Proteins (biochemistry) Flashcards
What elements do proteins contain?
Carbon, Hydrogen , Oxygen, Nitrogen (and Sulfur)
What are proteins polymers of?
amino acids
How many different types of amino acids are there?
20
What is an R group?
the variable group in an amino acid
What do all amino acids contain?
an amine group, a carboxyl group, an variable group, alpha Carbon + hydrogen
What is a zwitter ion?
when H from COOH has moved to the lone pair on the N in the NH2 group
What is it called when 2 amino acids are linked?
Dipeptide
What reaction enables formation of a dipeptide?
condensation reaction
What bond is formed between 2 amino acids?
peptide bond
How is a peptide bond broken?
Hydrolysis
Where does the peptide bond form during condensation reaction of 2 amino acids?
the peptide bond forms between the C atom of the carboxyl group of one amino acid and the Nitrogen Atom of the amine group of the adjacent amino acid
What is a polypeptide?
consists of a chain of amino acids linked by peptide bonds
What do the ends of a polypeptide look like?
at one end there is an amine group at the other end there is a carboxyl group
What are the 4 structures that a protein can show?
primary
secondary
tertiary
quaternary
What is primary structure in a protein?
the type, number, and sequence of amino acids in a polypeptide linked by peptide bonds only, forming a linear chain
What is the most common secondary structure in a protein?
most common is alpha helix formed by hydrogen bonding
Where do hydrogen bonds from in alpha helix structure?
between oxygen atoms of carboxyl groups and hydrogen atoms of amine groups
what is another secondary structure of proteins?
a beta-pleated sheet
What is tertiary structure of a protein?
the folding of the alpha helix as shown by globular proteins, to form very specific 3-d shapes. (one polypeptide)
What other bonds forms in a tertiary structure?
disulfide bridges, ionic bonds, hydrogen bonds (secondary), hydrophobic interactions
What is quaternary structure?
Where 2 or more polypeptide chains in tertiary form combine to form complexes
What is an example of a protein with quaternary structure?
Haemoglobin
What are the 2 groups of proteins?
globular and fibrous
What is the function of a globular protein?
metabolism (soluble)
What is the function of a fibrous protein?
structural (insoluble)
What is the molecular shape of a globular protein?
Spherical in tertiary or quaternary structure
What is the molecular shape of a fibrous protein?
Chains in secondary structure
What are examples of globular proteins?
Enzymes (lysozome), insulin
What are examples of fibrous proteins?
keratin, collagen
What is the function of keratin?
strengthens hair, nails, scales, feathers etc.
What is the function of collagen?
strengthens bones, tendons, ligaments, skin
What is elastin?
elastic fibrous tissue that allows many tissues in the body to resume their shape after stretching or contracting
What does elastin do?
helps skin to return to its original position when it is stretched
What test is used for proteins?
Biuret test
What is a negative result for biuret test?
blue
What is a positive result for biuret test?
violet
