Biology Paper 1 (2)

• Name the two types of cells

  Prokaryotic and Eukaryotic
• What is a prokaryotic cell?


  A cell without a nucleus
• Give an example of a prokaryote (Prokaryotic cell)

  Bacteria
• What is a eukaryotic cell?

  cell with a nucleus
• Give two examples of eukaryotic cells

  Plant & Animal cells
• What three sub-cellular structures do plant cells have which animal cells do not?

  Permanent vacuole, cell wall and chloroplasts
• What is the function of the nucleus?

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

  A gel-like substance where most of the chemical reactions happen. It contains enzymes that control these reactions
• What is the function of the cell membrane?

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


  These are where most of the reactions for aerobic respiration take place. Respiration transfers energy that the cell needs to work
• What is the function of the ribosome?

  These are were proteins are made in the cell through protein synthesis
• What is the function of the cell wall?

  To strengthen and support the cell
• What is the function of the vacuole?

  Contains cell sap (a weak solution of sugar and salts), it keeps the cell turgid
• What is the function of the chloroplast?

  This is where photosynthesis takes place, which makes food for the plant. They contain a green substance called chlorophyll which absorbs the light required for photosynthesis
• 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
• What is the formula triangle for magnification?

  
• What do electron microscopes use to work?

  Electrons instead of light to form an image. They have a much higher magnification than light microscopes
• How are electron microscopes better than light microscopes?

  They allow us to see much smaller things in greater detail since they have a higher magnification and resolutions. For example, using an electron microscope, we can see the internal structure of mitochondria and chloroplast
• 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 cell differentiation?

  Cell differentiation is the process by which a cell changes to become specialised for its job.
• What is cell specialisation?

  The process of cells as they develop depending on their location in a tissue or organ.
• 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
• Define the term chromosome


  Coiled up lengths of DNA molecules, they contain your genetic information
• 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
• What can stem cells from embryos and bone marrow do?

  Produce clones and made to differentiate into specialised cells to use in medicine or research
• 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