Biological Molecules Flashcards
Hydrolysis reaction
Breaks a chemical bond between two molecules and involves the use of a molecule of water.
functions of carbohydrates
sources of energy
stores of energy
structural units
formula for monosaccharides
CnH2nOn
examples of monosaccharides
a-glucose
b-glucose
b-galactose
What are monosaccharides like?
Sweet tasting and soluble in water.
Maltose
A-glucose and a-glucose
Sucrose
A- glucose + fructose
Lactose
B-galactose + a-glucose
Cellulose
Long unbranched chains of b-glucose. Microfibrils are strong threads made of long cellulose chains running parallel to one other that are joined by h bonds. Stops cell wall bursting under osmotic pressure as it exerts inwards pressure. Cells stay rigid.
Starch
Plant cells
Energy store and source
A-glucose monomers joined by glycosidic bonds in a condensation reaction.
20-30% made of amylose(unbranched)
70-80% made of amylopectin (branched)
Glycogen
Animal cells
Energy store and source
A- glucose monomers
Dense granules in liver cells
Branched 1-4 and 1-6 glycosidic bonds so has many ends for glucose monomers to be removed when needed for respiration.
What are isomers?
Two or more molecules with the same molecular formula but who differ structurally.
Qualitative tests
If sample (carbohydrates) is present or not
Quantitative tests
How much of substance is present
Testing for reducing sugars
Benedicts reagent which is Copper (II) sulphate.
Add 2cm3 of food sample. Add 2cm3 of bendedicts reagent. ) Heat in water bath for 5 mins and if colour turns brick red there’s a pos result.
Testing for non-reducing sugars
Carry out reducing sugar test
Add HCl which hydrolyses disaccharides and polysaccharides into monosaccharides and put in water bath for 5 mins.
Add sodium hydrogencarbonate to neutralise test.
Add Benedict’s Reagent and place in water bath again. Colour turns brick red.
functions of lipids
source of energy in human diet
store of energy
helps to insulate body
around internal organs for protection
waterproofing
part of the structure of membranes
Trigylcerides
Glycerol and 3 fatty acids.
Non-polar so are hydrophobic and do not dissolve in water.
Contain a large number of carbon and hydrogen atoms so a great deal of energy can be released from triglycerides.
Glycerol
A 3 carbon molecule with an OH group bonded to each of the 3 carbons.
Saturated fatty acids
No C-C double covalent bonds
Mono-unsaturated fatty acids
A single double covalent bonds between carbon atoms
Polyunsaturated fatty acids
More then one double covalent bond between carbon atoms
formation of triglycerides
Glycerol molecule and fatty acid molecule react together to form an ester bond - esterification.
We also make a molecule of water so it’s a condensation rection.
Carry out reaction with 2 more fatty acid molecules.
Phospholipid
2 fatty acids+ glycerol + phosphate
Fatty acid tails are non-polar so are repelled by water. Hydrophobic.
When surrounded by water the phosphate group has a neg charge so is polar so the phosphate head is attracted to water. Hydrophilic.
Cholesterol
A lipid. Is hydrophobic and sits inbetween the fatty acid tails in the middle of the hydrophobic layer.
amino group
NH2
what is a gene
a sequence of bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide chain.
DNA triplets
specific sequences in sets of threes which don’t overlap.
each triplet encodes for a singe amino acid.
there are 64 DNA triplets which code for 20 amino acids.
what elements do amino acids contain?
carbon, hydrogen, nitrogen, oxygen and sulphur
(cysteine is the only amino acid that contains sulphur in it’s R group)
Dipeptides
formed by condensation of two amino acids
peptide bonds
Peptide bond forms between 2 amino acids in condensation reaction.
primary structure
a specific sequence of amino acids in a polypeptide chain
secondary structure
A chain of amino acids is not straight but twists. Formed when the chain of amino acids coils or folds to form an alpha helix or beta pleated sheet. Hydrogen bonds hold the coils or folds in place.
tertiary structure
The precise 3D shape of a protein held in place by bonds between the amino acids that lie close to each other.
