PHTH1011 001 The Cell Illustrations - Anderson.pdf

The cell N McFarlane-Anderson Topics ◼ ◼ ◼ ◼ ◼ ◼ Cell theory Pro- and eukaryotic cells Plant and animal cells Organelles Plasma membrane Specialized cells Cell theory – 1830s ◼ ◼ ◼ All organisms are composed of one or more cells The cell is the structural unit of life Cells can arise only by divisio...

The cell N McFarlane-Anderson Topics ◼ ◼ ◼ ◼ ◼ ◼ Cell theory Pro- and eukaryotic cells Plant and animal cells Organelles Plasma membrane Specialized cells Cell theory – 1830s ◼ ◼ ◼ All organisms are composed of one or more cells The cell is the structural unit of life Cells can arise only by division from a preexisting cell Cell ◼ ◼ ◼ Smallest living unit Highly complex and organised Capable of ◼ ◼ ◼ ◼ ◼ ◼ ◼ growth movement reproduction acquiring and utilising energy carrying out a variety of chemical reactions engaging in numerous mechanical activities responding to stimuli Prokaryotes & Eukaryotes ◼ ◼ ◼ ◼ ◼ ◼ bacteria long before 1st eukaryotes nucleoid no comparable structures non sexual reproduction simple movement ◼ all other organisms evolved from prokaryotes nucleus organelles and cytoskeleton sexual reproduction ◼ complex movement ◼ ◼ ◼ ◼ Escherichia Coli ◼ ◼ DNA is the lighter appearing area in the center of each cell - nucleoid The two main cells in the centre have finished dividing and have not yet separated completely Bacteria ◼ E Coli ◼ ◼ ◼ other bacteria ◼ ◼ Can live in very simple medium Convert them to complex metabolites Live on inorganic substances Many of our essential dietary requirements produced by gut bacteria Smaller eukaryotes ◼ ◼ ◼ ◼ Very complex cells Cell – unicellular organism Has to have machinery for all activities in which organism engages E.g. ciliated protist, slime mold, amoeba Amoeba ◼ ◼ a single-celled organism named for the Greek god Proteus has extensions to the cell, known as pesudopodia, which allow it to move and capture prey. Chlamydomonas ◼ ◼ a photosynthetic eukaryotic cell cilia cilia Chlamydomonas ◼ Visible organelles are ◼ ◼ ◼ ◼ Nucleus (center) Mitochondrion chloroplasts (dark, irregularly shaped) The large circle near the bottom of the cell is the organism's food reserve, in the form of starch granules Pandorina ◼ ◼ ◼ ◼ ◼ green-algae protist 32 cells, held together by a jelly like substance, each of these cells can survive independently of the others to reproduce, each cell divides, producing a new cell inside parent colony then breaks apart Relative sizes Multicellular organisms ◼ Cells become specialised to perform different functions Plants and animals ◼ ◼ ◼ Essentially same Plant cells have chloroplasts Large vacuoles Corn cell ◼ ◼ ◼ the nucleus is the large circle on the right side of the central cell diagonal to the nucleus is a vacuole, quite characteristic of plant cells. there are also many mitochondria and chloroplasts (the dark, membrane-enclosed objects chloroplast Chloroplast ◼ ◼ surrounded by two membranes contains an elaborate internal membrane system where the lightcapturing reactions of photosynthesis occur Living poplar tree cell Animal cell Cell ◼ ◼ ◼ ◼ Smallest living unit capable of growth, movement, reproduction Cells → tissues → organs Cells divide – mitosis (15–20 min) Life span ◼ ◼ ◼ Few minutes GI tract cells 3-4 months – RBCs Years - nerve General features All cells have an outer membrane ◼ ◼ ◼ ◼ separates it from it's environment and from other cells Within the outer membrane there is a solution of proteins, electrolytes and carbohydrates cytosol. This is divided up into specialist compartments known as organelles by inner membrane systems. Shape and fluidity partly determined by internal protein filaments which form the cytoskeleton. Cell structures ◼ External membrane covers a cytoplasm riddled with interconnecting channels – ◼ ◼ the endoplasmic reticulum -ER- which is studded with ribosomes. Scattered throughout the cytoplasm are small structures ◼ ◼ ◼ ◼ ◼ ◼ ◼ Nucleus Mitochondria Golgi apparatus (body) Lysosomes Centrioles Vesicles Peroxisomes organelles ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ organelles are a hallmark of eukaryotic cells concentrate enzymatic