2.1.2 Biological Molecules Flashcards
Name the interaction between the two molecules of water
Hydrogen bond
Explain how hydrogen bonds form between two molecules of water
Unequal sharing of the electrons in the O-H bonds of water. Oxygen atom is slightly negative and hydrogen atoms are slightly posiitve. Slightly positive hydrogen atoms in one water molecule are atracted to the slightly negative atom in another water molecule
Describe how polymers are found from their constituent monomers
Polymers(long chain of induvidual monomers) formed by condensation reactions between many monomers where a water molecule is released in each of these reactions
Define a monosaccharides
Monosaccharides are the simplest carbohydrates, soluble, full of carbon hydrogen bonds for energy storage
Define an isomer
Molecules with the same formula but different atom arrangements in space, such as glucose
Define a disaccharides
Formed when two monosaccharides react in a condensation reaction,forming a glycosdic bond
Two glucose molecules can combine to form maltose. Describe the chemical reaction that give rise to maltose
Join togther covalently through a condensation reaction, relesse a water molecule, forms a glycosdic bond between 2 monosachharides to form maltose
Describe the procedure when performing a Benedicts test
Sample is heated with Benedict solution (alkaline copper(2) sulfate)
Changes colour of the solution from blue to green to yellow and then orange- red
Orange red precpitate would form if reducing sugars are present
State wether amylose or amylopectin of starch is hydrolysed faster and why
Amylopectin because it has branches, more free ends so can be hydrolysed more rapidly
State the bond that link glucose molecules together in amylose molecules
1-4 glycosdic bond
Give a summary of starch
Plant based energy storage molecule - made of 2 types of alpha glucose polymers- amylose and amylopectin
Insouble - no effect on WP
Branching - site for hydrolysis
Large molecule- many glucose molecules for respiration
Describe the structure of glycogen and explain how its structure is related to its function
Polysacharide made of ALPHA glucose molecule joined together by 1-4 and 1-6 glycosdlic bond
Chains with glucose monomers joined only by 1,4 glycosdic bonds are small, glycogen has less tedency to coil
1,6 glycosdic bonds present, give gylcogen a highty branched strcuture therefore high number of acessible ends, enable many enzymes to rapidly hydrolyse glycogen
State where glycogen is stored in humans
Liver and muscles
Describe the structure of cellulose
Polysacharide made up of beta glucose monosacharides bonded togther by 1,4 glycosdic bonds
Chains of beta glucose straight and lie side by side
Straight due to hydroxyl and hydrogen groups being inverted on carbon-1 of beta glucose
Within a chain, rotation of sucessive beta glucose molecules by 180 for glycosidic bond formation between them
Explain how the function of cellulose is related to its structure
H bonding within the chains of BETA glucose in a molecule of cellulose strengthens them and prevents spiralling
H bonding between different chains of the cellulose gives the whole structure strength
Strong glycosidic bonds within chains and h bonds between chains give the cell wall of the plant a high tensile strenght
Compare the structure of triglyceride and phospholipids
Triglycerides made up of glycerol and three fatty acids joined by condesation reaction
Phospholipids made up of glycerol, 2 fatty acids and one phosphate group
Describe the difference between saturated and unsaturated fatty acids
Saturated - no carbon carbon double bonds in the hydrocarbon atom, max number of hydrogen
Unsaturated - double bonds in the fatty acid chain
What are ester bonds
Ester bonds ( C- O-C=O) are covalent bonds formed in condensation and broken in hydrolysis. Formed between fatty acids and glycerol Fatty acids can join any of the 3 hydroxyl groups on glycerol
Describe how the structure of chlosetrol is different from triglyceride
Chlosterol is not made from fatty acids or glycerol
4 fused hydrocarbon rings (isoprene units) forming the steroid structure, not present in triglycerides
State 2 different roles of lipids
Important component of the CSM
use as a source of energy
Give an overal summary of AA
Contain an amino group, carboxyl group, hydrogen and one 20 variable R groups
Plants synthesise all thier AA, if they have enough nitrogen
Describe the chemical reaction that links AA into a polypetide
Condesation reactions between carboxyl group of one AA and the amino group of the next
Explain the importance of primary protein structure in protein functionality
Primary structure determines the R group and bonds that will determine the rest
Provide the protein with its unique shape
Importanr im enabling the protein to perform its specfic function
Describe why secondary structure arise in a protein
Alpha helices and beta pleated sheets arise naturally due to the structure of AA, contain a carboxyl and amino group when bonded in a chain. H bond between AA because the amino group is slightly positive and the oxygen in the carboxyl group is slightly negative
Describe 2 common features of fibrous proteins
Long polypeptide chains w repeating sequence of AA
AA mainly have non polar R groups, insoluble in water
What is the function of elastin
Cross links and coils for strong extensible tissues such as skin or lungs
State the structural role of collagen
Strengh to the skin
What and give examples of globular protein
Spherical shape with a core of hydrophobic interactions and surface hydrophilic AA, water soluble
Haemoglobin,Insulin, Pepsin
Describe how the structure of haemoglobin relates to its function with reference to the levels of protein structure
Globular protein, 4 polypeperide chain, primary: sequence of AA in the 4 PPC,each of the polypeptide chains is coiled into alpha and beta pleated sheets
Quaternary structure of haemoglobin is formed when all 4 PPC are linked,spherical molecule
Each polypeptide is linked with a haem group, making it a conjugated protein
Describe what is meant by a prosthetic group, give example
Non proteins that are associated with the PPC of a proten
E.g haem (iron containing) group in haemoglobin
Describe how to test for proteins in a sample
Biuret test confirms presence of peptide bond
1) add equal volume of sodium hydroxide to sample at room temp
2) Add drops of dilute copper sulfate solution
positive - colour changes from blue to purple
Negative - solution remains blue
Describe how to test for lipids in a sample
Dissolve solid samples in ethanol
Add an equal volume of water and shake
Positive result: milky white emulsion form
Describe how to test for reducing sugars
1) add an equal volume of Benedict’s reagent to a sample
2) Heat the mixture in an electric water bath at 100 for 5 min
3) positive result: blue to orange and brick red
Or use test strip coated in a reagents that changes colour If reducing sugar is present
Describe the benedicts test for non reducing sugars
1) negative result: Benedicts reagent remains blue
2) Hydrolyse non reducing sugars e.g sucrose into their monomers adding 1cm of HCI
3) Neutralise the mixture using sodium carbonate solution
4) proceed
Describe the test for starch
Add iodine solution
Positive , orange to blue black
