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Flashcards in 1 biological molecules (concepts) Deck (32):

reducing sugars test (4)

1. Add 2cm3 of grinded sample to tube 2. Add 2cm3 of Benedict's solution (alkaline sol of Cu II sulfate) 3. Boil in water bath for 5 mins 4. Reducing sugars present > insoluble brick red precip of Cu I oxide


non-reducing sugars test (5)

1. Benedict's test > Blue? > no reducing sugars 2. Add 2cm3 of sample to 2cm3 of dilute HCl in a test tube and boil for 5 mins (to hydrolyse and di into mono) 3. Slowly add sodium hydrogencarbonate solution (to neutralise solution bc Benedict's doesn't work in acidic conditions) 4. Test with pH paper to check the solution is alkaline 5. Re-test Benedict's test > if non-reducing sugars were present, solution goes brick red due to reducing sugars produced from hydrolysis of non-reducing sugar


starch test (3)

1. At room temp, place 2cm3 of sample in test tube/depression in spotting tile 2. Add 2 drops of (yellow) iodine solution 3. Shake/stir > blue-black colour means starch is present


lipids test (2)

1. Dry, grease-free tube 2. Add ethanol, shake, water, shake > cloudy-white? Lipids present > Due to any lipid in sample finely dispersed in water to form an emulsion and light passing is refracted as it passes from oil to water droplets > cloudy Control: same, but with water instead of sample > should remain clear


proteins test (2)

1. At room temp, add equal vol of NaOH to sample in test tube 2. Add few drops of v dilute Cu II sulfate solution (Biuret's reagent) and mix > blue to purple? Peptide bonds present > protein present


starch: 1 info, 4 structure, 5 functions

Grains/granules in plants (seeds, chloroplasts, storage organs) Alpha glucose (200-100,000) Branched and unbranched Coiled and uncoiled Longer Insoluble - Y Large and insoluble - no diff Compact - stored Hydrolysed - transferred for resp Branched - enz > imp for animals w high met rates and therefore, high resp rate bc active


glycogen: 1 info, 4 structure, 5 functions

Granules in animals and bacteria (liver, muscles) Alpha glucose Highly branched Coiled Shorter Insoluble - Y Large and insoluble - no diff Compact - stored Hydrolysed - transferred for resp Branched - enz


cellulose: 1 info, 4 structure, 2 functions

Structural roles in cell walls Beta glucose Unbranched Long and straight and run parallel, link by H bonds between adjacent chains Grouped > microfibrils, grouped > fibres Strength, support, rigidity Prevents cell bursting as water enters, by exerting inward pressure preventing further influx of water > living plant cells turgid and push against each other > non-woody parts of plants semi-rigid > plants and leaves max s.a. for photosynthesis


4 lipid characteristics

contain C, H, O proportion of O to C and H is smaller than carbs insoluble in water soluble in organic solvents e.g. alcohol, acetone


4 roles of lipids

1. Source of energy - 2x more energy than same mass of carbs when oxidised and release valuable water 2. Waterproof - Insoluble in water, soluble in organic solvents (alcohol/acetone), plants and insects have waxy lipid cuticles conserving water, mammals produce oily secretion from sebaceous glands in skin 3. Insulation - slow conductor of heat > retain body heat, electrical insulation in myelin sheath of nerve cells 4. Protection - stored around delicate organs (kidney)


triglycerides structure related to function (4)

1. High energy storing C-H:C - energy 2. High H:O - water (animals in dry deserts) 3. Low mass:energy - storage (reduces mass for animals) 4. Large and non polar > insoluble > no effect on Y and no osmosis


phospholipids structure related to function (4)

