Biology

Nota:

• Additional AQA spec

1. DNA and cell divsion
   1. DNA
      1. Genes
         1. A short section of DNA
         2. Each gene codes for a specific protein
            1. This specifies which order the amino acids join together
         3. Alleles- forms of gene
            1. Dominant
               1. Represented by an uppercase letter
               2. Characteristics from a dominant allele develop if there is one or two of this allele in a pair
            2. Recessive
               1. Represented by a lowercase letter
               2. The characteristics from this are only present if there are two in a pair
            3. heterozygous (2 different alleles) homozygous (2 of the same allele)
      2. Chromosomes
         1. A cell nucleus contains these
         2. Made from long DNA molecules
         3. Found in pairs
   2. Mitosis

      Nota:

      • It's important to remember the spelling as you have to spell it right to get the marks in your exam
      1. This is the process by which BODY cells divide
      2. The genetic material is copied
      3. The cell divides to form two genetically identical body cells
      4. Occurs during:
         1. Growth
         2. Cell repair
   3. Gametes and fertilisation
      1. Gametes
         1. Male Gametes are Sperm
         2. Female Gametes are Eggs
      2. Contain one set of genetic information
      3. Divide by Meiosis

         Nota:

         • See meiosis section
      4. Fertilisation is the fusion of a male and female gamete
   4. Differentiation and stem cells
      1. Most animal cells become specialised at an early stage
      2. Stem Cells
         1. Made to form different types of cell
            1. Come from embryos or adult bone marrow
   5. Meiosis

      Nota:

      • It's important to remember the spelling as you have to spell it right to get the marks in your exam
      1. Cells divide by meiosis to form gametes, when this happens:
         1. Copies of the genetic information are made
         2. The cell divides twice to form 4 gametes
      2. Each gamete has a single set of chromosomes

         Nota:

         • BBC bitesize has an awesome diagram- http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/inheritance/dna_cell_divisionrev5.shtml
2. Cells
   1. Parts of a cell
      1. Animal and plant cells
         1. Nucleus

            Nota:

            • Contains genetic material
         2. Cytoplasm

            Nota:

            • Most chemical processes happen here
         3. Cell Membrane

            Nota:

            • Controls, which substances enter and leave the cell
         4. Mitochondria

            Nota:

            • Energy released by respiration here
         5. Ribosomes

            Nota:

            • Protein synthesis happens here
      2. Only plant cells
         1. Cell Wall

            Nota:

            • Strengthens the cell
         2. Chloroplasts

            Nota:

            • Absorbs light energy for photosynthesis
         3. Permanent Vacuole

            Nota:

            • Filled with cell sap to help keep the cell enlarged
   2. Bacterial cells
      1. Single cell organism
      2. The genetic material is not in a distinct nucleus
   3. Specialised cells
      1. Leaf cells
         1. Absorbs sunlight for Photosythesis
         2. Packed with chloroplasts closley packed cells
      2. Root hair cell
         1. Absorbs water and mineral ions from the soil
         2. Long-large surface area
      3. Sperm Cell
         1. Fertilises an egg cell
         2. Head contains genetic information and enzyme middle-food end-movement
      4. Red blood cell
         1. Contains haemoglobin to carry oxygem
         2. Large surface area- no nucleus so more haemoglobin
   4. Diffusion
      1. Particles move from an area of high concentration to an are of low concentration
3. Photosynthesis
   1. Carbon Dioxide+water--------> Glucose + Oxygen Light energy
   2. Light energy is absorbed by chlorophyll
      1. Then it is used to convert CO2 & H20 to 02 & C6H12O6
   3. Some glucose is used for respiration some is converted to starch for storage
      1. Storage of and use of glucose
         1. Stored as starch, fats and oils
         2. Used to produce Cellulose and proteins
   4. Limiting Factors
      1. Temperature
         1. Plants cant photosynthesis if it is too cold or hot as the enzymes become denatured.
      2. Light intensity
         1. Increasing the light intensity increases the rate of photosynthesis
      3. Carbon dioxide concentration
         1. As CO2 concentration increase so does the rate of potosyntthesis
      4. Graphs

         Nota:

         • See her for graphs showing limiting factors: http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/photosynthesis/photosynthesisrev2.shtml
         1. Plateau-something else is the limiting fator
4. Proteins & enzymes
   1. Amino Acids
      1. Proteins made from long chains of amino acids
   2. Enzymes
      1. Biological catalysts

         Nota:

         • Catalyst-a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change
      2. They have optimum temp. and pH at which their activity is greatest
      3. Active site
         1. Area were if hit the enzyme
5. Distribution of organisms
   1. Quadrats
   2. Physical factors that may effect the distribution
      1. Temp.
      2. Niutrients
      3. amount of light
      4. water avaliability
      5. CO2 &O2 avaliability