biological molecules Flashcards
what is a monomer?
a large molecule made of a single repeating unit
what is polymer?
a large molecule made of a chain of repeating units covalently bonded
formed by a condensation reaction
define metabolism
the sum total of all biochemical reactions that occur in cells of living organisms
what is a condensation reaction?
-chemical reaction where a larger molecule is formed by joining smaller molecules
- new covalent bond is formed
-a water molecule is released
- anabolic
what is a hydrolysis reaction?
-splitting larger molecules into smaller ones
-covalent bond is broken
- a water molecule is used
-catabolic
how is water used as a metabolite?
water is used as a reactant in metabolic reactions
-required in photosynthesis or splitting disaccharides by hydrolysis
give 2 examples of where high latent heat of vaporisation is usefull?
-transpiration in plants
-sweating (for reducing dogs body heat with their tongue)
explain waters property of high latent heat of vaporisation?
-evaporation of water requires a lot of energy to break hydrogen bonds
-when water evaporates, from a surface it removes heat and has a cooling effect
why is a high boiling point for water important?
so water remains liquid over a wide range of temps
this means water is a good transport medium eg plasma in blood and mineral ions in xylem
what is the importance of water having a low density of ice?
-creates habitats, solid surface as ice floats
-insulation for organisms living under ice
explain how water creates thermostability?
-through high specific heat capacity
-large amounts of energy required to increase the temp of the water as H bonds prevent movement of water molecules
whats the importance of thermostability for life?
-large bodies of water are thermostable even when there are large external fluctuations of temp
explain cohesion?
whats the importance?
- H bonds cause molecules to stick together
- surface tension allows some organisms to walk on water eg pond skaters
-water can be transported up the xylem as it makes long thin colums of water dificicult to break
what is adhesion?
when water molecules stick to other surfaces eg wall of xylem
think adhesion, adhesive
how does water act as a solvent?
-due to polarity water can dissolve polar molecules like ions
-water molecules tend to cluster around charged parts of solute molecules
how does the transparency of water help life?
-aquatic organism such as algae and seaweed are able to photosynthesis as sunlight passes through the water
what is the role of ion in the blood?
the iron can attract and bind with an oxygen molecule
whats the structure of haemoglobin?
-a large protein molecule
-4 subunits
-found in eutheocytes (RBC)
-each subunit has a polypeptide chain and a non-protein haem group containing a single Fe2+ ion
whats the role of sodium ions in transporting glucodse/amino acids into cells?
used to co-transport in co-transporters linking with either glucose or amino acids
-co-transporters are specialised instrinsic proteins which span the phospholipid bilayer
what do phosphate groups in DNA and RNA allow?
phosphodiester bonds form between nucleotides forming polynucleotides
what are the 3 properties of monosacchardies?
- soluble in water
2.sweet tasting - form crystalls
whats the bonds that from between two monosaccarides?
glycosidic bond
what monosaccarides make the disacarides maltose,sucrose,and lactose?
maltose=glucose+glucose
sucrose=glucose+fructose
lactose=glucose+galactose
define monossacharide
simple sugars eg glucose fructose and ribose
define polysaccharides
polymers formed by combining many monoscharide molecules together by glycosidic bonds formed by condensation reaction
describe the stucture of starch
a coiled, compact polysacharide made from two polymers amylose and amylopectin and forms the main storage carbohydrate in plants
what are the characteristics of starch?
-insoluble=does not effect water potential, no osmosis
-coiled=compact,stored small spaces, can store large amount of energy in small space
describe amylose
alpha glucose monomers are joined by 1,4 gycosidic bonds
describe amylopectin
branched polymer with 1,4 glycosidic bonds between the alpha glucose and 1,6 glycosidic bonds between C1 and C6 of the adjescent alpha glucose
describe the structure of glycogen
-large polysaccharide formed by condensation reaction between an alpha glucose monomers with 1,4 and 1,6 glycosidic bonds
1,4=coiled
1,6=compact
what are the characteristics of glycogen?
-insoluble=water potential not affected so no osmosis
-compact=can be stored in small spaces
-coiled=large amount of energy can be stored in small space
-highly branched= many ends, meaning the glycosidic bonds can be rapidly hydrolised by enzymes to form alpha glucose monomers . easily transported, respiraton
describe the structure of cellulose
made of beta glucose monomers held by 1,4 glycosidic bonds formed by condensation reaction
each beta glucose is rotated 180 degrees to next resulting alternate glycosidic bonds
many straight chains forming parallel to each other linked together through hydrogen bonds between many -OH groups to from bundles called microfibrils
whats the role of the microfibrils?
very strong, support the cell wall and prevent from bursting when a plant cell becomes turgid
whats the structure of triglycerides?
one molecule of glycerol joined by three covalent ester bonds formed in a condensation reaction to 3 fatty acids
three molecules of water are removed
what are the 2 groups of lipids?
triglycerides and phospholipids
define saturated triglycerides
fatty acid has no C to C double bonds
all carbon atoms are linked to the maximised
in the fatty acid, what does the kinks do?
kink outwards
prevents closeness
functions of triglycerides?
-source of energy=higher H:O proportion when oxidised releases twice the energy
-act as insulators=fat is slow conductor of heat, helps retain body heat (thermal insulator)
=electrical insulator in myelin sheath in nerve cells
-waterproofing= large non-polar molecules, insoluble in water
-protection=shock absorber around delicate organs
whats the structure of phospholipids?
contain a glycerol molecule and 2 fatty acids
the third fatty acid is replaced by a phosphate group
the phosphate head is polar so attracts water (hydrophyllic)
the hydrocarbon chains are non-polar so repels water (hydrophobic)
how are phospholipids arranged in a bilayer?
-phospholipids form a bilayer of 2 layers
-the hydrophobic fatty acid tails point towards the centre of the bilayer
-hydrophillic heads point outwards
what does the phospholipid biayer do?
forms a barrier which controls the movement of molecules through it
hydrophobic tails prevent water soluble (e.g. ions) molecules directing directly through the bilayer
lipid soluble, non-polar, small molecules can diffuse through directly
what are the functions of proteins?
structural
enzymes
hormones
antibodies
protein receptors
transport proteins
antigens
what are proteins used for?
as structural components used in making new cells for growth and repair
also important as enzymes that controll metabolic reactions
what are amino acids?
monomer units of protein
what do amino acids consist of?
a central carbon atom linked with:
a hydrogen atom
amine group
variable region
carboxylic acid group
how many diff types of amino acids are there?
20
how is a dipeptide formed?
-condensation reaction between carboxylic acid of one amino acid and the amine group of another
-strong covalent bond called a peptide bond is formed
-water molecule is released
describe the primary structure of protein
the sequence of amino acids held by peptide bonds
describe the secondary structure of a protein
further folding of primary structure
polypeptide chain coils=alpha helix
or folds=beta pleated sheet
both held by many hydrogen bonds
describe the tertiary structure of a protein
further folding of the polypeptide chain to give a more complex shape
stabilised by:
-hydrogen bonds = between R groups
-ionic bonds =between R groups
-Disulphide bonds= covalent between sulfurs in R group of amino acid cyteine
-hydrophobic interations= between non-polar R groups - centre
describe the quaternary structure of a protein
more than one polypeptide chain
give an example of a protein with a quaternary structure, what does it consist of?
haemoglobin
-4 polypeptide chains
-2 alpha chains
-2 beta chains
-each chain has a haem group with an Fe2+ ion
what are the 2 main groups of 3D shaped molecules?
globular and fibrous proteins
what are fibrous proteins?
-they form long fibres
-have a regular, repetitive sequences of amino acids
-insoluble in water usually
-tend to have structural roles
give 3 examples of fibrous proteins
myosin in muscles
collagen in skin
keratin in hair
describe the structure of collagen
-3 left handed helixes - triple helix so more strength
-3 polypeptide chains held by hydrogen bonds
-every 1/3rd amino acid is glycine
what gives collagen its strength?
collagen molecules cross-link through covalent bonds to form fibres
describe the structure of globular proteins
-these fold up into a compact ball like shape
-hydrophobic R groups turned inwards to centre and hydrophilic R groups on outside means more water soluble
so metabolic role
role of globular proteins
metabolic role in living organisms
define precipitate
solid forming in a solution (benedicts)
define emulsion
fine droplets of one liquid dispensed in another liquid
(lipids test)
what are reducing sugars capable of giving away?
electrons
examples of reducing sugars?
fructose
glucose
galactose
describe the test for reducing sugars
add benedicts to sample of equal volumes in test tube
heat at 80 degrees in a waterbath
blue to brickred
describe the test for non-reducing sugars
-need to test for reducing first, if negative then can carry out non-reducing test
-place 1cm3 of sample in test tube
-add 5 drops of HCL (beaks glycosidic bonds releasing sugars)
-boil for 3 mins in water bath
-neutralise with 5 drops of NaOH
-add 1cm3 benedicts solution
-heat at 80 degrees for 5 mins in waterbath (hydrolyses the glycosidic bond releasing monosaccharides)
describe the test for starch
add 3 drops of iodine to 1cm3 sample
shake gently
orange to black
describe the test for protein
add equal volume of 1cm3 of biuret solution to sample in test tube
blue to lilac
describe the test for lipids
place 1cm3 of sample in a test tube
add 1cm3 of ethanol
shake
add water
shake
clear to white emulsion
after adding ethanol why should u shake?
to quicken the dissolving of fats
what chemicals are biological molecules made of?
carbon
hydrogen
oxygen
