Vienna Jamaica Cari-cari, RMT Lesson Objectives: 1. Differentiate cell organelles according to their functions 2. Describe the structures of human chromosomes 3. Organize human chromosomes according to its characteristics The Cell Cells are the basic, living, structural, and functional units of the organs. Cytology – the scientific study of cells Property: Eukaryotic cell Prokaryotic cell Found in… Multicellular organisms like Unicellular organisms like Animals, Plants, Fungi Bacteria Nucleus True Nucleus No True Nucleus Cell Wall Present in Fungi and Plants Present Organelles Present Absent Cell Structure Cell Structure - Two main parts: - Nucleus - Cytoplasm - Organelles - Cytosol - Protective outer covering: - Plasma membrane Cell Structure The Plasma Membrane Cell Structure: Plasma membrane Functions and Properties: - Thin, pliable, elastic - Outermost layer that protects and separates the cell’s internal from the external environment - Selective barrier that facilitates passage of materials into and out of the cell Cell Structure: Plasma membrane Fluid Mosaic Model - Resembles a continually moving sea of fluid lipids that contains a mosaic of many different proteins - Some proteins float freely while others seem anchored at specific locations Cell Structure: Plasma membrane Cell Structure: Plasma membrane Composition: Approximately: - Phospholipid bilayer - 55% proteins - Cholesterol - 42% lipids - Carbohydrates - 3% carbohydrates - Proteins Of the membrane lipids… - Integral proteins - Peripheral proteins - 75% are phospholipids - 20% are cholesterol - 5% are glycolipids Cell Structure: Plasma membrane Composition: - Phospholipid bilayer – basic structural framework; amphiphatic - Cholesterol - Carbohydrates - Proteins - Integral proteins - Peripheral proteins Non-polar, Fat-soluble Fatty acids Polar, Water-soluble phosphate- containing Cell Structure: Plasma membrane Composition: - Phospholipid bilayer - Cholesterol Inserted among closely packed - Carbohydrates phospholipids, restricting their movements - Proteins - Integral proteins modulates fluidity and - Peripheral proteins movement of membrane components Cell Structure: Plasma membrane Composition: - Phospholipid bilayer Form the Glycocalyx ○ “molecular signature’’ that enables - Cholesterol cells to recognize one another - Carbohydrates ○ Cell attachment to one another - Proteins ○ Hydrophilic - Integral proteins makes RBCs “slippery” as - Peripheral proteins they flow through narrow blood vessels Protects cells lining the airways and digestive canal from drying out Cell Structure: Plasma membrane Composition: - Phospholipid bilayer Function as: - Cholesterol Ion channel - Carbohydrates Carrier Receptor - Proteins Enzyme - Integral proteins Linker - Peripheral proteins Cell identity marker Cell Structure: Plasma membrane Composition: - Phospholipid bilayer - Cholesterol - Carbohydrates - Proteins Integral protein - Integral proteins - Peripheral proteins Transmembrane proteins Directly embedded in the lipid bilayer Many are Glycoproteins Can only be extracted upon destruction of lipid bilayer Cell Structure: Plasma membrane Composition: - Phospholipid bilayer - Cholesterol - Carbohydrates - Proteins Peripheral - Integral proteins protein - Peripheral proteins Attached to either of the polar sides or to integral proteins SPOT CHECK! What makes the cell membrane selectively permeable? Cell Structure The Cytoplasm Cell Structure: Cytoplasm - Houses all the cellular contents between the plasma membrane and the nucleus - Two components: - Cytosol – fluid portion (aka intracellular fluid) – 55% of total cell volume – 70-90% water - Site of many chemical reactions - Organelles – “little organs” – specialized structures with characteristic shapes and have specific functions Cell Structure: Cytoplasm Cytoskeleton A. Microfilaments B. Intermediate filaments C. Microtubules Cell Structure: Cytoplasm Cytoskeleton A. Microfilaments Thinnest Actin and myosin B. Intermediate filaments Generate movement, C. Microtubules mechanical support, cell’s shape and strength Microvilli Cell Structure: Cytoplasm Cytoskeleton A. Microfilaments Thicker Stabilize position of B. Intermediate filaments organelles C. Microtubules Cell Structure: Cytoplasm Cytoskeleton A. Microfilaments Thickest among the three Long, unbranched, hollow B. Intermediate filaments tubes C. Microtubules Tubulin Assembly begins from the centrosome toward the periphery of the cell Cilia and flagella Cell Structure: Cytoplasm