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Nucleolus Nucleus Endoplasmic reticulum Cell Membrane Lysosome Golgi Complex Exocytosis Peroxisome Centrosome Ribosomes Endocytosis Mitochondrion Endoplasmic reticulum 10 microns Endoplasmic Reticulum Cell Membrane Mitochondrion Nucleus Nucleolus Centrosome/ centrioles Ribosome Lysosome Peroxisome Golgi Complex Movement across the cell membrane Cytoskeleton Cytoplasm Protoplasm Cell Division Protein Synthesis Cell Anatomy Cell Physiology Enzyme Function Energy Production Cilia
Nucleolus - May be several in the cell nucleus - Contain RNA - Ribosomes are assembled from RNA and protein - Ribosomes then move into the cytoplasm through the nuclear pores and begin protein synthesis. Ribosomes Protein Synthesis
Ribosomes manufacture protein can float free in the cytoplasm (these make soluble proteins) can attach to Endoplasmic Reticulum (ER) making Rough ER. Proteins made here are transported away for use elsewhere in the cell or for secretion. Rough ER Manufacturing Protein
Endoplasmic Reticulum Ribosomes Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Nuclear Membrane Click here to find out about membranes - membranous network within the cell cytoplasm Rough ER Smooth ER There are two types of 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 which are assembled in tips of the channels (cisternae) bud off in transport vesicles vesicles for secretion travel to the Golgi Complex Ribosomes Golgi Complex
Flattened membranes forming a stack Proteins formed by the Rough Endoplasmic Reticulum are sorted and packaged into vesicles Vesicles can be for secretion (see exocytosis) or internal use (e.g. lysosomes) Lysosomes exocytosis
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 used in cell respiration. Mitochondria contain some DNA and can replicate themselves. enzymes
Mitochondria ATP Cell Division Protein Synthesis Ion Pumps
ATP Adenosine Triphosphate contains energy gives up energy to power chemical reactions disintegrates into ADP and a free P reassembled into ATP by cell respiration processes. cell respiration AB AB synthesis Adenosine Tri = 3 Phosphates Substrate molecules A&B: (energy is required to join them together)
Cell Membrane Phospholipid bilayer bilayer Protein Carbohydrates bilayer bilayer Cytoskeleton ein Click here to find out more about molecules moving through the cell membrane.
The Phospholipid bilayer Water (polar) Phosphate heads (hydrophilic) Phospholipid Bilayer Lipid tails (hydrophobic) Phospholipid
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. Intermediate Filaments Intermediate Filaments are another strong protein strand that supports the inside of the cell like guy wires. Microtubules For Microtubules, click the next button The Cell Skeleton
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
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. Diagram golgi vesicles complex Electron Microscope photograph Vesicle
Lysosomes Membranous packets of enzymes that can digest nearly anything.
Peroxisomes Tiny membranous sacs Contain powerful enzymes These utilise oxygen (O 2 ) to oxidise toxic compounds such as alcohol and free radicals. Electron Microscope view approx. x 25000 enzymes mitochondrion
Centrioles Bundles of short microtubules occur in pairs (Centrosome) the Centrosome duplicates before cell division microtubule rods extend and attach to chromosomes during cell division microtubules cell division
Cilia Small, hairlike projections of cell membrane Produce movement at the cell surface Reinforced with pairs of microtubule rods that slide over each other to create movement microtubule
The Nucleus With Chromosomes With Chromosomes Nucleolus Nuclear membrane Nuclear membrane Nucleus
The Nuclear Membrane (or Envelope) Two layers of membrane (each a phospholipid bilayer) The outer layer is continuous with the Endoplasmic Reticulum Nuclear pores are holes in the nuclear membrane that allow large molecules through Electron Microscope view approx. 40,000x magnified Endoplasmic Reticulum
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 2) Those based on carbon chains: Steroids Fats
Based on the four carbon ring Cholesterol: used in - Cell membrane structure, Hormone manufacture STEROIDS
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
Cell Membrane Phospholipids are an important part of cell membrane structure: HydrophobicHydrophilic Phosphate
Movement across the cell membrane Diffusion Passive processes - no energy used for transporting material across the cell membrane Osmosis Facilitated Diffusion Active processes - Energy is used for transporting material across the cell membrane Solute pumps Phagocytosis Pinocytosis Active Transport Transport Bulk (using vesicles) Exocytosis What the heck What the heck was ATP again? was ATP again?
