B3 Summary

B3 Summary

1. Cell division and Growth

   • Meiosis = Gametes
     • Haploid
     • Each cell is genetically different
   • Mitosis = New cells for growth
     • Genetically identical
     • Diploid
   • Multicelluar
     • Grow larger
     • More complex
     • Use cell differentiation
   • Undifferentiated cells (Stem Cells) can develop into different cells, tissues and organs
   • Growth can be measured in; Height, Dry Mass and Wet Mass
     • Dry mass is best
   • Plants and animals grow differently

2. Respiration and the Circulation

   • Aerobic respiration uses oxygen
     • Glucose + Oxygen > Carbon Dioxide + Water (+ ATP)
       • C6 + H12 + 6O2 > 6CO2 + 6H2O +ATP
   • Anaerobic respiration takes place during hard exercise when there is insufficient oxygen available
     • Glucose > Latic Acid + ATP
       • Latic acid builds up in muscles causing pain and fatigue
         • acts as oxygen debt and has to be broken down in the liver after exercise
   • Red blood cells carry oxygen around the body
   • Mammals have a double circulatory system
   • Arteries carry blood away from the heart
   • Veins carry blood back to the heart
   • Capilaries link arteries to veins

3. Changing Genes and Cloning

   • Nuclear transfer (Dolly the Sheep ) involves placing the nucleus of a body cell into an egg cell
   • New Cloning Technology
     • Produce a certain number of benefits
     • Involve certain risks
     • Raise ethical issues
   • Plants can be cloned by tissue culture or cuttings
   • Cloning plants is easier than animals because plant cells retain the ability to differentiate
   • Selective breeding may reduce the gene pool leading to inbreeding
   • Genetic engineering is useful but raises ethical issues
   • Gene therapy involved changing a persons genes to cure disorders

4. DNA, Proteins and Mutations

   • Chromosome > Gene > Base
   • Proteins are coded for by DNA
     • The base sequence codes for the order of amino acids
     • Each amino acid is coded for by 3 bases
   • Enzymes are specific and work by a "lock and key" mechanism
   • Protein synthesis occurs on ribosomes in the cytoplasm
   • The code needed to produce a protein is carried from DNA to ribosomes by a molecule call mRNA
   • Enzyme activity is affect by pH and Temperature
     • Lower collision rates at lower temperatures
     • Denaturing at extremes of pH and high temps
   • Proteins are long chains of amino acids
     • Can be structural (Collagen), hormones (insulin), enzymes or carrier molecules (mRNA)
   • Mutations lead to production of different proteins
     • Change in bases in DNA can change the amino acid sequence