centrosome Centrosome - Microtubule organizing center - Two components: - Centrioles (2) – cylindrical; nine clusters of microtubular triplets arranged in a circular pattern - Pericentriolar matrix – surrounds centrioles – forms mitotic spindle centrioles during cell division Cell Structure: Cytoplasm Centrosome (with 2 centrioles) Cell Structure: Cytoplasm Mitochondrion - Powerhouse of the cell - Active cells that use ATP at higher rate have larger number of mitochondria - Liver, Kidneys, Muscles - Inner and Outer membrane - Cristae - infoldings of inner membrane - Matrix - has quantities of enzymes used to extract energy from nutrients Cell Structure: Cytoplasm Mitochondrion - Self-replicating - Contain DNA similar to that of found in the Nucleus - Plays a role in Apoptosis (normal/programmed cell death) Cell Structure: Cytoplasm Endoplasmic Reticulum - A network of flat tubular structures (cisternae) and flat vesicular structures - Extends from nuclear envelope, projects throughout the cytoplasm. - Process molecules made by nucleus and transport them - Lipid bilayer with proteins Cell Structure: Cytoplasm Endoplasmic Reticulum Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum - With Ribosomes attached - With Enzymes – Mixture of RNA and Proteins - Functionally diverse – Protein synthesis – Fatty acids and Steroid synthesis - glycoprotein and phospholipid – in liver cells: releases glucose, synthesis detoxify lipid-soluble drugs – in muscle fibers: release Calcium (Sarcoplasmic Reticulum) Cell Structure: Cytoplasm Endoplasmic Reticulum Ribosomes are the sites of Protein Synthesis Cell Structure: Cytoplasm Golgi Complex - 3-20 flattened saccules - Prominent in secretory cells - Functions in association with the endoplasmic reticulum - ER vesicles continually pinch off from the ER and shortly fuse with the Golgi apparatus - Modifies, sorts, packages, and transports proteins from ER Cell Structure: Cytoplasm Golgi Complex - Cis face = entry - Faces the Rough ER - Trans face = exit - Faces the Plasma Membrane - Intermediate saccules Cell Structure: Cytoplasm Golgi Complex All proteins exported from the cell are processed in the Golgi Complex Cell Structure: Cytoplasm Lysosome - Forms by breaking off from the Golgi apparatus - Dispersed throughout the cytoplasm - Intracellular digestion (endocytosis) - damaged cellular structures - food particles ingested by the cell - unwanted matter (ex. bacteria) - Extracellular digestion - Example: sperm cells during fertilization Cell Structure: Cytoplasm Lysosome - Hydrolytic enzymes - Enclosed by a lipid bilayer membrane - Autophagy – digestion of worn-out organelles – Autophagosome - Autolysis – digestion of entire cell Good to know: Tay Sachs disease – hereditary – absence of lysosomal enzyme Hex A Cell Structure: Cytoplasm Peroxisome - Structurally similar to lysosomes, but smaller - Formed from self-replication (while lysosomes are from golgi bodies) - Contain oxidases (while lysosomes have hydrolases) - Oxygen + hydrogen → Hydrogen peroxide (H2O2) - Ex: Alcohol is detoxified into acetaldehyde by Liver peroxisomes - Catabolizes long-chain fatty acids SPOT CHECK! Which cytoskeleton structure gives rise to Cilia and Flagella? SPOT CHECK! The site of Protein Synthesis Cell Structure The Nucleus Cell Structure: Nucleus Cell Structure: Nucleus Nucleus Functions: - Control Center of the cell - Houses most of the cells’ DNA - Most prominent feature seen in light microscope Cell Structure: Nucleus Nucleolus - Highly-staining structure - 1 or more in a nucleus - Not enclosed in a membrane - Site of rRNA synthesis Cell Structure: Nucleus Nuclear Envelope - Separates nucleus from the cytoplasm - 2 separate bilayer (one inside the other) - Outer membrane is continuous with ER - Nuclear pores – control movement of substances between nucleus and cytoplasm Genes Genes Functions: - Functional units of Genetic information - segments of DNA which determine unique characteristics - Hair color, eye color, height, and more - Control and promote cell reproduction - Genome – total genetic information carried in a cell or in an organism DNA DNA - Deoxyribonucleic Acid - Raw material of inheritance - Double stranded - Located within the nucleus DNA: DNA Structure The Double Helix Model (1953) - James Watson and Francis Crick - Twisted spiral ladder - Two long chains wound around each other, held together by H bonds - Repeating units: the Nucleotides - The two strands are antiparallel DNA: DNA Structure