Biological Molecules Flashcards
A level - AQA
describe how a peptide bond is formed between two amino acids to form a dipeptide
condensation reaction between amine and carboxyl
peptide bond formed between c and N
how is the secondary structure of a polypeptide produced by bonds between amino acid
hydrogen bonds
between NH and C=O
forming a helix
two proteins have the same number and type of amino acids but different tertiary structure, explain why
different sequences of amino acids which cause different primary structures
this forms ionic/hydrogen/disulphide bonds in different places
compare and contrast the processes by which water and inorganic ions enter
comparison :
• both move down a concentration gradient
• both move throught protein channels in membrane
contrast :
• ions can move against a concentration gradient by active transport
how to test for lipids
dissolve in alcohol and then add water
white emulsion shows presence of lipid
describe the structure of glycogen
polysaccharide of α glucose
joined by glycosidic bonds with branched structure
how is glycogen used as a source for energy in animals
hydrolysed into glucose
glucose used in respiration
how is glycogen used as a source for energy in animals
hydrolysed into glucose
glucose used in respiration
difference between phospholipid and triglyceride
in phospholipid a fatty acid is replaced by a phosphate
difference between saturated and unsaturated fatty acids
saturated only has single bonds between carbon and unsaturated has single and double bonds between carbons
why wouldn’t a fat substitute be digested by lipase
Enzymes are specific, the fat substitute isnt complementary so is unable to bind to lipase
Give ways ATP is a suitable source for cells to use
NOTICE IN CONTEXT OF STORAGE
- releases relatively small amount of energy (small manageable bursts)
- releases energy instantaneously
- phosphorylates other compounds, making them more reactive
- can be rapidly synthesized
- is not lost from cells
does anaerobic reaction occur in organelles?
is electron transport chain involved?
no
does aerobic reaction and photosynthesis occur in organelles?
is electron transport chain involved?
yes
write a simple equation to show how ATP is synthesized from ADP
ADP + Pi -> ATP
Give two ways that the properties of ATP make it a suitable source of energy in biological processes
NOTICE tHAT THE qUESTION IS ASKING IN CONTEXT OF RELEASE NOT STORAGE
- Energy released in small suitable amounts
- Soluble
- involves a simple/single reaction
why is it necessary for them tp synthesise such a large amount of ATP
- ATP can not be stored (bc its an immediate store of energy)
- ATP only releases a small amount of energy af a time
why would you suspend a mitochondria in an isotopic solution
prevent damage to mitochondria caused by differences in water potential/osmosis/water
when glucose is released what happens to energy not incorporated into ATP
released as heat
when one mole of glucose is respired anaerobically, only 2 moles of ATP are produced,
explain why less energy is released
glucose is only partly broken down
only broken down to lactate
at the end of a sprint race, a runner continues to breathe rapidly for some time, explain the advantage of this
lactis acid has been built up
oxygen used to break down lactic and convert it back to glucose
name the substance that muscles use as their immediately energy source
ATP
cats are lactose intolerant, lactase is used to hydrolyse lactose, making milk hydrolysis lactose free
why used lactase coated beads instead of direct lactase
1 beads are reusable 2 no need to remove lactase afterwords 3 allows continuous process 4 enzyme is more stable 5 avoid end product inhibition
suggest why does lactose-free milk (galactose is hydrolysed) tastes sweeter after than the cows milk with lactose
lactose is hydrolysed to glucose and galactose so more sugar molecules present
suggest why does lactose-free milk (galactose is hydrolysed) tastes sweeter after than the cows milk with lactose
lactose is hydrolysed to glucose and galactose so more sugar molecules present
give two ways the structure of starch is similar to cellulose
1 are polymers 2 contain glucose/carbon/hydrogen and oxygen 3 contain glycosidic bonds 4 have 1-4 links hydrogen bonding
give two ways starch is different from cellulose
1 starch contains α glucose and cellulose contains β glucose
2 starch is branched and coiled while cellulose is unbranched and straight
3 starch also has 1-6 branching
4 starch doesn’t have hydrogen bonds berween moleculess
5 starch has glucose/monomers same way up
6 starch doesn’t have fibres
explain difference between the structure of statch molecule and cellulose molecule
1 starch formed from α glucose but cellulose formed from β glucose
2 position of hydrogen and hydroxyl groups on carbon atom 1 inverted
explain one way in which starch molecules are adapted for their function in plant cells
1 insoluble 2 so dont affect water potential or 1 helical 2 compact or 1 large molecules 2 can not leave cells
explain how cellulose moelcules are adapted for their function in plants
long straight chains
become linked together by many hydrogen bonds to form fibrils
provide strength to cell wall
when wheat ia hydrolysed what sugars would you sugar would you expect and why?
maltose
salivary amilase breaks down starch
using the ides of water potential, explain why adults that can not digest lactose get diarrhoea when they drink milk
SOLUBLE lactose isnt hydrolysed
lowers water potential in the lumen
causing water to enter lumen by osmosis
explain the difference of effect of chewing vs chopping on the digestion in wheat
some strach is already digested when chewing in mouth
faster digestion of chewed starch
same amount of digestion at the end of time
describe competitive and non competitive inhibition of enzymes
1 inhibitors reduce binding of enzyme to substrate/prevent formation of enzyme substrate complex
2 competitive inhibition, inhibitor similar shape to substrate
3 binds in to active site
4 inhibition can be overcome by more substrate
5 non competitive inhibition, inhibitor binds to site on enzyme other than active site
6 changes shape of active site
7 cannot be overcome by adding more substrate
explain how sports drinks could provide an energy boost when running
1 drink contains carbohydrates so raises blood glucose concentration quickly
2 contains salt so glucose more rapidly absorbed
3 increases glucose to muscles for respiration
4 faster energy release
for enzyme related reactions how could you set up a control experiment?
boil the enzyme
describe the structure of proteins
polymers of amino acids
joined by peptide bonds
formed by condensation
primary structure is sequence of amino acids
secondary structure is folding of polypeptide chain due to hydrogen bonding to form alpha sheet or beta pleated sheet
tertiary structure is 3D folding due to hydrogen bonding, ionic bonding and disulphide bonds
quarternary structure is two or more peptide chains
describe how proteins are digested in the human gut
hydrolysis of peptide bonds
endopeptidaeses break polypeptides into smaller peptide chains
exopeptides remove terminal amino acids;
dipeptidaeses hydrolyse/break down dipeptides into amino acids
what sugars do you expect to produce when chewing and why
maltose
salivary enzymes breaks down starch
