2. Specification 3. Specification 4. Water 75% of the human body
is water Between 70 to 90% of your cells is water Water is a polar
molecule That is, one end is a bit positive, and one end is a
bitnegative This means it acts as a solvent for polar compounds
Hydrogen bonding between oxygens and hydrogens ispossible due to
this dipolar character and allows water to 5. Due to the polar
nature of water, anything dissolved in water issurrounded by the
water molecules and this aids in dissolution.Once dissolved, the
chemicals are free to react and so many ofthe bodies reactions
require water to take place. Non-polar compounds such as lipids and
some proteins do notdissolve in water and so cluster together. This
is due to thehydrophobic nature of these compounds and this
property ishighly important in the function of some proteins. As
water is ubiquitous throughout the body, water is the primaryWater
as a solvent 6. Water with a volume of One litre What is its
molarity (concentration)? 1 litre = 1 kg = 1000 grams (as water has
a densityof 1)Moles = mass/RFMMoles = 1000/18 (the RFM of water is
18)Moles = 55.555555The number of moles in 1 litre is called the
Molarity55.555 mol/l is the same as 55.555 MWater: Concentration
trickquestion 7. Inorganic ions and compounds K+ - Potassium
Involved in nervous transmission and in plant guard cell turgidity
Ca2+ - Calcium Involved in nervous transmission and muscle
contraction and calcium phosphateis important in bone and teeth
structure. In plants makes up calcium pectate inthe middle lamella
of membranes. PO43- - Phosphate Highly important in cellular
signalling and in construction of DNA nucleotides,also a part of
calcium phosphate important for teeth and bones. ATP
andphospholipids are also phosphate dependent Mg2+ - Magnesium
Important in the structure of chlorophyll and some enzymes utilise
magnesium intheir active site and it can also form part of DNA
tertiary structure Fe2+/3+ - Iron Important in the structure of
haemoglobin as a carrier of oxygen HCO3- - Hydrogen Carbonate
Present in the blood as a buffering agent responsible for keeping
blood pH withina narrow biological range NO3- - Nitrate Important
in formation of proteins Na+ - Sodium Involved in nervous
transmission and in the kidney to reabsorb water and 8. Past-Paper
Questions 9. Cn(H2O)n i.e. Glucose is C6H12O6 Carbohydrate carbon
and hydrate (water)! Primarily used as short-term energy storage
Secondary function is intermediate-term energystorage i.e. starch
or glycogen Other functions include cell signalling, protein
agingand cell wall components of plantsCarbohydrates 10.
Carbohydrates -Monosaccharides The simplest of the sugars and the
major ones are;-Glucose and -GlucoseFructose 11. Condensation
Reaction This is a reaction between two or more moleculesthat ends
up with formation of a bond and theremoval of water The opposite
reaction is a hydrolysis reaction,where you use water to break a
bond 12. Carbohydrates - Disaccharides The bond formed between the
condensation of twomonosaccharides is called a GLYCOSIDICLINKAGE
Sucrose and Maltose are two of the most commondisaccharides++ 13.
Sucrose Glucose and fructose combined by condensationresults in
sucrose Bonded by a (1-2) glycosidic bond Has structural formula
C12H22O11 Sometimes called saccharose Common table sugar 14.
Maltose Glucose plus glucose results in formation of maltose Bonded
by a (1-4) glycosidic linkage Formed when amylase breaks down
starch 15. Carbohydrates - Polysaccharides Monosaccharides are
single sugars Disaccharides are two monosaccharides joinedtogether
Polysaccharides are chains of tens to thousands ofmonosaccharides
16. The structure of starch, cellulose and glycogen areall
different even though are all made of the samebasic block
(glucose)Carbohydrates - Polysaccharides 17. Carbohydrates -
Polysaccharides CelluloseConsists of thousands of (1-4) linked
glucosePresent in plant cell walls due to its rigidity and
strengthA straight chain polymer full of hydrogen bonds
StarchConsists of (1-4) linked glucosePresent in plant cells as a
storage moleculeConsists of linear and helical amylose and
branchedamylopectin GlycogenConsists of (1-4) linked glucose and
also (1-6) glucose atbranch pointsPresent in animal cells as a
storage molecule 18. Starch Amylose Amylopectin 19. Glycogen 20.
