Biology 2.1.6- Cell division, diversity and cellular organis

• What are the three main stages of the cell cycle

  interphase, mitosis, cytokinesis
• What are the three stages of interphase and what do they do?

  G1- Cell increases in size, Proteins synthesised, Organelles replicated

  S- DNA is replicated in the nucleus

  G2- Cell increases in size, Energy stores increased, DNA checked for errors
• What happens in mitosis and cytokinesis

  Mitosis: division of nucleus

  Cytokinesis: division of cytoplasm- two cells produced
• What are the three checkpoints of the cell cycle, where are they placed and what happens if cells don't pass them?

  G1 checkpoint- End of G1 - Goes to G0 stage

  G2 checkpoint- End of G2 - Goes to growth arrest to fix issues

  Spindle assembly checkpoint- Main point of mitosis - Delayed mitosis (D-mitosis) to correct errors
• What do each of the checkpoints check?

  G1- Cell size, DNA damage?, Nutrients, If growth factors are synthesised

  G2- Cell size, Is DNA replicated correctly, Enough energy?

  Spindle assembly- If chromosomes are correctly attached to spindle
• Why could a cell enter G0

  How long does it last

  Once it is differentiated, If it fails at a checkpoint, Old age (Senescence)

  G0 is permenent for most cells (Lymphocytes can be stimulated to enter again)
• What are the 4 stages of mitosis

  prophase, metaphase, anaphase, telophase
• What happens in prophase

  Nucleus and DNA:

  Chromatin fibres condense to form chromosomes- Nucleolus dissappears- Nuclear membrane breaks down and disappears

  Centrioles and spindle:

  Centrioles move to poles of the cell and help the formation of spindle fibres- kinetochore, on chromosomes attach to spindle fibres

  
• What happens in metaphase

  Chromosomes are moved by spindle fibres to the equator of the cell, forming the metaphase plate

  Spindle assembly checkpoint checks chromosomes are attached

  
• What happens in anaphase

  Centromeres divide

  Spindle fibres shorten

  Chromatids are pulled to opposite poles of the cell
• What happens in Telophase

  Nuclear envelope reforms

  Chromosomes uncoil

  Nucleus is formed
• Cytokinesis in animal cells

  Cleavage furrow forms and the cell surface membrane is pulled inwards by the cytoskeleton

  
• Cytokinesis in plant cells

  Vesicles assemble on the equator

  Vesicles fuse with each other and the cell surface membrane, forming a new membrane

  Cell is divided in two
• What are homologous chromosomes and how many do typical human cells have

  They have the same gene, in the same order, along their length

  23 homologous pairs in a human somatic cell

  
• What is the aim of sexual reproductions and how does it achieve this

  To produce genetic variation in off-spring

  Gametes are different from each other

  Random fusion of gametes
• What are the differences in Prophase 1 to Prophase

  Homologous chromosomes pair up, forming bivalents

  Crossing over occurs

  
• What are the differences in metaphase 1 to metaphase

  Homologous pairs of chromosome assemble

  Independant assortment occurs

  
• What are the differences in anaphase 1 to anaphase

  Homologous chromosomes are pulled to opposite poles

  Entangled strands break and rejoin at chiasmata forming recombinant chromatids

  
• What are the differences in metaphase 2 to metaphase

  Independant assortment occurs

  
• Describe specialised cells


  Have special features that allow them to do a specific function

  No longer capable of mitosis
• Describe tissues

  Group of specialised cells, working together to perform a specific function
• Describe organs


  Collection of tissues, adapted to perform a particular function
• Function and adaptations of erythrocyte

  Transport oxygen to tissues

  Contains Haemoglobin- to bind to oxygen

  No nucleus or membrane bound organelles- more space for Hb

  Biconcave shape- Higher SA:Vol ratio for diffusion

  Flexible- Squeeze through capilaries

  
• Function and adaptations of Neutraphil

  Destroys pathogens by phagocytosis

  Granular cytoplasm- containing lysosomes with hydrolic enzymes

  Multi-lobed Nucleus- Easier to squeeze through small gaps in capillary walls

  
• Function and adaptations of sperm cell

  Deliver genetic information to female gamete

  Flagellum- enable movement

  Many mitochondria- Supply ATP for movement

  Acrosome- Contains enzymes which break down protective layers around the ovum

  
• Function and adaptations of root hair

  Take up minerals from the soil

  long extension of membrane- Increases SA:Vol to maximise absorbtion of water and dissolved minerals

  Many mitochondria- Provide ATP for active transport

  No chloroplasts- Underground
• Function and adaptations of palisade cell

  Enable photosynthesis

  Many chloroplasts- photosynthesis

  Thin cell walls- CO2 can diffuse quickly

  Rectangular shape- can be packed in continuous layer

  Chloroplasts can move- absorb more light
• Function and adaptations of guard cells

  Open and close stomata

  Cell wall is thicker on one side- Shape changes asymmetrically
• Why does water move into the guard cell

  Phototropin proteins are excited by blue light, causes a chain of events called a phosphorylation cascade

  H+-ATPase pump, pumps H+ ions out the cell, which causes a negative electrical potential across the plasma membrane

  Hyperpolarization of the membrane allows K+ and Cl- ions to move into the cell, causing water to move by osmosis

  
• Function, make up and location of simple squamous epithelium tissue

  Allows rapid diffusion

  Flattened, thin cells, one cell thick

  Capillary walls, alveolar lining, glomeruli, Pericardial and pleural lining
• Function, make up and location of stratified squamous epithelium

  Protect the body from desiccation and water loss

  Multiple layers of cell (outermost layer is squamous epithelial cells), other layers may have cuboidal and/or columnar cells

  Skin and respiratory, digestive, excretory systems
• Function, make up and location of ciliated epithelium

  Move mucus and dust out the respiratory duct

  made of ciliated epithelial cells and goblet cells (make mucus)

  Lining trachea and oviduct
• Function, make up and location of cartilage

  Rigid and resistant to compression. Firm, flexible and smooth

  Chondrocytes isolated in lacunae (gap) within extracellular matrix (which contains fibres of proteins: elastin and collagen)

  Outer ear, end of bones, nose

  
• Function, make up and location of skeletal muscle

  Individual muscle fibres which can shorten and lengthen

  Individual muscle fibres contain myofibrils, which contain contractile proteins (actin and myosin)

  Attached to the bone
• Function, make up and location of epidermal tissue

  Protects the plant from infection and water loss

  A single layer of closely packed cells, usually covered with a waxy cuticle (waterproff)

  Stem, root, leaf, flower, fruit, seed
• Function, make up and location of xylem tissue

  Transport water up the plant

  Elongated, dead cells, strengthened with lignin

  Vascula bundles, toward the centre of the stem
• Function, make up and location of phloem tissue

  Transport organic nutrients

  Columns of seive tube cells, which have perforated cell walls (sieve plates)

  Root, stem leaves
• Describe stem cells


  Undifferentiated cells that have potential to differentiate and can repeatedly undergo mitosis
• Describe cell potency and how stem cells are defined by it

  Describes how many cell types a stem cell can differentiate into, greater number of cell types the greater the potency

  Stem cells can be Totipotent, Pluripotent, Multipotent
• Describe totipotent stem cells (Differentiate into, example, found?)

  Differentiate into any type of cell of the foetus and extraembryonic tissues, e.g. early embryonic stem cells

  Found in fertilised egg, zygote, emrbyo (<4 days old)