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AVBS2005 STUDY NOTES ANIMAL CELL STRUCTURE AND INTRODUCTORY CYTOLOGY/HISTOLOGY TERMS Magnification – ration of image to object size Resolution – alibility to produce see images of closely positioned object, the level of detail Tissue – aggregation of cells of the same type or mixtures an intercellular structure. (four types epithelium, connective tissue, muscle tissue, nervous tissue) Organ – consist of various arrangements of the four basic tissues Prokaryotes – are mostly single celled organisms without a nucleus with replication for reproduction Eukaryotes – are single celled or complex multicellular organisms that have a nucleus and organelles. Glycocalyx – cell coating Endocytosis – the injection of large substances into the cell e.g. phagocytosis Exocytosis- removal of small substances out of the cell Cytosol – compartment within cells that consist of a water based jell, where reactions take place Heterophagosomes – contain external particulate matter that is incorporated into the cell via phagocytosis Autophagosomes – contain particular matter that originates from within the cell Basophilic – tendency to bind to basic alkaline dyes Eosinophilic – tendency to bind to acidic dyes Eumelanin – dark brown pigment Pheomelanin – yellow red pigment Easter – compound formed between acid and alcohol reaction. Carboxylic head is reactive and forms ester bond. Oligosaccharides – short chains of carbohydrates Polysaccharides – long chains of carbohydrates Gene – functional information containing element

Genome – full set of genetic information Chromosome – linear set of DNA Nucleoside – base + sugar Nucleotide – base + sugar +phosphate Pyrimidine – single ring nucleotide (T,C,U) Purine. Double rings nucleotide (A,G) Glycolysis: Ubiquitous metabolic pathway in the cytosol in which sugars are degraded into common metabolic intermediates and energy is produced. (ECB) Gluconeogenesis: Metabolic pathway in the cytosol in which sugars are generated from metabolic intermediates. Common Metabolic Intermediates: Common degradative products of catabolism of energy yielding nutrients. (sugars, protein and lipids) Citric Acid Cycle: Central metabolic pathway in all aerobic mechanisms that oxidize acetyl groups derived from food molecules to CO2. Located in the mitochondria and generates reducing power (electrons) (ECB) Oxidative Phosphorylation: Process in the mitochondria in which ATP formation is driven by the transfer of electrons to oxygen molecules. (ECB)

IMPORTANT INFORMATION Cell theory -

All cells are membrane enclosed units filled with an aqueous solution of chemicals Organism consist of nothing else of nothing but cells, transferred cells and material produced by cells All cells arise from pre-existing cells by division Transformed cells  bone and other material produced by cells

DESCRIBE THE TECHNO LOGIES INVOLVED IN THE STUDY OF CELL STRUCTURE. light microscope -

Include a condenser, stage, objective lens, ocular lens Magnification up to 100x Resolution 0.2/200nm Light must pass through specimen, therefore has to be thin, often requires staining

Fluorescence -

Use of florescence dyes to highlight specific structures/molecules. Light pass through 2 sets of filters: the first filter allows only wavelength to pass that excites

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the specific dye. And the second filter allows only those wavelengths that are emitted by the dye Instead of using white light its florescent, we narrow down by filtering so particular wavelengths go through and the light we see also goes through a filter. When excited it will glow.

Confocal microscopy -

Specialized florescence microscope, creating optical sections that can be combined to create a 3d image Used precise wavelengths Uses lasers

Scanning electron microscope -

Specimen coated with thin layer of heavy metal is scanned by beams of electrons, creates 3d image with a resolution of 3nm – 20nm. Bounces off a surface

UNDERSTAND THE PRINCIPLES O F OPERATION AND BE COMPETENT IN THE USE OF A LIGHT MICROSCOPE.

