Biology

• Mitochondria produce energy through aerobic respiration.
• Chromosomes are made up of genes that determine inherited characteristics.
• Variation:

  May be due to differences in:

  • Genes they have inherited e.g eye colour (genetic cause)
  • environmental in which they have developed (environmental cause)
  • Combination of genes and environment
• Mutation:

  . Genetic variation within a population of species arises from mutations
• Mutation= change in DNA sequence:

  • Mutations occur continuously
  • Very rarely a mutation will lead to a new phenotype
  • Some mutations may change an existing phenotype and most have no effect
• Mutations:

  • if a new phenotype is suited to an environmental change, can lead to rapid change in species

  . This is the theory of evolution by natural selection
• Transpiration~> WATER transport

  • Transports water and dissolved minerals through plant
  • Roots~> leaves
• Translocation~> through PHLOEM tubes

  • Has holes to allow cell sap to pass between cells
  • BIDIRECTIONAL
• Adaptations of XYLEM cells

  • No end walls~> long tube for easy transport
  • Dead~> tubes hollow, resistance to water flow is low
  • Lignin~> strengthens cell wall
• Stomata:

  • Found in lower epidermis
  • Gaps make diffusion of gases in and out easier
  • Reduce water loss
• Coronary Heart Disease:

  • NON- communicable disease
  • Coronary arteries become narrower due to build up of fatty deposits
  • Reduces blood flow as a lack of oxygen to heart
• Coronary Heart Disease Treatment:

  • STENTS = OPERATION

  . Keep coronary arteries open

  . Drugs must be taken to prevent blood clotting on stents

  • STATINS = DRUG

  . Drugs to DECREASE blood cholesterol levels

  . Slows down fatty material built up
• Tumour types from Cancer:

  • Malignant tumours

  . invade neighbouring tissues and spread throughout body by blood

  • Benign tumours

  . stay in SPECIFIC parts of body

  . often within a membrane
• What is the function of bile in digestion?

  Neutralises hydrochloric acid from stomach + emulsifies fat to form small droplets with large surface area
• What are the 3 enzymes produced in pancreas?

  Amylase, lipase and protease
• How do white blood cells protect the body?

  Engulf pathogens + produce antitoxins to neutralise toxins or antobodies
• Function of AMYLASE:

  = Break down starch into simple sugars
• Function of proteases:

  = Break down proteins into AMINO ACIDS
• Function of lipases:

  = Break down lipids into fatty acids and gylcerol