1. Polar - in aq env, molecules form bilayer in cell-surface membs > hydrophobic barrier between in and out of cell 2. Heads help to hold at surface of cell-surface membrane 3. Allows glycolipids to form by combining w carbs within cell-surface memb > cell recognition 4. Flexibility & transfer of lip-sol subs across cell membs


role of 3 bonds in protein structure (3)

disulfide bridge - between 2 cysteine aa's, fairly strong, covalent bonds, not easily broken ionic bonds - between any carboxyl and amino groups not involved in making peptide bonds. weaker than disulfide and easily broken in pH changes hydrogen bonds - numerous, easily broken, between -NH and -C=O groups, causes 3D alpha helix


primary, secondary, tertiary, quaternary protein structure and function (4)

1. the sequence of amino acids that makes up the polypeptides of a protein 2. the way in which the chain of amino acids of the polypeptides of a protein is folded and twisted into a 3D coil - alpha helix 3. the twisting and folding of a whole polypeptide chain in a precise way, to get a complex, specific 3D structure, as determined by the amino acids of which it is composed 4. a number of polypeptide chains linked together, and sometimes associated with non-protein prosthetic groups, to form a large, complex protein


fibrous vs globular proteins

e.g. collagen (tendons - muscle to bone) - structural functions e.g. haemoglobin & enzymes - metabolic functions


collagen, 1, 2, 3, 4 structures (2+4)

-long chains running parallel linked by cross-bridges > stable -points where one collagen molecules starts and next begins are spread throughout fibre than all at same position along it unbranched polypeptide chain polypeptide chain v tightly wound (aa glycine helps close packing) chain twisted into a second helix three polypeptide chains wound together like fibres in a rope held by bonds between aa's of adjacent chains


induced fit model

flexible enzyme, the active site forms as the enzyme and substrate interact - the proximity of the substrate leads to a change in the enzyme that forms the functional active site, the enzyme puts a strain on the substrate, distorting bond(s) in the substrate, lowering the Ea needed to break the bond


lock and key model

rigid enzyme, substrate fits into the active site of one particular enzyme because "enzymes are specific in the reactions they catalyse" but "allosteric site binding altered enzyme activity!" therefore, the shape was altered by binding molecule - flexible not rigid


conditions for a chemical reaction to take place (3)

substrates must collide with sufficient energy to alter the arrangement of their atoms to form the products free energy of products must be less than substrates the minimum amount of energy needed to activate the reaction is required


for enzyme to work... (2)

1. physical contact w substrate 2. has complementary active site


measure enzyme-catalysed reactions by... (2)

1. Formation of products 2. Disappearance of substrate


measure rate of enzyme-catalysed reactions by...

drawing a normal line at chosen point and measure gradient


our bodies are 37oC because... (3)

1. Though high temp increases met activity, additional energy needed to maintain higher temps 2. Other proteins may denature 3. At high temps, further rise (illness) might denature enzymes


temperature affects enzymes by... (2)

1. Substrates have more kinetic energy > more successful collisions > more ESC 2. H bonds and others break > active site changes shape > denaturation


pH affects enzymes by... (2)

1. H+ ions affects bonding (H and ionic) of amino acids (between -NH2 and -COOH groups) that make up active site > substrate cannot attach > ESC can't form > may cause bonds of tertiary to break so active site changes shape 2. ! pH fluctuations usually small in organisms > only reduce enzyme activity, not denature


enzyme conc affects RoR by...

Low - excess substrate, limiting enzymes > low RoR Intermediate - max RoR / Vmax High - still max RoR


substrate conc affects RoR by...

Low - limiting substrate, excess enzymes, > low RoR Intermediate - max RoR / Vmax High - still max RoR


competitive inhibitors (6)

1. Active site 2. Not permanently bound 3. Doesn't change enzyme shape 4. Eventually all catalysed 5. Similar shape to substrate 6. Increase in substrate decreases inhibitor effect


non-competitive inhibitors (6)

1. Allosteric site 2. Permanently bound 3. Changes enzyme shape 4. Eventually none can be catalysed 5. Not ness similar shape to substrate 6. Increase in substrate has no effect on inhibitor


alpha and beta glucose structure


saturated and unsaturated fatty acid structure


amino acid structure

central carbon atom, amino group, carboxyl group, single hydrogen, variable R group