Bio 2 real

• Give an example of a prokaryote (Prokaryotic cell)

  Bacteria
• What is a eukaryotic cell?

  cell with a nucleus
• What is the function of the nucleus?


  Contains genetic materials that controls the activities of the cell
• What is the function of the cell membrane?

  Holds the cell together and controls the passage of substances
• What is the function of the cell wall?

  To strengthen and support the cell
• What do bacterial cells have instead of a nucleus?

  A single circular strand of DNA that floats freely in the cytoplasm, and some may also contain one or more small rings of DNA called plasmids.
• How many mm are in um?

  1000
• What do light microscopes use to work?


  Light and lenses to form an image of a specimen. They let us see individual cells and large sub cellular structures such as nuclei
• Describe the steps to prepare a slide [Required Practical]


  1) Add a drop of water to the middle of a clean slide

  2) Cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one the layers

  3)Using the tweezers, place the epidermal tisse into the water on the slide

  4) Add a drop of iodine solution. Iodine solution is a stain which is used to highlight objects in the cell by adding colour to them

  5) Place a cover slip on top. To do this, stand the cover slip upright on the slide, next to the water droplet. Then carefully tilt and lower it so it covers the specimen. Try not to get any air bubbles underneath it - they'll obstruct your view of the specimen
• Describe the steps needed to use a light microscope to look at your slide [Required Practical]


  1) Clip the slide you've prepared onto the stage

  2) Select the lowest-powered objective lens

  3) Use the coarse adjustment knob to move the stage up to just below the objective lens

  4) Look down the eyepiece. Use the coarse adjustment knob to move the stage downwards until the image is roughly in focus.

  5) Adjust the focus with the fine adjustment knob, until you get a clear image of what's on the slide

  6) If you need to see the slide with greater magnification, swap to a higher-powered objective lens and refocus
• What is a stem cell?

  A type of undifferentiated which are able to become any type of cell
• How are sperm cells specialised?


  For reproduction: they have a long tail and a streamlined head to help it swim to the egg, there are lots of mitochondria in the cell to provide the energy needed and it also carries enzymes in its head to digest through the egg cell membrane
• How are nerve cells specialised?


  For rapid signalling: these cells are long to cover more distances and have branched connections at their ends to connect to other nerve cells and form a network throughout the body
• How are muscle cells specialised?


  For contraction: these cells are long so that they have space to contract and have lots of mitochondria to generate the energy needed for contraction
• How are root hair cells specialised?


  For absorbing water and minerals: they grow into long "hairs" that stick out into the soil. This gives the plant a large surface area for absorbing water and mineral ions from the soil
• How are phloem and xylem cells specialised?


  For transporting substances: phloem cells form phloem tubes and xylem cells form xylem tubes which transport substances such as food and water around plants - the cells are joined end to end. Xylem cells are hollow in the centre and phloem cells have few sub cellular structures, so that stuff can flow through them
• How many pairs of chromosomes are there in humans?

  23
• What is mitosis?


  Part of the cell cycle where one set of new chromosomes is pulled to each end of the cell forming two identical nuclei during cell division
• What is the purpose of mitosis in multicellular organisms?


  For growth, development and repair
• What is the end result of mitosis?

  2 identical daughter cells
• What are stages of growth and DNA replication during mitosis?

  1) In a cell that's not dividing, the DNA is all spread out in long strings

  2) Before it divides, the cell has to grow and increase the amount of sub cellular structures such as mitochondria and ribosomes

  3) It then duplicates its DNA - so there's one copy for each new cell. The DNA is coped and forms X-shaped chromosomes. Each 'arm' of the chromosome is an exact duplicate of the other.
• What are the stages of mitosis?


  Once its contents and DNA have been copied, the cell is ready for mitosis:

  4) The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell

  5) Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells - the nucleus has divided

  6) Lastly, the cytoplasm and cell membrane divide: the cell has now produced two new daughter cells. The daughter cells contain exactly the same DNA - they're identical. Their DNA is also identical to the parent cell
• Where are stem cells found in the human body?

  Early human embryos, bone marrow and umbilical cords
• How can stem cells cure diseases?


  By replacing faulty cells (e.g. faulty blood cells), by making insulin-producing cells for people with diabetes, nerve cells for people paralysed by spinal injuries
• What is the name for the type of cloning that gives the offspring the identical genetic informations as the patient?

  Therapeutic cloning
• Why are some people against stem cell research?


  They feel that human embryos shouldn't be used for experiments since each one is a potential human life
• Where can stem cells be found in plants?


  Meristem
• What factors effect effect the rate of diffusion?

  The size of the concentration gradient (the bigger the gradient, the faster the rate) and the temperature (the higher the temperature, the faster the rate)
• Define osmosis


  The movement of water molecules from an area of high concentration to an area of low concentration with the concentration gradient across a partially permeable membrane
• What is meant by a partially permeable membrane?

  A membrane with very small holes in it, which allows tiny molecules to pass through
• Describe the steps to observe the effect of sugar solutions on plant tissue [Required Practical]


  1) Cut up a potato into identical cylinders and get some beakers with different sugar solutions in them. One should be pure water and another should be a very concentrated sugar solution. Then you can have a few other with concentrations in between

  2) Measure the mass of the potato cylinders, then leave one in each beaker for 24 hours

  3) Then take them out, dry with a paper towel to remove any access water/solution and measure the masses again

  4) If the potatoes have drawn in water by osmosis, they'll have an increase in mass. If water has been drawn out, they'll have a decrease in mass

  5) The dependant variable is the chip mass and the independent variable is the concentration of the sugar solution

  6) To reduce the effect of errors (e.g. from the potato cylinders not being fully dried or water being evaporated) complete the experiment three times and calculate the mean percentage change at each concentration
• Why do we calculate the percentage of the mass of the chips?

  For control
• Give an example of how exchange surfaces are used in the human body


  When oxygen and carbon dioxide are transferred between cells and the environment during gas exchange
• What factor effects how easy an organism exchanges substances?

  Surface area to volume ratio
• How can you work out the surface area to volume ratio?


  By working out the total surface area using the equation: length x width, and by working out the volume using the equation: length x width x height, then put your answer into the ratio x:y (with x being the surface area and y being the volume)
• Why do multicellular organisms need exchange surfaces?

  To allow the necessary amount of substances to pass through
• How are exchange surfaces adapted to maximise effectiveness?

  By having a thin membrane, so substances only have a short distance to diffuse, by having a large surface area so lots of a substance can diffuse at one, exchange surfaces in animals have lots of blood vessels, to get stuff into and out of the blood quickly and gas exchange surfaces in animals (e.g. alveoli) are often ventilated to let the air move in and out
• Annotate the diagram of the lungs

  
• What is the stomata and what is it's function?


  Openings in the leaves of plants, particularly on the underside, they open and close by guard cells, allowing gasses to enter and leave the leaf
• What is the function of gills?


  Gas exchange