Biology paper 2

• Photoropism in shoots

  Auxins move towards shaded part. Shaded part grows longer and shoot grows to light
• Shoots display negative gravitropism where auxins move towards the lower part of the shoot, resulting in the lower side becoming longer and the shoot growing upwards
• Opposite processes occur in roots and shoots regarding phototropism and gravitropism
• Auxins inhibit cell elongation in roots
• Roots exhibit negative phototropism, where auxins move towards the shaded part of the root causing the lit side to become longer, resulting in the root growing away from the light
• Roots display positive gravitropism, with auxins moving towards the lower part of the root, causing the upper side to become longer and the root to grow downwards
• Roots and shoots grow straight when auxin levels are equal on both sides
• Neuroscientists use electrical stimulation and MRI scanning to map brain regions to specific functions by studying patients with brain damage
• The complexity and delicacy of the brain makes investigating and treating brain disorders very difficult
• Negative feedback controls blood sugar after a meal:

  • Increase in blood glucose (to 6.5 mmol / dm³)
  • Glucose detected by pancreas
  • Pancreas secretes insulin, causing glucose to move out of blood into liver cells
  • Liver converts glucose to glycogen, leading to a fall in blood glucose
  • Low blood glucose is detected by pancreas, which releases glucagon
  • Liver converts glycogen to glucose, raising blood glucose levels
  • Higher blood glucose concentration triggers ADH release, increasing kidney tubules' permeability to water, leading to increased water reabsorption into the blood and minimizing changes in substance levels
• Effects of hyperthyroidism:

  • Too much thyroxine released into the blood raises BMR
  • Causes an increase in the formation of glycogen, lipids, proteins, or rate of respiration
  • Increases breakdown of excess proteins
• Organ rejection occurs when the immune system (B lymphocytes) produce antibodies that attack the antigens on the transplanted organ cells

  • Organ rejection can be prevented by tissue typing to find a matching donor and treating the patient with immune system-suppressing drugs
• Geotropism in roots:

  • More auxin is produced on the lower side of the root
  • Auxin slows the growth of cells on the lower edge
  • As a result, cells grow faster on the top side of the root, making the root grow downwards
• Sequence for protein synthesis:

  1. DNA unzips

  2. Complementary mRNA is formed

  3. mRNA leaves the nucleus

  4. mRNA attaches to ribosomes

  5. Bases decoded

  6. Polypeptide formed

  7. Protein formed
• Explain pulpil dialtaion

  Pupils dilate in low light beacuse circular muscles in the iris relax and the radial muscles contract
• Explain why a long sighted person can't see short things

  Lens can't be thickened enough so light focuses behind the retina
• What is a gene

  Particular sequence of bases which code for a protein
• What is a genome

  Entire set of genetic material
• What can discovering the genome help with

  Identifying genetic diseases

  Find migration of ancestors
• Structure of a nucleotide

  Has phosphate connected to sugar

  On the side there is a base connected

  Exactly the same sugar and phosphate

  4 different types of bases can be used
• Why do bases stick out

  Hold complementoy strands together
• What I'd a sugar phosphate backbone

  Repeating unit of a phosphate bonding to an other sugar
• Explain vasodilation 


  Blood vessels supplying the skin become wider (dilated) so more blood flows through capillaries causing more energy to be transferred to the environment
• Explain sweating and its use

  Sweet is relaesd and energy must be transferred for evapritaiton kf sweat so there is a transfer of energy from the skin
• Explain vasoconstriction 


  Blood vessels supplying the skin narrow so less blood goes to the capillaries by the skin causing less energy to be lost to the surroundings