IDENTIFY AND DESCRIBE VARIOUS CELLUL AR STRUCTURES IN ANIMAL CELLS. EPITHELIA -

Closely adherent cells found on the surface Epithelium lines the respiratory track, digestive system, vessels and ducts; the body cavities, organ, the body surface Varies in function, location, shape and arrangement

CO NNECTIVE TISSUE

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Provides framework Supports the entire body Consists of loosely aggregated cell dispersed in intercellular material Can be described as loose, dense, regular, irregular Specialised connective tissue are cartilage, bone and fat Proteins and carbohydrates

MUSCUL AR TISSUE -

Mechanical force of contraction Aliened fibres in the direction of a contraction

NERVOUS TISSUE -

Highly specialised neurons and their supporting neuroglia Neurons transmit electron and chemical stimuli and are characterised by their specialised processes: dendrites and axons

CELL MEMBRANES -

About 8 nm thick Composed out of lipid molecules, cholesterols and associated proteins Lipids in constant motion, not rigid Cholesterol can fit in between lipids and hence change the fluidity and what can diffuse Phospholipid bilayers form sealed compartments Cell membrane proteins are not fixed with the lipid bilayer but move Channels formed by proteins Carbohydrates are attached to the lipid proteins to form a cell coat, call glycocalyx, which stick to other cells by carbohydrates localised on the membrane.

Function -

Creates a selectively permeable barrier to external medium Controlled transport through membranes for uptalking nutrients and secretion of waste Capacity of movement and growth Receptive to information from outside the cell Creates compartments within the cell Nucleus, most organelles and inclusions are separated from the cytosol by similar structures internal membrane to create compartments

Formation -

endoplasmic reticulum grows by the direct incorporation of molecules of lipid and protein other structures are derived either directly or indirectly from the endoplasmic reticulum flow of membrane is largely through vesicles that bud or are pinched off from the donor structure and then fuse with and become a part of the recipient structure

Challenges

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Transporting correct proteins to correct organelles Retrieving and degrading old components Controlling water flow and cell volume Getting selected molecules through membranes Distribution of cell organelles in cell division

Transport -

Diffusion Active transport Membrane transport proteins

UNDERSTAND THE GENERAL CORREL ATIONS BETWEEN THE STRUCTURE OF CELLUL AR ORGANELLES AND THEIR FUNCTION. Nucleolus Site of ribosomal RNA production initial ribosomal assemblage. Contains dense, basophilic nucleus. Is more acidic and not membrane bound Ribosomes Small electron dense particles not visible in light microscope and is the site of proteins synthesis. Has two subgroups. Are basophilic 3 TYPES OF VESICLES LEAVE THE GOLGI COMPLEX: - Transport vesicles containing lysosomal enzymes destined to late endosomes - Transport vesicles of the constitutive secretory pathway to the plasma membrane - Continuous transport of membrane proteins and lipids for the plasma membrane, and proteins for secretion (e.g. extracellular matrix proteins) - Secretory vesicles (or secretory granules) of the regulated secretory pathway to the plasma membrane - transport vesicles with condensed proteins that discharge protein in response to extracellular stimulus

MITOCHONDRIA THE OUTER MEMBRANE   

mitochondrion is enclosed by two separate membranes space between the two membranes is called intermembranous space outer membrane is smooth and permeable to all molecules of 5000 daltons or less  (due to protein channels – porins)

THE INNER MEMBRANE  inner membrane is folded into cristae or tubuli:  to enlarge the surface area  to provide partially separated compartments  inner membrane is impermeable to ions and most small molecules  very rich in three groups of proteins:  highly specific transport proteins  enzymes that carry out the oxidation reactions of the electron transport chain  the ATP synthase, that makes ATP  no charged ions can get through the inner permeable membrane  enclosed by the inner membrane is the mitochondrial MATRIX  the matrix includes  enzymes for oxidation of pyruvate and fatty acids  enzymes for the citric acid cycle  identical copies of mitochondrial DNA  mitochondrial ribosomes,  tRNAs  enzymes required for gene expression

Organelle Mitochon dria

Function Are involved in energy production and the main type of energy is chemical energy known as ATP The mitochondria matrix contains enzymes that break down organic fuels via oxidative catabolism

Peroxisom es

Ribosome s

Rough Endoplasmic reticulum

Smooth ER

Uses oxygen to carry out reactions – they use oxygen to oxidize and strip hydrogen off certain molecules to produce hydrogen peroxide, which then oxidizing toxic substances, breaking down fatty acids and synthesizing certain phospholipids. Non membrane bounded organelles that are responsible for protein synthesis

Rough ER – polypeptides synthesized pass through the membrane to the lumen where enzymes folds these polymers into the correct shape. The RER also is a membrane factory and additionally synthesize cholesterol and phospholipids Calcium storage, detoxification reaction and lipid synthesis No ribosomes

Structure Membrane surrounded with a biolipid layer with a number of folds called cristae. This creates two spaces the intermembrane space and the matrix

