module 2.1.2 - biological molecules Flashcards
what is a monosaccharide
these are the single sugar units that are used as monomers. they are soluble and sweet reducing sugars
what is glucose
it is a hexose sugar, C6H12O6. it is used for respiration
–> used as a respiratory substrate to provide energy for the formation of atp
what is a pentose pentose sugar
contains 5 carbons
eg. deoxyribose and ribose
what are the 2 types of glucose molecules
alpha and beta
draw both alpha and beta glucose
same but they differ by flipping the -OH and -H
what are dissacharrides
2 monosaccharides bonded by glycosidic bonds. they are soluble and sweet. most are reducing sugars except sucrose
what is the most common bond found in carbohydrates
1,4 glycosidic bonds
what does glucose and fructose form and what bonds are in between them
sucrose - 1,6 glycosidic bond
what do 2 glucose molecules formand briefly describe the components of its structure
maltose
- contains alpha glucose with alpha glycosidic bonds
- same direction
- 1,4 glycosidic bond
what does glucose and galactose form
lactose
- beta glucose
- beta glycosidic bonds
- sugars in opposing orientation
- 1,4 glycosidic bonds
how are disaccharides converted back to monosaccharides
by hydrolysis
what is a polysaccharide
large insoluble molecules consisting of many monosaccharides joined together via condensation reaction
what are the 3 examples of polysaccharides
starch, cellulose and glycogen
what is starch made up of
it is made up of 2 molecules
amylose and amylopectin
what is the structure of amylose
consists of a long, unbranched chain of alpha glucose subunits joined by 1,4 glycosdic bonds and all have same orientation
the chain of subunits coil up
the -OH group on the 2nd carbon of each subunit is hidden in the coil
- makes it less insoluble
- prevents amylose from affecting the water potential of the cell
- doesnt affect osmosis
what happens when an amylase-iodine complex is heated
when an iodine-amylose complex is heated to 60 degrees,the hydrogen bonds break, the helix unravels, and the iodine is released
what is the function of amylose
used for the storage of glucose subunits and energy in plants
- stored as grains within the cell
it is compact
glucose subunits can be easily removed from the molecule
- can be used as building blocks for other substances or as a substrate in respiration to release stored energy
describe the structure of amylopectin and glycogen
amylopectin and glycogen are made up of a glucose subunits bonded by 1,4 and 1,6 glycosidic bonds
- means they are branched and non-helical
- consists of 1 chain with no crosslinks between molecules
amylopectin branches form per 20 subunits and form per 10 subunits for glycogen
describe the function and properties of amylopectin
amylopectin is used for storage for glucose subunits and energy in plant cells. it is insoluble and compact. stored as granules and have all the glucose units in the same orientation
describe the function and properties of glycogen
use for storage for glucose subunits and energy in animal cells. it is insoluble and compact. stored as granules and have all the glucose units in the same orientation
has more 1,6 glycosidic bonds so it is more branched and there is more space where the enzymes can attach
- increase SA so that the molecule can be hydrolysed quickly
describe the structure of cellulose
consists of a long unbranched chain of β-glucose subunits
- the subunits are joined by 1,4 glycosidic bonds
- its beta glucose monomers alternate at 180 degrees to each other
- the chain of β-glucose subunits form a straight chain
state and explain the properties of cellulose
it is fibrous
- the hydroxyl groups on carbon 2 of each subunit are exposed, allowing hydrogen bonds to form between adjacent cellulose molecules
- some 60–70 molecules bind together to form a cellulose microfibril and many microfibrils join together to form macrofibrils
- cellulose is strong (high tensile strength) -because of the the hydrogen bonds that can form between adjacent fibrils- and completely insoluble
