AQA a level biology topic 2

• structure of nucleus: envelope, pores, nucleolus
• structure of golgi apparatus: folded membrane cristernae and vesicles
• function golgi apparatus: modifies and sorts proteins and lipids
• structure endoplasmic reticulum: folded membrane cristernae, rough has ribosomes small doesnt have ribosomes
• function endoplasmic reticulum: synthesis of protein and lipid molecules
• structure lysosomes: bags of digestive enzymes
• function lysosomes: break down dead cells, digest worn organelles, hydrolyse phagocytic cells
• structure ribosomes: made of proteins and rRNA, 80s eukaryotic, 70s prokaryotic
• function ribosomes: site of protein synthesis
• structure mitochondria: cristae, double membrane
• function mitochondria: site aerobic respiration, ATP production
• structure vacuoles: central vacuole, tonoplast (membrane), cell sap
• fuction vacuole: maintains cell shape
• structure chloroplast: thylakoid
• function chloroplast: site of photosynthesis
• structure cell wall: plants cellulose, fungi chitin
• function cell wall: provide structual strength
• give 3 organelles prokaryotic cells may also contain

  plasmids, capsule, flagella
• list parts of virus

  attatchment proteins, envelope, capsid
• define magnification

  how many times larger the image is compared to object
• define resolution

  minimum distance between 2 objects where they are still viewed as separate
• why does optical microscopes have poorer resolution

  they have a longer wavelength of light
• compare optical and electron microscopes

  optical- poorer resolution (longer wavelength)

  lower magnification

  colour image

  view live sampleelectron microscopes-

  • have higher resolution (shorter wavelength) higher magnification
  • black and white
  • sample viewed must be non living as in a vacuum
• 2 differences between TEM and SEM

  TEM- thin specimen, 2D

  SEM- doesnt need to be thin, 3D
• why does solution for cell fractionation need to be cold

  reduce enzyme activity therefore reduce damage to cells
• why does solution for cell fractionation need to be isotonic

  same water potential so no excess water moving by osmosis so no bursting/ shrivel
• why does solution for cell fractionation need to be buffered

  to prevent pH damage to the cell
• give 3 steps for cell fractionation

  1)homogenise using blender to open cell with cold, isotonic, buffered solution

  2) filter to remove large debris

  3) ultracentrifugation- spin at different speeds. remove pellet formed at the bottom on most dense organelle
• list organelles from most to least dense

  nucleus, chloroplast, mitochondria, lysosomes, ER, ribosomes
• how do prokaryotic cells divide

  binary fission
• what is simple diffusion

  net movement of molecules from areas high to low concentration with no ATP
• requirements for diffusing molecules across membrane

  lipid soluble and small
• what is facilitated diffusion 


  proteins used to transport molecules which arent lipid soluble/ small e.g. ions and polar molecules. transported using protein channels and carrier proteins
• what is osmosis

  movement of water molecules from area high to low concentration across partially permeable membrane
• what is the water potential of pure water

  0
• isotonic meaning

  water potential is same in solution and cell within solution
• hypotonic meaning

  water potential of solution more positive than cell
• hypertonic meaning 


  water potential of solution more negative than cell
• meaning of active transport

  movement of substance from low to high concentration using metabolic energy and carrier proteins using ATP
• describe 3 step process of active transport

  transport through carrier proteins

  bind to receptor complementary to proteins

  ATP binds to carrier proteins from inside cell and hydrolysed into ADP +Pi