Biological molecules Flashcards
Hydrolysis reaction
Reaction which uses water to break down a polymer (incl. disaccharide or polysaccharide) into its constituent monomers by breaking glycocidic bonds
Condensation reaction
Reaction between monomer units to form polymers held together by glycosidic bonds, also forming small molecules of H20
Metabolism
The sum of all reaction in a cell or organism
Isotopes
Atoms of the same element with the same number of protons but different number of neutrons
General formula of a monosaccharide
(CH20)n where n=any number between 3 and 7
Isomer
Molecules with the same molecular formula but with atoms connected differently
Isomers of glucose
ALPHA glucose: on carbon 1 has H on top the OH
BETA glucose: on carbon 1 has OH on top then H
Glucose + glucose =
maltose
Glucose + fructose =
sucrose
Glucose + galactose =
lactose
Test for reducing sugars
- add benedict’s solution (copper (ii) suplfate) to food sample
- heat
- an insoluble red precipitate of copper (ii) oxide will form
Test for non-reducing sugars
- add Benedict’s solution to to foood sample
- heat
- if remains blue = no reducing sugar present
- add HCl + heat (HCl hydrolyses any disaccharides)
- add sodium hydrogencarbonate solution to neutralise
- check pH
- test with Benedict’s again
Test for starch
- add iodine
- if present = blue/black
which sugars are reducing?
all monosacharrides and some disaccharides
which sugars are non-reducing?
some disaccharides
3 main functions of starch in relation to structure
1) insoluble in water = good storage material and doesn’t affect water potential
2) amylose helixs forms compact shape = allows tight packing
3) amylopectine has many protruding ends which can be hydrolysed rapidly = allows rapid release of glucose
what is starch made up of?
made of two polymers of alpha glucose: - amylose - amylopectin monomers connected by glycosidic bonds formed in condensation reactions can be branched or unbranched
what is the structure of amylose?
- polysaccharide
- unbranched = coils
- glucose linked linearly with alpha 1-4 linkage
what is the structure of amylopectin?
-branched
structure of glycogen
- polymer of alpha glucose
- has more branches + shorter branches than starch
- more compact than amylopectin
function of glycogen
- compact structure allows faster hydrolysis than starch = faster release of glucose in animals/bacteria (higher surface area for enzymes to work)
- insoluble = doesn’t affect osmosis + doesn’t diffuse out cells
where is glycogen stored in animals
muscles and liver as small granules
what is cellulose made up of?
- alpha AND beta glucose (different to starch + glycogen)
- forms straight, unbranched chains (not coiled) which run parallel to each other with hydrogen bonds forming cross linkages
- cellulose molecules grouped together to form microfibrils then fibres
how is the structure of cellulose suited to its function?
- hydrogen bond cross links in thr long, unbranched fibrous structure gives great physical strenght - good for cell walls
- hydrogen bonds prevent water entering molecule so molecules are resistant to enzyme hydrolysis = strong
what are lipids made up of?
carbon, oxygen, hydrogen
the proportion of carbon to oxygen and hydrogen is smaller than in carbohydrates
are lipids insoluble or soluble?
insoluble in water
soluble in organic solvents, e.g. acetone or alcohols
what are the four roles of lipids?
- insulation
- energy source (when oxidised, more than carbs)
- waterproofing
- protection
what is the structure of a triglyceride?
- consists of : 3 fatty acids and 1 glycerol
- each fatty acid forms an ester bond with glycerol in a condensation reaction
- the difference between different lipids is due to the varying structure of fatty acids
whats the difference between a saturated, mono-unsaturated and a polyunsaturated fatty acid?
- saturated = no double bonds
- monounsaturated = a single double bond
- polyunsaturated = more than 1 double bond
functions of triglycerides related to their structure
- have a high ratio of energy-strong carbon-hydrogen bonds to carbon atoms = good energy source
- low mass to energy ratio = lots of energy in small area
- insoluble: doesn’t affect cell water potential
- when oxidised release water due to lots of hydrogen/oxygen
whats the difference between a triglyceride and a phopholipid
one fatty acid molecule is swapped for a phosphate group
where are phopholipids used and why?
cell membranes because they have:
- a hydrophobic tail (repel water)
- a hydrophillic head (attracts water)
so they form a bilayer, controlling what can enter/exit the cell (water-soluble substances can’t easily pass through)
steps in the emulsion test for lipids
- place test substance in test tube w/ ethanol + shake
- add distilled water
- any lipid = milky emulsion
