unit 1A - biological molecules Flashcards
carbs, lipids, proteins, enzymes
what is a polymer
they are large, complex molecules composed of long chains of monomers joined together
what is a monomer
small, basic molecular units
what are 3 examples of monomers
monosaccharides, amino acids and nucleotides
what are carbohydrates made from
monosaccharides (glucose, fructose and galactose)
what is a hexose sugar
glucose is a hexose sugar which is a monosaccharide with 6 carbon atoms in each molecule
what are the two types of glycoses
alpha and beta - they’re isomers (molecules with the same molecule formula as each other but with the atoms connected in a different way)
what is a condensation reaction?
this is a reaction when two molecules join together with the formation of a new chemical bond, and a water molecule is released when the bond is formed.
what joins together by a condensation reaction?
monosaccharides
what bond is formed between two monosaccharides as a molecules of water is released?
glycosidic bond
what does two monosaccharides become when they are joined together?
a diaccharide
give 3 examples of disaccharides and their monomers
two alpha glucose molecules = maltose
glucose + fructose = sucrose
glucose + galactose = lactose
what is a hydrolysis reaction?
this is a reaction that breaks the chemical bond between monomers using a water molecule
what is the test for reducing sugars and how would you conduct it?
1) reducing sugars include all monosaccharides (e.g. glucose) and some disaccharides (e.g. maltose and lactose)
2) you add benedict’s reagent (blue) to a sample and heat it in a water bath that’s been brought to a boil
3) if the tests positive it will form a coloured precipitate (solid particles suspended in the solution)
4) the higher the concentration of the reducing sugars, the further the colour change goes - you can use this to compare the amount of reducing sugar in different solutions. a more accurate way of doing this is to filter the solution and weigh the precipitate.
what is the test for non reducing sugars?
1) if the result of the reducing sugars test is negative, there could still be a non-reducing sugar present. to test for non-reducing sugars, like sucrose, first you have to break them down into monosaccharides
2) you do this by getting a new sample of the test solution, adding dilute hydrochloric acid and carefully heating it in a water bath that’s been brought to a boil. you then neutralise it with sodium hydrogencarbonate. then just carry out the benedict’s test as you would for a reducing sugar.
3) If the tests positive it will form a coloured precipitate (as for the reducing sugars test). if the tests negative the solution will stay blue, which means it doesn’t contain any sugars (either reducing or no-reducing).
what’s a polysaccharide
this is formed when more than two monosaccharides are joined together by condensation reactions. (loads of sugars joined together)
what are 3 components of starch are there
1) insoluble in water and doesn’t affect water potential so it doesn’t cause water to enter cells by osmosis which would make them swell. this makes it good for storage
2) its a mixture of two polysaccharides of alpha-glucose –> amylose and amylopectin
3) cells get energy from glucose and store this as starch
structure and function of amylose in starch?
- A LONG UNBRANCHED CHAIN of alpha glucose.
- the angles of the glyosidic bonds give it a COILED STRUCTURE almost like a cylinder.
- COMPACT so its really good for storage because lots can be fitted in a small place.
structure and function of amylopectin in starch?
- a long unbranched chain of alpha glucose
- its side branches allows the enzymes that break down the molecules to get at the glyosidic bonds easily (hydrolysis reaction) so glucose can be released quickly
what test is conducted for starch?
iodine test:
just add iodine dissolved in potassium iodine solution to test the sample
if there is starch present, the sample changes from browny orange to a dark blue black colour
3 components of glycogen and what is this a main energy store for?
main energy store in animals.
1) store glucose in glycogen (another polysaccharide of alpha glucose)
2) loads of branches –> quick release of glucose (e.g. fight of flight)
3) very compact molecules so good for storage
where is cellulose found and 3 components of it?
its a major component of cell walls in plants.
1) long, unbranched chains of beta glucose
2) when beta- glucose bond they form straight cellulose chains
3) cellulose chains are connected by hydrogen bonds to form strong fibres called microfibrils. the strong fibres mean cellulose provides structural support for cells (cell wall e.g.)
what is a triglyceride
they are a kind of lipid
what is the structure of a triglyceride?
1 glycerol and 3 fatty acids
fatty acid molecules have long ‘tails’ made of hydrocarbons. the tails are ‘hydrophobic’. these tails make lipids insoluble in water. all fatty acids have the same basic structure, but the hydrocarbon tail varies (which is to do with the variable ‘R’ group)
what are the two kinds of fatty acids and how are they different?
- saturated fatty acids don’t have any double bonds between their carbon atoms. the fatty acid is ‘saturated’ with hydrogen
- unsaturated fatty acids have at least one double bond between carbon atoms, which causes the chain to kink
(the difference is is in their hydrocarbon tails (R group)
how are phospholipids similar and different to triglycerides?
