BIOLOGY F211

BIOLOGY F211

CELLS
1. MICROSCOPES
  1. Light microscopes
    1. Resolution 200nm
    2. Magnification x1500
  2. Magnification = the degree to which the size of an image is larger than the object itself...Magnification=image/actual size
  3. Resolution = the degree to which you can distinguish between 2 objects that are very close together. the higher the resolution the more detailed it is.
  4. Electron Microscopes
    1. Scanning Electron
      1. Resolution 0.2nm
      2. Magnification x100000
      3. 3D image of surface of sample because electrons bounce of the surface.
    2. Transmission Electron
      1. Resolution 0.2nm
      2. Magnification x500000
      3. Transmits THROUGH the sample to produce 2D image.
        Denser parts of the cell will take up less electrons so it gives more contrast.
    3. Expensive
    4. Need to put it in a vaccum
  5. Preperation
    1. Staining...chemicals bind to the organelles to provide contrast
    2. Sectioning...cutting up the sample really thin and embed them in wax.
    3. Needs a high degree of skill
2. STRUCTURE AND FUNCTION OR ORANGELLES
  1. Nucleus
  2. Endoplasmic Reticulum
  3. Golgi Apperatus
  4. Lysosomes
  5. Mitochondria
  6. Vacuole
  7. Plasma membrane
  8. Chloroplast...they have a double membrane with a layer of fluid inbetween. They have thylakoids that look like piles of plates. A stack of thylakoids are called a granum. Used in photosynthesis in plant cells.
  9. Centrioles
  10. Cilia and Flagella...they are both structurally the same. They are hair like extension. They are made up of a cylinder containing 9 microtubules in central bundle. Can make the whole cell move and can help move things within the cell. Cilia less than 10 micrometers long.
  11. Cytoskeleton refers to the network of protein fibres found within a cell that give structure and shape to the cell and also moves organells around inside the cell. provides mechanical strength
    1. REMEMBER - provides mechanical strength to cells -aiding transport within cells and enabling cell movement.
  12. Plant Cell vs Animal Cell
    1. Have got, amyloplast containing starch grains, golgi apperatus. SER and RER, nucleus, plasma membrane, cell wall, vacuole, ribosomes, mitochondria
    2. Have got Nucleus, mitochondria, ribosomes, RER and SER, lysosomes, golgi apparatus, plasma membrane.
    3. Both have nucleus, SER and RER, golgi, Plasma membrane, ribosomes, mitochondria
3. PROKARYOTES VS EUKARYOTES
  1. Eukaryotes - have a complicated internal structure - they have a nucleus
  2. Prokaryotes - 1-5 micrometers, smaller than eukaryotes - they show all characteristics of living organisms (they respire, they produce waste)
    1. One plasma membrane
    2. Do not contain membrane bound organelles like mitochondria and chloroplasts.
    3. Surrounded by cell wall not made up of cellulose, made up of peptidoglycan.
    4. Slippery layer outside cell wall called capsule.
    5. Contain ribosomes (simple things) they are much smaller 20nm in diameter
    6. No cytoskeleton
    7. DNA is circular
4. CELL MEMBRANES
  1. Role is to separate cell content from outside cell, separates cell components from cytoplasm, cell recognition and cell signalling, holding components of metabolic paths in place, regulate the transport of materials in and out of cell.
  2. Partially permeable
  3. Fluid Mosaic Model - molecular arrangement in membrane. There is a bilayer of phospholipid molecules. Various proteins floating around in the phospholipid bilayer. Some exintric proteins sticking out of bilayer.
  4. Cholesterol - gives stability. Fit between fatty acid tails to help make barrier more complete so substances like water molecules and ions can't pass through easily.
  5. Glycolipids and glycoproteins - molecules with small carbohydrate parts attached.
  6. Channel proteins - allow movement of some substances across membrane that are too large and to hydrophilic to pass through bilayer.
  7. Carrier proteins - move substances across membrane. e.g. magnesium ions activly pumped through into root hair cells from soil using ATP. Nitrate ions are actively transported into xylum vessel to lower water potential gradient.
  8. Temperature - Increase temp molecules get more kinetic energy. Move faster. Membrane is leaky so molecules enter and leave the cells when they shouldnt
  9. Cell Signaling - cells communicate via signals.
    1. Surface 'sensors' must be on (receptors)
    2. Any cell with receptor for hormone molecule is called a target cell
    3. Hormone molecule binds to receptor, they are complementary. Target then responds.
    4. E.g Insulin receptor
    5. Medical Drugs - Drugs developed with complementary shapes to receptor molecule. They block receptors.
  10. Passive Transport
    1. Diffusion...net movement of ions or molecules down their concentration gradient
    2. Facilitated Diffusion...Ions passing through membrane by diffusion down concentration gradient but through channels e.g chloride ions
  11. Active transport...moving ions through transported proteins using ATP (energy) up their concentration gradient e.g. sodium potassium pump
  12. Bulk Transport
    1. Exocytosis..moving substances out, in vessicle via microtubules. fuses with membrane substance emptied outside cell
    2. Endocytosis...moving substances in (e.g. phagocyte engulfs bacterium). Fingers around substance. Ring around it. contained in vacuole. enzymes secrete into vacuole to digest it. Use energy
