CELL BIOLOGY J

•  Animal and plant cells are Eukaryotic. 
•   Cells = basic building blocks of life , smallest unit of life that can replicate independently.
•  ANIMAL CELL : cell membrane , nucleus , cytoplasm , mitochondria,  ribosomes 
•  PLANT CELL = cell membrane , nucleus , cytoplasm , mitochondria , ribosomes , cell wall , permanent vacuole , chloroplasts .
• CELL MEMBRANE- controls which substances can pass in and out of the cell
• NUCLEUS- contains genetic material 
• CYTOPLASM- where chemical reactions take place 
• MITOCHONDRIA- provide cells with the energy they need to function
• RIBOSOMES- where protein synthesis takes place 
• CELL WALL- made of cellulose and supports and strengthens the cell
• PERMANENT VACUOLE- contains cell sap 
•  CHLOROPLASTS- where photosynthesis takes place, contains chlorophyll 
•  

  BACTERIAL CELL: prokaryotic cells: cell membrane , cell wall , ribosomes , cytoplasm , circular strand of DNA , plasmids , flagella 
•  CIRCULAR STRAND OF DNA- contains all genes need to survive 
• PLASMIDS- extra rings of DNA 
• FLAGELLA- propel bacterial along.
•  Object : the real object or sample that you are looking at eg onion cells 
• Image : what you see when looking down the microscope 
•  How does it work: Light hits the mirror and reflects upward through object we want to look at. It then passes through one of the objective lenses and then through the eyepiece lens and into our eye. The image we see is far large than the actual object
•  Magnification: how many times larger the image is then the object. 
•  Magnification= image size 

                           Object size 
• Resolution: shortest distance that two parts of an object can be apart without appearing blurred. Measures of detail of an image.
• ELECTRON MICROSCOPES 

  Very big , very expensive 

  Hard to use 

  Use electrons 

  High resolution and higher magnification 
• LIGHT MICROSCOPES 

  Easy to use and cheap 

  Low resolution and low magnification 

   Cannot see sub cellular structure 

  Rely on light 
• Lots of conditions are due to faulty cells eg type 1 diabetes and paralysis 

  1. Extract embryonic stem cells from early embryos 
  2. Grow them in a lab 
  3. Stimulate then to differentiate into whichever type of specialised cell that we want 
  4. Then inject them into patient to replace faulty cells. 
• Is great in theory however… 

  CONS: requires embryonic stem cells ( limited supply ) 

  Genomes are different so immune system may reject cells
• Adult stem cells: can only differentiate into different types of blood cells. So we could only treat blood diseases. 

  PROS: Taken from patient themselves so won’t face rejection 

  Are taken from patient so are not in limited supply.
• Risks using stem cells in medicine 

  VIRUS TRANSMISSION: if the donor stem cells are infected with a virus , when transferred into patient it will also transfer virus. This infects the patient and potentially causes every more problems. 

  TUMOUR DEVELOPMENT: as stem cells can divide really quickly they may get out of hand and could develop into tumour or cancer, 
• Ethical objection to embryonic stem cells 

  -human embryos have potential to human life so people object to their use in research 

  • some belief curing existing people is more important 
  • Most of the time the embryos are unwanted ones from fertility clinics 
  • Governments regulate this area of research. Eg tightly controlled in uk 
• Diffusion : passive and doesn’t require energy 

  Net movement of particles from an area of high concentration than area of low concentration. Down the concentration gradient. 
• Diffusion can happen in gases and liquids as particles are free to move about randomly. 
• Bigger concentration gradient = faster rate of diffusion 
• Higher temperature = faster rate of diffusion as particles have more energy so move around faster
• Larger surface area = faster rate of diffusion , because more particles can pass through at once 
• Cell membranes 

  They hold the cell together but they let stuff in and out as well

  Dissolves substances can move in and out of cells by diffusion 

  Only very small molecules can diffuse through the cell membrane like amino acids , oxygen , glucose , water 

  Big molecules like start and proteins cannot fit through the membrane 
• Osmosis : passive and doesn’t require energy 

  Net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration. 
• • water molecules can pass both ways across the membrane as water molecules move about randomly all the time 
  • On side will have more water and be highly concentrated this will move into the area with a lower concentration to try and even out the concentrations either side of the membrane 

  Moves down concentration gradient 
• Active transport : active and requires energy moves against the concentration gradient 

  Movement of molecules from an area of lower concentration to an area of higher concentration, across a partially permeable membrane. Against the concentration gradient.

  Energy comes from cellular respiration. When glucose breaks down to release energy. 
• Where active transport is used 

  Root hair cells absorb water and mineral ions. Minerals plant need ( magnesium and nitrates) are at a higher concentration inside the cell than outside in the soil. So can’t be absorbed by diffusion. So energy is used.  Root hair cells use active transport to absorb mineral ions are adapted to that role by having a large surface are and lots of mitochondria.
• Surface area to volume ratio

  Smaller organisms have a larger surface area to volume ratios.