biological molecules Flashcards
- role of water - food tests - carbohydrates, fats and proteins - enzymes
what are the three types of carbohydrates?
monosaccharides, disaccharides and polysaccharides
examples of simple sugars/monosaccharides
glucose, fructose and galactose
examples of complex sugars/disaccharides
sucrose, lactose and maltose
examples of polysaccharides
starch, glycogen and cellulose
functions of carbohydrates
- energy source
- used in the formation of nucleic acids (DNA, RNA)
- can be converted to other organic compounds like fats and amino acids
- used to synthesise lubricants
- form supporting structures (cellulose cell wall in plants)
- used in the production of nectar in some flowers
what are carbohydrates made up of?
carbon, hydrogen and oxygen
chemical formula of glucose
C6H12O6
what are fats made up of?
carbon, hydrogen and oxygen
what does a fat molecule consist of?
1 glycerol molecule attached to fatty acid molecules
are saturated fats healthy or unhealthy?
saturated fats are unhealthy
functions of fats
- efficient source and storage form of energy
- solvent for fat-soluble vitamins, sex hormones and related hormones
- an essential part in cells, especially in cell membranes
- restrict water loss from skin surface
- acts an insulating material that prevents excessive heat loss
fats can be broken down into?
fatty acids and glycerol
what are proteins?
- made up of 20 amino acids
- each amino acid has an amino group (-NH2), a carboxylic acid group (-COOH) and a carbon side chain (denoted by R) which can contain sulfur and nitrogen
functions of proteins
- synthesis of protoplasm, for growth and repair of worn-out body cells
- synthesis of enzymes
- synthesis of hormones
- synthesis of antibodies
- source of energy
glycogen is synthesised from?
glucose
polypeptides and proteins are synthesised from?
amino acids
what are lipids synthesised from?
fatty acids and glycerol
examples of reducing sugars
glucose, fructose and maltose
what is used to test for presence of reducing sugars?
Benedict’s test using Benedict’s solution
describe procedure of Benedict’s test
- Place 2cm^3 of each food sample into a test tube
- Add 2cm^3 of Benedict’s solution to the food sample
- Shake the mixture and place the test tube in a boiling water-bath for 2-3 mins
- Record the colour of the solution
observation when no reducing sugar is present
Benedict’s solution remained blue
observation when traces of reducing sugar is present
Benedict’s solution turned from blue to green
observation when moderate amounts of reducing sugar is present
Benedict’s solution turned from blue to yellow/orange
observation when large amounts of reducing sugar is present
Benedict’s solution turned from blue to red/ red precipitate formed
describe procedure for test for starch
- Add a few drops of iodine in potassium iodide solution to a food sample
- Record your observations
observation when there is starch present
iodine solution turns from yellowish-brown to blue-black
observation when there is no starch present
iodine solution remains yellowish brown
what test is done to test for fats?
ethanol emulsion test
describe procedure for ethanol emulsion test on samples in liquid state
- Add 2cm^3 of ethanol to a drop of liquid sample in a test tube and shake the mixture thoroughly
- Add 2cm^3 of water to the mixture and shake the mixture
- Record your observation
describe procedure for ethanol emulsion test on samples in solid state
- Crush the solid sample into small pieces using a mortar and pestle and place the pieces in a test tube
- Add 2cm^3 of ethanol into the test tube and shake thoroughly
- Allow the solid particles to settle. Carefully decant (pour off the top layer of ethanol) the ethanol into another test tube containing 2cm^3 of water and shake the mixture
- Record your observation
observation when there is presence of fats
cloudy white emulsion is formed
what test is done to test for proteins?
biuret test
describe procedure of biuret test
- To 2cm^3 of liquid food sample, add an equal volume of biuret solution
- Shake well and allow the mixture to stand for 5 minutes
- Record your observation
observation when there is presence of proteins
the biuret solution changes from blue to violet
observation when there is no presence of proteins
the biuret solution remains blue
roles of water
- essential component of protoplasm
- medium for chemical reactions
- transport agent for digested substances and excretory products from tissue cells to excretory organs
- transport agent for hormones from glands to target organs/tissues - essential component of lubricant found in joints, digestive juices and blood
- required for hydrolytic reactions
- regulates body temperature by production of sweat
what are the main chemical elements found in all biological molecules?
oxygen, carbon and hydrogen
define enzymes
enzymes are biological catalysts made up of proteins which speed up the chemical reactions within an organism and remain chemically unchanged at the end of the process
define catalyst
a catalyst is a substance that can speed up a chemical reaction, and remain chemically unchanged at the end of the reaction
what enzymes digest carbohydrates?
carbohydrases such as amylase
amylase is found in the mouth (saliva) and the small intestine
amylase digests starch to?
maltose
what enzymes digest protein?
proteases (pepsin and trypsin)
pepsin (found in stomach)
trypsin (found in the small intestine)
pepsin digests proteins to?
polypeptides
trypsin digests proteins to?
polypeptides
what enzymes digest fats?
lipases
lipase digests fats to?
fatty acid and glycerol
maltase digests maltose to?
glucosew
why are enzymes required in minute amounts?
enzymes remain chemically unchanged after a reaction and can be re-used
why are enzymes highly specific?
each enzyme has an active site with a specific shape which will fit only a certain substrate
do enzymes catalyse reversible or irreversible reactions?
reversible reactions!
2 factors that enzymes are affected by
pH and temperature
are substrates the “lock” or the “key”?
substrates are the KEY
are the enzymes the “lock” or the “key”?
enzyme is the lock
what is formed when the substrate binds to the active site of the enzyme?
enzyme-substrate complex
what is an active site?
an enzyme has a specific 3D shape. It has a depression called the active site.
what is the lock and key hypothesis?
- only the substrate with a 3D shape COMPLEMENTARY to that of the active site can fit into the enzyme which results in the formation of an enzyme-substrate complex
- the enzyme is like a lock while the substrate is a key
- the substrate fits into the enzyme just like a key fits into a lock
what occurs after the substrate binds to the active site of the enzyme and forms a enzyme-substrate complex?
a chemical reaction occurs and the substrate is converted to the products. later, the products leave the active site. the enzyme remains unchanged and can catalyse another reaction.
is an enzyme more or less active at low temperatures?
less active! at low temps, the kinetic energy of molecules is low. enzyme and substrate molecules move slowly. the rate of the substrate colliding with the enzyme is very low
what is the optimum temperature of most human enzymes?
40-45°C
define optimum temperature
temperature at which the enzyme is most active
what does increasing the temperature above the optimum temperature do to the enzyme and the rate of enzyme reaction?
the enzymes become denatured. the active site of the enzyme molecule begins to lose its original shape and is no longer complementary to the shape of the substrate molecules
optimum pH if amylase in saliva
pH 7
optimum pH of protease in stomach
pH 2
optimum pH of protease in small intestine
pH 8
