Module 2 - Biological Molecules Flashcards
Name some fibrous proteins
Collagen
Keratin
Elastin
Name some globular proteins
Haemoglobin
Pepsin
Insulin
What are globular proteins?
They tend to roll into spherical shapes where hydrophobic R group are inside and hydrophilic groups are outside so they are soluble in water
They have specific shapes, making them good as hormones and enzymes
What are the features of collagen?
Provide mechanical strength to: Artery walls, prevents bursting when high pressure blood is pumped Tensions connecting muscles to bones Bones are made of collagen Cartilage and connective tissue
What are the features of Keratin and Elastin?
Keratin:
Rich in cysteine so many disulfide bridges and hydrogen bonds for strength
Nails, hair, horns, fur
Impermeable so barrier to infections/ waterproof
Elastin:
Cross linking and coiling make it stronger
Stretch
Skin stretches and uses elastin to go back to original shape
Blood vessels to stretch
What are the features of haemoglobin
Quartinary structure made of four polypeptides: 2 alpha-globin chains and 2 beta-globin chains
Prosthetic group in each chain (haem group) containing iron ions
Is a conjugated protein
Iron ions react with oxygen to help carry it around the body
What are the two approaches regarding computer modelling of protein structures?
Ab initio protein modelling: model on physical and electrical properties of atoms within each amino acid
Comparative protein modelling: protein threading which scans the amino acid sequence against a database of solved structures and produces possible models that match it
What are cations?
Positive ions
What are anions?
Negative ions
Name some cations
Calcium - Ca2+ Sodium - Na+ Potassium - K+ Hydrogen Ammonium
Name some anions
Nitrate
Hydrogencarbonate
PRACTICALS
How to test for Carbohydrates
STARCH
1) Add iodine solution to sample
2) if starch is present you will see the sample change from yellow-brown to BLUE-BLACK
PRACTICAL
Testing for reducing sugars
1) heat reducing sugar with benedict’s solution ( alkaline copper II Sulfate)
2) colour change from blue to green to yellow to orange-red
The red indicates reducing sugar is present
What are reducing sugars?
They are either monosaccharides or disaccharides that reduce or give electrons to other molecules
Why would the precipitate of a present reducing sugar be red
Benedict solution contains copper 2+ ions reduced to copper + ions forming the red precipitate copper oxide
What is an alternative way of testing for reducing sugars?
Commercially manufactured test strips : dip into solution and compare colour to calibration card
PRACTICAL
Testing for Non-reducing sugars
1) test sample for reducing sugars to ensure there are none
2) take another sample and boil with hydrochloric acid to hydrolyse the sucrose into glucose and fructose
3) cool solution and use sodium hydrogencarbonate solution to neutralise
4) test for reducing sugars again
A positive result (green-red) indicates non reducing sugars present in original sample
When does a condensation reaction occur?
It occurs when to molecules joined together with the REMOVAL of water
What is meant by ‘polar’?
One molecule exerts a greater attraction because it may have a greater number of protons than the other molecule it’s bonded to. This means that molecule will become slightly negative and the other slightly positive
What is meant by a hydrogen bond?
A hydrogen bond is a weak interaction which happens whenever a molecule contains a slightly negatively charged atom bonded to a slightly positively charged hydrogen atom
What is hydrolysis?
It’s the splitting apart of two molecules with the addition of water
Why are Polysaccharides good energy stores?
- Compact meaning they occupy a small amount of space. Occur in dense granules
- hold glucose molecules in chains so they can be easily snipped off by hydrolysis for respr
- branched chains (amylopectin) are more compact, allows many glucose molecules to be snipped off for quick energy
- 1-4 g linkages (amylase)
- 1-6 g linkages (glucosidase)
- less soluble in water
What are the features of Amylose?
- Coils into a spiral (hydrogen bonds hold it in place)
- Hydroxyl group on inner coil so it’s less soluble
- has 1-4 g bonds
- a glucose molecule
What are the features of Amylopectin?
- coils into a spiral shape
- has branches
- 1-4 g bonds and 1-6 g bonds
What are the features of cellulose?
