CH.2 Biological Molecules Flashcards
Benedict’s Test - test for what? Procedure and result
test for reducing sugars
Add Benedict’s solution and heat in a water bath
clear blue to red-brown precipitate
Non-reducing sugars
hydrolysis using HCl will give the monosaccharides.
Neutralise the solution (Benedict’s reagent needs alkaline conditions)
Then add Benedict’s solution and heat in a water bath.
If reducing sugar and non-reducing sugar are present the precipitate will be heavier
Emulsion Test - test for what?, result
Test for lipids
cloudy result
Biuret Test - test for what?, result
Test for proteins
pale blue to purple
a dilute solution of potassium hydroxide or sodium hydroxide, and a dilute solution of copper(II) sulfate. Alternatively, you can use a ready-made biuret reagent
Iodine Test - test for what?, result
Test for starch
Orange-brown to blue-black
What is a macromolecule?
A large molecule such as polysaccharides, nucleic acids or protein
What is a monomer?
y simple molecule which is
used as a basic building block for the synthesis of
a polymer
What is a polymer?
a giant molecule made from many similar
repeating subunits (monomers) joined together in a chain
many monomers are joined together
by covalent bonds to make the polymer, usually
by condensation reactions
What is a monosaccharide?
a molecule consisting of a
single sugar unit and with the general formula
(CH2O)n
Functions of monosaccharides
- Source of energy in respiration
large number of carbon-hydrogen bonds can be broken to release energy which is transferred to make ATP from ADP - Important building blocks for larger molecules (ex. polysaccharides like starch, and ribose in RNA)
What is a Disaccharide?
a sugar molecule consisting of
two monosaccharides joined together by a
glycosidic bond
Give the monomers for
maltose
sucrose
lactose
maltose: alpha glucose + alpha glucose
sucrose: alpha glucose + beta fructose
lactose: beta glucose + beta galactose
glucose, fructose and maltose are reducing sugars and sucrose is a non-reducing sugar
What is the glycosidic bond?
a C–O–C link between two sugar molecules, formed by a condensation reaction; it is a covalent bond
What are polysaccharides?
a polymer whose subunits are monosaccharides joined together by glycosidic bonds.
What are amylose and amylopectin?
Amylose- a long, unbranching chain of several thousand 1,4 linked glucose molecules made from condensation reactions. Chain and curved and coil up into helical structures like springs
Amylopectin- made of many 1,4 linked α-glucose
molecules, but the chains are shorter than in amylose and also contain 1,6 linkages. These start branches out to the sides of the chain
What is triglyceride?
a type of lipid formed when three fatty acid molecules combine with glycerol, an alcohol with three hydroxyl (−OH) groups
3 ester bonds formed -COO-
triglycerides are non-polar hydrophobic molecules hydrocarbon tails are non-polar)
Functions of triglycerides
excellent energy stores because
they are even richer in carbon-hydrogen bonds than carbohydrates (it has a higher calorific value)
act as an insulator against loss of heat
metabolic source of water. When oxidised in respiration, triglycerides are converted to carbon dioxide and water
Describe the molecular structure of phospholipids
hydrophilic (polar) phosphate heads and hydrophobic(non-polar) fatty acid tails
one of the three fatty acid molecules is replaced by a phosphate group, the phosphate group is hydrophilic
What is a peptide bond?
the covalent bond joining neighbouring amino acids together in proteins; it is a C–N link between two amino acid molecules, formed by a condensation reaction
Primary structure of a protein
the sequence of amino acids in a polypeptide or protein
Secondary structure of a protein
the structure of a protein molecule resulting from the regular coiling or folding of the chain of amino acids (an α-helix or β-pleated sheet)
What is an alpha-helix structure?
a helical structure formed by a
polypeptide chain, held in place by hydrogen
bonds; an α-helix is an example of a secondary
structure in a protein
What is a beta-pleated structure?
a loose, sheet-like structure formed by hydrogen bonding between parallel polypeptide chains; a β-pleated sheet is an example of a secondary structure in a protein
Tertiary structure of proteins
the compact structure of a protein molecule resulting from the three-dimensional coiling of the chain of amino acids
Describe the types of interaction that hold protein molecules in shape
- hydrophobic interactions
- hydrogen bonding
- ionic bonding
- covalent bonding, including disulfide bonds