What does an increase in the relative concentration of inhibitor molecules do?
more inhibitors collide with active sites and the effect of inhibitation will be greater as less enzyme-substrate complexes can form
an increase in substrate concentration
reduce effect of reversible competitive inhibitation as enzyme molecule is more likely to collide with substrate molecule then inhibitor molecule.
what does a non-competitive inhibitor do?
Binds to an enzyme of the allosteric site and disrupts the tertiary structure. This changed the shape of the active site so it’s no longer complementary to the substrate and prevents the formation of an ESC.
What is the induced fit model?
Shape of enzyme is altered so active site of the substrate fits around the substrate.
examples of polynucleotides
DNA and RNA
What are nucleotides formed from?
a pentose sugar
a nitrogen containing organic base
a phosphate group
pentose sugar in a DNA nucleotide
deoxyribose
pentose sugar in a RNA nucleotide
ribose
phosphodiester bonds
Formed from a condensation reaction between 2 DNA or 2 RNA nucleotides.
Linkage when two of the hydroxyl groups in phosphoric acid react with hydroxyl groups on the pentose sugars of two adjacent nucleotides to form two ester bonds.
Is DNA double or single stranded?
double
Is RNA double or single stranded?
single so it can move out the nucleus via the nuclear pore
What bases does DNA contain?
Adenine
Cytosine
Guanine
Thymine
What bases does RNA contain?
Adenine
Cytosine
Guanine
Uracil
purine bases
Adenine and guanine as they have a double ring structure
pyrimidine bases
Thymine, uracil and cytosine as they have a single ring structure
structure of a DNA molecule
Double helix with 2 polynucleotide chains being held together by hydrogen bonds between specific complementary base pairs.
how many hydrogen bonds between G and C?
3
how many hydrogen bonds between A and T?
2
Where is DNA?
In the nucleus of an eukaryotic cell each DNA molecule is tightly wound around histone proteins to form a chromosome.
Where does RNA transfer genetic info from and to?
From DNA to the ribosome.
Is a DNA or RNA strand longer?
DNA is longer.
Why is mRNA shorter?
Formed during transcription and consists of a sequence of nucleotide bases which are complementary to just a single gene
When does DNA replicate in the cell cycle?
During the S phase of interphase.
In what direction are nucleic acids synthesised?
5’-to-3’ direction.
Leading strand
As the DNA polymerase enzyme assembled new strands, this new strand is synthesised in one continuously growing length without interruption.
Logging strand
As the DNA polymerase is unable to move continuously it has to start and stop again resulting in the synthesis of short fragments. Opposite direction of growing replication fork.
Okazaki fragments
Joined by DNA ligase
Water
High latent heat of vaporisation so evaporating of water has a cooling effect.
High heat specific capacity which acts as a buffer and regulates temperature of things.
What is tension?
A pulling force that allows water to be pulled up
What is cohesion?
The strong attraction between water molecules as a result of hydrogen bonds
What is adhesion?
The attraction between the water molecules and the walls of the xylem vessel
What happens when body temp increases?
It is detected by thermoreceptors and the body responds by increasing the secretion of sweat on the skins surface.
As water has a high latent heat of vaporisation a lot of heat energy has to be transferred to make water evaporate into a gas to have a cooling effect.
ATP
Adenine tri phosphate
Formed from a molecule of adenine a molecule of ribose and their phosphate group
Immediate source of energy
Hydrolysis of ATP
H2O + ATP = ADP + Pi
Phosphocreatine
Found in muscle cells.
Broken down into phosphate and creatine by creatine kinase.
Phosphate used to resynthesise ATP.
Inhibitor
Substance that reduces or stops a reaction
Competitive inhibitors
Prevents formation of enzyme substrate complex by fitting to active site to form enzyme inhibitor complex
DNA replication
DNA helicase breaks h bonds between bases
DNA strands separate
Complementary DNA nucleotides base pair to template strand
DNA polymerase joins adjacent nucleotides
Phosphodiester bond
Semi-conservative
Test for starch
Iodine and colour turns from orange to blue/black
Emulsion test
Dissolve food sample in ethanol
Shake and add water
Cloudy white emulsion should form if lipids present
