Cells and cell techniques 1

• what are prokaryotic cells?


  Cells without a nucleus or membrane-bound organelles. They are much smaller than eukaryotic cells.
• How do prokaryotic cells form new cells?

  Binary fission
• Describe DNA and function in prokaryotes

  short, circular molecule of DNA, not associated with protein and free in cytoplasm which carries genetic codes for proteins
• Describe Cell wall and function in prokaryotes

  Contains murein (glycoprotein) and prevents osmotic lysis which is rigid and strengthening
• Cytoplasm Prokaryotes


  Solution where many dissolved molecules are found, no membrane bound organelles. Site of many metabolic reactions
• Cell surface membrane prokaryotes

  Phospholipid bilayer with embedded proteins. Controls passage of substances across exchange surfaces by passive or active transport
• Small ribosomes prokaryotes 


  Small structures in cytoplasm 70s, protein synthesis
• Which 3 structures are only found in pathogenic bacteria?

  Simple flagellum, plasmids, capsule
• Simple flagellum pathogenic bacteria

  Thin rotating fibre which is responsible for movement of cell
• Plasmids pathogenic bacteria


  One or more small loops of DNA, can replicate independently. It can pass on genetic info via conjugation to other bacteria
• Capsule pathogenic bacteria


  Extra layer outside cell wall which protects cell from desiccation, phagocytosis and some pathogens
• What are eukaryotes?


  Extra features compared to prokaryotic cells. Have membrane bound organelles. Form new cells by mitosis and meiosis.
• Plasma membrane (eukaryotic)


  Double layered membrane found on cell surface and most internal organelles. Made of phospholipid belayer which contains embedded proteins. Selectively permeable which allows cell identification.
• Nucleus 


  Contains chromosomes which are long, linear DNA molecules associated with histone protein. Surrounded by nuclear envelop, with nuclear pores. Has one or more nucleoli. DNA contains genetic code for making proteins. Nucleolus manufactures ribosomes.
• Mitochondria 


  Oval shaped organelle surrounded by 2 membranes. Inner membrane folded & forms cristae. Fluid inside called matrix. Contains circular DNA like that in prokaryotes. Produces ATP from respiration, used in active transport.
• Rough endoplasmic reticulum


  Series of tubes in the cytoplasm of cell. Appears rough due to ribosomes attached to membranes. Synthesis & transport of proteins through cytoplasm
• Ribosomes (eukaryote)


  Small organelle made of RNA and protein, not surrounded by a membrane. 80s, larger than prokaryotic cells. Site of protein synthesis
• Smooth endoplasmic reticulum


  Series of tubes in cytoplasm, no ribosomes attached. Synthesises and transports lipids
• Golgi body and vesicles

  Stack of flattened sacs with vesicles continually budding off from the ends of these sacs. Modifies and processes proteins that are made in the cell and packages them into vesicles ready for export from the cell. Forms lysosomes
• Lysosomes


  Golgi vesicle, contains hydrolytic enzymes, called lysozymes. Digest unwanted material in cell like excess organelles or pathogens
• Cytoplasm 


  Site of many metabolic reactions
• What 3 structures do plant cells have which animal cells do not have

  Cell wall, vacuole and chloroplast
• Cell wall plant cell

  Made of cellulose which provides high tensile strength that prevents osmotic lysis
• What is the cell wall in fungi made from

  Chitin
• Vacuole


  Filled with cell sap (solution of sugar and salts) which gives rigidity
• Chloroplast


  Found in plant and algal cells, in green plants most chloroplasts occur in the mesophyll cells of leaves. Site of photosynthesis
• Envelope in chloroplast 


  Double membrane surrounding the chloroplast
• Granum in chloroplast


  A stack of membrane bound discs called thylakoids. The thylakoid membranes contain chlorophyll- the membranes provide a large surface area for light absorption (to maximise rate of photosynthesis)
• Stroma


  Contains enzymes needed for photosynthesis and stores starch grains
• DNA in chloroplast 


  Short circular and not associated with proteins
• Ribosomes in chloroplast 


  70s
• Define tissue


  Group of similar cells , e.g muscle, nervous and elastic tissue
• Define organ


  Group of different tissues e.g liver
• Define organ system


  Group of different organs working together to perform a complex function e.g digestive system
• Describe viruses


  Acellular, cannot undergo cell division so instead they attach to and enter a host cell and use that cell’s machinery to replicate.
• What are the 3 components of viruses?

  • genetic material- either DNA or RNA
  • Capsid- protein coat
  • Attachment protein- allow virus to attach to a host cell (complementary to receptors on host cell membran)
• Define magnification 


  How much bigger an image appears compared to its actual size
• Define resolution


  The ability to distinguish between two points so they can be seen as separate
• Describe optical microscopes 


  Use light to illuminate the specimen and glass lenses are used to focus the light. There’s an eyepiece lens of fixed magnification and a selection of objective lenses of various magnification. Specimens must be thin enough to transmit the light e.g tissue should ideally be one cell thick
• Why do light microscopes have low resolution?

  Light has a long wavelength