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The Interactive Cell Version 1.3 Welcome to the Interactive Cell study aid. This slide show contains a stack of linked pages, with graphics, text and sound. Test the sound level now by pointing here: If the sound needs adjusting, do it now - click on the tiny speaker on your bottom right taskbar or go to START/PROGRAMS/ACCESSORIES/MULTIMEDIA/VOLUME CONTROL. © Labels on the “Cell Master” diagram have sound descriptions that you will hear as the mouse points to them. Clicking on the any of the labels on the “Cell Master” will take you to other pages with more information. Throughout the stack you can move around by clicking the yellow labels that look like this - or you can click on the cell diagram on the bottom right of the page that takes you to the “Cell Master” page. You can also use a variety of buttons if they are present, such as: next page return (last page viewed). If you see a label you want to follow up, you can go there and then use the return button to go back and carry on. Cell Anatomy Cytoplasm Cell Physiology Cell Membrane Mitochondrion Centrosome/ centrioles Movement across the cell membrane Protein Synthesis Cytoskeleton Endoplasmic reticulum Endoplasmic Reticulum Cell Membrane Enzyme Function Mitochondrion Golgi Complex Lysosome Energy Production Lysosome Nucleus Nucleolus Cell Division Mitochondrion Endoplasmic reticulum Nucleolus Ribosomes Golgi Complex Nucleus Exocytosis Centrosome Peroxisome Protoplasm Ribosome Peroxisome Cilia 10 microns Endocytosis Nucleolus - Contain RNA - May be several in the cell nucleus Ribosomes are assembled from - Ribosomes RNA and protein - Ribosomes then move into the cytoplasm through the nuclear pores and begin protein Protein synthesis. Synthesis Ribosomes Manufacturing protein Protein manufacture can float free in the cytoplasm (these make soluble proteins) can attach to Endoplasmic Reticulum (ER) Rough ER making Rough ER. Proteins made here are transported away for use elsewhere in the cell or for secretion. Endoplasmic Reticulum - membranous network within the cell cytoplasm Nuclear Membrane Click here to find out about membranes There are two types of Endoplasmic Reticulum : Rough ER Smooth ER Rough Endoplasmic Reticulum Ribosomes Smooth Endoplasmic Reticulum Smooth Endoplasmic Reticulum Channels that extend from Rough ER contains enzymes that synthesize lipids such as cholesterol, steroid hormones and fat for transport In some muscle smooth ER stores calcium ions Rough Endoplasmic Reticulum Membrane channels Ribosomes make proteins Ribosomes which are assembled in tips of the channels (cisternae) bud off in transport vesicles vesicles for secretion travel to the Golgi GolgiComplex Complex Golgi Complex Flattened membranes forming a stack Proteins formed by the Rough Endoplasmic Reticulum are sorted and packaged into vesicles Vesicles can be for exocytosis secretion (see exocytosis) or internal use (e.g. lysosomes) Lysosomes Mitochondria - Energy Producing organelles that perform cell respiration. Mitochondria vary in shape from tiny threadlike organelles to classic bean shaped structures. They have two membranes - the inner one is highly folded into cristae, which hold enzymes used in cell respiration. Mitochondria contain some DNA and can replicate themselves. Mitochondria Ion Pumps Protein Synthesis Cell Division ATP ATP Adenosine Triphosphate contains energy gives up energy to power Adenosine chemical reactions disintegrates into ADP and a free P reassembled into ATP by cell respiration processes. cell respiration Tri = 3 Phosphates Substrate molecules A&B: (energy is required to join them together) AB A B synthesis Click here to find out more about molecules moving through the cell membrane. Cell Membrane Carbohydrates ein Protein Phospholipid bilayer bilayer Cytoskeleton The Phospholipid bilayer Water (polar) Phosphate heads (hydrophilic) Phospholipid Phospholipid Bilayer Lipid tails (hydrophobic) Intermediate Filaments are another strong The Cell Skeleton Microfilaments Thin protein strands (actin, stained green) crosslinked and braced, these help hold the cell in shape. (e.g. supporting the cell membrane) - they also link with motor proteins (e.g. Mysosin) to help create movement. protein strand that supports the inside of the cell like guy wires. For Microtubules, click the next button Microtubules Hollow protein tubes made of tubulin Microtubules form the major support framework in the cell special arrangements of microtubules