biological molecules Flashcards
what are polymers
large, complex molecules made of long chains of monomers (e.g most carbohydrates)
what are monomers
small, basic molecular units (e.g monosaccharides, amino acids, nucleotides)
what elements do all carbohydrates contain
C (carbon), H (hydrogen), O (exygen)
what are monosaccharides
sugar that can be hydrolysed to give a simpler sugar (e.g glucose, fructose, galactose)
what is glucose
hexose sugar (monosaccharide with 6 carbon atoms in each molecule) , with two types (alpha and beta) which are isomers (molecules with same molecular formula, but atoms connected in a different way)
alpha
H at top, HO at bottom (same as other side)
beta
OH at top, H at bottom
what is a condensation reaction
when 2 molecules join together with the formation of a new chemical bond, and a water molecule released when bond is formed
condensation reaction example
two alpha glucoses joined together to form maltose (disaccharide), a glycosidic bond and a water molecule
glucose +… = disaccharide examples
2 alpha glucose = maltose
glucose + fructose = sucrose
glucose + galactose = lactose
what are disaccharides
2 monosaccharides joined by a condensation reaction
what is hydrolysis reaction
break down of the chemical bond between monomers using a water molecule
hydrolysis reaction example
carbohydrates broken down into monosaccharides using a water molecule
what is the test for sugars
Benedicts test
types of sugars
reducing (all monosaccharides and some disaccharides) and non-reducing (do not have an OH group attached to carbon atom)
test for reducing sugars
1) add benedicts reagent (blue) to sample
2)heat in a water bath thats been brought to the boil
positive = coloured precipitate (solid particles suspended in solution)
(none) blue-green-yellow-orange-red (most)
test for non-reducing
1)break down into monosaccharides by adding silute hydrochloric acid
2) heating in a water bath thats been brought to the boil
3)neutralise with sodium hydrogencarbonate
4)carry out same test as for reducing sugars
positive = coloured precipitate blue-red
what are polysaccharides
more than 2 monosaccharides joined by condensation reactions (e.g starch, glycogen, cellulose)
polysaccharide formation example
lots of alpha glucose joined with glycosidic bonds to form amlyose and water
starch function
plants store of excess glucose
starch structure
mixture of the polysaccharides amylose and amylopectin, insoluble in water (so doesn’t affect water potential, so water doesn’t enter cells through osmosis and cells don’t swell as a result = good for storage)
amylose
long, unchained branch of alpha glucose, coiled structure (due to angles of glycosidic bonds) = compact and good for storage
amylopectin
long, branched chain of alpha glucose, enzymes can break glycosidic bonds easily (due to side branches) = glucose can be released quickly
what is the test for starch
iodine test
the test for starch
1)add idoine dissolved in potassium iodide solution to sample
positive = colour change from browny-orange ti blue-black
glycogen function
animals store of excess glucose
glycogen structure
lots of side branches = glucose can be released quickly, long, compact = good for storage
cellulose function
structure in plant cell walls
cellulose structure
long, unbranched chains of beta glucose, straight chains (due to the bonds), hydrogen bonds linked to form microfibrils (making it strong= good for structural support)
what are triglycerides
kind of lipid
triglyceride structure
one molecule of glycerol with three fatty acids (forming hydrocarbon tail, which is insoluble in water (hydrophobic))
fatty acid structure
carbon atom in centre, attached to HO on the bottom left, O on bottom left with double bond, and variable R group hydrocaron tail on the right
triglyceride formation
condensation reaction between fatty acid and glycerol molecule, with the formation of an ester bond and a water molecule ( occurs 3 times total, one for each fatty acid)
types of fatty acids
saturated or unsaturated - difference is hydrocarbon tails (R groups)
saturated fatty acid
don’t have double bonds between carbon atoms (fatty acid is ‘saturated’ with hydrogen
unsaturated fatty acid
at least one double bond between carbon atoms, causing a kink in the chain
what are phospholipids
lipids found in the cell membrane
phospholipid structure
glycerol attached to 2 fatty acids (hydrophobic hydrocarbon tail) and a phosphate group (hydophilic)
triglyceride structure - function
energy storage molecules (long hydrocarbon tails contain lots of energy so lots is released when broken down, and they’re insoluble so doesn’t affect water potential and water doesn’t enter through osmosis)
triglyceride droplets
clump to form insoluble molecules as hydrophocib fatty acids face inwards
phospholipid structure - function
make up bilayer of cell membranes (hydrophobic tails and hydrophilic heads form a double later where water passes on either side, but can’t pass easily through it
what is the bilayer job
control what enters and leaves a cell
test for lipids
emulsion test
emulsion test
1) shake test substance with ethanol for a minute (suntil it dissolves)
2) pour solution into water
positive = milky emulsion - more milky means more fat
what are proteins
