2.2 BIOLOGICAL MOLECULES Flashcards
Describe a water molecule (2)
- Polar
- Weak hydrogen bonding
State and explain the 4 properties of water
1) Solvent (water is polar so dissolves molecules)
2) Transport medium (can carry polar substances and is cohesive)
3) Coolant (high specific heat capacity and large latent heat of vaporisation)
4) Habitat (high specific heat capacity so acts as a buffer, cohesion creates surface tension for bugs, ice less dense than water so is insulator)
What elements are carbohydrates,lipids,proteins and nucleic acids made of?
carbohydrates - C,H,O
lipids - C,H,O
proteins - C,H,O,N,S
nucleic acids - C,H,O,N,P
What kind of reaction bonds together monosaccarides into a disaccaride?
Condensation (water removal)
What kind of reaction splits up a dissacharide back into its monosaccarides?
Hydrolysis (addition of water)
Draw alpha and beta glucose
Alpha has hydrogen above, Beta has hydrogen below
What type of bond forms between disaccharides and polysaccarides after condensation?
Glycosidic bond
How is the disaccharide MALTOSE formed?
(a)-GLUCOSE + (a)-GLUCOSE
How is the disaccharide LACTOSE formed?
(a)-GLUCOSE + GALACTOSE
How is the disaccharide SUCROSE formed?
(a)-GLUCOSE + FRUCTOSE
How are polysaccarides formed from monosaccarides?
via many condensation reactions (water removal)
Name the three polysaccarides.
- Starch (amylose and amylopectin)
- Cellulose
- Glycogen
Describe glycogen (4)
- energy SOURCE material in animals
- C1 to C4 and C1 to C6 glycosidic bonds
- alpha glucose
- large surface area and densely packed
- branched
What are the two types of starch?
amylose and amylopectin
Describe amylose starch (5)
- energy STORAGE material in plants
- C1 to C4 glycosidic bonds
- alpha gluocse
- densely packed
- insoluble
- branched
Describe amylopectin starch (5)
- energy STORAGE material in plants
- C1 to C6 glycosidic bonds
- alpha glucose
- large surface area
- insoluble
- branched
Describe cellulose (5)
- a structural component in plant cell walls
- C1 to C4 glycosidic bonds
- beta glucose
- long/straight/unbranched
- hydrogen bonds
The three types of lipids
- Triglyceride
- Phospholipid
- Cholesterol
Explain the solubility of lipids
- insoluble in water because they are nonpolar/uncharged
How to make triglycerides?
- one glycerol
- three fatty acids
- esterification to form ester bonds
Uses of triglycerides?
- as an energy source (broken down to release energy during respiration)
- as an energy store (insoluble so no effect on cells water potential)
- keeping animals afloat (its less dense than water)
- insulation/protection
Structure of phospholipids?
- one glycerol
- two fatty acids (one saturated, one unsaturated)
- one phosphate group
Describe the phospholipid bilayer (3)
- hydrophobic tails (polar, water soluble)
- hydrophilic heads (nonpolar, insoluble)
- selectively permeable (to small nonpolar molecules)
Describe the properties and uses of cholesterol (2)
- small and hydrophobic
- sits in membrane phospholipid bilayer to regulate membrane fluidity
General structure of an amino acid?
- NH2 amine group
- COOH carboxyl group
- R variable group
- H hydrogen group
How are dipeptides/polypeptides formed?
- two amino acids
- condensation to form a peptide bond (water removal)
How are dipeptides/polypeptides broken?
- hydrolysis to break peptide bond (addition of water)
State the levels of protein structure
Primary - the sequence of amino acids in the polypeptide chain
Secondary - alpha helix or beta pleated sheet
Tertiary - 3D shape
Quaternary - proteins with more than one polypeptide chain
Explain primary structure of proteins
- the unique sequence of 20 different amino acids in the polypeptide chain
Explain the secondary structure of proteins
- the hydrogen bonds between carboxyl and amine groups of amino aicds of the polypeptide chain fold it into either alpha helix or beta pleated sheet
Explain the tertiary structure of proteins
- unique 3D structure formed by; hydrophobic/hydrophillic interactions, hydrogen bonds, ionic bonds, disulfide links (all between R variable groups)
Explain the quaternary structure of proteins
- proteins with more than one polypeptide chain have a quaternary structure (e.g haemoglobin)
State the two types of proteins
Globular and Fibrous
State and explain the two globular proteins
- insulin (metabollic protein)
- haemoglobin (4 pp chains, 2 alpha, 2 beta, conjugated , 4 haem Fe2+ prosthetic groups)
State and explain the three fibrous proteins
- collagen (mechanical strength in skin)
- keratin (skin/hair/nails)
- ellastin (flexibility/elasticity in blood vessels)
Describe globular proteins (3)
- complex (quaternary)
- spherical
- water soluble
Describe fibrous proteins (3)
- strong
- insoluble
- not complex
Chemical test for proteins?
- add drops of biuret solution
- BLUE to PURPLE
Chemical test for starch
- add drops of iodine
- BROWN to BLUE/BLACK
Chemical test for lipids
- add ethanol, shake, pour extract into water
- COLOURLESS to WHITE EMULSION
Name the only non-reducing sugar
Sucrose
Chemical test for reducing sugars
- add benedicts reagent, heat 80 degrees
- BLUE to BRICK RED
Chemical test for non-reducing sugar (sucrose)
- do the reducing sugar test first (benedicts and heat)
- boil with HCl then cool and neutralise with NaOH
- repeat benedicts test
- BLUE to BRICK RED
What can reagent test strips test for?
- Can identify presence of reducing sugars by dipping into test solution and determine concentration when compared to calibration card
What do colorimeters and biosensors do?
- obtains quantitative results for the concentration of each biochemical test
State the 5 steps of how to use a colorimeter
1) Zero the colorimeter
2) Add red filter
3) Calibrate using distilled water
4) Insert different known concentrations (e.g of glucose with benedicts solution) with serial dilutions
5) measure percentage transmission of light and create calibration curve
