what are hydrogen bonds
Force of attraction between oppositely charged regions of neighbouring water molecules
define cohesion
Attraction between molecules of the same substance
define adhesion
attraction between molecules of different substances
properties of water
Good solvent
Can transport dissolved substances into and out of cells
Cohesive properties
Adhesive properties
high specific latent heat
high specific heat capacity
Why is water a good habitat (3)
Difference in structure between alpha and beta glucose
In alpha glucose OH below C1
In beta glucose OH above C1
which 2 polysaccharides are in starch
Amylose and Amylopectin
How is glucose stored in plants
As starch
How is glucose stored in animals and fungi
As glycogen
Examples of monosaccharides
glucose, fructose, galactose, ribose
Examples of disaccharides
maltose, sucrose, lactose
Examples of polysaccharides
starch, glycogen, cellulose
Condensation reaction
when 2 molecules join together releasing H2O
Hydrolysis reaction
1 water molecule required to break each bond
advantages of glucose being soluble
glucose can dissolve in cytosol of cells
can be transported in blood
Structure of alpha glucose
Structure of beta glucose
Structure of ribose
Structure of deoxyribose
Which monosaccharides make lactose
beta glucose + galactose
Which monosaccharides make sucrose
glucose + fructose
Which monosaccharides make maltose
glucose + glucose
How to use colorimeter?
(6 steps)
precipitate is filtered so only the blue benedicts solution remains
red light is shined through the solution because red is complimentary to blue light
a photoelectric cell measures the amount of red light transmitted through the blue benedicts solution
more red light is transmitted, higher the concentration of glucose
this is repeated with a range of known concentrations of glucose and the amount of red light transmitted is noted down
a calibration curve can be drawn, which can be used to work out unknown concentrations based on amount of red light transmitted
Structure of cellulose
Chain of beta glucose monomers
Each alternate monomer is flipped
Bonded with 1,4 -beta glycosidic bonds
Properties of cellulose (5)
Structure of Starch
branched molecule
made of 2 polysaccharide chains - amylose and amylopectin
Structure and properties of amylose
Structure
Unbranched
1,4 -alpha glycosidic bonds
twists to form helical structure and stabilised by hydrogen bonds
Properties
compact
insoluble
Why is amylose being insoluble an advantage
It does not affect osmotic balance of cells
Structure and property of amylopectin
Structure
branched
made of alpha glucose monomers
1-4 and 1-6 alpha glycosidic bonds
Properties
compact
glucose quickly hydrolysed
more insoluble than amylose
why is starch a good storage molecule of energy in plants (3)
insoluble so doesn’t affect osmotic balance of cell
large so cannot diffuse out of cell
compact so can store lots of glucose in small space
structure of glycogen (3)
more branched than amylopectin
made of alpha glucose monomers
1-4 and 1-6 alpha glycosidic bonds
why is glycogen a good store of glucose in animals (3)
compact
lots of free ends so glucose can be rapidly added or removed
useful as animals move around alot - high metabolic rate
where are major stores of glycogen found in animals
liver and muscle cells
how to test for reducing sugars
add sample to test tube
add equal volume benedicts reagent
heat gently in waterbath
observe colour change
why does benedicts reagent change colour in presence of reducing sugars
Cu2+ ions in benedicts are reduced to Cu+ ions
how to test for non reducing sugars
boil sample with dilute hydrochloric acid to hydrolyse into monosaccharides
add NaHCO3 to make solution alkaline
add benedicts reagent and heat in water bath
observe colour change
How to test for starch
Add few drops of iodine to sample
colour change from orange to black if positive
how does a biosensor work
proteins such as enzymes or antibodies are used to detect presence of biological molecules
what is the substance being tested in a biosensor called
analyte
3 types of lipids
triglycerides, phospholipids, sterols
structure of triglycerides
3 fatty acid molecules attached to 1 molecule of glycerol
What is a saturated triglyceride
no double bonds between carbon atoms in fatty acid tails
why is boiling point of unsaturated triglycerides lower (3)
double bond causes kinks in structure of fatty acid tails
molecules cannot pack closely together
weaker Van der Waals forces
function of triglycerides (6)
energy store
respiratory substrate
thermal insulator (blubber in seals)
protection of internal organs
aids in buoyancy (whales)
waterproofs fur (otters)
Why are triglycerides a good energy store (3)
2x more energy dense compared to same mass of glucose
due to large number of C-H bonds
insoluble so does not affect osmotic balance of cells
why are triglycerides insoluble
because nonpolar fatty acid chain does not form hydrogen bonds with water
structure of phospholipids
1 phosphate group and 2 fatty acid chains bound to 1 glycerol molecule
why is the head of phospholipids hydrophillic
due to negatively charged phosphate group
function of phospholipids (3)
cell membrane