form the - Centrioles - Cilia Together Microtubules, Microfilaments and Intermediate fibres form the Cyto, or cell, skeleton. Endocytosis Using endocytosis large particles can be engulfed and brought into the cell. There are two main forms of endocytosis: Phagocytosis Pinocytosis Phagocytosis Pinocytosis Diagram golgi vesicles complex Vesicle Electron Microscope photograph Exocytosis Secretions are wrapped in membranous sacs called vesicles - produced by the golgi complex. Vesicles transported to the cell membrane can fuse with it so that contents are expelled to the outside into the interstitial (tissue) fluid. Cells release hormones and other secretions (mucus, enzymes) in this way. Lysosomes Membranous packets of enzymes that can digest nearly anything. Peroxisomes Tiny membranous mitochondrion Electron Microscope view approx. x 25000 sacs Contain powerful enzymes enzymes These utilise oxygen (O2) to oxidise toxic compounds such as alcohol and free radicals. Centrioles Bundles of short microtubules microtubules occur in pairs (Centrosome) the Centrosome duplicates before cell division microtubule rods extend and attach to chromosomes during cell cell division division Cilia Small, hairlike projections of cell membrane Produce movement at the cell surface microtubule rods Reinforced with pairs of microtubule that slide over each other to create movement The Nucleus Nucleus Nucleolus With Chromosomes Nuclear membrane The Nuclear Membrane (or Envelope) Two layers of membrane (each a phospholipid bilayer) The outer layer is continuous with the Endoplasmic Reticulum Reticulum Endoplasmic Nuclear pores are holes in the nuclear membrane that allow large molecules through Electron Microscope view approx. 40,000x magnified Lipids Largely Nonpolar molecules that normally repel water but dissolve in solvents such a chloroform, ether and alcohol. 2 key types of Lipid: 1) Those based on carbon rings Steroids 2) Those based on carbon chains: Fats STEROIDS Based on the four carbon ring Cholesterol: used in Cell membrane structure, Hormone manufacture Fats and Fatty Acids More about Saturation of fats Triglycerides (neutral fat) Found mostly in adipose (fat) cells as a way of storing energy. Fat is also useful as insulation and padding…… But are insoluble in water - though triglycerides can be modified into Phospholipids Movement across the cell membrane Passive processes Active processes - no energy used for transporting material across the cell membrane - Energy is used for transporting material across the cell membrane Diffusion Osmosis Facilitated Diffusion Bulk Transport (using vesicles) Phagocytosis Pinocytosis Exocytosis What the heck was ATP again? Active Transport Solute pumps ENZYMES Active Sites This yellow structure represents a vitamin: click here to find out why vitamins are important: Enzymes are made of protein. protein They are Biological catalysts. The lock and key model: The Sodium/ Potassium pump The pump is activated by 3 sodium ions entering the protein channel. ATP is required for the pump to work ATP Na+ K+ The Sodium/ Potassium pump ATP gives up its energy. The pump proteins ADP Na+ K+ P change shape, expelling sodium ions into the extracellular fluid. Sodium ions are pumped against their concentration gradient The Sodium/ Potassium pump Potassium ions outside the cell then enter the pump ADP Na+ K+ P The Sodium/ Potassium pump Two Potassium ions Na+ K+ are pumped to the inside of the cell. Each transport pump moves specific ions across the cell membrane - others include Ca2+ or H+ Back to membrane transport Review Na+k+ pump Diffusion Substances that are free to move will spread out evenly into a medium they will mix with. Container with a high concentration of molecules Diffusion Substances that are free to move will spread out evenly into a medium they will mix with. Diffusion Substances that are free to move will spread out evenly into a medium they will mix with. Diffusion Water soluble chemicals that are also lipid soluble can diffuse through cell membranes e.g. cholesterol, alcohol But if they are not water nor lipid soluble they cannot penetrate the lipid based cell membrane Cell Review Diffusion Water can also diffuse freely through protein channels Back to in the cell membrane (See Osmosis) movement across the membrane Osmosis Diffusion of water across a selectively permeable membrane - Larger solute molecules cannot penetrate the membrane Water moves from where it is in higher concentration ….. A stronger solution with