B1-Cell Biology

• What are eukaryotic cells?

  They are plant and animal cells that have a cell membrane, cytoplasm and genetic material enclosed in a nucleus.

  Also bigger than prokaryotic cells.
• What are prokaryotic cells?


  Bacterial cells which re much smaller than eukaryotic cells.

  They have a cytoplasm and a cell membrane, surrounded by a cell wall.

  The genetic material is not enclosed in nucleus, instead it is a single DNA loop and there may be one or more small rings of DNA called plasmids.
• Function on nucleus


  Contains genetic material ,that controls activities of cell.
• Function of cytoplasm


  gel like substance where most chemical reaction happen.

  Contains enzymes.
• Function of cell membrane

  holds cell together and controls what goes in and out.
• Function of mitochondria


  Most of the reactions for aerobic respiration take place.

  Respiration, transfers energy that the cell needs, to work.
• Function of ribosomes


  Where proteins are made in the cell
• Function of chloroplast


  Where photosynthesis occurs
• Function of vacuoles


  contains cell sap with sugar and salts.
• What are light microscopes?

  use light and lenses to form an image of a specimen and magnify it.

  lets us see large sub cellular structures and individual cells.
• What are electron microscopes?

  use electrons instead of light to form an image.

  have a much higher magnification and higher resolution than light microscopes.

  lets us see much small things more detail like internal structure of mitochondria.
• What is resolution?


  Resolution is the ability to distinguish between two points.Higher resolution gives sharper image.
• What is the formula for magnification?


  Magnification = image size / real size
• How do we convert micrometers to millimetres?

  Divide by 1000
• How do we prepare a slide for microscopy?

  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 of these layers.

  3)Using tweezers, put epidermal tissue into the water drop on the slide.

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

  5)Place the cover slip, and carefully tilt and lower the slide so it covers the specimen.Try not to get any air bubbles as it obstruct view of the specimen.
• How do we use a light microscope to look at our slide?

  1)Clip the slip onto the stage

  2)Select lowest powered objective lens

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

  4)Look down the eyepiece,Use the copper adjustment knob until you get a clear image of what on the slide.

  5)If we need to see the slide with greater magnification,swap to a higher powered objective lens and refocus.
• How do you draw the observations made through the light microscope?

  1)Draw what you see under the microscope, using a pencil with a sharp point.

  2)Make sure drawing takes up at least half of the space given and drew with clear, unbroken lines.

  3)NO COLOURING OR SHADING.

  4)If drawing cells, subcellular structures must be drawn in proportion

  5)Write title and magnification of what was observed.

  6)Label important features of your drawing.
• What is the difference in light microscopes and electron microscopes in scientific advancements?

  An electron microscope has a much higher magnification and resolving power than a light microscope.

  This means it can be used to study cells in much finer detail.

  This has enabled biologists to see and understand many more sub-cellular structures.
• What is differentiation?

  the process by which a cell changes to become specialised for its job

  They develop different sub cellular structures and turn into different types of cells.Which allows them to carry out specific functions.
• When does differentiation occur for plants and animal cells?

  Most differentiation occurs as an organism develops.

  in animal cells-ability to differentiate is lost at early stage after being specialised.

  in plants cells-ability to differentiate is never lost.
• Why does cell differentiation take place in mature animals?

  In mature animals, cell division is mainly restricted to repair and replacement.As a cell differentiates it acquires different sub cellular structures to enable it to carry out a certain function.
• How are sperm cells specialised?

  For reproduction.

  Function-to get the male DNA to the female DNA.

  1)Has a long tail and a streamlined head to help it swim to the egg.

  2)There are lots of mitochondria in the cello provide the energy needed.

  3)Also carries enzymes in its head-to digest through the egg cell membrane.
• How are nerve cells specialised?

  For rapid signalling.

  Function-to carry electrical impulses from one part of the body to another.

  1)Cells are long to cover more distance

  2)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.

  Function-to contract quickly.

  1)Cells are long so that they have space to contract.

  2)Contain lots of mitochondria to generate energy needed for contraction.
• How are root hair cells specialised?

  For absorbing water and minerals.

  Are cells on the surface of plant roots which grow into long "hairs" that stick into the soil.

  1)long hair give a big surface area for absorbing water and mineral ions from the soil.
• How are phloem and xylem cells specialised?

  For transporting substances.

  Phloem and Xylem cells form tubes, transporting substances such as food and water around plants.

  1)Cells are long and joined end to end to form tube

  2)Xylem cells are hollow in the centre and phloem cells have few sub cellular structures-stuff can flow through both.
• What are chromosomes?


  The nucleus of a cell contains chromosomes (coiled up lengths of DNA molecules).

  Each chromosomes carries a large number of genes-the amount of genes control the characteristic.

  In body cells-chromosomes found in pairs, one bring from mother and the other from father.

  Human cell-23 chromosomes.
• What is mitosis?


  The stage of the cell cycle where the cell divides.

  Multicellular organisms use mitosis to grow and replace cells that have been damaged.

  The end of the cell cycle results in is two new cells identical to the original cell ,with the same number of chromosomes.
• What happens in the first stage of Growth and DNA replication?

  Growth and DNA replication.

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

  2)Before dividing the cell has to grow and increase the mount of sub cellular structures such as mitochondria and ribosomes.

  3)It then duplicates the DNA- so there is one copy for each new cell.DNA is copied and forms X-shaped chromosomes.
• What happens during 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. Becoming ,the nuclei of the two new cells-The nucleus has therefore divided.

  6)Lastly the cytoplasm and cell membrane divide.

  The cell has now produced 2 new daughter cells.The daughter cells contain exactly the same DNA-they're identical.
• What is a stem cell?

  A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.
• What can stem cells from embryos do?

  Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.
• What can stem cells from bone marrow do?


  Stem cells from adult bone marrow can form many types of cells including blood cells.
• What can meristem tissue in plants do?

  Meristem tissue can differentiate into any type of plant cell, throughout the life of a plant.
• What treatment are stem cells used for?

  Diabetes and paralysis
• What is the risk and benefit of using stem cells in medical treatment?

  Stem cells from the embryo are not rejected by the patients body so they may be used for medical treatment.

  
  

  The use of stem cells has potential risks such as transfer of viral infection and some people having ethical or religious objections.
• What is diffusion?


  Diffusion is the spreading out of particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration.
• What are examples of diffusion?

  -oxygen and carbon dioxide in gas exchange

  -the waste product urea diffusing into the blood plasma for excretion in the kidney.
• What are the factors affecting diffusion?

  -Difference in concentrations (Concentration gradient)-faster

  -Temperature-high-faster diffusion-particles have more energy

  -Surface area of the membrane-more particles, pass through at once

  Talk about surface area to volume ratio.
• Why does diffusion happen in both solutions and gases?

  The particles in these substances are free to move about randomly.

  If a lot more particles there is a net movement.