Module 1: Cells 2

Unit 1 Cell Division and Mitosis moducle 1.1 unit 10-12

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  • Created by: lizi
  • Created on: 04-11-09 17:06

Exchange Across the Membrane

Active Processes:

  • Active transport:
    • Against a concentration gradient via carrier proteins that use energy from ATP in order to change shape.
  • Endocytosis and Exocytosis:
    • Bulk transport of materials via vesicles that can fuse with or break from the cell surface membrane.

Passive Processes:

  • Diffusion:
    • Down a concentration gradient lipid soluble or very small molecules throught lipid bilayer and osmosis..
  • Facilitated Diffusion:
    • Down a concentration gradient charged or hydrophilic molecules or ions via channel or carrier protiens.
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Passive Processes

  • Diffusion:
    • Diffusion is a passive molecules diffuse down gradient with not energy needed, they have their own kinetic energy.
  • The rate is affected by
    • Temperature
    • Concentration gradient
    • Stirring/moving
    • Surface area
    • Distane/thickness
    • Size of molecule
  • Channel Proteins:
    • Are like pores, only allow one type of ion through sometimes are gated. Ions like Na ions and Ca ions
  • Carrier Proteins:
    • shaped for specific molecule, protien changes shape to allow mollecule through eg. Glucose and amino acids.
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Water Potential/ Osmosis


  • is a special kind of diffusion, it is only the movement of water molecules by diffusion and across a partially permeable membrane.
  • Water potential is a measure of the concentation of water molecules that are able to diffuse. Pure water has the highest amount of free molecules 0kPA (kiloPascals). Lower water potential is -10kPA.
  • In Pure Water
    • Animal cells take in water from osmosis until they burst open (haemolysed)
    • Plant Cells have a cell wall which prevents bursting. Membrane pushes against the wall (Turgid).
  • In Concentrated solution
    • Animal cell loses water through osmosis and shrinks and appears wrinkled (Crenated).
    • Plant cell loses water through osmosis and plant cell membrane pulls away from cell wall as water leaves. (Plasmolysed)
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Mitosis is significant in a cell because it is involved with:

  • Growth .e.g. cells in an eymbryo divide to form tissue stem cells
  • Replacement of Bome marrow to Red blood cells and neutrophils.
  • Repair, e.g. in wound healing.
  • Asexual reproduction

The Stages of mitosis:

  • Prophase - replicated chromosomes supercoil (shorten and thicken),each chromosome is now two chromatids.Nuclear envelope breaks down. Centrioles move to opposite poles of the cell.
  • Metaphase - Chromatids come to the middle of the cell. Centrioles organise microtubules into the spindle which attach to centromes.
  • Anaphase - Chromatids break apart at the centromere and are pulled by the spindle towards poles. Once separated they become chromosomes.
  • Telophase - Nuclear envelopes re-form around each group of chromosomes at each end of the cell. The chromosomes uncoil.
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Cell division and mitosis

The cell cycle is divided into stages:

  • Interphase - DNA replicates in this stage.
  • mitosis - the nucleus divides and chromatids separate.
  • cytokinesis - the cytoplasm divides or cleaves.
  • Growth phase - each new cell grows to full size.

Mitosis is involved in :

  • Growth eg. cells in an embryo divide to form tissue stem cells
  • Replacement of cells, e.g. tissue stem cells in bone marrow divide to produce red blood cells and neutrophils.
  • Repair, e.g. in wound healing
  • asexual reproduction
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Mitosis in four stages

Mitosis in four stages:

  • Prophase
    • Replicated chromosomes supercoil (shorten and thicken), each chromosome has two chromatids. The nuclear envelope begins to break up. Centrioles move to opposite ends of the cell to make the poles.
  • Metaphase
    • Chromosomes line up down the middle of the cell (equator). Centrioles organis microtubules into the spindle that straches across the cell. Chromosomes are attached to the spindle at the centromere.
  • Anaphase
    • Chromatids break apart at the centromere and are pulled by the spindle towards the poles. Once separated, the chomatids are chromosomes.
  • Telophase
    • Nuclear envelopes re-form around each group of chromosomes at either end of the cell. The chromosomes uncoil.
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Cell cycle and life cycles are not the same

  • Stem cell - Undifferentiated cells that are capable of becoming differentiated to a number of possible cell types.
  • Homologous pair of chromosomes - chromosomes that have the genes at the same loci. Members of an homologous pair of chromosomes pair up during meiosis.


  • Budding - nucleus divides first, followed by the cytoplasm
  • Meiosis
    • Adult human carries out meiosis only in (specialised regions) sex organs to prodice gametes.
    • Meiosis produces cells in humans containing 23 chromosomes
    • Egg and sperm fuse to form a zygote with 46 chromosomes in humans
    • Repeated mitosis from zygote results in a adult.
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Cell specialisation


  • Erythrocytes:
    • have no nucleus, mitochondria, Golgi apparatus and rough ER.
    • are packed full of haemoglobin
    • shape changes so they become biconcave disces and they are then capable of transporting oxygen from lungs to tissues.
  • Neutrophils
    • keep their nucleus
    • cytoplasm appears granular because enormous number of lysosomes produced.
    • ingest invading microorganisms - so potent enzymes in lysosomes enable the neutrophils to be specialised for killing microorganisms.
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Organising the organism


  • A collection of cells that are similar to each other and perform a common function. They may be found attached to each other, but not always. eg. xylem and phloem in plants.


  • A collection of tissues working together to perform a particular function is called an organ. eg. leaves in plants and the liver in animals.

Organ systems

  • An organ system is made up of a number of organs working together to perform an overall life function. eg. excretory system and the reproductive system.
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Plant Tissues

Plant tissues :

  • Xylem and phloem come from diving meristem cells such as cambium.
  • Meristem cells undergo differentation to form the different kinds of cells in the transport tissues.
  • Xylem transports water and ions.
  • Phloem transports sugars (mainly sucrose) and other compounds made by plants.
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Animal Tissues

Animal tissues:

  • Squamous epithelial tissue:
    • made of flattened cells, thin, smooth, flat surface. Ideal for lining inside of tube ie. blood vessels, Where fluids can pass easily over them.
    • are held in place by the basement membrane, it is made out of collagen and glycoprotiens.
  • Ciliated epithelial tissue:(
    • made up of column-shaped cells
    • found on the inner surface of the tubes eg. trachea, bronchi and bronchioles.
    • "exposed" surface covered with tiny projections called cilia, which wave in rhythm and move stuff like mucus.
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