biology P1

• what are all living things made from?

  cells
• what are the two types of cells?

  eukaryotic cells (complex) and prokaryotic cells (simple)
• what are examples of eukaryotes?

  plant and animal cells
• what are examples of prokaryotes?

  bacteria
• what do most animal cells contain?

  nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
• what is the function of the nucleus?

  contains genetic material that controls activities of the cell
• what is the function of the cytoplasm?


  site of most chemical reactions
• what is the function of the cell membrane?


  holds cell together and controls what goes in and out
• what is the function of the mitochondria?

  where most reactions for aerobic respiration takes place
• what is the function of the ribosomes?

  where proteins are made in the cell
• what do plant cells only have?

  vacuole, cell wall and chloroplasts
• what is the function of the vacuole?

  contains cell sap
• what is the function the cell wall?

  made of cellulose which supports the cell and strengthens it
• what is the function of the chloroplasts?

  where photosynthesis occurs, contains green substance (chlorophyll), absorbing light needed for photosynthesis
• what is the structure of a bacterial cell?


  CONTAINS:

  cytoplasm

  cell wall

  cell membrane

  single circular strand of DNA floating freelt in the cytoplasm

  plasmids - small rings of DNA

  
  

  DOESN'T CONTAIN:

  chloroplasts

  mitochondria

  'true' nucleus
• EQ: Give two differences in the structure between prokaryotic ad eukaryotic cells?

  Prokaryotes do not contain a 'true' nucleus, they contain plasmids or a single strand of DNA, meaning they are also simpler than eukaryotes
• how do light microscopes form an image?

  they use light and lenses and magnify it, they let us see individual cells and large subcellular structures like nuclei
• how do electron microscopes form an image?

  uses electrons, they have a much higher magnification than light microscopes and a higher resolution
• what is the formula for magnification?

  magnification = image size / real size
• EQ: A cheek cell is viewed under a microscope with x40 magnification. The image of the cell is 2.4mm wide. Calculate the real width of the cheek cell. Give your answer in µm.

  magnification = image size / real size

  so:

  real size = image size / magnification

  = 2.4 / 40

  = 0.06mm

  mm --> µm = x1000

  0.06 x 1000 = 60

  ANSWER: 60µm
• how do we prepare a slide to view onion cells?

  1) use a pipette to add a drop of water in the middle of a clean slide

  2) cut up an onion and separate it into layers

  3) use tweezers to cut off some epidermal tissue from the bottom of a layer

  4) using the tweezers place the epidermal tissue onto the slide

  5) Add a drop of iodine solution to stain the onion

  6) place a cover slip on top (stand cover slip upright on the slide, carefully tilit and lower it so it covers the specimen)
• how can we use a light microscope?

  1) Clip prepared slide onto the stage

  2) Select lowest powered objective lens

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

  4) Look down the eyepiece. use coarse knob until image is roughly in focus

  5) Adjust focus with fine adjustment knob until you get clear image of what is on the slide

  6) If you need to see the slide with a greater magnification, swap to a higher-powered objective lens and refocus
• how do we draw observations neatly?

  - use a sharp pencil

  - make sure the drwang takes up at least half of the space available and use unbroken and clear lines

  - subcellular structures should be in proportion

  - include a title of the observation

  - label important features (eg. nucleus) using straight lines
• EQ: Why might you add a stain to the sample on a microscope slide?

  To be able see subcellular structures clearly and and highlight objects in a cell by adding colour to them
• what is differentiation?


  process by which a cell changes to become specialised for its job
• what are undifferentiated cells called?

  stem cells
• what are sperm cells specialised for and how is it specialised?

  specialised for reproduction

  - it has a long tail and a streamlined head to help it swim to the egg

  - contains a lot of mitochondria to provide energy

  - enzymes in its head to digest through the egg cell membrane
• what are nerve cells specialised for and how?

  specialised for rapid signalling

  - cells are long

  - have branched connections at their ends to connect to other nerve cells to form a network throughout the body
• what are muscle cells specialised for and how?

  specialised for contraction

  - cells are long so they have space to contract

  - contains a lot of mitochondria to generate energy
• what are root hair cells specialised for and how?

  specialised for absorbing water and minerals

  - cells on the surface of plant roots, which grow into long 'hairs' that stick out into the cell

  - gives the plant a large surface area for absorbing water and mineral ions
• what are phloem and xylem cells specialised for and how?

  specialised for transporting substances

  - phloem and xylem cells form respective tubes, which transport substances like water and food around plants

  - cells are long and joined end to end

  - xylem cells are hollow in the centre

  - phloem cells have few subcellular structures so things can flow through it
• EQ:

  1- Give one feature of a phloem cell that makes it specialised for its function.

  2- Describe how a root hair cell is specialised for its function.

  1- It has few subcellular structures so food and water can travel through it easier.

  2- cells grow into long 'hairs' that stick out of the soil, giving the plant a large surface area for absoving water and mineral ions
• what are chromosomes?


  coiled up lengths of DNA molecules
• how many copies of chromosomes do body cells normally have?

  two copies, one from the organism's mother and the other from its father
• what is the stage of the cell cycle when the cell divides?

  mitosis
• what are the two main stages of the cell cycle?

  growth and DNA replication and mitosis
• what is the growth and DNA replication stage of the cell cycle?

  1) the DNA is spread out in long strings

  2) the cell has to grow and increase the amount of subcellular structures such as mitochondria.

  3) the cell duplicates its DNA - so there is one copy for each cell. The DNA is copied and formes X shaped chromosomes. Each 'arm' of the chromosomes is an exact duplicate of the other.
• what is the process of differentiation?

  a cell changes to become specialised for its job
• where are adult stem cells found?

  bone marrow
• why are some people against stem cell research?

  - people are against stem cell research because they feel that human embryos are each one is a human life

  - in some countries, stem cell research is banned