act as emulsifiers in food
regulate cellular activities such as cell migration
how do phospholipids act as emulsifiers in food
they prevent water and oil forming seperate layers by dispersing oil droplets
name of bond between phosphate group and glycerol in phospholipids
phosphate ester bond
function of cholesterol in body (4)
regulates fluidity of cell membrane
used in liver to produce bile
used to make vitamin D
used as starting point for many hormones
what is the general structure of an amino acid
amino group (NH2), carbon, hydrogen, R-group and carboxyl group (COOH)
how is a peptide bond formed
when amino group and carboxyl group react in a condensation reaction
which enzyme catalyses formation of peptide bonds in ribosome
peptidyl transferase
what is a dipeptide
molecule formed by 2 amino acids
what is a polypeptide
molecule formed from 3 or more amino acids
what are the 4 levels of protein structure
primary, secondary, teritiary, quaternary
what is the primary structure of proteins
the specific sequence of amino acids in the polypeptide chain
what determines the primary structure of proteins
base sequence in the gene for that protein
what does primary structure of proteins affect
determines final 3d shape of protein
what is the secondary structure of proteins
either alpha helices or beta pleated sheets are formed due to hydrogen bonds forming between peptide bonds
what is the tertiary structure of proteins
interactions between R - groups of amino acids
determines final shape of polypeptide chain
what are the interactions that occur in tertiary structure of proteins
hydrophillic and hydrophobic - weak interactions between polar and non-polar R groups
hydrogen bonds - formed formed between OH groups of R groups
ionic bonds - bonds between oppositely charged R groups
disulfide bridges - covalent bonds between sulfur atoms in R groups
what is the quaternary structure of proteins
interactions between 2 or more different polypeptide chains called subunits
properties of globular proteins (3)
Soluble
roughly spherical in shape
play a metabolic role in body
why are globular proteins soluble
because they have hydrophillic R groups on the outside
Structure of haemoglobin (2)
conjugated protein made of 2 alpha and 2 beta subunits
each subunit has prosthetic haem group
which metal ion is in a haem group
Fe2+
function of haemoglobin
binds reversibly to oxygen to transport it in blood
Structure of insulin
2 subunits linked by disulfide bridges
function of insulin
regulates blood sugar levels
structure of lyzozyme
single polypeptide chain
folds to form groove on surface which is the active site
function of lyzosyme emzyme
catalyse breakdown of a molecule in bacterial cell wall
where is lyzosyme enzyme found
tears and saliva
structure of catalase
conjugated protein with 4 haem groups
function of catalase (2)
breaks down hydrogen peroxide into hydrogen and oxygen
prevents build up of hydrogen peroxide in cells
properties of fibrous proteins (4)
insoluble
play a structural role in body
long rope-like molecules
organised structure
why are fibrous proteins insoluble
have large proportion of amino acids with hydrophobic R groups
why do fibrous proteins have an organised structure
repetitive amino acid sequence in primary structure
what is collagen (2)
connective tissue found in skin, tendons, ligaments and nervous system
used for shock absorbtion
properties of collagen
strong and flexible
what is keratin
strong protein found in hair and nails
properties of keratin
very strong due to large number of disulfide bridges
what is elastin
protein found in elastic fibers in skin, walls of blood vessels, alveoli
properties of elastin
very flexible - allows elastic recoil
how to perform emulsion test for lipids
mix sample with ethanol
mix ethanol-sample solution with water and shake
look for white emulsion
why is starch compact
has lots of branches
helical shape
3 marks
describe how structure of llama haemoglobin is likely to be different from that of camel haemoglobin with reference to the four levels of protein structure (6 marks)
difference in primary structure
different amino acid sequence
one amino acid changed
amino acid change could cause change in secondary structure
initial coiling of polypeptide change different
different number of hydrogen bonds formed
different arrangement of alpha helices, beta pleated sheets
amino acid change could cause change in tertiary structure
different 3d shapes of polypeptide chains
ionic bonds, disulfide bridges
amino acid change has not changed quaternary structure
alpha and beta subunits still able to form haemoglobin in both camel and llama
2 marks
3 marks`
describe and explain how the structure and properties of different carbohydrates suit them to their role as energy storage molecules in plants and animals (6)
describe and explain how the structure and properties of lipids suit them to their role as energy storage molecules in plants and animals (4)
1 mark
Lipids less dense than protein
explain how water molecules can form hydrogen bonds with nitrate ions (NO3-) (2 marks)
water molecules are polar
nitrate ion is negatively charged
hydrogen bonds form between H on water and O on nitrate