- it is used in plant cell walls and provides enough strength to support the whole plant
describe the function of cellulose
used in plant cell walls and provides enough strength to support the whole plant
name roles of lipids in living organisms
- as thermal insulation
- as an energy store
- to protect organs from mechanical damage
- in the membranes around cells to control the exit and entry of molecules into the cells
- as a component of steroid hormones such as testosterone
- for buoyancy
- to waterproof parts of the body (i.e skin)
- as a source of water via respiration
- as electrical insulation around neurones
- to aid the absorption, storage, and production of fat-soluble vitamins A, D, E, and K
what is a lipid and name a property
lipids are a large compound. are insoluble in water but soluble in organic solvent (ethanol)
what are the elements that make up lipids
C, H and O
name 3 examples of lipids
triglycerides, phospholipids and steroids
what is a triglyceride
a macromolecule containing 1 glycerol molecule, 3 fatty acid chains. the bonds between the glycerol and fatty acid is ester bonds
comment on the energy aspect of triglycerides and explain
are rich in energy and used to store excess energy
- can be broken down in aerobic respiration to release this energy
- water is also released, which can be useful for animals that live in dry environments — hence camels store fat in their humps
- the stores can be held under the skin and around major organs. it has the benefit of protecting the major organs from physical shock
comment on the insulation aspect of glycerides and explain
are also good insulators
- insulate animals that live in cold environments such as polar bears and aquatic mammals such as whales
- provide buoyancy for these mammals
what is a saturated fatty acid and where it is found
when each carbon atom has 2 H atoms attached so there is no double or triple bonds and found in animal fats
what is the melting point of saturated fatty acid and where is it found
they have a high melting point and more solid at room temp (eg. butter)
what happens when saturated fatty acids is eaten
can cause an increase in low density lipoprotein (LDL)
how does mycoprotein help with saturated fatty acid
has less lipid than meat from animals and more of it is unsaturated
- results in less of an increase in LDL
what is an unsaturated fatty acid
when there is less than 2 H atoms per carbon, there will be double or even triple bonds between adjacent
- may be called polyunsaturated
where are unsaturated fatty acids found
found in plant fats and oils
comment on the melting points of the unsaturated fatty acids
have lower melting points and more likely to be liquid at RTP (eg. spread and vegetable oil)
describe the structure of phospholipids
has 2 fatty acids and a phosphate group
- tails are hydrophobic (insoluble in water)
- head is hydrophilic (soluble in water)
explain how it forms a phospholipid bilayer
- phospholipids form bilayers with the hydrophobic ‘tails’ in the centre and the hydrophilic ‘heads’ pointing outwards to interact with the surrounding aqueous solution
what does the middle of the bilayer being hydrophobic mean
makes it difficult for polar molecules to pass through
what is a protein
are polymers consisting of long, unbranched chains of amino acids, which are held together by peptide bonds
how are the bonds between amino acids formed
by condensation reaction and occurs between the amine group of 1 amino acid and the carboxylic acid of another
how do 2 amino acids form. what do multiple amino acids form
dipeptide and polypeptide
name the 4 types of structure
primary, secondary, tertiary and quaternary structure
describe the primary structure
- sequence of amino acids, held together in a chain by covalent bonds called peptide bonds
- peptide bonds occur between the amine group of one amino acid and the carboxyl group of another
- the H from the amine group combines with the OH from the carboxyl group in a condensation reaction, with a molecule of water being produced.