Nucleotides - 1 deoxyribose sugar - 1 phosphate group } “backbone” - 1 nitrogen-containing base DNA: DNA Structure Nitrogen-containing Bases Purines: - Guanine - Adenine Mnemonics : “@ GC” (AT GC) Pyrimidines: A T → Adenine pairs with Thymine - Cytosine G C → Guanine pairs with Cytosine - Thymine DNA: DNA Structure Nitrogen-containing Bases Purines: - Guanine - Adenine Mnemonics : “@ GC” (AT GC) Pyrimidines: A T → Adenine pairs with Thymine - Cytosine G C → Guanine pairs with Cytosine - Thymine Pure As Gold → Purines: Adenine & Guanine DNA: DNA Structure Nitrogen-containing Bases Purines: - Guanine - Adenine Mnemonics : “@ GC” (AT GC) Pyrimidines: A T → Adenine pairs with Thymine - Cytosine G C → Guanine pairs with Cytosine - Thymine Pure As Gold → Purines: Adenine & Guanine CUT a Py (Pie) → Pyrimidines: Cytosine, Thymine, Uracil (RNA) DNA: DNA Structure Erwin Chargaff’s rule - Nitrogenous bases are unequal in concentration; but → concentrations of Adenine = Thymine → concentrations of Guanine = Cytosine DNA: DNA Structure Watson and Crick - Postulated that to fulfill Chargaff’s rule, and to maintain a uniform shape of the DNA molecule - Adenine must pair with Thymine - Guanine must pair with Cytosine DNA: DNA Structure recap SPOT CHECK! Give a function of the Nucleus SPOT CHECK! What are the components of a nucleotide? DNA The DNA Organization DNA: DNA Organization 1.First level of condensation: DNA Double Helix 2.Octamer (protein core) - 2 molecules of each of the histones H2A, H2B, H3, and H4 3.Double Helix winds twice around octamer: Nucleosome (10-nm) 4.Repeats of nucleosomes give “Beads on a string” appearance 5.Further coiling: Solenoid (30-nm) (have 6 nucleosomes each) 6.DNA looped domains 7.Chromatin 8.Chromosomes  First level of condensation  Octamer H2A, H2B, H3, and H4  Double helix winds twice around octamer “Beads” = nucleosome “String” = Linker DNA “beads on a string” Solenoid (60-nm) DNA looped domains Chromatin Chromosome Chromosome Chromosome - A highly-coiled and folded single molecule of DNA associated with several proteins - Consists of 2 sister chromatids - Only seen in light microscope during the metaphase - 46 (23 pairs) of chromosomes - 22 pairs of Autosomes - 1 pair of Sex Chromosomes Chromosome: Nomenclature Autosomes: Numbered 1 to 22 (based on decreasing size; except chromosome 22 which is slightly larger than chromosome 21) Sex Chromosomes: Noted by letters X and Y Chromosome: Nomenclature Chromosome: Structure p arm ”petite” q arm Chromosome: Structure Chromatin Euchromatin Heterochromatin - Gene-rich - Gene-poor - A single continuous - Active - Inactive - Early-replicating - Late-replicating molecule of DNA - Light-staining - Dark-staining complexed with histone - Loose, extended, uncoiled - Compacted, heavily coiled and nonhistone proteins Constitutive Facultative Heterochromatin Heterochromatin - Around centromeres of all - one X chromosome of chromosomes and at distal female cell that is randomly end of Y chromosome inactivated and condensed - no transcribed gene - regulates gene function - no effect on phenotype Chromosome: Structure Telomere - Physical ends of chromosomes - Protective caps - Synapsis during meiosis - Tandem repeats of TTAGGG - Telomerase - Synthesizes new copies of the TTAGGG using RNA template - Counteracts progressive shortening (from cycles of normal replication) - Length gradually decreases - Due to normal aging and increased cell divisions in culture - Tumor-Suppressing Mechanism Chromosome: Structure Centromere - Constriction where two sister chromatids join together - Interacts with mitotic spindle fibers Types of chromosomes according to centromere: - Metacentric – near the middle - Acrocentric – near one end - Submetacentric – between the middle and end - Telocentric – at the terminal end Chromosome: Structure Types of Chromosomes according to Centromere At terminal end Near one end Between the In the middle middle and end Chromosome: Structure Nucleolar organizer regions - Satellite stalks of acrocentric chromosomes - Where nucleoli form in interphase cells SPOT CHECK! How many chromosomes does a child normally inherit from each parent? Any Questions? Thank you for learning! Thank you for listening References: Gersen, S. and Keagle, M. (2013) The Principles of Clinical Cytogenetics. 3rd Edition. Hall, J. E. (2021). Guyton and Hall Textbook of Medical Physiology. 14th edition. Tortora, G. J. and Derrickson, B. (2020). Principles of Anatomy & Physiology. 15th edition.