biological molecules Flashcards
how is water a polar molecule? ( H2O )
shared negative hydrogen electrons attracted to oxygen
other side of each hydrogen - slight positive charge
unshared negative electrons on oxygen - slight negative charge
partial positive + negative charge
what does water having a high specific heat capacity mean?
a lot of energy needed raise temp - hydrogen bonds between water molecules absorb a lot of energy ( not enough for water )
how is water having a high heat capacity helpful?
water doesn’t experience rapid temp changes
good habitat
what does water having a high latent heat of evaporation mean?
lots of heat needed to break hydrogen bonds
lots of energy used up when it evaporates
how is water having a high latent heat of evaporation helpful?
good for cooling things like mammals
what does water being cohesive mean?
good attraction between the molecules - polar
helps water flow
how is water’s cohesion helpful?
easily transported up plant stems in transpiration stream
how is water a good solvent?
polar
slight negative end of water molecule attracted to positive ion .etc
ions get completely surrounded by water molecules - dissolve
why is ice less dense than water?
water molecules further apart in ice - each forms 4 hydrogen bonds to other water molecules
lattice structure
how is ice being less dense than water useful?
ice forms insulating layer
organisms in water beneath don’t freeze
3 elements that make up a carbohydrate?
carbon + hydrogen + oxygen
monosaccharide?
disaccharide?
polysaccharide?
single sugar unit
2 monosaccharides joined
more than 2 monosaccharides
why is glucose a hexose monosaccharide?
six carbon atoms
what is the difference between alpha and beta glucose?
their OH groups are reversed
what is ribose?
a pentose monosaccharide
how are monosaccharides formed?
glycosidic bonds
what happens in a condensation reaction?
hydrogen atom on a monosaccahride bonds to an OH group on other
releases molecule of water ( lost )
what happens in a hydrolysis reaction?
molecule of water reacts with glycosidic bond
breaks glycosidic bond
( reverse of condensation )
what is the polysaccharide starch used for?
energy storage material in plants
broken down to release glucose - energy
what is starch made up of?
2 polysaccharides of alpha glucose
amylose + amylopectin
what is the structure of amylose?
long + unbranched chain of alpha glucose
angles of glycosidic bonds give a coiled structure
glycosidic bonds between carbons 1-4
explain the properties of amylose?
good for storage - compact
insoluble so water doesn’t enter cells by osmosis ( don’t swell )
what is the polysaccharide glycogen used for?
energy storage material in animals
what is glycogen made up of?
a polysaccharide of alpha glucose
what is the structure of glycogen?
lots of branches - stored glucose released quick
compact molecule - good for storage
what is the polysaccharide cellulose used for?
component in cell walls in plants
what is cellulose made up of?
beta glucose
what is the structure of cellulose?
long + unbranched + straight chains - beta glucose molecules bond
chains linked by hydrogen bonds - microfibrils ( strong fibres )
what is the structure of amylopectin?
long + branched chain of alpha glucose
side branches
glycosidic bonds between 1-4 + 1-6
explain the properties of amylopectin?
branches - allow the enzymes that break down the molecules to easily get glycosidic bonds easily
so glucose can be released quickly
what are triglycerides?
lipids
macromolecules - complex molecules + big molecular mass
carbon + hydrogen + oxygen
what do triglycerides have attached to it?
3 fatty acids
describe fatty acids?
have ‘long tails’ - hydrocarbons
tails are ‘hydrophobic’ - repel water molecules
tails make lipids insoluble in water
all have different hydrocarbon tails
how are triglycerides synthesised?
by formation of ester bond between each fatty acid + glycerol molecule
( esterification )
how is each ester bond formed?
condensation reaction
how do triglycerides break down?
when ester bonds are broken by hydrolysis
what are saturated + unsaturated fatty acids?
saturated - no double bond between carbon atoms + saturated with hydrogen
unsaturated - at least 1 double bond between carbon atoms
what are phospholipids + how do they differ from triglycerides?
macromolecules
1 fatty acid replaced with phosphate group
phosphate group - hydrophilic - attracts water molecules
what are triglycerides used for?
energy storage molecules in plants + animals
explain the properties of triglycerides from its structure?