describe the secondary structure
when the chain of amino acids becomes folded and coiled into regions with repeating patterns. two shapes are formed:
* alpha (α) helix — shaped like a coil spring
* beta (β) sheets — pleated like a folded sheet of paper
hydrogen bonds hold the folds and coils in place
describe the tertiary structure
final folds and coils are caused by the interactions between the R groups on the amino acids. some R groups attract or repel each other, and so interact to form a range of bonds that hold the 3D shape. these bonds include:
* hydrogen bonds between polar R groups
* ionic bonds between R groups with opposite charges
* covalent disulfide bonds between two sulfur-containing R groups
R groups are hydrophobic and twist away from water into the centre of the molecule and vice versa
describe the quaternary structure
consist of more than one polypeptide chain
describe the structure and properties of globular proteins
proteins that are highly folded to form a spherical shape
- these proteins are water soluble as they are folded so that the hydrophobic groups are on the inside and the hydrophilic are on the outside, so they can form hydrogen bonds with water
- they are active in metabolism and their activity relies on their three-dimensional shape
- their shape and activity are sensitive to temperature changes
- higher temperatures can cause distortion of their shape
describe the structure of haemoglobin
haemoglobin contains four polypeptide chains called subunits — two alpha (α) chains and two beta (β) chains
- haemoglobin is a conjugated protein as each subunit has a non-protein prosthetic group attached, called a haem group, which contains a single iron ion (Fe2+)
- one oxygen molecule can attach to each haem group, so a haemoglobin molecule can carry four oxygen molecules
describe the function of haemoglobin
is used to transport O2 in the form of oxyhaemoglobin
name an enzyme
amylase
describe the function and structure of amylase
hydrolyses the bonds between glucose subunits in amylose
- the molecule has regions that are coiled in an alpha (α) helix and other regions that are folded into beta (β) sheets
- the compact globular shape contains an active site that has a specific shape that is complementary to the shape of the substrate (in this case, amylose)
- the active site holds at least one calcium ion that acts as a cofactor — it is essential for the correct action of the enzyme
name a hormone
insulin
describe the function and structure of insulin
used to stimulate removal of excess glucose from the blood
- there are two polypeptides held together by disulfide bridges
- one polypeptide is 21 amino acids long and the second is 30 amino acids long
- the molecule has a specific three-dimensional shape that is complementary to the shape of a glycoprotein receptor on the surface of cells in the liver
describe the properties and structure of fibrous proteins
- have a regular sequence of amino acids that is repeated many times
- they are less soluble in water (usually totally insoluble) as they have few hydrophilic groups
- they have a quaternary structure, and tend to form fibres that have structural functions
- they are strong due to the bonding between their polypeptide chains
describe the function and structure of collagen
has three polypeptide chains wound around one another, forming a left handed helix
it contains C, H, O, and N. Its chains when adjacent are joined together by covalent bonds otherwise known as crosslinks
the crosslinks are staggered to avoid weak points in the molecule
collagen contains a high proportion of glycine (which is small, and is every 3rd amino acid in its structure) so its chains can lie close together and to twist. Its monomers are amino acids, which are not identical, and they are joined together by peptide bonds
it is not easily stretched as it is not elastic, however it is flexible
it provides strength in the walls of arteries to withstand the high blood pressure. it is found in tendons, which hold muscle to bone, and in bone, where it is hardened by calcium phosphate. it it also found in cartilage, ligaments, connective tissue, the bronchi, bronchioles, and trachea, and in skin
- it is insoluble as it only has a few hydrophilic R-groups on the outside of its molecules. many collagen fibres can join together via hydrogen bonding to form a fibril
what is the structure of keratin
has 2 polypeptide chains coiled together
what is the function of keratin
strong and is used for protecting delicate parts of the body (eg. fingernails, claws, hooves, horns, scales, hair and feathers)
the cells in the outer layer of skin also contain keratin, which makes them impermeable to water
what is the structure of elastin
linked by tropoelastin
- coiled like a spring and can stretch and recoil
what is the function of elastin
used whenever stretching and recoil is required
- eg. in the walls of arteries and airways, alveoli, skin and the wall of the bladder
what is an inorganic ions
are charged particles that have a number of important roles