Carbohydrates - Pentose sugars Pentose sugars have FIVE sugars
present Structurally they look like pentagons HIGHLY important
class of sugars as ribose forms thebackbone of RNA (ribose nucleic
acid) anddeoxyribose forms the backbone of DNA 21. Tests for
carbohydrates Iodine test to look for the presence ofSTARCH Add a
solution of iodine and potassium iodideto a sample you think
contains starch. Ablue/black colours means you have starchpresent,
due to the presence of amylose thatallows the colour to form. If no
starch ispresent the colour remains yellow/orange. Clinistix test
for GLUCOSE Tests for glucose and glucose ONLY.Reagents in the
stick result in a colour changewhen glucose is oxidised by the
immobilisedenzyme present on the stick. The more 22. Benedicts test
to test for REDUCING SUGARS Reducing sugars like glucose can reduce
copperhydroxide present in the reagent in the presenceof heat
resulting in a positive brick red colourseen.Tests for
carbohydrates 23. Past-Paper Questions 24. Past-Paper Questions 25.
Past-Paper Questions 26. Lipids Lipids are things such as fats and
oils They do not mix with water (immiscible) They are formed from
the condensation ofGLYERCOL and FATTY ACIDS The structural building
block is a TRIGLYCERIDE 27. Saturated and unsaturated lipids The
fatty acid chains that makeup the lipid can beeither; saturated
unsaturated poly-unsaturated (just means more unsaturatedthan most)
The number of double bonds present leads to adecrease in melting
temperature 28. Fatty-acids in water In water, some lipids can
dissolve and form monolayerson the surface Other molecules may form
circular structures calledmicelles that sequester the hydrophobic
tails away fromthe water, encased within the outward facing
hydrophilic 29. Phospholipids A special kind of lipid Special
properties allow it to form double layeredmembranes Hydrophobic
tail Hydrophilic head 30. Phospholipids in water Phospholipids
contain two fatty acid chains Like fatty-acids they can form
monolayers on thesurface of water Or form double membrane
structures called 31. Phospholipid membranes Cholesterol is also an
important constituent ofmembranes It aids in permeabilising the
membrane The cell membrane and all the membranes of theorganelles
are made from phospholipid doublemembranes Due to the hydrophobic
centre and hydrophilicexternal regions of the membrane, this
explains why 32. Past-Paper Questions 33. Past-Paper Questions 34.
Proteins No matter how complex (and proteins can get VERYcomplex),
they are all formed from basic buildingblocks called Amino Acids
Condensation reactions between amino acids makePEPTIDES Combining
peptides is responsible for PROTEINformation 35. The peptide bond
CO-NH Peptide linkage Formed bycondensationreaction Results in
adipeptide This has an N and Cterminus 36. Protein Primary (1o)
Structure The amino acid sequenceof a polypeptide involvingpeptide
bonds The amino acids caneither be given as their fullnames of by
their oneletter abbreviations Just a string of aminoacids arranged
in apolypeptide chain 37. Protein Secondary (2o) Structure
Secondary structure elements are held together byhydrogen bonds
There are many more types of secondary structure Local regions
ofstructure; -helix -pleated sheet 38. Protein Tertiary (3o)
Structure The folding of apolypeptide uponitself into a complex3D
structure Regions of thepolypeptide are heldtogether by; Disulphide
bonds Ionic bonds Hydrogen bonds Hydrophobic 39. Protein Quaternary
(4o) Structure Not all proteins have thislevel of structure Formed
by a collection ofpolypeptides interacting in a3D structure
Haemoglobin is an exampleof a protein displayingquaternary
structure 40. Shape in relation to function Protein shape is a
major determinant of proteinfunction Globular proteins Such as
enzymes are more compressed and roundedin shape Water soluble
Contain 3o and 4o structure organisation Fibrous proteins Such as
collagen and other structural proteins aredrawn out in shape Water
insoluble 41. Shape in relation to function 42. Conjugated Proteins
A protein that functions through an interaction withother chemical
groups attached by covalent bondsor other types of bonding The
non-amino-acid group attached to conjugatedproteins is called the
PROSTHETIC GROUP Usually this is a vitamin or vitamin derivative
Examples include haemoglobin and glycoproteinsfound on cell
membranes. Glycoproteins containcarbohydrate as the prosthetic
group. 43. Haemoglobin and chlorophyll Haem is the prosthetic
