cell and control

• what is mitosis?



  a type of cell division
• what does mitosis make?


  mitosis makes 2 genetically identical diploid daughter cells
• what are the stages of mitosis in order?


  prophase, metaphase, anaphase, telophase and cytokinesis
• Prophase



  The DNA in chromosomes and their copies condenses to become more visible. The membrane around the nucleus disappears. spindle fibres are formed
• Metaphase



  Chromosomes line up on the spindle fibres across the middle of the cell
• Anaphase


  Chromosomes and their copies are pulled to different ends of the cell.
• Telophase


  New membranes form around the chromosomes at each end of the cell.
• Cytokenisis


  The cell membrane pinches in and eventually divides into two daughter cells.
• Interphase


  The cell spends most of its life in this phase. The DNA in chromosomes copies itself ready for mitosis.
• why does mitosis occur?


  growth and repair and asexual reproduction
• what is a specialised cell?


  cells designed to carry out a particular role in the body
• how is a red blood cell specialized


  bi-concave shape, No nucleus, Contains haemoglobin
• how is a plant root hair cell specialised?


  thin cell wall, large vacuole, root hair cells that increase the surface area
• how is a nerve cell specialised?


  nerve cell is long, myelin sheath
• how is an egg cell specialised?


  egg cell contains nutrients, haploid nucleus, jelly coating
• what are enzymes?


  enzymes are biological catalysts, enzymes are specific to their substrates
• Lock and key theory


  the shape of the active site matches the shape of its substrate molecules. This makes enzymes highly specific. Each type of enzyme can usually catalyse only one type of reaction (some may catalyse a few types of reactions)
• how does temperature affect the rate of enzyme action?


  rate of an enzyme-catalysed reaction increases as the temperature increases. However, at high temperatures the rate decreases again because the enzyme becomes denatured and can no longer function
• how does pH affect the rate of enzyme action?


  as the pH increases so does the rate of enzyme activity. An optimum activity is reached at the enzyme’s optimum pH. A continued increase in pH results in a sharp decrease in activity as the enzyme’s active site changes shape. It is now denatured.
• How does substrate concentration affect the rate on enzyme action?


  As the concentration of the substrate increases, so does the rate of enzyme activity. However, the rate of enzyme activity does not increase forever. This is because a point will be reached when the enzymes become saturated and no more substrates can fit at any one time even though there is plenty of substrate available.
• what do enzymes do with digestion?


  They digest large food molecules into smaller molecules into smaller molecules that are absorbed in the small intestine
• what is diffusion?


  Diffusion is the movement of a substance from an area of high concentration to an area of lower concentration.
• what is Osmosis?



  Osmosis is the diffusion of water molecules from a dilute solution (high concentration of water) to a more concentrated solution (low concentration of water) across a selectively permeable membrane.
• what is Active transport?


  Active transport is the movement of particles against the concentration gradient. The substance moves from an area of low concentration to an area of high concentrations, across a partially permeable membrane. This process requires energy produced from cell respiration
• what is meiosis?



  meiosis is a form of cell division which produces four non-identical, haploid sex cells or gametes (sperm and ova in humans). sexual reproduction
• what are stem cells?


  cells that can divide to produce many type of cell
• What are the 3 types of stem cells?


  Embryonic stem cells, Adult stem cells, plants : meristems.
• embryonic stem cells



  cells of an early-stage embryo and can produce any type of specialised cell
• Adult stem cells



  can only from a limited number of cell types:
• Plant meristem cells



  cells divide elongate and then differentiate into specialised plant cell. found in rapidly growing parts of the plant