Module 2 bio

• Examples of organelles


  ribosomes, golgi apparatus, mitochondria, nucleus, RER, SER, permanent vacuole
• ribosomes in eukaryotic and prokaryotic

  2 protein sub units, 80s in eukaryotes and 70s in prokaryotes. site of protein synthesis and found both in cytoplasm an on RER
• golgi apparatus

  stack of membranes in the cell that modifies, sorts, and packages proteins from the endoplasmic reticulum. form vesicles that contain digestive enzymes and these excrete its contents outside of the cell via exocytosis by fusing with the plasma membrane
• RER

  flattened sacs called cristae, has ribosmes on the surface so protein synthesis can take place
• SER


  site of lipid synthesis
• nucleus


  contains DNA packaged on histone proteins to form chromatids which then go on to form chromosomes
• nucleous


  dense part inside the nucleus that makes ribosomes and RNA
• mitochondria

  double membrane, contains folds called cristae and the fluid inside called the matrix which contains enzymes that help make ATP
• permanent vacuole


  contains inorganic ions and maintains turgor pressure
• chloroplasts


  double membrane, membrane found flattened discs called thylakoids, this contains chlorophyll and enzymes needed to absorb light

  
  

  thylakoids stacked ontop of each other = granum

  
  

  granum connected = via lamellae, allow chemicals to pass between the grana

  
  

  fluid = stroma
• plasma membrane


  phospholipid bilayer but contains proteins, cholesterol and glycoproteins/lipids as a part of it
• phospholipids

  form a bilayer, ester bonds, hydrophobic tails inwards and hydrophyllic phosphate heads on the outside, controls what moves through the membrane and only small and non charged molecules can move through (water is an exception to this rule as it's so small)
• proteins


  integral and peripheral proteins. can act as receptors for cell to cell signalling

  
  

  channel proteins = allow charged molecules (ions) to pass through pores to the other side of the membrane, a type of facilitated diffusion

  
  

  carrier proteins = freely move around the molecule and use active transport to move larger molecules through the membrane, facilitated diffusion & it:

  1) binds to the molecule

  2) changes its shape

  3) releases it to the other side
• glycoproteins & glycolipids


  glycoprotein/lipid = carbohydrate groups attached to membrane proteins, good for:

  
  

  -binding sites for hormones/drugs/antibodies as they are receptors that can detect signaling molecules

  
  

  -form hydrogen bonds with water which strengthens the membrane

  
  

  (also 2 GLYCOPROTEINS can help 2 cells join together to form a tissue)
• cholesterol


  -adds to hydrophobic barrier as it's also hydrophobic

  -helps increase thermal stability and therefore it doesn't move too much when it gets warmer but isn't as rigid when its cooler
• what is the overall function of a cell membrane?

  -barrier

  -cell signalling (hormones)

  -cell recognition (cancer)

  -control movement in and out of the cell
• factors affecting the cell membrane

  -solvents i.e. ethanol increase membrane permeability

  -below 0 degrees C = huge increase in membrane rigidity and increase in membrane permeability (membrane so denatured everything can go in)

  
  

  between 0 and 45 degrees C = fluid and semi permeable so normal, movement restricted or increased by cholesterol depending on temperature

  
  

  above 45 degrees C = can burst, membrane freely permeable, bilayer breaks down
• but how do we know?

  microscopes: light, scanning electron microscope and transmission electron microscope
• resolution


  the smallest distance by which two objects can be separated and still be distinguished
• magnification


  the size of the image over the size of the real object
• light microscopes


  magnification of 1000x and resolution of 200 nm. focuses a beam of light onto an object and there's a series of lenses that are used to magnify the specimen to get an image. cheap and easy to use but worst resolution and magnification. both living and dead cells
• SEM


  specimen to be covered in a thin layer of metal i.e. gold and then electrons are beamed at it and then are reflected off and this produces a 3D image of the surface of the specimen. best magnification (along with TEM) of 500 000 x and middle resolution of about 3-10 nm. expensive though especially with the gold. only dead cells
• TEM


  electrons beamed at specimen and travel through, provides a 2D image of the internal structure in black and white and it can only be used to study dead cells. best magnification of 500 000 x and resolution of 0.5 nm. expensive and hard to use
• prokaryotes


