bio topic 1

• parts in animal cell

  nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
• parts in plant cells

  nucleus, cell membrane, cytoplasm, mitochondria, ribosomes, cell wall, vacoule, chloroplasts
• function of nucleus


  contains DNA and genetic material of cell, controls everything happening in the cell

  in both animal and plant cells
• function of cytoplasm


  the place where chemical and metabolic reactions take place in order for the cell to keep functioning

  in both animal and plant cells
• function of cell membrane


  controls what enters and exits the cell

  present in both animal and plant cells
• function of mitochondria


  where respiration occurs in order to produce energy for the cell

  in both animal and plant cells
• function of ribosomes


  where proteinsynthesis occurs

  in both animal and plant cells
• function of cell wall

  help strengthens cell

  only in plant cells
• function of vacoule


  contains cell sap, helps maintain turgidity of cel

  only in plant cells
• function of chloroplasts


  contain chlorophyll which absorbs light energy for photosynthesis and the place where this process takes place

  only in plant cells
• special feature for plant and algal cells

  also have a cell wall made of cellulose which strengthens the cell
• cm - mm - micrometre - nanometre

  cm to mm is x10 and vice versa, mm to micrometre is x1000 and vice versa, micrometre to nanometre is x1000 and vice versa
• Challenge Q: the cells of algae are very similar to plants, how do they feed?

  sunlight enters via the cell membrane which travels to the chloroplasts where photosynthesis occurs to make energy and nutrients for their food.
• What is diffusion?

  Diffusion is the movement of particles from an area of high concentration to low concentration down a concentration gradient through a partially permeable membrane.
• why is diffusion important to humans

  helps with breathing and transportation of blood around the body - necessary for respiration
• diffusion in plants


  part of photosynthesis - CO2 diffuses from atmosphere through stomata into leaf, O2 diffuses from leaf through stomata into atmosphere, water molecules diffuse using evaporation
• diffusion in humans(kidney)


  waste product urea diffuses from cell into blood plasma for excretion in the kidney
• diffusion in humans(gas exchange)

  O2 diffuses from alveoli into blood cells while CO2 diffuses from blood cells into alveoli
• how does temperature affect diffusion

  as the temperature increases, diffusion increases as particles have more energy once they are heated so they can move and spread out faster thus requiring a higher rate of diffusion.
• how does concentration affect diffusion

  as the concentration gradient increases so does the rate of diffusion as there are more particles to diffuse - this occurs until the maximum rate of diffusion is reached
• how does SA affect diffusion?

  bigger the cube, more volume than SA - smaller the cube, more SA than volume

  bigger SA, higher rate of diffusion as more particles are exposed to the surface, closer to membrane
• A single celled organism has a relatively large SA:V ratio - what does this mean?


  This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism.
• Students should be able to calculate and compare surface area to volume ratios.
• Students should be able to explain the need for exchange surfaces and a transport system in multicellular organisms in terms of surface area to volume ratio.
• The small intestine is adapted for exchanging nutrients between digested food in the small intestine and the blood.
• The lungs are adapted for exchanging carbon dioxide and oxygen between the blood and air.
• The gills are adapted for exchanging oxygen that is dissolved in water, with the carbon dioxide in a fish's bloodstream.
• Roots are adapted for taking up both water and minerals from the soil around them.
• Leaves are adapted for exchanging carbon dioxide and oxygen between the leaves and the surrounding air.
• In multicellular organisms, surfaces and organ systems are specialised for exchanging materials - why?


  This is to allow sufficient molecules to be transported into and out of cells for the organism’s needs. The effectiveness of an exchange surface is increased by

  : • having a large surface area

  • a membrane that is thin, to provide a short diffusion path

  • (in animals) having an efficient blood supply

  • (in animals, for gaseous exchange) being ventilated
• what is active transport?

  movement of particles from an area of low concentration to high concentration against a concentration gradient.
• why does active transport need energy?

  as it is an active process
• where does active transport get energy from?

  cellular respiration in mitochondria
• what transport the particles in active transport?

  carrier proteins
• active transport in plants


  Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil. Plants require ions for healthy growth

  minerals move from soil (low conc.) to root hair cell (high conc.)
• active transport in humans

  It also allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration

  also occurs in epithelial cells in small intestine
• Students should be able to:

  • describe how substances are transported into and out of cells by diffusion, osmosis and active transport

  • explain the differences between the three processes
• What is osmosis?


  movement of water particles from a dilute (high water concentration) to a more concentrated solute solution (low water concentration) through a partially permeable membrane
• Students should be able to:

  • use simple compound measures of rate of water uptake

  • use percentages

  • calculate percentage gain and loss of mass of plant tissue.

  Students should be able to plot, draw and interpret appropriate graphs.
• Osmosis


  Differences in the concentration of solutions inside and outside a cell can cause water to move in and out via osmosis