1) the lipids found in the cell membrane are phospholipids not triglycerides
2) phospholipids are pretty similar to triglycerides except one of the fatty acid molecules is replaced by a phosphate group
3) the phosphate group is hydrophilic. the fatty acid tails are hydrophobic. this is important to the cell membrane
what’s the structure of a phospholipid and a triglyceride?
phospholipid –> 1 phosphate ion, a glycerol and 2 fatty acids
triglyceride –> 1 glycerol and 3 fatty acids
name 2 structures and their related function of a triglyceride
1) the long hydrocarbon tails of the fatty acids contain lots of chemical energy - a load of energy is released when they’re broken down. because of these tails, lipids contain about twice as much energy per gram as carbohydrates.
2) they’re insoluble, so they don’t affect the water potential of the cell and cause water to enter the cell by osmosis (which would make them swell). the triglycerides clump together as insoluble droplets in cells because the fatty acid tails are hydrophobic - the tails face inwards, shielding themselves from water with their glycerol heads.
name 2 structures and their related function of a phospholipid
1) their heads are hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side.
2) the centre of the bilayer is hydrophobic, so water-soluble substances cant easily pass through it - the membrane acts as a barrier to those substances
what is the test for lipids and how do you conduct it?
emulsion test
1) shake the test substance with ethanol for about a minute so that it dissolves, then pour the solution into water
2) any lipid will show up as a milky emulsion
3) the more lipid there is, the more noticeable the milky colour will be
what are proteins made out of
amino acids
what are the monomers of proteins
amino acids
what is formed when two amino acids join together?
dipeptide
what is formed when more than two amino acids join together?
a polypeptide
what are proteins made up of?
one or more polypeptides (more than two amino acids joined together)
what is the structure of an amino acid
R
l
H2N - C - COOH
l
H
carboxyl group (COOH)
amine/ amino group (h2N)
variable group (R)
^ amino acids have the same general structure
what reactions joins two amino acids together
polypeptides are formed by condensation reaction between two amino acids. the bond formed is a peptide bond.
the reverse reaction happens during digestion
what four structural levels do proteins have?
primary structure
secondary structure
tertiary structure
quaternary structure
what is the primary structure of a protein?
this is the sequence of amino acids in the polypeptide chain
what is the secondary structure of a protein?
the polypeptide chain doesn’t remain flat and straight.
hydrogen bonds form between the amino acids in the chain.
this makes it automatically coil into alpha helix or fold into a beta pleated sheet - this is the secondary structure.
what is the tertiary structure of a protein?
the coiled or folded chain of amino acids is often coiled and folded further. more bonds form between different parts of the polypeptide chain, including hydrogen bonds and ionic bonds (attractions between negative and positive charges on different parts of the molecule).
disulfide bridge also form whenever two molecules of the amino acid cysteine come close together - the sulphur atom in one cysteine bonds to the sulphur atom in the other. for proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure
what is a quaternary structure of a protein?
some proteins are made from several different polypeptide chains held together by bonds. This is the way that these polypeptide chains are assembled together. this structure can be 3D if the protein has more than one polypeptide chain.
name 4 different kinds of proteins specialized to carry out particular jobs in your body?
enzymes —> roughly spherical in shape due to the tight folding of the polypeptide chains
antibodies —> two light (short) polypeptide chains and two heavy (long) polypeptide chains bonded together.
transport proteins—> these proteins are hydrophilic and hydrophobic amino acids which causes the protein to fold up and form a channel which transports ions across membranes.
structural proteins —> long polypeptide chains lying parrel to each other with cross links between them. they also have keratin and collagen
what is the biuret test for and how do you conduct it?
this test is used for proteins
1) the test solution must be alkaline, so you add a few drops of sodium hydroxide solution
2) then you add some copper sulfate solution
-if the protein is present the solution turns purple
-if there is no protein, the solution will stay blue. the colours are pale, so you need to look carefully.
what are enzymes? what do they have?
enzymes are biological catalysts that speed up chemical reactions. so they catalyse metabolic reactions - both at a cellular level (e.g. respiration) and for the organism as a whole (digestion)
they are proteins
they have an active site which is a specific shape due to the tertiary structure complimentary to a substrate so they bind.
they can affect structures in organisms as well as functions.
how do enzymes affect a reaction
they lower the activation energy which usually has to do with lowering the heat.
why do enzymes lower the activation energy?
so once a enzyme substrate complex has formed this lowers the activation energy because:
-if two substrate molecules need to be joined being attached to the enzyme holds them close together reducing any repulsion between the molecules so they can bond more easily.