these roles range from creating skeletal structures to nervous conduction and activating enzymes
what is the use of NH4+ (ammonium)
a component of amino acids, proteins and nucleic acids Involved in the:
* nitrogen cycle
* maintenance of pH
what is the use of Ca2+
increases the hardness of bones, teeth and the exoskeletons of crustaceans. it is also found in the middle lamella between plant cells, and:
* a factor in blood clotting
* involved in the control of muscle contraction and synaptic action
* activates enzymes such as amylase and lipase
what is the use of Na+
involved in:
* the regulation of water potentials in cells and body fluids
* the selective reabsorption of sugars and amino acids in the kidney
* the reabsorption of water in the kidney
* nervous transmission and muscle contraction
what is the use of K+
improves growth of leaves and flowers in plants involved in the:
* regulation of water potentials in cells and body fluids
* nervous transmission and muscle contraction
what is the use of Mg2+
absorbed by soil via active transport, found at the centre of chlorophyll as a component for absorbing light during photosynthesis
what is the use of H+
involved in:
* oxidative phosphorylation in respiration
* photophosphorylation in photosynthesis
* the transport of carbon dioxide in the blood
* the regulation of blood pH
* reduction reactions in metabolism
what is the use of Cl-
a cofactor in amylase and is involved in the:
* reabsorption of water in the kidney
* regulation of water potentials in cells and body fluids
* transport of carbon dioxide in the blood
* production of hydrochloric acid in the stomach
what is the use of OH-
involved in the regulation of blood pH
what is the use of PO4 3-
a component of phospholipids, ATP and nucleic acids
* increases the hardness of bones, teeth and the exoskeletons of crustaceans
* improves root growth in plants
what is the use of HCO3 -
Involved in the:
* regulation of blood pH
* transport of carbon dioxide in the blood
what is the use of NO3 -
absorbed by plants from the soil to be used as a component of amino acids, proteins and nucleic acids Involved in the nitrogen cycle
what is the test for proteins
biuret test
- dissolve in water . add Biuret
- colour change from blue to purple
biuret solution contains copper sulfate and sodium hydroxide
- if no protein is present, the mixture stays blue
what is the test for reducing sugars
eg. glucose
benedicts test
- dissolve in water. add Benedict’s reagent. heat at 80-90 degrees
- a precipitate forms. colour change from blue to brick red
what is the test for non reducing sugars
benedicts test
- test it for a reducing sugars to ensure none are present. then dissolve in water
- add a few drops of dilute HCl and boil for 2 mins
- neutralise by adding dilute NaOH. add benedicts reagent and reheat for 2 mins
- precipitate. goes from blue to brick red
what is the test for starch
iodine solution test
- dissolve in water. add iodine solution
- changes to black (if not present, remains orange
what is the test for lipids
emulsion test
- dissolve in alcohol and filter and add water to filtrate
- when water is added to filtrate, it will turn clooudy/milky
what is the purpose of a biosensor
converts a chemical variable into an electrical signal
- when the biosensor is dipped into a solution, the glucose diffuses towards immobilised enzymes
- these catalyse a reaction that releases hydrogen peroxide
- the hydrogen peroxide reacts with a platinum electrode to generate a current
- the current generated is proportional to the glucose concentration
how is a biosensor made
you would immobilise an enzyme/antibody/single strand of DNA, add your sample, and then if it (for DNA) hybridized, or forms a complex (for enzymes or antibodies) then a transducer would convert it into an electrical signal and this signal would be sent to a display where a quantitative concentration would be shown
what is meant by chromatography
a process used to separate mixtures of coloured compounds
what is meant by mixture
contains more than one compound, with compounds not being chemically bonded to each other, each of which has a different solubility in a given solvent
what are the stages of chromatography
- placing a small concentrated sample of the mixture solution onto a pencil line drawn above the bottom of the strip of chromatography paper
- the paper is then placed with one end in a shallow layer of solvent below said pencil line
- the solvent rises up through the paper by capillary action. when it passes the sample of mixture, the molecules in the mixture start to travel up the paper with the solvent
- the more soluble a compound is, the further it will travel in the mobile phase, so compounds separate in order of their solubility. non-polar substances move more quickly up the paper strip
- the paper acts as the stationary phase, and the solvent acts as the mobile phase
- if the compounds in the mixture are colourless, then you will need to stain them (i.e: ninhydrin for amino acids)