tails - lots of chemical energy - energy released when broken so lipids have x2 energy as carbohydrates
insoluble - don’t cause water to enter by osmosis + don’t swell
bundle together as insoluble droplets as tails hydrophobic
tails face inwards - shield from water with glycerol heads
what are phospholipids used for?
in cell membrane of eukaryotes + prokaryotes - phospholipid layer
explain the properties of phospholipids from its structure?
phospholipid heads - hydrophilic
tails - hydrophobic
double layer with heads facing out towards water on each side
centre of bilayer - hydrophobic - soluble substances can’t easily pass through membrane
what is the structure of cholesterol?
hydrocarbon ring attached to hydrocarbon tail
ring - polar hydroxyl group attached
what is cholesterol used for?
regulating fluidity of cell membrane by interacting with phospholipid bilayer - eukaryotic cells
explain the properties of cholesterol from its structure?
small + flattened shape - fit in between phospholipid molecules in membrane
bind to tails of phospholipids at high temps - packed closely together - membrane less fluid
prevents phospholipids from packing closely together at low temps - increases membrane fluidity
what are proteins?
polymers
what are amino acids in proteins?
monomers
how is a dipeptide + polypeptide formed?
dipeptide - 2 amino acids join
polypeptide - more than 2 amino acids join
what are proteins made up of?
1 or more polypeptides
( lots of amino acids joined )
what is the structure of all amino acids?
carboxyl group ( -COOH )
amino group ( -NH2 ) attached to carbon atom
whats the difference between all amino acids?
the variable group ( R )
what elements make up amino acids?
carbon + oxygen + hydrogen + nitrogen
sometimes sulfur
how are amino acids joined together?
linked by peptide bonds - dipeptides + polypeptides
condensation reaction releases molecule of water
reverse adds water molecule to break peptide bond - hydrolysis
what is the primary structure of a protein?
sequence of amino acids in polypeptide chain
each protein has a different sequence
one change to an amino acid - changes structure of whole protein
what is the secondary structure of a protein?
hydrogen bonds form between amino acids nearby
coils into alpha helix / folds into beta pleated sheet
what is the tertiary structure of a protein?
coiled / folded chain of amino acids is further coiled / folded
more bonds form between parts of polypeptide chain
proteins made from 1 polypeptide chain- 3D structure
what is the quaternary structure of a protein?
how proteins from more than 1 polypeptide chain are assembled
e.g haemoglobin is made of 4 polypeptide chains
3D structure
what bonds hold primary structure together?
peptide bonds
what bonds hold secondary structure together?
hydrogen bonds
what bonds hold tertiary structure together?
ionic bonds - negatively charged R groups and postively charged R groups
disulfide bonds - 2 molecules of amino acid cysteine come close + the sulfur in one bonds to sulfur in other
hydrophobic + hydrophilic interactions - hydrophobic R groups come close so clump and hydrophilic R groups pushed to outside affecting how protein folds up
hydrogen bonds - between slightly positively charged hydrogen atoms in R groups + slightly negatively charged hydrogen atoms in other R groups
( polypeptide chain )
what bonds hold quaternary structure together?
determined by tertiary structure so influenced by all the bonds
how does a globular protein form + what does this make them?
hydrophobic + hydrophilic interactions in protein’s tertiary structure
soluble so easily transported in fluids
what are the 3 globular proteins + their functions?
haemoglobin - carries oxygen in red blood cells
conjugated protein - protein with a non protein group attached ( prosthetic group )
4 polypeptide chains has a prosthetic group - haem - contains iron for oxygen to bind to
insulin - hormone secreted by pancreas + regulates blood glucose level
soluble - transported in blood to tissues
2 polypeptide chains held by disulfide groups
amylase - enzyme catalyses breakdown of starch
single chain of amino acids
alpha helix + beta pleated sheets - secondary structure
what are fibrous proteins?
structural proteins
unreactive + insoluble + strong
what are the 3 fibrous proteins + their functions?
collagen - in animal connective tissues
( bone + skin + muscle )
strong molecule
minerals can bind to protein - increases rigidity
keratin - in external structures of animals
( skin + hair + nails )
flexible - skin or hard / tough - nails
elastin - in elastic connective tissue
( skin + large blood vessels + some ligaments )
tissues can return to original shape after being stretched
what is the role of calcium?