lots of solute in it thus appears to “suck” water into it through the membrane .. Click the left mouse button to see the effects of osmosis in this demonstration: Selectively permeable membrane More water less solute .. to where it is less concentrated More solute less water Osmosis creates enough pressure to raise the height of the fluid : Osmotic Pressure Osmosis and Cells A cell with its selectively permeable membrane is quickly affected by osmotic pressure changes. It is important for body fluid concentrations to be maintained within narrow limits to stop cells shrinking or swelling and bursting. A salt solution that develops the same osmotic pressure as normal body fluids is 0.9% (0.9 grams of NaCl per 100mls water). This is isotonic or medical saline. Click the left mouse button to see the effects of putting a cell into a hypertonic solution: Water is sucked out Cells for testing: cell shrinks Solutions: Hypertonic: High salt concentration Click again to see the effects of putting a cell into a hypotonic solution: Water diffuses in -swells and bursts Hypotonic: Low salt concentration Review osmosis Back to movement across the membrane Facilitated Diffusion Special protein channels Protein Channel allow certain chemicals to diffuse through the cell membrane along their concentration gradients (High to Low) There are different channels each with a slightly different shape for each substance for example glucose, and different ions such as Mg2+ Amino Acids Amino acids are protein subunits. A central carbon has two groups added to it: A nitrogen based amine group Different amino acids have different side groups: There are 24 different side groups - some attract water, others repel it - giving each amino acid different characteristics. A carboxyl group which acts as a weak acid CH H 3 H C O H N C C O H H H O H O alanine glycine Peptide bond - links amino acids Amino acids can link acid to amine group if lined up properly this is the basis of protein structure. H+ Proteins amino acids acids . Proteins are formed from chains of amino Short chain proteins can be called peptides. Long chains of amino acids (100+) we call proteins but all amino acid chains belong to the protein class. Key: Histadine Alanine Leucine Glutamine Lysine Tyrosine - there are 24 different amino acids, each with a different side chain. Protein Structure Each protein is made by linking a specific sequence of amino acids linking together through peptide Aminoacid acid page if you haven’t yet) bonds (see the amino As the amino acid chain forms the side groups will attract or repel each other and the surrounding polar water molecules. As long as conditions stay constant (e.g. homeostatic temperature and pH) a protein of a particular amino acid sequence (primary structure) will always bend (Secondary structure) coil wrap the same way forming the same shape. (Tertiary structure) Protein levels of structure To find out how the amino acid sequence is determined: Click here to go to Protein Synthesis SEQUENCE DETERMINES SHAPE, SHAPE DETERMINES FUNCTION For an illustration, see enzyme function Chromosomes and DNA DNA Deoxyribose Nucleic Acid The molecule of inheritance - passed on from cell to cell through cell division processes - is formed into chromosomes by coiling around proteins called histones - Uncoiled a small piece of DNA is seen to be in the form of a DOUBLE HELIX and linked by base pairs (next slide). DNA base pairing Sugar phosphate “backbone” linked by bases that pair: Adenine Thymine Cytosine Guanine How DNA controls the cell C G A T C G T A How DNA replicates and gets passed on to new cells Protein Synthesis Part 1: Transcription DNA is copied using ribose A section of DNA nucelic acids to form a strand of mRNA. The mRNA breaks away from the DNA and moves through nuclear pores to the cytoplasm, where it is used as a template to make protein. In RNA strands, the base Thymine is not used -Uracil takes it’s place. Base pairing is G-C U-A Translation Each group of three bases that codes for an amino acid is called a triplet code in DNA e.g. AGT - a Codon in mRNA e.g. UCA - and an Anticodon in tRNA e.g. AGU With four bases, there are 64 possible triplets. With only 24 different amino acids, there are often 2 or more triplets coding for an amino acid. The Second part of protein synthesis Transfer RNA has just 3 bases. It attaches to an amino acid which amino acid depends on the 3 bases: AAU attaches to leucine CGA or CGG attaches to alanine etc Nucleus mRNA leaves the nucleus