reactions separate competing metabolic processes segregate harmful products from the rest of the cell. nucleus - segregates replication and transcription mitochondria - concentrates energy-producing reactions secretory system - responsible for organizing the synthesis, transport, and quality control of proteins and lipids peroxisome lysosome Organelle function ◼ ◼ ◼ ◼ ◼ ◼ ◼ ER – protein & lipid synthesis Golgi – sugars made, linked to fats & proteins, proteins modified, stored, secretions stored Lysosome – debris degraded, contents recycled Peroxisome – catalyses several reactions Nucleus – DNA Vesicle – temporarily stores or secretes Mitochondrion – releases energy from nutrients Vesicles ◼ temporary packages of material undergoing transport around the cell. Nucleus ◼ ◼ ◼ The nucleus is covered in a porous membrane and contains DNA and chromatin material. The nucleolus contains RNA which acts as a messenger to the DNA of the nucleus about cellular activity, repair and synthesis. The rod like centrioles are involved in the process of mitosis. Chromosomes, chromatin Sea urchin – 2 cell stage Cell cycle DNA damage ◼ Cells with DNA damage ◼ ◼ ◼ mutations disruption of embryonic development cancer Nucleolus ◼ ◼ ◼ The nucleolus is organized from the "nucleolar organizing regions" on different chromosomes. A number of chromosomes get together and transcribe ribosomal RNA at this site. pars fibrosa (PF) - newly transcribed ribosomal RNA. pars granulosa (PG) - Transcribed rRNA + protein- ribonucleoprotein Nucleolus Nucleolus Ribosomes ◼ ◼ ◼ Large and small subunits leave via nuclear pores In cytoplasm, subunits connected and attach to Endoplasmic Reticulum Protein synthesis Golgi ◼ The Golgi bodies act as "marshalling yards" for materials synthesized elsewhere in the cell. Golgi body Golgi, vesicles, secretory pathways Golgi and disease ◼ ◼ Fragmented and defective Golgi bodies associated with several diseases Autoimmune diseases Peroxisomes Peroxisomes ◼ ◼ ◼ ◼ ◼ ◼ Protect the cell from its own production of toxic hydrogen peroxide e.g. WBC produce H2O2 to kill bacteria Catalase →H2O + O2 most important metabolic processes oxidation of long and very long chain fatty acids synthesis – bile acids, cholesterol synthesis amino acid and purine metabolism Peroxisomes ◼ The importance of the peroxisome and these processes is underscored by the existence of numerous genetic disorders associated with defects in the peroxisome Adrenoleukodystrophy - ALD ◼ ◼ Lack of protein which transports an enzyme to break down long chain fatty acids Muscle weakness, heart beat irregularities - early death Lysosomes ◼ ◼ ◼ ◼ ◼ ◼ Pick up foreign invaders such as bacteria, food and old organelles Break down proteins, lipids, polysaccharides Contain 40 or more hydrolytic enzymes made for the lysosome by the rough endoplasmic reticulum Enzymes work only at low pH (highly acidic) levels Neutralized if they accidentally escape from the lysosome (normal pH) Excess, uncontrolled release → cell death (necrosis). Tay-Sachs disease ◼ ◼ NS degeneration Absence of a lysosomal enzyme → fat build up on nerve cells Adrenal cell nb lysosomes Mitochondria ◼ ◼ ◼ ◼ "powerhouse of the cell" more abundant in cells which have a high metabolic rate many internal folds rich in enzyme systems vital to energy production mitochondrion mitochondrion Mitochondrial DNA ◼ ◼ ◼ ◼ ◼ ◼ Codes for some of the proteins it needs not all Comes from mother Cell contains several copies of genes Used to study relatedness, evolutionary patterns Inheritance of disease Mothers pass on genetic diseases Mitochondrial disease ◼ ◼ ◼ Cell injury and even cell death follow mitochondrial defects most damage to cells of the brain, heart, liver, skeletal muscles, kidney and the endocrine and respiratory systems. symptoms may include ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ loss of motor control muscle weakness and pain gastro-intestinal disorders and swallowing difficulties poor growth cardiac disease liver disease Diabetes respiratory complications Seizures visual/hearing problems lactic acidosis developmental delays susceptibility to infection Cytoskeleton ◼ ◼ ◼ ◼ Actin - microfilaments