-if the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate so the substrate molecule breaks up more easily.
what is the lock and key theory
where the substrate fits into the enzyme in the same way that a kay fits into a lock.
what is the induced fit?
the enzyme has a basic shape which is flexible and can mold/ slightly change when there is a substrate to get an exact fit.
how to enzymes differ from other enzymes
they have different tertiary structures and so a different shaped active site.
the primary structure of a protein is determined by a gene. if mutated, occurs in that gene it could change the tertiary structure of the enzyme produced.
what happens if an enzyme is denatured or the tertiary structure is altered?
a enzyme substrate complex wont form as the substrate wont fit and carry out the function so the rate of reaction will decrease
what happens to the rate of reaction when temperature increases?
1) temp increases which makes the enzyme molecules vibrate more.
2) if temp goes over a certain level then the vibration breaks some of the bonds that holds the enzymes shape
3) then the active site changes shape and the enzyme and the substrate no longer fit together
4) this leads to the denature of the enzyme and no longer functions as a catalyst
how are enzymes affected by pH?
most enzymes work best with the optimum pH 7 (neutral) value but there are some exceptions. pepsin, works best at pH2 which is found in the stomach.
however below or above the optimum pH value can mess up the ionic and hydrogen bonds that hold the enzymes tertiary structure in place which would damage the active site (denatured)
how does enzyme concentration affect rate of reaction?
there more enzymes, the higher the chance that a substate molecule will collide to form a enzyme-substrate complex. therefore increasing the rate of reaction.
if there is limited substrate and there is enough enzymes to deal with the amount of substrate so adding more enzymes will have no further effect.
how does the substrate concentration affect the rate of reaction up to a point?
the higher the concentration the faster the reaction as there is an increased chance for more successful collisions so more active sites will be used.
this is only true up until a saturation point. after that there are so many substrate molecules that the enzymes have about has much as they can cope with (active sites are full) so adding more will be no difference.
substrate concentration decreases with time during the reaction so if no other variables are changed the rate of reaction will decrease over time too. this makes the initial rate of reaction the highest rate of reaction.
what happens when enzyme activity becomes competitive inhibition
1) competitive inhibitor molecules have a similar shape to that of the substrate molecules
2) they compete with the substrate molecules to bind to the active site, but no reaction takes place.
3) instead they block the active site, so no substrate molecules can fit in it
4) how much the enzyme is inhibited depends on the relative concentrations of the inhibitor and the substate.
5)if there’s a high concentration of the inhibitor, it’ll take up nearly all the active sites and hardly any of the substrate will get to the enzyme.
6) but if there’s a higher concentration of substrate, then the substrates chances of getting to an active site before the inhibitor increase. so increasing the concentration of substrate will increase the rate of reaction (up to a point)
what is non-competitive inhibition?
1) non-competitive inhibitor molecules bind to the enzymes away from its active site
2) this causes the active site to change shape so the substrate molecules can no longer bind to it.
3) they don’t ‘compete’ with the substrate molecules to bind to the active site because they are different shape.
4) increasing the concentration of substrate wont make any difference to the reaction rate - enzyme activity will still be inhibited.
how can you measure the rate of an enzyme - controlled reaction?
1) measure how fast the product of the reaction is made
2) can measure how fast the substrate is Brocken down
how would you conduct the test for how fast the product of the reaction is made?
1) set up boiling tubes containing the same volume and concentration of hydrogen peroxide. to keep pH constant, add equal volumes of a suitable buffer solution (to resist change in pH when small amounts of acids or alkaline are added )to each tube.
2) set up the rest of the apparatus with the boiling tube contained with hydrogen peroxide solution and catalase enzyme secured with a bung with a hole for the delivery tube which leads through the water and up the measuring cylinder that is face down in the water.
3) put each boiling tube in a water bath at different temperatures (e.g. 10, 20, 30 and 40 degrees) along with another tube containing catalase then wait 5 mins before moving on so the enzymes heat up)
4) use a pipett to add the same volume and concentration of catalase to each boiling tube. then quickly attach the bung and delivery tube.
5) record how much oxygen is produced in the first minute of the reaction. use a stopwatch to measure the time.
6) repeat the experiment at each temperature three times and use the results to find an average (mean)
7) calculate the average rate of reaction at each temp by dividing the volume of oxygen produced by time taken (seconds). units cm^3s^-1
how would you conduct the test for how fast the substrate is broken down?
enzyme amylase catalyses the breakdown of starch to maltose.
set up with a spotting tile, pipett, test tube with starch solution and amylase enzyme and a stop watch.
1) a drop of iodine is placed in each well on the spotting tile.
2) drop the solution into each well with iodine using a pipett at regular intervals and the resulting colour is observed.
3) the iodine solution goes dark blue- black when starch is present but remains its normal browny- orange colour when starch isnt present
4) to test how fast the reaction takes for fast amylase works use a stop watch to time how long it takes for the iodine solution to no longer turn blue-black when starch/amylase mixture is added.
5) repeat the experiment three times at each amylase concentration