and attaches to a ribosome mRNA Ribosome in the cytoplasm Translation (2) The ribosome lines up the tRNA molecules with their amino acids. Translation (3) When the amino acids are lined up beside each other they will form a peptide bond. Translation (4) After the first peptide bond formation the first amino acid detatches from it’s tRNA. The tRNA then breaks away to find another amino acid in the cytoplasm. The ribosome moves along the mRNA strand, and another tRNA lines up another amino acid……. Translation (5) After each peptide bond forms the ribosome moves along and lines up the next tRNA with its amino acid. The amino acid chain (protein) grows with the amino acid sequence determined by the base sequence - which was determined originally by the DNA base sequence. Review the Protein Synthesis section again? In proteins, the amino acid sequence determines the shape of the protein the shape of the protein will determine it’s function: Find out about Protein and its uses Cell Division To duplicate itself, a cell first has to duplicate it’s DNA. This occurs when all the DNA is unwound in the nucleus of the cell - DNA wound into a chromosome DNA (DNA is often pictured wound up in the form of chromosomes, but they spend little time in this form. Most of the time DNA spends unwound so that protein synthesis can occur, and the DNA winds up around histone proteins to form visible chromosomes so the DNA can be pulled apart during cell division). Cell Division Centrosome with a pair of centrioles - protein tubules that will pull apart chromosomes during the cell division DNA wound into a chromosome Nucleus with DNA unwound ( Between cell divisions = Interphase) Centrioles Cell Division - DNA Replication Free nucleotides: DNA Chromosomes and DNA DNA unzipped by enzymes: Free nucleotides then attach to the exposed bases to replicate the original DNA. Base sequence is maintained due to base pairing C-G; A-T Cell Division Chromosome spread: 46 in total Chromosome Chromatid Chromatid Centromere (holds chromatids together) DNA molecules The two DNA then coil around their histone proteins and form the visible chromosome. Each chromosome has two chromatids, each containing a complete DNA molecule . What is a Karyotype? On to mitosis Cell Division - Mitosis When DNA has been duplicated, the cell can then actually divide Prophase - chromosomes become visible centrioles form 2 pairs and move apart nuclear membrane breaks down Cell Division - Mitosis When DNA has been duplicated, the cell can then actually divide Metaphase - chromosomes line up across the cell and centriole tubules extend to form the spindle apparatus (attaches to centromeres) Diagram shows only 2 pairs of chromosomes for clarity: humans have 23 pairs. Cell Division - Mitosis When DNA has been duplicated, the cell can then actually divide Anaphase - chromatids (each containing a complete DNA molecule) are pulled apart Cell Division - Mitosis When DNA has been duplicated, the cell can then actually divide Telophase - chromatids unwind, nucleus reforms Cytokinesis occurs - the acutal separation of the cell into two new identical cells Go over mitosis again Cell Division Microtubules and Centrioles More about DNA and chromosomes Maximum rate of cell division rate is about once every twelve hours once a day is more typical. The mitosis part takes about an hour or two. Karyotype Chromosomes arranged in pairs from largest to smallest (22 autosome pairs) - and the sex pair of chromosomes, pair 23 XY for males (shown) XX for females Chromosome bands Special lab techniques can show different patterns on chromosomes to help identify particular chromosomes. Carbohydrates These simple sugars are all variations on C6H12O6 They are all ISOMERS. There are other types of simple sugars in the body as well - for example the Ribose 5 carbon sugars found in nucleic acids. Made of C, H, O Carbohydrates are made of base units called simple sugars or monosaccharides The commonest example in the body is the 6 carbon sugar glucose. -OH groups make the sugars water soluble. Di- and Poly- saccharides Disachharides have two simple sugars joined Sucrose = Glucose + Fructose Lactose = Glucose + Galactose Maltose = Glucose + Glucose Polysaccharides of importance to the body are made of chains of glucose: Protoplasm Descriptive term for the souplike contents of a cell, including the fluids of the nucleoplasm (inside the nucleus) and cytoplasm (outside the nucleus) H Li He Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca