Topic 4 Using Food and Controlling Growth

• Cellular respiration


  1. Glucose is broken down

  2. Products are combined with oxygen

  3. Carbon dioxide and water are produced

  4. Energy in the form of ATP is produced
• Aerobic respiration


  Respiration that occurs in the presence of oxygen
• Anaerobic respiration


  Respiration that occurs in the absence of oxygen
• Anaerobic respiration is less efficient than aerobic respiration, only producing ~2 ATP molecules compared to ~38
• Both aerobic and anaerobic respiration are catalysed by enzymes
• Mitochondria


  • Site of most respiration reactions in eukaryotic cells
  • Contain enzymes for respiration
  • Have a large surface area
  • Have proteins in the membrane to help molecules move in and out
• Aerobic respiration


  Glucose + oxygen → carbon dioxide + water
• Anaerobic respiration in animal cells

  Glucose → lactic acid
• Anaerobic respiration in yeast

  Glucose → alcohol + carbon dioxide
• Electron microscopy


  Uses a beam of electrons to view small structures like cell organelles
• Cell growth cycle and mitosis

  Interphase: DNA replication, cell growth

  Mitosis: Cell division to produce two genetically identical daughter cells
• Cancer is a result of uncontrolled cell growth and division due to a mutation in the cell's DNA
• Meiosis


  Cell division to produce four genetically unique gamete cells, each with half the normal chromosome number

  Fertilisation: Two gametes fuse to form a zygote with the full chromosome number
• Stem cells


  Unspecialised cells that can differentiate into many cell types
• Stem cell therapy benefits

  • Can treat a variety of diseases

  Stem cells not rejected like donor organs

  Generally lower risks than other treatments

  No need to match stem cells to patient
• Stem cell therapy risks

  • Risk of contamination or mutation of stem cells

  Long-term risks unknown

  Side effects like rashes, infections, bleeding
• There are ethical issues with using stem cells harvested from embryos, as this involves destroying the embryo
• Tropisms


  Growth movements of a plant part in response to a stimulus
• Main plant tropisms


  • Phototropism (response to light)

  Gravitropism (response to gravity)
• Auxins


  Plant hormones that control tropisms by stimulating cell elongation
• Gibberellins


  Plant hormones that react to water, causing seed germination and bolting in adult plants
• Uses of plant hormones in agriculture

  • Ethene to control fruit ripening

  Selective weedkillers using hormones

  Gibberellins to promote flowering and fruit growth

  Auxins in rooting powders to promote root growth
• Adult stem cell


  A stem cell found in the certain tissues (e.g. bone marrow, liver, heart) that can form some types of cell
• Aerobic respiration


  A form of respiration that uses a plentiful supply of oxygen to release energy from glucose
• Anaerobic respiration


  A form of respiration that releases energy from glucose when there is insufficient oxygen
• Auxin


  A plant hormone that is responsible for cell elongation
• Biomass


  The mass of all the living material present in a particular area or particular organism
• Bolting


  Production of flowers in an attempt to reproduce before death
• Cancer


  A non-communicable disease in humans caused by changes in a person's DNA. The changes cause a cell to divide many times by mitosis, which can create a tumour
• Cell cycle


  A series of events that take place in a cell in preparation for cell division
• Cell differentiation


  The process in which cells become specialised by switching genes off and on to form tissues with particular functions
• Cellular respiration


  A universal, continuously occurring chemical process that occurs in all living cells. It is exothermic and releases energy (in the form of ATP) from the breakdown of organic compounds such as glucose
• Chloroplasts


  The organelles that are the site of photosynthesis. They contain chlorophyll (a green pigment) which absorbs light energy, and important enzymes for photosynthesis
• Chromosome


  A long, coiled molecule of DNA that carries genetic information in the form of genes
• Consumer


  An organism that cannot produce its own food, so must obtain energy by feeding on the producer
• Cytokinesis


  The last stage of the cell cycle in which two identical diploid daughter cells are formed
• DNA (Deoxyribonucleic acid)


  A polymer made of two strands twisted around each other to form a double helix. It contains all the genetic information
• Dormancy


  A period of time in which the seeds hibernate. This stops when they germinate
• Electron microscope


  A microscope that uses electrons to produce an image of a specimen
• Embryo


  An organism in its early stages of development