( cation )
involved in transmission of nerve impulses
involved in release of insulin
cofactor for enzymes
helps with bone formation
what is the role of sodium?
( cation )
generates nerve impulses
muscle contraction
regulates fluid balance
what is the role of potassium?
( cation )
generates nerve impulses
muscle contraction
regulates fluid balance
activates the enzymes for photosynthesis
what is the role of hydrogen?
( cation )
affects PH of substances - more H+ ions so creates acid
important for photosynthesis reactions
what is the role of ammonium?
( cation )
absorbed from soil by plants
important source of nitrogen
what is the role of nitrate?
( anion )
absorbed from soil by plants
important source of nitrogen
what is the role of hydrogencarbonate?
( anion )
acts as a buffer - maintains PH of blood
what is the role of chloride?
( anion )
involved in ‘chloride shift’ - maintains PH of blood in gas exchange
cofactor for enzyme amylase
involved in some nerve impulses
what is the role of phosphate?
( anion )
involved in photosynthesis + respiration
needed for synthesis of biological molecules: nucleotides, phospholipids, calcium phosphate
what is the role of hydroxide?
( anion )
affects PH of substances - more OH- ions so creates alkali
what is an inorganic ion?
an ion without carbon
test for reducing sugars?
add benedict’s to sample
heat in water bath
positive - precipitate - blue to brick red
higher concentration of reducing sugar = further colour change
negative - non reducing sugar present
test for non reducing sugars?
add dilute hydrochloric acid + heat in water bath
neutralise with sodium hydrogencarbonate
carry out benedict’s
positive - coloured precipitate
negative - stays blue - no sugar
test for glucose?
test strips coated in reagant
present - colour change
test for starch?
iodine
present - blue black
test for proteins?
biuret test:
add sodium hydroxide solution - makes it alkaline
add copper sulfate
present - purple
not present - stays blue
test for lipids?
emulsion test:
shake substance with ethanol
pour solution in water
present - milky emulsion
how does a calorimeter work?
measures the strength of coloured solution by seeing how much light passes through
measures absorbance
the more concentrated the colour of solution - the higher the absorbance
how do you measure the concentration of a glucose solution?
serial dilution technique:
make 5 serial dilutions with a dilution factor of 2:
line up 5 test tubes
add 10 cm of intial 40 Mm glucose solution to first test tube + 5 cm distilled water to other 4
draw 5 cm of solution from first test tube + add to distilled water in 2nd test tube + mix ( now 10 cm of solution half as concentrated as solution in first test tube - 20 Mm )
repeat 3x to give solutions of 10, 5, 2.5
how do you make calibration curve?
do benedict’s test on each solution
remove any precipitate
measure absorbance with calorimeter
make calibration curve with absorbance against glucose concentration
test unknown solution in same way as known + use curve to find its concentration
how does a biosensor work?
uses a biological molecule ( enzyme ) to detect a chemical
molecule produces a signal that is converted into an electrical signal by transducer ( part of biosensor )
electrical signal processed
how do glucose biosensors work?
determines concentration of glucose in a solution
uses enzyme glucose oxidase + electrodes
enzyme catalyses oxidation of glucose at electrodes
creates a charge + becomes electrical signal
electrical signal processed to work out initial glucose concentration
2 types of chromotography?
paper
thin layer
what is the mobile + stationary phase + what are they in each type?
mobile - molecules can move
mobile phase is the liquid solvent in both
stationary - molecules can’t move
paper - chromatography paper
thin layer - thin layer of solid ( glass / layer of solid / plastic plate )
what is the basic principle of chromatography for both?
mobile phase moves over stationary phase
components of each mixture spend different amounts of time in each phase
ones that spend longer in mobile - travel further
how do you identify unknown amino acids with chromatography?
draw pencil line near bottom of chromatography paper + put concentrated spot of the mixture of amino acids on it
( roll paper into cyclinder with spot on outside so it stands up )
add small amount of solvent ( butanol, glacial ethanoic acid, water ) to beaker
dip bottom of paper into it ( not spot )
cover with lid to stop solvent evaporating
different amino acids move with solvent
when solvent nearly reached top take paper out + mark solvent front with pencil
amino acids not coloured so spray with ninhydrin solution to turn them purple to see it
use Rf values to identify separated molecules