Consist of two subunits, depending on their location they are categorized as free or bound Large folded membrane that surrounds the nucleus

Other Contain its own DNA and enzymes and ribosome 0.2 and 12nm long - Double membrane - High number in activated cells Hydrogen peroxide is toxic so when levels get to high an enzyme turns excess into oxygen and water -

The RER recognized proteins that have been folded incorrectly and send then to the cytosol where they are degraded

Found in large amount in the liver and adrenal cortex

Golgi apparatus

Lysosome s

Endosom es

Peroxisom es

Consists of groups flattened vesicles off to various destinations Receives proteins and lipids from the ER and modifies them

Contain hydrolytic or digestive enzymes in a low pH environment. Digest microorganisms, damaged cells , debris Early endosomes located close to the plasma membrane, sorting the components of endocyclic vesicles. Receptor bound Late endosomes located close to the Golgi and receive endocytic material from digestion from early endosomes. Fuse with transport vesicles and become lysosomes after ph decreases to 5 Contain enzymes that produce h202 contain catalase that uses hydrogen peroxide to oxidize a variety of substances Contain catalase that uses hydrogen peroxide of oxidase a variety of substances

Located between the ER and the plasma membrane. Each sac contains different enzymes as each has a different function Small membrane bounded organelles Membrane bounded tubes and vesicles

Small membrane bounded spheres. Contain a finely granular electron dense content

Shows no basophilia due to lake of ribosomes Stains with silver and osmium. Consists of several layers and an associated network of tubules and vesicles.

Hydrogen peroxide forms chemical reactive free radicals capable of attaching nucleic acid and proteins.

SMALL MOLECULES, ENERGY AND BIOSYNTHESIS IN ANIMALS TERMS IMPORTANT INFORMATION More abundant in non-dividing cells and increasing with age Glycogen -

Storage form of carbohydrates Abundant in liver, cardiac, skeletal muscles cells store of carbohydrates Glycogen storage disease is caused by the inability to degrade glycogen and cells become enlarged and the functional loss of glycogen as cell energy as a blood glucose buffer

LIPIDS -

Energy reserve Abundant in adipocytes and steroid producing cells More energy dense then glycogen

MELANIN -

Dark brown or black pigment responsible for skin colour Occurs in basal layer of epidermis, external sheath and hair matrix of hair follicles, epithelium of rectum Is synthetised by melanocytes – specialised with long dendritic process Melanosomes pinch off and are phagocytized by surrounding cells Several melanosomes can aggregate and form a melanosome complex tyrosinase is required for the production of melanin

HEMOSIDERIN -

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forms as a result of haemoglobin degradation contain iron occurs as granular cytoplasmic inclusions in the spleen, liver, bone marrow. If iron increases beyond normal levels, excess hemosiderin is deposited in the liver and heart. This can reach a point in which the function of the heart is impaired. Hemosiderosis (disorder caused by excessive deposition of iron – multiple blood transfusion) ongoing accumulation of iron, localised arrogation.

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Hemochromatosis (inherited iron disease)

LIPOFUSCIN -

End products of lysosomal activity Golden brown pigment Stainable with fats and lysomol dyes Cannot be broken down, accumulation in long lived areas

CYTOSKELETON Intermediate filaments – important for lateral strength, interlocking of filaments that attach to junctions between cells Function -

Cell mechanical strength Control of shape Drives and guides its movements

MICROFILAMENTS  ACTIN -

Thinnest filament 7nm in diameter Helical polymer of identical globular actin molecules Assemble and disassemble Throughout the cell but most abundant beneath plasma membrane

Permanent or transeunt -

Micro villi on brush boarder cells, more membrane absorption Contractable bundles Protrusions in crawling cells Contractile ring in cell division

Function -

Actin associated with myosin to from contractile structures  Movement of vesicles within the cell cytoplasmic streaming, walks along track  Movement of actin filaments against a plasma membrane  Actin filaments slide against myosin filaments

INTERMEDIATE FILAMENTS -

Intermediate in diameter (10nm) Rope like fibres – great tensile strength From network throughout the cytoplasm – often anchored to plasma membrane at cell-cell junction From a nuclear lamina that strengthens the nuclear envelope

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Enable cells to withstand mechanical stress, muscle and peripheral nerve Do not form and reform in the continuous manner of microtubules and microfilaments Rope like Lateral stretch Gastric, muscle and skin Can be attached to actin filaments too