long chains of amino acids (amino acids = monomers) , one or more polypeptides joined together
what are dipeptides
2 amino acids joined together
what are polypeptides
more than 2 amino acids joined together
amino acid structure
C (carbon) attached to a carboxyl group (COOH), amino group (NH2) and R group (variable R group)
polypeptide formation
condensation reaction, amino acids join to form peptide bonds and a water molecule
protein structural levels
primary, secondary, tertiary, quaternary
primary structure
sequence of amino acids in the polypeptide chain
secondary structure
hydrogen bonds form between amino acids making it coil into an alpha helix, or fold into a beta pleated sheet
tertiary structure
more bonds form (hydrogen, ionic, disulfide bridges) so chain is coiled and folded further , for single polypeptide chain proteins its the final 3D structure
what are ionic bonds
attractions between negative and positive chrges on the molecules
what are disulfide bridges
bonds formed when 2 molecules of cysteine come close together (sulfur atoms in each bond to each other)
quaternary structure
the way that several different polypeptide chains are held together by bonds, for proteins with more than 1 polypeptide chain its the final 3D structure
protein functions
enzymes, antibodies, transport proteins, structural proteins
proteins as enzymes
roughly spherical (due to tight folding), soluble, often have roles in metabolism (e.g digestive enzymes)
proteins as antibodies
involved in immune response. made up of 2 light (short) and 2 heavy (long) polypeptide chains bonded together, have variable regions
proteins as transport proteins
(a.k.a channel proteins) present in cell membranes, contain hydrophobic and hydrophilic amino acids (= protein folds up to form channel), transport ions and molecules across membranes
proteins as structural proteins
physically strong, consist of long polypeptide chains lying parallel with cross-links between them (e.g keratin - hair and nails, collagen - connective tissue)
test for proteins
biuret test
biuret test
1) add sodium hydroxide solution (to make alkaline)
2) add copper sulfate solution
positive = solution turns purple from blue
negative = solution stays blue
what are enzymes
biological catalysts (for metabolic reactions) at a cellular level and for the organism as a whole, have an active site, can affect structures of an organism
what are catalysts
substance that speeds up a chemical reaction without being used up in the reaction itself
enzyme action
can be intracellular (within cells) or extracellular (outside cells)
how enzymes work
lower activation energy which speeds up the rate of a reaction by forming an enzyme-substrate complex with the complimentary substrate
enzyme in a joining reaction
being attached to the enzyme brings the substances close together, reducing repulsion meaning they can bond more easily
enzyme in a breakdown reaction
fitting into the active site puts strain on the bonds in the substrate, so they break up more easily
what is activation energy
certain amount of energy that needs to be supplied to the chemicals before the reaction can start (usually heat)
enzyme-substrate models
lock and key, induced fit
lock and key model
substrate fits into the enzyme as it is complimentary to the shape (enzyme is unchanged after reaction)
induced fit model
the substrate changes the active site shape to fit the substrate (active shape changes back once substrate is broken down)
active site shape
determined by tertiary structure (so if its altered, active site will change and substrate won’t fit) (e.g mutation in gene in primary structure = different tertiary structure)
factors that affect enzyme action
temperature, pH, enzyme/substrate concentration, inhibitors
temperature on enzyme action
higher temperature = faster rate up to a certain point
high temp. means molecules vibrate faster, so collide more with more energy so more likely to react) (become denatured
denatured due to temperature
particles vibrate more, which breaks bonds that hold enzyme in shape, so active site changes shape and can’t form an enzyme-substrate complex so can’t function as a catalyst
pH on enzyme action
optimum pH = fastest rate (lower/higher = denatured) (e.g pepsin optimum pH is 2, and is found in stomach which has acidic conditions)
denatured due to pH
above and below pH = H+ and OH- ions mess up the ionic and hydrogen bonds in tertiary structure, so changes shape
concentration of enzyme on enzyme action
more enzyme conc = faster rate (more likely to collide, so reaction rate increases) up to certain point if substrate is limited (as no more substrate will be available)
concentration of substrate on enzyme action
higher substrate conc = faster rate (more likely collisions so more complexes formed, so faster rate) up to a certain point (all active sites will be full so will be saturated) initial rate = fastest
types of inhibitors
competitive and non-competitive
competitive inhibitors
similar shape to substrate, bind to active site but no reaction takes place (blocks active site)
concentration of competitive inhibitors
high conc of inhibitor = take up nearly all active sites
high conc of subtrate = chance of substrate forming enzyme-substrate complex before inhibitor fills it increases, so rate of reaction increases
