bio mock Flashcards
describe the structure of a triglyceride
- three fatty acid chains attached by a glycerol backbone
- fatty acids- chains of carbon atoms with the end carbon possessing a carboxyl group
describe the structure of cellulose
polysaccharide
- polymer consisting of long unbranched chains of beta-glucose joined together by 1, 4 glycosidic bonds
-to form the 1, 4 glycosidic bonds every other beta-glucose molecule has to be inverted.
inversion gives strength as many hydrogen bonds form between the long chains, this is important because cellulose is the main structural component of cell walls
describe the structure of glucose
and draw an alpha and beta glucose molecule
- glucose is the monomer for carbohydrates
glucose is a monosaccharide and can exist in two different forms (isomers) which are alpha-glucose and beta-glucose
describe the structure of starch
- starch is a storage polysaccharide (macromolecule)
- it is constructed from two different polysaccharides (amylose and amylopectin)
amylose - unbranched helix with 1, 4 glycosidic bonds between alpha glucose molecules (helix shape allows for it to be more compact and more resistant to digestion)
amylopectin - 1,4 glycosidic bonds between alpha glucose molecules but also 1, 6 glycosidic bonds form between glucose molecules creating a branched molecule (branched so glucose molecules can be easily added to for storage
describe the structure of glycogen
- storage polysaccharide of animals and fungi
- highly branched and not coiled
- more compact then amylopectin
- branches enable more free ends where glucose molecules can either be added or removed allowing for condensation and hydrolysis reactiosn to occur more rapidly
coversions for cm to mm to um to nm
cm ——> mm = x10
mm —–> um = x1000
um ——> nm = x1000
DIVIDE FOR REVERSE
describe different types of microscopes
LIGHT MICROSCOPE
- uses light to form an image
- using light makes if impossible to distinguish between two objects that are closer than half the wavelength of light (500-650 / 2)
- low max resolution
- can only used to see eukaryotic cells and their nuclei (sometimes chloroplasts and mitochondria
ELECTRON MICROSCOPES
- uses electrons to form an image
- electrons have a much smaller wavelength than light, so it can distinguish between two objects that are extremely close together
TRANSMISSION ELECTRON MICROSCOPES
- beam of electrons transmitted through the specimen
- denser parts of the specimen absorb more electrons making the denser parts appear darker on the final image
- gives high res images and allows internal structures to be seen
- cannot be used to observe live specimens
- lengthy treatment to prepare specimens which can introduce artefacts
- do not produce colour image
- used only with very thin specimens
SCANNING ELECTRON MICROSCOPE
- uses beam of electrons which bounce off the surface of the specimen, the electrons are detected which form an image
- this means 3-D images can be produces
- can be used on thick or 3-d specimens and allow the external, 3-d structure of specimens to be observed
- give lower res than TEMs
- cannot be used to observe live specimens
- do not produce colour image
how are peptide bonds formed and broken
draw a diagram of amino acids bonding together
peptide bonds are what bond amino acids together
- a hydroxyl group (OH) is lost from a carboxylic group of one amino acid and a hydrogen atom is lost from an amine group of another amino acid
- the carbon double bonded with oxygen from the first amino acid bonds to the nitrogen of the second amino acid
- this is a condensation reaction so water is released, the resulting molecule is a dipeptide
- during hydrolysis reactions polypeptides are broken down to amino acids when the addition of water rbeaks the peptide bonds
describe the secondary structure and the two shapes that can form within the proteins
- the secondary structure occurs when the weak negatively charged nitrogen and oxygen atoms interact with the weak positively charged hydrogen atoms to form hydrogen bonds
- alpha-helix and beta-pleated sheet are the two shapes that can form within proteins due to the hydrogen bonds
BETA PLEATED SHEET
- forms when the protein folds so that two parts of the polypeptide chain are parallel to each other enabling hydrogen bonds to form between parallel peptide bonds
ALPHA-HELIX
- occurs when the hydrogen bonds form between every fourth peptide bond (between the oxygen of the carboxyl group and hydrogen of the amine group)
describe the three stages in cell fractionation
HOMOGENISATION
- breaking up of cells
- sample of tissue is placed in a cold isotonic buffer solution
- ice cold = reduce activity of enzymes that break down organellses
- isotonic = same water potential as tissue to prevent osmosis and water damage
- buffered = to prevent organelle proteins from becoming denatures
- tissue containing solution is then homogenised using a homogeniser
- homogenisers are a blender like machine that grinds up cells which breaks the plasma membrane of the cells and releases the organelles into a solution called the homogenate
FILTRATION
- the homogenate is then filtered through a gauze
- this separates any large cell debris or tissue debris that were not broken up leaving a solution that contains a mixture of organelles
ULTRACENTRIFUGATION
- the filtrate is placed in a tube which is then placed in a centrifuge (machine that separates materials by spinning)