groupfound in haemoglobin. It is theiron that carries the
oxygenaround the body, not the rest ofthe protein. Chlorophyll is a
pigment foundin the chloroplasts of plants.Magnesium is required
forsynthesis of this group. 44. Chromatography of amino acids Using
a piece of chromatography paper, mark a line afew centimetres up
from the bottom of the page. Using acapillary tube, spot on small
volumes of amino acids orsamples for analysis. Once dry, lower the
page carefully into a chamber full ofthe resolving agent you are to
use. BE CAREFUL NOTTO SHAKE THE VESSEL OR GET SOLVENT PAST THELINE
YOU MARKED. Once the page is securely in the vessel, close the lid
andleave the chromatogram to run until the solvent is a
fewcentimetres from the top of the page (half an hour to afew
hours, it caries). 45. Analysing the chromatogram Once the run is
complete, mark the solvent front andallow the paper to dry. Once
fully dry, spray the paperwith ninhydrin to visualise the amino
acid spots. Markthe centre of the spots and measure the
distancetravelled using a ruler. Also measure the solvent
frontdistance. Calculate the Rf values. 46. Tests for proteins
Biuret test Detects the presence of peptide bonds and can be used
toquantitate the amount of protein present. In the presence
ofpeptides, copper (II) ion formation leads to the formation of
aviolet/purple coloured coordination complex in alkalinesolution. A
sample is treated with an equal volume of 1% potassiumor sodium
hydroxide (strong base) followed by a few drops ofaqueous copper
(II) sulphate and a stabilising reagent. It willturn from blue to
violet in the presence of proteins. 47. Nucleic Acids DNA is the
molecule thatstores all of an organismsgenetic information. RNA is
a more robustmolecule, carrying themessage encoded by DNA(mRNA),
forming thebackbone of ribosomes(rRNA) and also allowingprotein
translation (tRNA). DNA and RNA are thecondensation products of 48.
Nucleotides Nucleic acids are condensation products ofnucleotides
The bond formed between nucleotides is aPHOSPHODIESTER BOND Forms
between the ribose sugar and thephosphate groups Nucleotides are
condensation products of; A pentose sugar Nitrogenous base 49.
Phosphodiester bond formation 50. The DNA double helix DNA is
double helical and isheld together bycomplementary base-pairs Two
anti-parallel helices This means that bothstrands are running
indifferent directions The phosphate-ribosebackbone is the legs of
theladder The rungs of the ladder are 51. Between A and T bases
there are 2 hydrogenbonds Between G and C bases there are 3
hydrogen 52. Differences between RNA and DNA 53. RNA species
Ribosomal RNA (rRNA) 80% of all RNA is thisspecies Forms the
backbone ofthe ribosome Transfer RNA (tRNA) Carries amino acids
tothe ribosome Necessary for proteinsynthesis Messenger RNA (mRNA)
Synthesised from DNA 54. The genetic code The order of the bases
along the double helixladder carries the information necessary
toproduce proteins The bases are read in three-letter groups
calledcodons 55. Past-Paper Questions 56. DNA replication
Replication of DNA is a SEMI-CONSERVATIVEprocess Involves the
opening of the DNA helix by DNAHELICASE. This is followed by the
synthesis ofcomplementary nucleic acid chains alongside each of 57.
Semi-Conservative One of each of the two template strands ends up
inone of the two new molecules 58. DNA Polymerase DNA polymerase is
the enzyme that synthesisesthe new strands of DNA It works in the 3
to 5 direction of DNA This creates a strand that runs 5 to 3 59.
The lagging strand HOWEVER The 5 to 3 DNA strand being replicated
Is called the LAGGING STRAND The polymerase cannot go in this
direction well So to transcribe the other DNA strand it makessmall
fragments called OKAZAKI FRAGMENTSthat get annealed together by DNA
LIGASE tomake a full copy of the lagging strand 60. Meselshn-Stahl
experiment They grew bacteria on a petri dish that contained15N
nitrogen The bacteria took this in and used it as theydivide and
synthesise new DNA The cells were then placed on a normal petri
dishand the bacteria were sampled from this timeforward The DNA was
analysed from each generation todetermine what happened to the
distribution of 61. Using a caesium density gradient (a type
ofcentrifugation) the 15N containing DNA from theparent generation
will be heavier than the 14Nnitrogen and so will be seen as a
different band The second generation will then contain a mixtureof
14 and 15N DNA as they started growing onnormal media and so only
had 15N nitrogen fromMeselshn-Stahl experiment
