biology bitches

• cells can be prokaryotic or eukaryotic

  1. all living things are made of cells
  2. eukaryotic cells are more complex all animal and plant cells are eukaryotic
  3. prokaryotic cells are smaller and simpler bacteria are prokaryotic cells
• the diffrent parts of a cell are called sub cellular structures
• 1. nucleus contains genetic material

  2. cytoplasm is where most of the chemical reactions happen

  3. cell membrane controls what goes in and out of the cell

  4. mitochondria is where aerobic respiration happens, respiration transfers energy

  5. ribosomes is where proteins are made in the cell
• plant cells have all the same sub cellular structures animal cells have except

  1. a cell wall made of cellulose that supports the cell and strengthens it
  2. a permanent vacuole containing cell sap, it also gives the cell structure
  3. chloroplasts where photosynthesis happens
• bacterial cells have these sub cellular structures

  1. cell wall
  2. cell membrane
  3. cytoplasm
  4. a single loop of dna not enclosed in a nucleus
  5. plasmids which are small rings of dna
• light microscopes can be used to look at cells they let us see large subcellular structures like the nucleus
• electron microscopes have a higher resolution than light microscopes they show things in more detail
• electron microscopes also have a higher magnification than light microscopes they can let us see really small things like ribosomes and plasmids
• electron microscopes where invented after light microscopes they helped scientists understand more about sub cellular structures
• you can work out the magnification of an image using this formula

  magnification = image size /

  real size
• you can write numbers in standard form

  standard form is useful for very big and very small numbers in a simpler way
• You Need to Prepare Your Slide

  Lots of different animal and plant cells can be looked at under a light microscope.

  1. Add a drop of water to the middle of a clean slide.
  2. Cut up an onion and take off one layer.
  3. Use tweezers to peel off some epidermal tissue (the clear 'skin') from the bottom of the layer.
  4. Using the tweezers, place the skin into the water on the slide.
  5. Add a drop of iodine solution. lodine solution is a stain.

  Stains can make different parts of a cell easier to see.

  6) Place a cover slip on top. Try not to get any air bubbles under it
• Use a Light Microscope to Look at Your Slide

  1. Clip the slide onto the stage.
  2. Select the objective lens with the lowest magnification.
  3. Use the coarse adjustment knob to move the stage up to just below the objective lens.
  4. Look down the eyepiece. Move the stage downwards until the image is roughly in focus.
  5. Move the fine adjustment knob, until you get a clear image of what's on the slide.
  6. If you want a bigger image, use an objective lens with a higher magnification and refocus.
• microscope diagram

  
• Cell Differentiation and Specialisation

  Cells don’t all look the same. They have different structures to carry out their different functions.
• Specialised Cells are Cells that Carry Out a Specific Function

  1. The process by which cells change to become specialised is called differentiation.
  2. As cells change, they develop different subcellular structures.

  They turn into different tupes of cells. This allows them to carry out specific functions.
• 1. Most differentiation occurs as an organism develops.
  2. Most animal cells can only differentiate at an early stage of the animal's life.
  3. But lots of plant cells can differentiate for the whole of the plant's life.
• 1. The cells that differentiate in adult animals are mainly used for repairing and replacing cells.
  2. Some cells are undifferentiated - they are called stem cells.
• SPERM CELLS take the MALE DNA to the EGG

  1. A sperm cell has a tail to help it swim to the egg.
  2. It has a lot of mitochondria These provide energy for swimming.
• NERVE CELLS carry ELECTRICAL SIGNALS around the BODY

  1. Nerve cells are long to cover more distance in the body.
  2. They have branches at the end to connect to other nerve cells.
• ROOT HAIR CELLS absorb WATER and MINERALS

  1. Root hair cells grow into long "hairs" that stick out into the soil.
  2. This gives the plant a big surface area for absorbing water and mineral ions from the soil.
• PHLOEM CELLS transport FOOD and XYLEM CELLS transport WATER

  1. Phloem and xylem cells form phloem and xylem tubes.
  2. To form the tubes, the cells are long and joined end to end.
  3. Xylem cells are hollow and phloem cells have very few subcellular structures.

  So there's lots of space inside the cells for stuff to flow through them.
• Chromosomes and Mitosis

  In order to survive and grow, our cells have got to be able to divide. And that means our DNA as well...
• Chromosomes Contain Genetic Information

  1. The nucleus of a cell contains chromosomes.
  2. Chromosomes are coiled up lengths of DNA molecules.
  3. Each chromosome carries a large number of genes.
  4. Different genes control the development of different characteristics, e.g. hair colour.

  5)

  Body cells normally have two copies of each chromosome

  6) There are 23 pairs of chromosomes in a human cell.
• The Cell Cycle Makes New Cells

  1. Body cells in multicellular organisms (e.g. like you, me or a plant) divide to make new cells.

  This is part of a series of stages called the cell cycle.

  2) The stage of the cell cycle when the cell divides is called mitosis.

  1. Multicellular organisms use mitosis to grow and develop.
  2. You need to know about these main stages of the cell cycle:
• Before it divides:

  The cell grows and increases the amount of subcellular structures such as ribosomes and mitochondria.

  2) The DNA is replicated (copied) - so there's one copy for each new cell.

  The left arm has the same DNA as the right arm of the chromosome.

  3) The DNA forms X-shaped chromosomes.

  Each 'arm' of the chromosome is an exact copy of the other.
• The cell is now ready for dividing...

  1. The chromosomes line up at the centre of the cell.
  2. The two arms of each chromosome are pulled apart to opposite ends of the cell.
  3. This divides the nucleus.
  4. Each set of chromosomes become the nucleus of a new cell.
  5. The cytoplasm and cell membrane divide.
  6. The cell has now produced two new cells.

  • They both contain the same DNA — they're identical.
  • They're also identical to the original cell.

  
• Stem Cells


  Undifferentiated cells that can differentiate (change) to become specialised for their job
• Stem cells


  • Can produce lots more undifferentiated cells
  • Can differentiate into different types of cell
• Embryonic stem cells


  Stem cells found in early human embryos
• Embryonic stem cells


  • Can turn into any kind of cell at all
• Adult stem cells


  Stem cells found in certain places in the body, like bone marrow
• Adult stem cells


  • Can only produce certain types of specialised cell, e.g. blood cells
• Embryo


  An unborn baby at an early stage of growth
• Stem cell cloning


  1. Stem cells from embryos and bone marrow can be cloned (copied) in a lab

  2. The cloned cells can be used in medicine or research
• Stem Cells


  May be able to cure many diseases
• Embryonic stem cells


  • Could be used to replace faulty cells in sick people
  • E.g. make nerve cells for people with paralysis or insulin-producing cells for people with diabetes
• Therapeutic cloning


  Making an embryo that has the same genes as a patient, so the stem cells from the embryo wouldn't be rejected by the patient's body
• Using stem cells in medicine

  Risks involved, e.g. stem cells could be infected with a virus and passed on to a patient, making them sicker
• Arguments against stem cell research

  • Embryos shouldn't be used for research because each one could be a human life
  • Curing patients who are suffering is more important than the rights of embryos
  • Embryos used in the research are usually unwanted ones from fertility clinics that would probably just be destroyed if not used for research
  • Scientists should be finding other sources of stem cells