Biological molecules Flashcards
Roles of lipids
Cell membrane
Insulation
Water proofing
Energy source
organ protection
Characteristics of lipids
C, H, O
Insoluble in water
Soluble in organic solvents e.g alcohol, acetone
Types of lipids
Phospholipids
Triglycerides
Structure of Phospholipid
CH2COO - Fa
I
CHCOO - Fa
I
Phosphate–CH2
Structure of triglyceride
CH2O-OC - FA
I
CHO-OC - FA. + 3H2O
I
CH2O-OC - FA
What are the bonds between lipids
Ester bonds
What are the bonds between proteins
Peptide bonds
What are the 2 types of protein
Fibrous - structure
Globular - Metabolic
What determines the shape and function of a protein
The primary structure
What are the 3 bonds in the tertiary structure of a protein
Disulphide bridges
Ionic bonds
Hydrogen bonds
Test for protein
Add sample in tube with equal volume of sodium hydroxide at room temp
Few drops of copper(II) sulfate solution
Purple colour positive test for peptide bonds
Negative remains blue
Test for lipids
2cm cubed of sample, 5cm cubed of ethanol
Shake solution
Add 5cm3 of water
Cloudy white emulsion colour means lipid present
Difference between a glucose and b glucose
b glucose only found in plants
B glucose has OH at top, a has H at top
Test for reducing sugars
2cm^3 of sample in tube, grind in water if not in liquid form
Add benedict’s reagent
Heat for 5 minutes
green - very low
yellow - low
orange - medium
Red - high
What are the reactants for the disaccharides
Glucose + Glucose —> maltose
Glucose + fructose —> sucrose
Glucose + galactose —> lactose
Test for non reducing sugars
Carry out benedict’s test
If no colour change, add 2cm^3 of dilute hydrochloric acid and place in gently boiling water bath for 5 minutes
Add Sodium hydrogen carbonate to neutralise HCl
Repeat benedict’s test
Lower pH and higher temp should have hydrolysed the glycosidic bonds
Test for starch
2cm^3 of sample
Add 2 drops of potassium iodide solution
Positive test - blue/black solution
Characteristics of starch
Insoluble, doesn’t affect water potential
Does not diffuse out of cells
Compact so stored in small place
Forms a-glucose when hydrolysed, ready use in respiration
Branched in many ends, rapid simultaneous enzyme action for hydrolysis
Glycogen characteristics
Insoluble, doesn’t draw water via osmosis or diffuse out of cells
Compact so stored in small space
More highly branched than starch, rapid hydrolysis for respiration, important in animals with high metabolic rate
Cellulose characteristics
Made of b-glucose
unbranched straight chains
Chains run parallel to form collective strength
group to form microfibril to form fibres
Prevents cell bursting
How are b-glucose arranged in cellulose
B-glucose rotates 180 degree each molecule to form glycosidic bond
Can form H bonds to parallel polysaccharides
