biology

• Egg cells have a haploid nucleus, contain nutrients in the cytoplasm and the cell membrane changes structure after fertilisation
• Sperm cells have a haploid nucleus, a long tail, lots of mitochondria and enzymes in the acrosome to digest through the cell membrane of the egg
• Ciliated epithelial cells are lined with millions of cilia to help move substances
• Eukaryotic cells are complex and include a nucleus e.g. animal cell
• Prokaryotic cells are simpler and don't include a nucleus e.g. bacterial cell
• Nucleus contains the genetic material
• Cytoplasm is where chemical reactions take place
• The cell membrane controls what goes in and out of the cell
• Mitochondria are where respiration takes place
• Ribosomes are involved in the synthesis of protein and translation of genetic material
• Cell wall gives the cell support and structure
• Chloroplasts are where photosynthesis takes place
• The vacuole contains the cell sap
• Plasmid DNA are small loops of extra DNA
• Chromosomal DNA floats free in the cytoplasm and controls the cells activities and replication
• Flagellum is a long hair-like structure that rotates and allows the cell to move
• magnification = image size / actual size
• total magnification = magnification of objective lens x magnification of eyepiece lens
• Enzymes are biological catalysts
• Carbohydrases (e.g. amylase) convert carbohydrates into simple sugars
• Proteases convert proteins into amino acids
• Lipases convert lipids into fatty acids
• Glycogen synthase joins together glucose molecules to form glycogen.
• Diffusion is the net movement of particles from an area of high concentration to an area of low concentration
• Osmosis is the movement of water molecules from a region of high water concentration to a region of low water concentration
• Active transport is the movement of molecules from an area of low concentration to an area of high concentration against a concentration gradient
• Mitosis forms 2 genetically identical daughter cells with a diploid nucleus
• Mitosis is a form of asexual reproduction
• Meiosis is a form of sexual reproduction
• Meiosis forms 4 gentically different daughter cells with a haploid nucleus
• Synapses are gaps between neurones
• Sensory neurones connects receptors to CNS
• Motor neurons connect CNS to effectors
• Relay neurone connects sensory neurone and motor neurone
• Reflex arcs prevent injury
• Haploid nucleus has half the number of chromosomes
• Light microscopes were invented in the 1590s. They work by passing light through the specimen. They let us see things like nuclei and chloroplasts and we can also use them to study living cells
• Electron microscopes were invented in the 1930s. They use electrons rather than light. Electron microscopes have a high resolution and magnification than light microscopes, so they let us see smaller things in more detail like the internal structure of organelles. This gives us a greater understanding of how cells work although they can't be used to study living cells
• To view a specimen:

  1. Place a thin slice of specimen on slide
  2. Add a drop of water to secure in place
  3. Add a drop of stain
  4. Place cover slip
  5. Select lowest objective lens
  6. Use coarse adjustment knob to change magnification until visible