- the filtrate is first spun at a low speed causing the largest, heaviest organelles to settle at the bottom of the tube where they form a thick sediment known as a pellet
- the rest of the organelles stay suspended in the solution above, this is known as the supernatant
- the supernatant is drained off and placed into another tube which is spun at a higher speed causing the heavier organells like mitochondria to settle at the bottom of the tube forming a new pellet
- the new supernatant is drained off and placed inot another tube which is spun at an even higher speed
- this process is repeated at increasing speeds until all the different types of organelle present are separated out
- each new pellet formed contains a lighter organelle than the previous pellet
- order of mass from heaviest to lightest is
nuclei, chloroplasts, mitochondria, lysosomes, endoplasmic reticulum, ribosomes
describe the three stages in cell fractionation
HOMOGENISATION
- breaking up of cells
- sample of tissue is placed in a cold isotonic buffer solution
- ice cold = reduce activity of enzymes that break down organellses
- isotonic = same water potential as tissue to prevent osmosis and water damage
- buffered = to prevent organelle proteins from becoming denatures
- tissue containing solution is then homogenised using a homogeniser
- homogenisers are a blender like machine that grinds up cells which breaks the plasma membrane of the cells and releases the organelles into a solution called the homogenate
FILTRATION
- the homogenate is then filtered through a gauze
- this separates any large cell debris or tissue debris that were not broken up leaving a solution that contains a mixture of organelles
ULTRACENTRIFUGATION
- the filtrate is placed in a tube which is then placed in a centrifuge (machine that separates materials by spinning)
- the filtrate is first spun at a low speed causing the largest, heaviest organelles to settle at the bottom of the tube where they form a thick sediment known as a pellet
- the rest of the organelles stay suspended in the solution above, this is known as the supernatant
- the supernatant is drained off and placed into another tube which is spun at a higher speed causing the heavier organells like mitochondria to settle at the bottom of the tube forming a new pellet
- the new supernatant is drained off and placed inot another tube which is spun at an even higher speed
- this process is repeated at increasing speeds until all the different types of organelle present are separated out
- each new pellet formed contains a lighter organelle than the previous pellet
- order of mass from heaviest to lightest is
nuclei, chloroplasts, mitochondria, lysosomes, endoplasmic reticulum, ribosomes
name and describe the purpose of each of the enzymes induced in DNA replication
DNA helicase - unzips double helix by breaking the hydrogen bonds which join the two polynucleotide strands together
DNA polymerase -
moves down the molecule and catalyses the formation of a phosphodiester bond between the activated nucleotides (condensation reaction)
DNA ligase - binds the new DNA together
What are enzymes and how do reactions happen
- enzymes are biological catalysts. All enzymes are globular proteins with a specific tertiary shape
- the part of the enzyme that acts as a catalyst is called the active site and the rest of the enzyme is much large and is involved in maintaining the specific shape of the enzyme
- when a reaction involving an enzyme occurs, a substrate is turned into a product. The substrate can be one or more molecules. The active site of an Enzyme is complementary to the substrate it catalyses
name all the biological molecules food tests and describe how to carry them out as well as what the results look like
BENEDICTS TEST FOR REDUCING SUGARS
- add benedicts reagent (blue) to the sample in a test tube making sure there is an excess
- heat the mixture in a water bath for a few minutes
- a positive test will lie along the scale from blue (no reducing sugar) through green, yellow, orange and a brown/brick red (high concentration of reducing sugar)
TEST FOR NON-REDUCING SUGARS
-add dilute hydrochloric acid to the sample and heat in a water bath that has be brought to a boil
- neutralise the solution with sodium hydrogencarbonate and add a bit more until the solution becomes slightly alkaline (monitor this using a suitable indicator)
- then carry out the benedicts test as normal
= if a colour change occurs then a non reducing sugar is present
IODINE TEST FOR STARCH
- add a few drops of orange/brown iodine in potassium iodide
- if starch is present the solution will turn a blue-black colour
EMULSION TEST FOR LIPIDS
- add ethanol to the sample being tested, shake to mix then add the mixture to a test tube of water
- if lipids are present a milky emulsion will form
- if no lipid is present the solution remains clear
BIURET TEST FOR PROTEINS
- a liquid solution of a sample is treated with sodium or potassium hydroxide to make the solution alkaline
- then add a few drops of copper (II) sulfate solution (blue) to the solution
- if a colour change is observed from blue to lilac/purple then proteins are present
describe the structure of a DNA nucleotide
- nucleotides contain a deoxyribose sugar with hydrogen at the 2’ position
- a phosphate group
- one of the four nitrogenous bases
adenine and guanine (purine-double ring structure)
and cytosine and thymine (pyrimidines-single ring structure)