- forms cell wall
- B glucose monomers
- B glucose is rotated 180 degrees ( prevents spiralling) (additional strength)
- form microfibrils ( additional tensile strength)
- form macrofibrils that criss-cross for extra strength
What are the features of a lipid?
- contain hydrogen, carbon and oxygen
- insoluble in water (not polar)
- they are macromolecules
What are the 3 most important lipids?
- steroids
- phospholipids
- Triglycerides
What is a triglyceride?
- molecule comprised of glycerol and fatty acids
- ‘essential fatty acids’ are fatty acids that are ingested ‘complete’
What is a glycerol?
- molecule comprised of 3 carbon atoms
- 3 OH groups are important to the structure of the TRIglycerol
What are the features of a fatty acid?
- Carboxyl group (-COOH) attached to hydrocarbon tail
- carboxyl group ionise into H+ and -COO- group. Therefore an acid
- If saturated it has no C=C bonds
- if there are C=C bonds they are unsaturated as no H molecules can bond
- having more than one C=C bond can change shape of the hydrocarbon
What are the functions of Triglycerides?
- Energy source= broken down for Resp
- Energy store= insoluble so can be stored without affecting water potential of cell
- Insulation= ‘blubber of wales’, animals in hibernation store extra fat for heat
- Buoyancy= fat less dense than water, help float
- Protection= fat around delicate organs, shock absorber
How are triglycerides formed?
- OH from the fatty acid and the H from glycerol react through a condensation reaction
- form ester bond (O-C=O) (covalent bond)
Behaviour of phospholipids in water?
- phosphate group is polar so it’s hydrophilic (head)
- fatty acid is not polar so it’s hydrophobic (tail)
- this makes phospholipid molecule amphipathic
Phospholipid bilayer
Amphipathic phospholipids are excellent at forming membranes around cell membranes in aqueous
What is cholesterol and what are it’s features?
- Cholesterol is a steroid alcohol (lipid not made from glyercol and fatty acids)
- small and hydrophobic, sits inside membrane
- regulates the fluidity of the membrane preventing it from becoming too fluid or stiff
- made in liver
- hormones such as testosterone, oestrogen and vitamin D are all made from cholesterol
What are proteins and its functions?
- polymer comprised of amino acids
- form components of animals eg muscles
- form enzymes, antibodies and some hormones
- membranes have protein constituents that act as carriers and pores for active transport across membrane and facilitated diffusion
What is the structure of amino acids?
- contain carbon, hydrogen, and Nitrogen
- 500 diff amino acids, only 20 are proteinogenic
- has an amine group (-NH2) at one end and a carboxyl group at the other (-COOH)
- has an R group ( different in each amino acid)
Peptide bonds?
- amino acids are joined by them
- involves condensation reaction
- Enzymes catalyse these reactions (protease)
- two amino acids is a dipeptide and more is a polypeptide
Primary structure?
The sequence of amino acids in a protein is called its PRIMARY STRUCTURE
- function of protein is determined by structure
- determines shape of protein molecule
- peptide bonds
- 20 to the power of 100 ways of ordering 100 amino acids
Secondary structure?
Chain of amino acids twist into a shape called the SECONDARY STRUCTURE
- some coil into a- helix (36 amino acids per 10 turns)
- held by hydrogen bonds
- can fold into a zig zag structure producing a B- pleated sheet
- some have more than one structure at either end
Tertiary structure?
Coils and folds begin to fold in on themselves to form the TERTIARY STRUCTURE
- precise shape held by bonds between amino acids
- May adopt a super coiled shape or spherical shape
- ionic bonds, disulfide bond
Quarternary Structure?
- describes how multiple polypeptide chains are arranged to make complete proteins
- more than one polypeptide
CHROMATOGRAPHY
AIM: separate a mixture into its constituents
- stationary phase= chromatography paper (made of cellulose) there are free OH groups in contact with mobile phase
- Mobile Phase= solvent for biological molecules (water or ethanol)
CHROMATOGRAPHY
- solvent travels up paper and molecules with it
- by the time the solvent reaches the top, some molecules moved slowly some faster
- Calculate Rf by measuring distance from pencil line to one molecule (x) and distance from pencil line to solvent front (y)
- Rf= x/y
