what is a condensation reaction?
a reaction where water is produced as the bond forms.
what is a hydrolysis reaction?
adding water to break bonds.
what do the following reactions result in?
1) glucose + glucose
2) glucose + fructose
3) glucose + galactose
1) maltose
2) sucrose
3) lactose
how do you test for reducing sugars?
- add benedicts solution to the sample
- it goes from blue to brick red
- this is because it forms an insoluble precipitate of copper (II) oxide.
- it’s a reduction reaction as electrons are gained.
how do you test for non-reducing sugars?
- heat with hydrochloric acid.
- neutralise the acid by adding an alkaline.
- test with benedict’s solution
- it goes from blue to brick red if non-reducing sugars are present.
how do you test for starch?
add iodine to the solution, it turns blue/black in the presence of starch.
how is starch adapted for its function?
- long, branched chains means that there’s lots of space for enzyme action.
- it’s compact so it can be packed into small spaces
- doesn’t change the water potential of the cell as it’s insoluble.
how is glycogen adapted for its function?
- found in small amounts in the muscles and liver as fat is the main storage molecule.
- it has many branched chains, it takes up some space but it’s easily hydrolysed for quick energy release.
how is cellulose related to its function?
- made of beta glucose.
- joined together by 1,4 glycosidic bonds.
- every 2nd b-glucose molecule is rotated 180 degrees as it makes the bonds stronger.
- they’re straight, they can line up along eachother to form hydrogen crosslinks in order to make stems semi-rigid.
what is a triglyceride and what’s it made of?
- it’s an ester of fatty acids and glycerol.
- fatty acids and glycerol joined by a condensation reaction.
- 1 glycerol, 3 fatty acids.
how does the structure of triglycerides make them useful in living organisms?
- energy source: insoluble, long term reserves of energy in plants, animals etc.
- insulation: poor conductor of heat, prevents heat loss.
- molecules: steroids and some hormones are lipids.
what is a phospholipid?
- made of glycerol and 2 fatty acid molecules.
- polar molecule.
- hydrophilic head, hydrophobic tail.
- used in emulsifiers and in membrane bilayers
how do you test for lipids?
emulsion test
- mix ethanol and sample in equal volumes.
- shake to dissolve lipids
- add an equal volume of water and mix
- a white suspension indicates the presence of lipids
what is the primary structure of a protein?
the order of amino acids.
what is the secondary structure of a protein?
the chain begins to coil into a helix
what is the tertiary structure of a protein?
the chain coils further into a shape.
what is the quaternary structure of a protein?
when 2 or more polypeptide chains join together.
what makes enzymes specific?
their active site is complementary to the substrate because of its tertiary structure
what does the lock and key hypothesis state?
it states that the active site is only specific to one substrate, the reaction doesn’t take place with a different substrate, similar to a lock and key.
what does the induced fit model show?
- when the substrate binds to the active site, the shape of the active site changes slightly as it moves around the substrate.
- this puts pressure on the bonds holding it together, breaking them
- this increases the rate of reaction
what factors affect the activity of enzymes?
- temperature: enzyme action slows at low temperatures, but they become denatured at high temperatures as their tertiary structures change and the active site is no longer complementary to the substrate.
- pH: it can also cause denaturation, enzymes have an optimum pH
- conc. of enzyme: rate increases as there are more active sites.
- conc. of substrate: it becomes constant when all active sites are occupied.
- inhibitors
what do non-competitive inhibitors do?
they bind to the allosteric site, this changes the shape of the active site so it’s no longer complementary to the substrate.
what do competitive inhibitors do?
they compete with the substrate for the active site. it’s complementary to the active site so the reaction can’t happen once it’s inhibited as it doesn’t fit.
what are nucleotides made of?
- pentose sugar (deoxyribose for DNA, ribose for RNA)
- organic base (A,T,C OR G)
- phosphate group.
how is the structure of DNA adapted for its function?
- sugar-phosphate backbone protects the chemically reactive bases.
- weak hydrogen bonds hold the bases together, makes semi-conservative replication easy.
what is the structure of RNA?
- ribose sugar.
- thymine is replaces by uracil
describe the process of semi-conservative replication
- DNA helicase breaks the hydrogen bonds which holds the double-helix together
- it halves and it results in 2 separate strands.
- free nucleotides bind to their complementary bases.
- a sugar phosphate backbone forms.
- it results in 2 double-helical strands of DNA.
what is ATP made of?
- adenosine
- 3 phosphate groups
how is energy released from ATP?
the phosphate group is snapped off, which releases energy. this is also used in active transport as the carrier protein is phosphorylated to change its shape.
how is ATP adapted for its function?
-the phosphate can be reattached to the ADP so that the reaction can happen again.
what are the functions of water?
-dipolarity and hydrogen bonding: oxygen carries a small negative charge, hydrogen carries a small positive charge. it has no net charge as they’re balanced.
solvent properties: ions and polar molecules readily dissolve in water due to the polarity of their molecules