B2 Proteins and Lipids Flashcards
What are proteins made up from?
amino acids
What are amino acids?
A monomer that makes up polypeptide
What is the structure of an amino acid?
H R 0
\ l //
N - C - C
/ l \
H H OH
What groups are in an amino acid?
Amine group , hydrogen group , carboxyl group and variable group
What is the formation of a peptide bond?
Amino acids combine to form dipeptide and water via condensation reaction
Combine (-OH) of one amino acid with (-H) from another amino acid
Amino acids then link by new peptide bond between carbon of one amino acid and nitrogen of another.
What is the primary structure of proteins?
The number and sequence of amino acids joined by peptide bonds
What happens if there is a change in a single amino acid in the primary sequence?
Leads to a change in the shape of the protein and it may stop carrying out its function
What is the secondary structure of protein?
When hydrogen bonds form between amino acids
What are the two secondary structures of protein?
Alpha helix and Beta pleated sheet
What is the tertiary structure of protein?
A twisted and folded 3D structure of protein maintained by hydrogen bonds , ionic bonds and disulphide bonds
What is the quaternary structure of protein?
More than one polypeptide chain eg. haemoglobin which has 4 polypeptide chains
What is the test for protein?
Biuret test- if protein is present then the colour will change from blue to violet
What are the two types of lipids?
triglycerides and phospholipids
What does a triglyceride consist of?
1 glycerol and 3 fatty acids
What are the two types of fatty acids?
Saturated fatty acids and unsaturated (monounsaturated and polyunsaturated)
What are saturated fatty acids?
They have no double bonds in their hydrocarbon chain
What is a monounsaturated fatty acid?
A fatty acid with 1 double bond
What is a polyunsaturated fatty acid?
A fatty acid with more than 1 double bond
What is the basic structure of a fatty acid?
O
C - R
/
HO
Describe how triglyceride is formed?
One glycerol and 3 fatty acids and a condensation reaction occurs which causes the removal of three water molecules and ester bonds are formed
What does a phospholipid consist of?
A phosphate head that is hydrophillic (attracts water). 1 Glycerol and 2 fatty acids that are hydrophobic (repel water)
What do phospholipids make up?
Cell membrane
What is the test for protein?
Add sample to test tube
Add biuret reagent
Shake gently
Positive result is mauve/violet
What is the test for lipids (emulsion test)?
Crush sample
Add ethanol
Shake
Add water
If lipid is present, a milky white emulsion is observed