  -no nucleus and contains no membrane bound organelles whatsoever

  -free floating chromosome that is essentially one continuous loop of DNA

  -cell wall made out of peptidoglycan

  -unicellular and about 1-5 micrometers big

  -plasma membrane

  -can have flagella, pili or cilia to help them move

  -can have a slime capsule and this is associated with antibiotic resistence
• water


  - polar as it is charged and asymmetrical so the dipoles don't cancel out, partial positive charge on the hydrogen and partial negative charge on the oxygen = can form hydrogen bonds

  -hydrogen bonds = can contain dissolved ions which can undergo chemical reactions so it can be used as a solvent

  -high specific heat capacity, lots of energy is needed to heat the water therefore seas and oceans don't just disappear on a hot day

  -high latent heat of vaporisation, a lot of energy is needed to convert water into steam and this means that if the top layer heats off, there is a cooling effect on the rest of the body of water.

  -water is most dense at 4 degrees and therefore water floats on top of ice keeping the fish alive

  -cohesion = helpful in xylem as water molecules go upwards just because they stick to each other

  -adhesion = useful in xylem as because it's narrow, the water flows up more

  -HYDROLYSIS
• test for proteins


  biurets reagent and equal amount of NaOH, then a bit of blue copper sulphate. should turn lilac if present
• test for starch


  Add iodine dissolved in potassium iodide solution to the test tube sample. If there's starch present, the sample changes from browny-orange to a dark blue-black colour.
• test for lipids


  emulsion test, add equal parts water and ethanol and emulsion should form
• test for reducing and non-reducing sugars


  benedicts test. add blue copper sulphate and heat, should be brick red if lots of sugar is present and orange/yellow if it's a smaller amount
• triglycerids


  ester bonds between 1 molecule of glycerol and 3 molecules of fatty acids
• monosaccharides


  join together to form disaccharides and then polysaccharides. main ones are glucose, fructose and galactose
• disaccharides


  glucose + glucose = maltose

  fructose + glucose = sucrose

  galactose + glucose = lactose

  form via a condensation reaction and the bonds formed are called glycosidic bonds
• alpha glucose


  H OH H H

  I I I I

  OH H OH OH

  
  

  (the difference is that the hydrogen and hydroxyl group on carbon 1, which is the one written last, is switched around and this greatly affects the types of bonds it can make) H group on top
• beta glucose


  H OH H OH

  I I I I

  OH H OH H

  
  

  (the difference is that the hydrogen and hydroxyl group on carbon 1, which is the one written last, is switched around and this greatly affects the types of bonds it can make) OH group on top
• alpha glucose can form starch (plants)


  -starch consists of amylose and amylopectin

  -amylose is un branched chain and therefore harder to break down, contains 1,4 Glycosidic Bonds (GB), compact and can store lots of energy

  -amylopectin is branched and therefore can be quickly digested by enzymes for glucose. 1,4 and 1,6 GB
• alpha glucose can form glycogen (animals)


  it is branched, large but compact and consists of both 1,4 and 1,6 GB meaning it can be broke down quickly and turn into glucose when needed but the amount of energy stored is maximised as it's so compact
• beta glucose can form cellulose (plants)


  1,4 GB and unbranched. long cellulose chains go on to form microfibrils that are joined by hydrogen bonds and provide structural support in plants
• inorganic ions


  hydrogen, potassium, magnesium, calcium, iron, phosphate, sodium
• hydrogen


  determines pH and also important in respiration
• potassium


  important for nerve impulses and also responsible for the opening of stomata in photosynthesis