non-competitive inhibitors
bind to enzyme away from active site and change the structure meaning active site changes shape, and substrate can’t bind
concentration of non-competitive inhibitors
doesn’t change the rate
what is DNA
deoxyibonucleic acid
DNA function
used to store genetic information (all instructions an organism needs to grow and develop)
DNA structure
nucelotide (pentose sugar = dexoyribose, nitrogen containing organic base = adenine thymine cytosine and guanine, phosphate group)
what is a nucleotide
type of biological molecule, monomers of DNA and RNA, contain pentose sugar, phosphate group, organic base
what does organic mean
contains carbon
what is RNA
ribonucleic acid
RNA function
transfer genetic information from DNA to ribosomes
RNA structure
nucleotide (pentose sugar = ribose, nitrogen containing organic base = adenine uracil guanine and cytosine, phosphate group)
what are polynucleotides
polymer of nucleotides (that have joined via condensation reaction)
condensation reaction between nucleotides
between phosphate group of one and pentose sugar of other, forms phosphodiester bond and water molecule = sugar-phosphate backbone
phosphodiester bond
phosphate group and 2 ester bonds
double helix DNA
anitparallel strands twisted , joined by hydrogen bonds in complementary base pairing
complementary base pairing
adenine-thymine (2 hydrogen bonds) , cytosine-guaning (3 hydrogen bonds)`
single chain RNA
relatively short, single polynucleotide chain
DNA carrying genetic code
doubted as it has a relatively simple composition, until 1953. double helix structure determined by Watson and Crick
DNA replication
semi-conservative replication
semi-conservative replication method
1) DNA helicase breaks hydrogen bonds between bases to seperate strands
2) free nucleotides bind to the complimentary bases on the template strand
3) free nucleotides are joined together by enzyme DNA polymerase with phosphodiester bonds
4) 2 identical strands of DNA are made, containing half of the original DNA and half of the new DNA
enzyme DNA polymerase
moves in opposite ways (due to being complimentary to the 3’ (3 prime) end) so starts at 3’ and ends at 5’ (opposite ends on each strand)
semi-conservative replication discovery
designed by Watson and Crick, validated by Meselson and Stahl
validation of semi-conservative replication
1) N15 - heavy -DNA strand placed in centrifuge (settled at bottom of centrifuge tube)
2)N15 placed in N14 - light -broth
3)left to replicate
4)new strands placed in centrigue, and settled mid-way up the tube showing it was a combination
if it was conservative = new strand would have settled at top (light) and bottom (heavy) of tube
water structure
2 hydrogen, 1 oxygen joined by shared electrons
water atom charges
polar
oxygen = delta negative (unshared negative electrons give a slight negative charge) which attracts the
hydrogen = shared negative electrons mean the other side of the hydrogen atom are slightly positive)
water functions
transport, metabolite, solvent, temperature control
water for transport
cohesive (molecules stick together) due to being polar, = flows, so good for transport (e.g in columns up the xylem) and high surface tension when in contact with air, so can form droplets (e.g sweat, to evaporate)
water as a metabolite
metabolic reactions = condensation/hyrolysis, so release or require water molecules
water as a solvent
polar, so surround ionic substances (negative attracted to positive and vice versa) (e.g salt), meaning substance dissolves
water as temperature control
1) high latent heat of vaporisation - takes lots of energy to break hydrogen bonds, so lots of energy used up when it evaporates = cools substance down
2) can resist changes in temperature - hydrogen bonds can absorb a lot of energy (has high specific heat capacity) which stops rapid temperature changes
what is ATP
adenosine triphosphate
ATP structure
nucleotide derivative - nucleotide base adenine, pentose sugar ribose, three phosphate groups
ATP function
immediate source of energy in a cell (energy stored in high energy phosphate group)
ATP energy release
hydrolysis reaction (ATP - ADP & Pi with break of the phosphate bond using a water molecule, catalysed by enzyme ATP hydrolase)
what is ADP
adenosine diphosphate
ATP energy used
uses ADP and Pi, occurs during respiration and photosynthesis, creates ATP, catalysed by enzyme ATP dynthase
what is an ion
atom/group of atoms that has an electrical charge
positive charge = cation
negative = anion
what is an inorganic ion
doesn’t contain carbon (e.g ions in solution in cytoplasms of cells and body fluid of organisms
important ions
iron, hydrogen, sodium, phosphate
iron ions
Fe2+ - important part of haemoglobin (binds the oxygen in the haemoglobin and becomes Fe3+, until the oxygen is released) (also the centre of each polypeptide chain)
hydrogen ions
H+ - determine pH which affects enzyme controlled reactions, more H+ present = lower pH
sodium ions
Na+ - co-transport for glucose and amino acids across membranes
phosphate ions
PO43- - when attached to another molecule = phosphate group, the bonds between these store energy in ATP, essential part of ATP, DNA and RNA