  13. Osmosis...net movement of of water down the water potential gradient because of random motion, no energy needed.
    1. Animal Cell...become crenated when water is lost. when too much water is taken in it bursts.
    2. Plant cells...water moves in, cell wall resists expansion force called pressure potential. water out means plasma membrane comes away from cell wall, it tears, cell dies.
5. Cell Division
  1. Mitosis takes up tiny amount of cell cycle most of it is in copying and checking
  2. Interphase.. DNA replicated and proteins and organelles a made.
  3. Mitosis
    1. Prophase
      1. Metaphase
        Anaphase
        Telophase
        Two new nuclei are formed
        Replicas pulled apart by centromere to opposite ends of cell
        Chromosomes line up at equator
      2. Replicated chromosomes supercoil
    2. Needed for growth, repair and asexual reproduction in animals and plants
  4. Cytokinesis...when the cell splits forming two identical daughter cells
  5. Meristem cells...only cells that are capable of mitosis and cytokinesis
    1. In plant cells a cell plate is formed at the start of cytokinesis. New cell membrane is laid along this cell plate.
  6. Homologous...chromosomes that have the same genes at the same loci. Pair up in meiosis. Diploid organisms, produce by sexual reproduction have homologous pairs - one member of each pairs from the male and the other from the female.
  7. Budding...when a yeast cell produced new cells off the side of an existing one. genetically identical.
  8. Meiosis
    1. Cells called gametes must be produced with half the number of chromosomes to be used in sexual reproduction.
    2. Fusion of 2 gametes is called a zygotes.
    3. Happens in sex organs.
    4. Normal adult cells of most eukaryotes are diploid.
    5. Their genome consists of pairs of homologous chromosomes , they contain the same genes but not necessarily the same versions (alleles) of each gene.
    6. During meiosis, one member of each homologous pair goes into each daughter cell.
    7. Daughter cells are haploid
  9. Stem cell...can divide and develop into any other type of cell. Can be in young embryos, they are totipotent. Can be in adult tissues, they are pluripotent. Can be in bone marrow to make blood and bone cell types.
6. Cell Diversity
  1. Differentiation...the changes occurring in cells of a multicellular organism so that each different type of cell become specialised to perform a specific funcition.
    1. Erythrocytes and neutrophils - human cells that each begin with the same set of chromosomes so each is potentially capable of carrying out the same functions. All blood cells are produced from undifferentiated stem cells in the bone marrow.
    2. Xylem Tissue - come from dividing meristem cells such as cambium. Consists of xylem vessels with parenchyma cells and fibres. meristem cells produce small cells that elongate. Walls become waterproofed and reinforced by deposits of lignin. This kills cell content. Ends of cells break down so it become continuous long tubes with a wide lumen. Helps support plant as well as taking water and minerals up plant.
    3. Phloem tissue - consists of sieve tubes and companion cells. Meristem tissue produces cell that elongate and line up end to end to form a long tube. Sieve plates form between cells. These allow movement of minerals up or down the tubes. Next to sieve plates there are companion cells they are metabolically active, they help get the produces of photosynthesis up and down the plant in the sieve tubes.
  2. Epithelial cells
  3. Sperm Cells
  4. Palisade cells - packed with chloroplast
  5. Root hair cells
  6. Guard Cells - can become turgid so its bulges and lets the stomata open
7. Cellular orangisation
  1. A tissue - a collection of cells that work together to perform a common function e.g xylem and phloem
  2. An organ - A collection of tissues working together to perform a particular function e.g leaves and the liver.
  3. An organ system - Made up of a number of organs working together to perform an overall function e.g excretory system and the reproductive system.
  4. Squamous Epithelial cells - very thin, cells together form thin flat smooth surface, ideal for lining blood vessel walls, also in alveoli it provides a short diffusion pathways. Held together by basement membrane, this is secreted by epithelial cells. its made of collagen and glycoproteins. Attaches epithelial cells to tissues.
  5. Ciliated Epithelial cells - column shaped cells, lining of tubes, e.g trachea and bronchi and bronchioles, and uterus and oviducts. Tiny projections of cilia, Cilia waves mucus in the breathing tract goes up to throat to be swallowed. Cilia moves the egg along the oviduct from the ovary.
  6. Cooperation between cells, tissues, organs and organ systems
    1. Harvesting light - transparent upper surface layer, layer of palisade cells, loosely packed spongy mesophyll (allows circulation of gases), pores called stomata, vein system (xylem and phloem)
    2. Muscular and skeletal system work together for movement. Nerve system instruct muscles. They need energy to work so you need to circulatory system to be involved. Which needs chemicals from the digestive and ventilation system.

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