Biological molecules
Carbohydrates
● Chemical equation: Cx(H2O)y
○ H:O is always 2:1
● Categories
○ Monosaccharides
■ Properties
● Simplest form of of carbohydrates
● Tastes Sweet
○ Small enough to fit into taste buds in tongue, the nerves in
tongue send signals to brain, making us feel that the taste is
sweet.
● Soluble in H2O
■ Function
● Source of energy
■ Examples
● Glucose, C6H12O6
○ Commonly found in all plant/animal cell
● Fructose
○ Commonly found in plants( eg. fruits)
● Galactose
○ Present in milk
○ Disaccharides
■ Properties
● 2 monosaccharides chemically joined together
● Tastes Sweet
○ Small enough to fit into taste buds in tongue, the nerves in
tongue send signals to brain, making us feel that the taste is
sweet.
● Soluble in H2O
■ Function
● Ready source of energy
■ Examples
● Sucrose
○ Found in sugar canes
● Maltose
○ Found in germinating seeds such as barley
● Lactose
○ Found in milk
○ Polysaccharides
■ Properties
■ Long chains of monosaccharides(3+ monosaccharides chemically joined
together)
■ Size is too big to dissolve in water, therefore not soluble
■ Too big to fit into taste buds, therefore not sweet
■ Example+functions
● Glycogen
○ Found in liver
○ Stores energy in animal’s livers
■ Excess carb converts to glycogen
● Starch
○ Found in plants
○ Stores energy in plants
● Cellulose
○ Found in plant cell wall
○ Structural support in plants
○ Source of dietary fibre in our diet
● Reducing sugar
○ Every monosaccharides and disaccharides except sucrose
○ *****Sucrose is NOT a reducing sugar
○ Reducing sugar reacts with benedict’s solution to give a brick red participate
○ Reducing sugar can be digested by amylase
● Benedict’s test for reducing sugar
○ Apparatus
■ Benedict’s solution
■ Hear source
○ Add benedict’s solution into sample solution in test tube
○ Heat at 60~70 degree c in water bath for 5 mins
○ Take testube out from water bath and observe color
■ Positive
● Color change from blue to brick red
● Solution with brick red precipitate
○ Minor traces of reducing sugar present in solution will give
green/yellow precipitate or orange red precipitate
■ Negative
● Color remain blue
● Iodine solution’s test for starch
○ Apparentus
■ Iodine solution
■ Spotting tile
○ Add sample into spotting tile
○ Add drops of iodine solution to sample in spotting tile
○ Positive result will show color change from brown to blue black
Lipids
● Fat vs Oil
○ Solid at room temp->fat
○ Liquid at room temp->oil
● Function
○ Store of energy
■ Only to be utilized after all carbohydrates are utilized
■ 3x energy of carbohydrates
○ Store for heat insulation
■ Reducing heat loss of body
○ Shock absorber
■ Preventing internal bleeding
■ Absorbs motions
○ As component of cell membrane
● Component
○ 3 fatty acid+1 glycerol—>triglyceride
■ Containing Carbon, Hydrogen and Oxygen
■ Hydrogen:Oxygen>2:1
■ Cx(H>2O)y
● Sources
○ Plant
■ Maize
■ Nuts
○ Animal
■ Butter
■ Fatty meat
● emulsion test for lipids
○ Apparatus needed
■ Ethanol, Distilled water, Test Tube
○ Add ethanol to sample(crush the sample if the sample is solid)
○ Shake the mixture vigorously
○ Add equal amounts of water
○ Let it sit
○ Positive result:
■ a cloudy white emulsion forming
■ 2 layers of immiscible liquids
Proteins
● Function
○ Growth and repair of body tissues
○ Formation of antibodies, enzymes, hormones, and cell membrane
● Component
○ Different amino acids
■ 20 types
○ Bond to form polypeptide chains
■ *any difference in the sequence(even order) gives a different type of protein
○ Coiling and folding to form molecules with specific functions(proteins)
○ Elements present
■ Carbon, Hydrogen, Oxygen, Nitrogen(might contain sulfur)
● When in excess, amino groups (H2N) are deaminated to form urea to be removed in urine.
● Biuret test for proteins
○ Apparatus needed
■ Biuret solution
■ Testube
○ Add 2cm3 drops of biuret solution to 2cm3 of sample
○ Shake
○ Let rest for 5 min
○ Positive result
■ Solutio turning violet
Vitamin
● Function
○ Prevent deficiency diseases
○ Vitamin c helps to maintain strong gums and healthy skin
○ Prevents the deficiency disease scurvy
○ Helps regulate metabolic reactions
● Properties
○ No energy value
○ Needed in small amt.
● DCPIP test
○ Apparatus
■ DCPIP solution, test tube
○ Add DCPIP solution to sample drop by drop, stop when the solution became colorless
Enzymes
● Catalysts
○ Substance that increases the rate of reaction without being changed by the reaction
○ An enzyme is a example of a biological catalyst
● Enzymes
○ Biological catalyst that speeds up the rate of metabolic reactions by lowering the energy
barrier
○ Type of protein
○ Active site
■ Complementary shape to one specific type of substrate
■ One enzyme can only form enzyme substrate complex with one type of
substrate(lock and key model)
● Temperature’s effect on enzyme
● Temperature too low:
○ Enzyme and substrate molecules does not have enough kinetic energy
○ Low chance of successful collisions to form enzyme-substrate complex
○ Low enzyme activity
● Temperature too high:
○ Destruction of shape of active site
○ No longer in complementary shape with the substrate
○ Can no longer form enzyme substrate complex
○ Enzyme is said to be denatured
● pH’s effect on enzymes
● As pH starts to derive from the optimum pH of the enzyme
○ The shape of the active site of enzymes are destroyed by the increasing/decreasing pH
condition
○ No longer in complementary shape with the substrate
○ Can no longer form enzyme substrate complex
○ Enzyme is said to be denatured