Tubulin – microtubules Keratin – intermedaite filaments (IF) 3 work together to enhance ◼ ◼ ◼ structural integrity cell shape cell and organelle motility. Muscular dystrophies ◼ ◼ ◼ Dystrophin holds skeletal muscle together Link cytoskeleton actin to cell membrane Missing or abnormal dystrophin → dystrophies IF - Immunocytochemistry Cell size ◼ ◼ ◼ ◼ most cells are small (microscope) about 50 μm (0.05mm) in diameter average bacterial cell - 3-5 μm in diameter. volume increases (more rapidly) and surface area increases are not equal Cell size ◼ ◼ ◼ Uptake and excretion from cell dependent on surface area (large cells food supply -egg yolk) Cell surface can be increased by dividing (embryos) Making cell long and skinny (muscle, nerve) Cell plasma/membrane ◼ ◼ ◼ ◼ ◼ ◼ ◼ Separates cell interior from outside all cells have a PM Semi-permeable Responsible for movement of substances in and out cells Contains proteins, lipids, CHOs Adhesion, cell signalling, ion channels , which are involved in a variety of cellular processes such as cell adhesion Attachment point – cytoskeleton, cell wall (plants), Cell membrane – cell surrounded by plasma membrane Taken from Human Biology by Daniel Chiras http://www.people.virginia.edu/~rjh9u/cellmemb.html ◼ ◼ Plasma membrane ◼ Lipid bilayer ◼ ◼ Hydrophobic ions Hydrophilic ions Membranes and transport ◼ Molecules in and out of the cell through its Plasma Membrane ◼ ◼ e.g. glucose, Na+, Ca2+ In eukaryotic cells, there is also transport in and out of membranebounded intracellular compartments ◼ ◼ nucleus, ER, mitochondria e.g. proteins, mRNA, Ca2+, ATP Molecules that need to enter cells – pass through membrane Yes ◼ ◼ ◼ ◼ ◼ ◼ ◼ Water Carbon dioxide Oxygen Other very small polar molecules such as ammonia Lipids such as cholesterol ◼ ◼ ◼ No All ions including hydrogen ions! mid to large polar molecules including glucose Amino acids Macromolecules such as proteins, polysaacharides Transport mechanisms ◼ Simple diffusion ◼ ◼ Facilitated diffusion ◼ ◼ Down concentration gradient Trans-membrane proteins create a water-filled pore through which ions and some small hydrophilic molecules can pass by diffusion. Channels opened/closed as needed. Active transport Trans-membrane proteins- transporters, use the energy of ATP to force ions or small molecules through the membrane e.g. – GLUT- glucose transporters Cell death ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ ◼ Necrosis Mechanical, chemical damage Cells swell, contents leak out inflammation Apoptosis – programmed cell death shrink, develop bubble-like blebs on their surface chromatin degraded (characteristic pattern) mitochondria break down (→ cytochrome C) proteases released, complexes - apoptosomes break into small, membrane-wrapped, fragments phosphatidylserine becomes exposed on surface bound by receptors on phagocytic cells macrophages & dendritic cells ◼ ◼ ◼ engulf the cell fragments. secrete IL-10 and TGF) No inflammation Cerebral cortex cells Pancreatic cell - EM ◼ ◼ ◼ ◼ ◼ ◼ large, central nucleus with scattered chromatin many mitochondria large quantities of rough ER many small vesicles plasma membrane nuclear membrane RBCs, RBCs + platelets Human WBC trapping bacteria lymphocyte Smooth muscle Sperm cell 1) Acrosome (2) Cell membrane (3) Nucleus (4) Mitochondria (5) Tail (flagella) Adipose cell Stem cells Adult stem cells e. g. Bone marrow cells ◼ ◼ ◼ ◼ ◼ ◼ Multipotent less plastic → limited number of tissues Grow slowly, not robust, not all cell types No longer capable of making germ cells More prone to errors Conditions have not yet been optimized Embryonic Stem Cells ◼ ◼ ◼ ES – pre-implantation - early embryo Divide for a long time in lab, → any cell type Totipotent: → every cell type, potentially functional organism Learning objectives Students should be able to ◼ Describe what is a cell and explain the cell theory ◼ Distinguish between eukaryotic and prokaryotic cells, giving examples ◼ Compare and contrast plant and animal cells ◼ List the cellular organelles and explain their roles ◼ Describe the features of the cell cycle ◼ Describe cell death ◼ Give examples of some specialised human cells ◼ Describe stem cells