b4

• Respiration

  Process that releases energy in the form of ATP from the breakdown of glucose
• Why does respiration occur continuously in living cells?

  ATP is required for many essential processes in living cells e.g. movement, homeostasis and active transport.
• What type of reaction is respiration?

  Exothermic reaction that releases energy in form of heat
• Aerobic respiration

  Respiration in the presence of oxygen that forms ATP from the breakdown of glucose.
• Word equation for aerobic respiration

  glucose + oxygen ---> carbon dioxide + water (+ATP)
• symbol equation for aerobic respiration

  • C6H12O6 + 6O2-----> 6CO2 +6H2O
• Where does aerobic respiration occur in eukaryotic cells?

  In the mitochondria. The mitochondria contains most of the enzymes needed to control aerobic respiration.
• Where does aerobic respiration occur in prokaryotic cells?

  Cytoplasm
• What is anaerobic respiration?

  Respiration that takes place without oxygen and forms ATP from the breakdown of glucose.
• When does anaerobic respiration take place?

  Takes place in the cytoplasm.

  • For human cells, it takes place when you're doing vigorous exercise.
  • Plant root cells, if the soil a plants growing in become waterlogged there'll be no oxygen available for the roots.
  • Bacterial cells - Bacteria can get under your skin through puncture wounds caused by things like nails. Little oxygen under your skin.
• What do animals and bacteria produce when respiring anaerobically?

  glucose --------> lactic acid
• What do plants and microorganisms produce when respiring anaerobically?

  glucose---------> ethanol + carbon dioxide
• ATP yield for aerobic respiration

  High- 32 ATP made per molecule of glucose
• ATP yield for aerobic respiration

  Much lower - 2 ATP made per molecule of glucose
• What's the cell cycle?

  Body cells in multicellular organisms divide to produce new cells as part of a series of stages called the cell cycle. Cell cycle makes cells for growth and repair.
• Stages of interphase (Mitosis)

  
  

  1. In a cell that's not dividing, the DNA is all spread out in long strings.
  2. Before it divides, the cell has to grow and increase amount of subcellular structures such as mitochondria and ribosomes.
  3. It then duplicates its DNA so there's one copy for each new cell. The DNA is copied and forms X shaped chromosome. Each arm of the chromosome is an exact copy of the other.
• Stages of mitosis

  Once its content and DNA have been copied, the cell is ready for mitosis.

  4) The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosomes go to opposite ends of the cell.

  5) Membranes form around each of the sets of chromosome. These became the nuclei of the two new cells - the nucleus has divided.

  6) Lastly the cytoplasm and cell membrane divide.

  Cell has produced exactly two new daughter cells. The daughter cells contain exactly the same chromosome - they're genetically identical to the parent cell and each other.
• Cancer

  Cancer is a case of uncontrolled cell division. The rate at which cells divide by mitosis is controlled. If there's a change in one of the genes that controls cell divisions, a cell may start dividing uncontrollably. This an result in a mass of abnormal cells called tumours. The tumour invades and destroys surrounding tissue.
• What is meiosis?

  Meiosis is a type of cell division. It produces genetically different cells with half the chromosome of the original cell. In human, it only occurs in reproductive organs (ovaries and testes)
• Interphase meiosis

  During this period, it duplicates its DNA (so there's enough for each new cell). One arm of each X shaped chromosome is an exact copy of the other arm.
• Division 1 meiosis

  1. In the first division in meiosis, the chromosomes line up in pairs of the centre of the cell, One chromosome in each pair came from the organisms mother and one came from the father.
  2. The pairs are then pulled apart so each new cell ends up with one chromosome from each pair. Some of the fathers chromosome and some of the mothers chromosome go into each new cell.
  3. This means the chromosome number of each new cell will be half that of the original cell. Each new cell will also have a mixture of the mothers and fathers chromosome. Mixing up the genes is important - variant.
• Division 2

  5) In the second division the chromosomes line up again in the centre of the cell. The arms of the chromosomes are pulled apart.

  6) You get four gametes- each only has a single set of chromosomes. The gametes are all genetically different.
• What are stem cells?

  Unspecialised cells which can become any cell type.
• What is differentiation?

  • Process in which stem cells become specialised. (Have a specific function).
  • Some genes switch on or off determining cell type,
• Why is cell differentiation important?

  It enables the formation of specialised tissues with specific functions e.g. muscle tissue.
• Embryonic stem cells

  • Stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type.
  • enable the growth and development of tissues in human embryos
• Adult stem cells

  • Stem cells that can differentiate into limited range of cell types. E.g. found in bone marrow stem cells.
  • They are important in replacing dead cells e.g. in making new red blood cells.
• Meristem stem cells

  • Stem cells found in meristem that are unspecialised and capable of differentiating into any cell type during the life of a plant.
  • Found in regions of plants that are growing e.g. in the tips of the roots and shoots.
• How can stem cells be used in medicine?

  • Stem cells collected
  • Stem cells differentiated into specific cell types e.g. heart muscle cell.
  • Specialised cells transplanted into the patient.
  • Used to treat damage or disease e.g. heart disease.
• Benefits of using stem cells in medicine

  • Treat damage or disease e.g. heart disease.
  • Treat diseases that would otherwise be untreatable.
  • Used in scientific research
  • Growing organs for transplants
• Risks of using stem cells

  • Transplanted stem cells may cause tumour
  • Finding suitable stem cell donors is a difficult task
  • Stem cells may be rejected by body
  • Potential side effects
  • Long term risk of using stem cells are unknown
• Electron microscope

  They use electrons rather than light. Electron microscopes have higher magnification and resolution than light microscope so they see much smaller things in more detail like the internal structure of mitochondria.