- whichever way you do chromatography, the stationary phase should be suspended in the mobile phase such that it does not touch the bottom of the container (i.e: clipped to some string hung over the container)
- you also want to stop the chromatography before the mobile phase reaches the top so that you can mark in pencil where the mobile phase got up to in order to measure Rf values for the compounds present
- the solvent front is the total distance moved by the solvent
what is the difference between paper chromatography and thin layer chromatography
its stationary phase tends to be a thin layer of absorbent material, such as silica gel, which spread onto a glass sheet
what does Rf stand for
retention factor
what is the equation for the Rf value
= distance moved by molecule
————————————–
distance moved by solvent front
explain how the students would use the calibration curve to estimate the glucose concentration (2)
– find the absorbance
– find the conc that corresponds to this absorbance
– by following the absorbance value across to line of best fit and then down to the conc
describe how you would carry out a controlled experiment to test this hypothesis without using a colorimeter
‘the higher the conc of glucose in the fruit juice, the sweeter it will be’ (4)
– taste the juice to see how sweet they are
– place a sample of each juice in a biosensor and take reading
– obtain rank order for sweetness
– compare rank orders for sweetness and glucose conc
– blind taste test to avoid biased
describe how a method that uses benedicts reagent and a colorimeter could be calibrated to measure the conc of lactose in an unknown conc (4)
– zero the colorimeter
– using a blank
– use red filter
– use known conc
– produce series dilutions
– construct calibration curve
– test unknown sample
– read from calibration curve to determine conc
suggest how you can test for the presence of trehalose
– carry out benedicts test
– if the test for reducing sugar negative, boil with dilute HCl and retest with benedicts
describe the specific heat capacity of water
water has a high specific heat capacity –> bc a lot of energy to overcome H bonds
- this means the water maintains a thermally stable environment for aquatic organisms and temperature of organisms change only slowly
- biological reactions functions correctly
describe the freezing of water
ice is less dense than water as it forms an open lattice structure so it floats, forming an insulating layer on the water
- prevents the water below the ice from freezing
- this means that the organisms beneath the ice do not freeze and nutrients can still circulate
- the ice itself can also act as a habitat for organisms such as polar bears
describe the evaporation of water
water has a high latent heat of vaporisation
- a lot of energy is needed to cause a liquid to change into a gas (evaporation), which is an efficient mechanism used to cool the surface of living things (eg. sweating)
describe the cohesion of water
the attraction of water molecules to each other, and produces surface tension
- this creates a habitat on the surface for invertebrates such as pond skaters
- enables continuous columns of water to be pulled up the xylem
describe the way water acts as a solvent
as the molecules are polar, water can dissolve a wide range of substances, and thus can transport substances around the body
- it allows ionic compounds like magnesium chloride to separate into their charged ions, and so dissolve in water as they are able to interact with it
- this allows organisms such as fish to take up said ions from the water
- water can thus act as both an external and an internal transport medium, and can be used to dilute toxic substances
describe the incompressibility of water
water cannot be compressed into a smaller volume. this means it can be pressurised and pumped in transport systems or used for support in hydrostatic skeletons
describe how water acts as a reactant
water molecules are used in a wide range of metabolic reactions such as hydrolysis and photosynthesis
describe the usefulness of water being transparent
this allows aquatic plants to carry out underwater photosynthesis
describe the usefulness of high density
this allows water to support organisms and allows for flotation
what are the monomers of nucleic acids
nucleotides
how many amino acids are there
20
what are the monomers of polysaccharides
monosaccharides
what are the monomers of proteins
amino acids
what are the monomers in carbohydrates and proteins joined by
covalent bonds
what is a condensation reaction
when 2 molecules join to become on larger molecule via the formation of a covalent bond and the release of a water molecule
how are bonds broken
by hydrolysis
what is a hydrolysis reaction
when molecules that were covalently bonded together are split apart using a water molecule
what is a carbohydrate made up of
carbon, oxygen and hydrogen
what is the general formula of carbohydrates
(CH2O)x
what are the 3 groups that carbohydrates are put into
monosaccharides, disaccharides and polysaccharides
