biological molecules Flashcards
what 3 elements make up carbohydrates?
carbon, hydrogen and oxygen
what 3 structures do carbohydrates exist in?
monosaccharides, disaccharides and polysaccharides.
monosaccharides
small chain molecules, soluble
examples of monosaccharides
glucose, galactose and fructose
disaccharides
2 monosaccharides
3 types of disaccharides
maltose (2 glucose)
sucrose (glucose + fructose)
lactose (glucose + galactose)
what are polysaccharides?
they are polymer containing many monosaccharides linked by glyosidic bonds.
features of glucose
it is a hexose (6 carbon) sugar.
formula of glucose
C6H12O6
are monosaccharides reducing sugars?
Yes, they all are, as they can donate an electron to another chemical.
what happens when a reducing sugar is in water?
the ring open up to display a free ketone or aldehyde group, this donates an electron and thus reduces the Benedict’s solution.
what is a condensation reaction?
joining of molecules to form chemical bonds, excluding water
it allows the formation of disaccharide molecules and eventually polysaccharide molecules.
how are polysaccharides formed?
through a condensation reaction
what are polysaccharides used for?
used as energy stores and as structural components of cells.
examples of polysaccharides
starch and cellulose in plants, and glycogen in animals.
features of starch
found in plants
helical structure
compact, can be hydrolysed back into alpha glucose for respiration
insoluble, cannot effect water potential
starch test
add iodine, if present turns blue-black
feature of glycogen
highly branched with 1-4 and 1-6 glycosidic bonds
broken down for respiration, storage molecule
animal cells, polymer of alpha glucose
features of cellulose
polymer of beta glucose
hydroxyl groups can form hydrogen bonds with other molecules
forms fibrils, provides strength for plant cell walls
straight chained 1-4 glycosidic hydrogen bonds
Benedict’s test for reducing sugars
reducing sugars= monosaccharides
1. test tube, add blue Benedict’s reagent, heat
2. reducing sugar goes brick red, negative stays blue
3. add Hal, boil to hydrolyse non-reducing sugar, add sodium hydrogen carbonate, do Benedict’s test again, positive result= non-reducing sugar
features of lipids
main functions= insulation, energy storage, protection
types of lipids
triglycerides (known as true fats or natural fats) and also waxes, steroids and cholesterol.
test for lipids
dissolve sample with ethanol
add water
lipid present= cloudy white emulsion
features of triglycerides
condensation of 3 fatty acids + 1 glycerol (forms ester bonds)
high ratio of C-H to C-C bonds= energy storage
metabolic water source (high ratio H-O atoms)
insoluble, no affect of water potential
low mass
features of phospholipids
1 fatty acids by a phosphate containing group
polar molecule
phosphate continuing group is hydrophilic due to negative charge
fatty acid chain= hydrophobic
form a bilayer to polar ends (membrane)
what is glycerol made up of?
three carbon atom, each has a hydroxyl group (OH) attached to it, hydrogen atoms occupy the remaining positions.
types of fatty acids
saturated, mono-saturated and polyunsaturated.
saturated fatty acids have?
no double bond between carbon atoms
mono-saturated fatty acids have?
one double bond between carbon atoms
polyunsaturated fatty acids have?
more than one double bond between carbon atoms, causes the molecule to bend and they can therefore pack together so closely, making them liquid at room temperature (oils).
features of amino acids
monomers from which proteins are made
what does a condensation reaction between 2 amino acid make?
dipeptide
what do many amino acids form?
polypeptide
features of protein structure
primary= sequence of amino acids
secondary= folding of sequence of amino acids into a-helices or b-pleated sheets, hydrogen bonds hold them together
tertiary= helices of sheets fold to form specific 3D structure
quaternary= more than 1 polypeptide chain, can bind to a prosthetic/ non-protein group.
Biuret test
add Biuret reagent to sample
positive= purple precipitate
negative= solution remains blue
features of enzymes
are proteins
catalyse reactions by lowering activation energy
induced fit model
substrate not complementary to active site
induces complementary change to active site
substrate binds forming enzyme-substrate complex
enzyme specificity
tertiary structure of active sit is extremely specific
only complementary substrates can bind to active site to form complex
effect of temp on enzyme activity
incr. slowly then rapidly, molecules gain kinetic energy
optimum temp at peak
after, rate decreases, enzyme denatures as H bonds broken
changes tertiary structure of active site
effect go pH on enzyme activity
similar trend to temp
imbalance of H+ and OH- ions can disrupt tertiary structure
effect on enzyme conc.
ready incr. then amount of substrates becomes limiting factor
effect of substrate conc.
steady incr. then amount of active sites becomes limiting factor
features of competitive enzyme inhibition
competitive inhibitor (structurally similar to normal substrate), can also bind
bad as normal substrate cannot so no complex formed
incr. in substrate conc. helps decrease effect of competitive inhibition
features of non-competitive enzyme inhibition
enzymes can have other sites (allosteric), non-competitive bind here
causes tertiary structure of active site to change permanently
substrate no longer complementary, cannot bind, no complex formed
what is DNA
deoxyribonucleic acid
holds genetic info
2 polynucleotide chains (double helix)
what is RNA
ribonucleic acid
transfers genetic info from DNA to ribosomes
1 short polynucleotide chain (single helix)
nucleotide structure
DNA + RNA are polymers of nucleotides so POLYNUCLEOTIDES
have a phosphate group, pentose and nitrogenous base
DNA bases
adenine, thymine, guanine, cytosine
RNA bases
adenine, racism guanine, cytosine
condensation of 2 nucleotides makes…
dinucleotide
what is semi-conservative DNA replication
one strand comes from original DNA (acts as template), other from newly synthesised strand
ensures genetic continuity between generations of cells
steps of semi-conservative replication
- DNA helices unwinds the double helix by breaking hydrogen bonds between complementary bases on the polynucleotide strand, forming 2 template strands
- new DNA nucleotides are attracted to exposed bases on template strands and base pairing occurs
- DNA polymerase joins adjacent nucleotides 5’ to 3’ to form phosphodiester bonds
evidence for semi-conservative replication
Meselson Stahl experiment= 2 test tubes with E-coli, one with 14N, other with 15N
let DNA grow from this then added together to grow for one generation
took 3 test tubes; 14N, 15N, 14+15N, spun in centrifuge
shows both sets of DNA were incorporated
structure of ATP
nucleotide derivative
ATP hydrolysis and synthesis is…
reversible
hydrolysis= ADP +Pi
synthesis is ADP + Pi= ATP
the forwards reaction of ATP is…
catalysed by ATP hydrolase
uses water to break off a phosphate
the backwards reaction of ATP is…
a condensation reaction
catalysed by ATP synthase
Pi can…
phosphorylate other compounds to make them more reactive
properties of ATP
releases small amounts of energy at a time
cannot leave the cell
immediate source of energy
soluble
feature of water
dipolar molecule
properties of water
important metabolite
important solvent in which metabolic reaction occur
relatively high heat capacity (amount of energy required to raise by 1 degree)
relatively ;are latent heat of vaporisation (cooling effect)
strong cohesion between water molecules provides surface tension
allows water molecules to attach to each other (cohesion)
important in formation of water columns