ENZYMES Enzymes are made of protein. They are Biological catalysts. The lock and key model: Active Sites protein This yellow structure represents a vitamin: click here to find out why vitamins are important:
The Sodium/ Potassium pump The pump is activated by 3 sodium ions entering the protein channel. ATP is required for the pump to work K+K+ Na + ATP
The Sodium/ Potassium pump ATP gives up its energy. The pump proteins change shape, expelling sodium ions into the extracellular fluid. Sodium ions are pumped against their concentration gradient K+K+ Na + ADP P
The Sodium/ Potassium pump Potassium ions outside the cell then enter the pump K+K+ Na + ADP P
The Sodium/ Potassium pump Two Potassium ions are pumped to the inside of the cell. Each transport pump moves specific ions across the cell membrane - others include Ca 2+ or H + K+K+ Na + Review Na + k + pump Back to membrane transport
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 Water soluble chemicals that are also lipid soluble can diffuse through cell membranes e.g. cholesterol, alcohol Cell Water can also diffuse freely through protein channels in the cell membrane (See Osmosis)See But if they are not water nor lipid soluble they cannot penetrate the lipid based cell membrane Review Diffusion Back to movement across the membrane
Osmosis Diffusion of water across a selectively permeable membrane - Larger solute molecules cannot penetrate the membrane Selectively permeable membrane More water less solute More solute less water Water moves from where it is in higher concentration ….... to where it is less concentrated 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: 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. Click the left mouse button to see the effects of putting a cell into a hypertonic solution: 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 again to see the effects of putting a cell into a hypotonic solution: Solutions: Hypertonic: High salt concentration Hypotonic: Low salt concentration Water diffuses in -swells and bursts Cells for testing: Water is sucked out cell shrinks Back to movement across the membrane Review osmosis
Facilitated Diffusion Special protein channels 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 Mg 2+ Protein Channel
Amino Acids Amino acids are protein subunits. A central carbon has two groups added to it: A nitrogen based amine group H H N C H A carboxyl group which acts as a weak acid H+H+ C O HO Different amino acids have different side groups: H glycine CH 3 alanine There are 24 different side groups - some attract water, others repel it - giving each amino acid different characteristics. C O HO Amino acids can link acid to amine group if lined up properly - this is the basis of protein structure. H Peptide bond - links amino acids
Proteins Proteins are formed from chains of amino acids. 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. amino acids Key: HistadineAlanine LeucineGlutamine LysineTyrosine - 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 bonds (see the amino acid page if you haven’t yet) Amino acid 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 (primary structure) sequence (primary structure) will always bend coil wrap the same way forming the same shape. (Secondary structure) (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 DOUBLE HELIX and linked by base pairs (next slide).
DNA base pairing Sugar phosphate “backbone” linked by bases that pair: AdenineThymine CytosineGuanine C G G C A T TA How DNA controls the cell How DNA replicates and gets passed on to new cells
Protein Synthesis Part 1: Transcription A section of DNA is copied using ribose 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 DNA
Translation The Second part of protein synthesis mRNA leaves the nucleus and attaches to a ribosome 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 Each group of three bases that codes for an amino acid is called a triplet code in DNAe.g. AGT - a Codon in mRNAe.g. UCA - and an Anticodon in tRNAe.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. Nucleus Ribosome in the cytoplasm mRNA
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. 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 Review the Protein Synthesis section again?
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 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). DNA DNA wound into a chromosome
Cell Division DNA wound into a chromosome Nucleus with DNA unwound ( Between cell divisions = Interphase) Centrosome with a pair of centrioles - protein tubules that will pull apart chromosomes during the cell division Centrioles
Cell Division - DNA Replication 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 Free nucleotides: DNA Chromosomes and DNA
Cell Division The two DNA molecules then coil around their histone proteins and form the visible chromosome. Each chromosome has two chromatids, each containing a complete DNA molecule. Chromatid Chromosome Centromere (holds chromatids together) Chromosome spread: 46 in total What is a Karyotype? On to mitosis DNA
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
Cell Division 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. Go over mitosis again Microtubules and Centrioles More about DNA and chromosomes
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 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. These simple sugars are all variations on C 6 H 12 O 6 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.
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)