B1 - Cell biology

• The organelles in an animal cell are nucleus, mitochondria, cytoplasm, cell membrane and ribosome
• The organelles in a plant cell are nucleus, mitochondria, cytoplasm, cell membrane, ribosome, chloroplast, cell wall and vacuole
• Nucleus = Contains genetic material that controls the activities of the cell and the instructions to make new cells and proteins
• Cytoplasm = A liquid gel substance where most chemical reactions take place
• Cell membrane = A partially permeable barrier that surrounds the cell content and controls what enters and leaves the cell
• Mitochondria = Where aerobic respiration takes places, the reaction that transfers energy from glucose for cells to use
• Ribosome = Where protein synthesis takes place, making all the proteins needed in the cell
• Chloroplast = Filled a green substance called chlorophyll, which absorbs light needed for photosynthesis
• Vacuole (permanent) = Contains a water liquid with sugar and salts called cell sap, which supports the cell from the inside and keeps it rigid
• Cell wall = Strengthens the cell and provides support , made of cellulose
• The organelles in a basic bacterium cell are pili, slime capsule, cell wall, cell membrane, cytoplasm, flagellum, ribosome, DNA loop and plasmids
• Plasmids = Replicates and moves between cells so that genetic information can be shared
• Pili = To attach a bacterial cell to specific surfaces or to other cells
• Slime capsule = It protects the cell from physical and chemical attacks
• A eukaryotic cell is a complex cell with a nucleus (e.g animal & plant cells)
• A prokaryotic cell is a smaller cell without a nucleus (e.g bacterial cell)
• Differentiation is the process when a cell changes, becoming more and more suited, or specialised, for a certain function
• Stem cells are special types of cells that can turn into other specialised cells
• Examples of stem cells in humans are embryonic stem cells and adult stem cells
• Embryonic stem cells:

  • Can differentiate in ANY type of specialised cell
  • Controversial
  • They can be used to replace cells that have been damaged or destroyed:

  1. In spinal cord or brain injuries which had led to paralysis
  2. In minute sclerosis, which can lead to paralysis
  3. In type 1 diabetes (where the patients pancreatic cells don't work)
• Adult Stem cells:

  • Used to create certain cancers and blood diseases
  • Can only differentiate into a limited number of specialised cells
  • They can be found in: Bone marrow, Skin, Brain Heart, Muscle and liver
  • They are multipotent (Meaning they can only differentiate into a limited number of cell types)
• Proteins are made in the ribosome
• The cell wall is made out of celluose
• Photosynthesis takes place in the chloroplast
• You wold bring a cell sample into focus by using the coarse adjustment knob to move the stage up to just below the objective lens. Look down the eyepiece and use the coarse adjustment knob to move the stage downwards until the image is roughly in focus. Then adjust the focus with the fine adjustment knob, until a clear image of the cells is visible
• True or false? - It's more difficult to exchange materials effectively in large, complex organisms than in small, simple organisms

  True
• Water molecules move in and out of cells by osmosis
• The function of a capillary is to provide efficient blood supply to the intestine
• Diffusion takes place in gases and liquids
• The small intestine is adapted for exchanging materials because it has a large surface area, a thin membrane, and an efficient blood supply.
• The effectiveness of the lungs in humans is improved by them being ventilated and this means that they constantly exchange air with the environment
• Independent variable = What is being changed

  Dependent variable = What is being measured

  Control variable = What is kept the same
• A semi-permeable membrane is a membrane where water molecules can cross the membrane but solute molecules can't
• Osmosis is a type of diffusion
• Active transport:

  • The movement of particles from a low concentration to a high concentration
  • Against a concentration gradient
  • Uses energy
• Osmosis:

  • The movement of water particles from an area of high concentration to an area of low concentration
  • Down a concentration gradient
  • Across a partially permeable membrane
  • A passive process
• Diffusion:

  • The spreading out of particles from an area of high concentration to an area of low concentration
  • Down a concentration gradient
  • A passive process
• Required practical: Osmosis

  1. Use a cork borer to cut five potato cylinders of the same diameter

  2. Trim off potato skin and make same length

  3. Accurately measure the mass of each potato cylinder

  4. Record measurements in a table

  5. Measure 10 cm³ of each concentration of sugar or salt solution and put into boiling tubes

  6. Measure 10 cm³ of distilled water and put into the fifth boiling tube

  7. Add one potato cylinder to each boiling tube

  8. Leave the potato cylinders in the boiling tubes for a chosen amount of time

  9. Remove the potato cylinders and blot them dry

  10. Measure the new mass of each potato cylinder again

  11. Calculate the percentage change in mass of each potato
• Potato cylinder preparation

  • Same diameter
  • Same length
  • Accurate mass measurement
• Concentrations of sugar solutions

  • 0.25 M
  • 0.50 M
  • 0.75 M
  • 1.0 M
  • Distilled water