MICROTUBULES -

Long hollow cylinders with a diameter of 25nm Made from tubulin Can rapidly disassemble and resemble One end attaches to a single microtubule organizer centre Alpha tubulin and beta tubulin from dimer tubulin Linear chains of dimer tubulin form protofilaments Polar structures with a + and – ends with continuous state of polymerisation at positive end and constant state of depolarisation at negative end Position organelles used in mitosis, and supporting structure in mobile cilia and flagella

CELL MOVEMENT CILIA -

Short structure Protruding from free surface of the cell Regular and synchronous undulating movement of rows of celia create a move that sweeps across the epithelium In the respiratory track – the movement of mucous

FLAGELL A -

Represents a single long cilium Rapid successive waves of bending, form the attachment to the free end Each spermatozoa possesses a single flagellum

MICROVILLI -

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Vary from small, bled like projections, uniform projections Increased surface area and increased absorption < 0.1 Mn diameter about 5Mn long Supporting by 20 – 30 parallel actin filaments for rigidity  Supported filaments anchor to the plasma membrane at the sides and tip of each of each microvillus and extend down into the apical cytoplasm Can be found n apical surface of epithelia

FILOODIA AND L AMELLIPODIA Irregular cell protrusion that allow crawling of cells, e.g.

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Migrate white blood cells Growing of axons in nerve cells Actin polymerisation pushes forward of the cell surface in sheet like (filiopodia) protrusions Protrusions stick to favourable surfaces via integrins Cell body is dragged towards attachment via actin and myosin action Actin filaments, that can grow and retract, lamellipodia (sheet like) membrane integrins can recognise each other, form a bind transcend binding and can be anchored

LATERAL AND BASEL CELL SURFACES FO LD - The lateral and basal surface of certain epitherial cells may show a tortuous boundary due to infolding or interditations of each with its neighbour or the basal - The folds are prominent in cells that transport fluid rapidly such as the cells of kidney and salivary gland tubules - Increase surface area between cells, so lateral and basil surface confulated boundries so they form close connections

INTERCELLUL AR JUNCTIONS TIGHT JUNCTION

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Only in epi cells Continuous belt of transmembrane proteins of neighbouring cells Link to outer leaflets of adjacent membranes which stops leaking and separates apical and basal surfaces to maintain cell polarity Typical apical surface, belt like interactions with multiple points which binding proteins from one cell to the other. Linking two membranes together

LINKED JUNC TION Cytoskeletal linked connection to other cells/ extracellular matrix and provides cell strength

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Cell to cell (adherent and desmosomes) Cell to basal lamina contract (hemidesmosomes)

ADHERNET JUNCTION -

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Belt like stuctures below tight Cells connected via transmembrane linker proteins (cadherins) linker proteins which are attached tointracellular actin filments All the way around the ousdie of the cell and lock cells together Locks cytoskeletons togther, cadherins calcium ions

DESMOSOMES -

Disc like junction between cells Connect via transmembrane linker proteins (cadherins) linked to intercellular intermediate filaments (kerintin) Links to cytoskeleton of neighbouring cells to maintain integrity of tissue and resist mechanical stress More focused and localised

HEMIDESMOSOMES -

Disc like skeleton linked junction between cell and extracellular matrix (basal membrane)

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Transmembrane linker proteins like the extracellular matrix protein at the outside of the clivi linker proteins to intercellular filaments

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Link between cytoskeleton to the underlying connective tissue

CO MMUNICATION -

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Gap junction Allow direct passage of inorganic ions/ small water soluble molecules to allow synchronisation of function and metabolic cooperation via electrical and metabolic coupling Six transmembrane proteins form a connexon, Two connexons of neighbouring cells form a hydrophilic channel Connect zone in each cell line up in neighbouring cells, form channel which spans the two cells

UNDERSTAND THE BIOCHEMICAL AND STRUCTURAL NATURE OF SMALL MO LECULES (AMINO ACIDS, FATTY ACIDS, SUGARS AND NUCLEO TIDES) AND THEIR REL ATIO NSHIP TO MACROMOLECULES (PROTEINS, LIPIDS AND CARBOHYDRATES, DNA). Above

UNDERSTAND THE CO NCEPTS AND DESCRIBE THE PROCESSES BY WHICH CELLS DERIVE ENERGY FROM THE ENVIRONMENT.

ATP -

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Most abundant in...