Proteins Flashcards
What are some of the functions of proteins?
Enzymes, neurotransmitters, hormones, antibodies, transport, cell structure
What are the monomers of proteins?
Amino acids
Which elements are amino acids made from?
Carbon, hydrogen, oxygen, and nitrogen. Some also have sulphur.
What do we call two amino acids joined together?
A dipeptide
What do we call a long chain of amino acids?
A polypeptide
What are the four main parts of an amino acid?
Amino group, Alpha carbon (with H attached), Carboxyl group, Variable ‘R’ group
Which part of an amino acid is variable?
The ‘R’ group
How many different amino acids are there?
20
Amino acids can be joined together with which type of bond?
A peptide bond
Describe a peptide bond
A bond between two amino acids, between the nitrogen in the amine group of one amino acid and the carbon in the carboxyl group of the next
What type of reaction would form a peptide bond?
Condensation reaction (that releases water)
What type of reaction would break a peptide bond?
Hydrolysis reaction (that releases water)
What is the primary structure of a protein?
The sequence or order of amino acids in a polypeptide
Which bonds hold together the primary structure of a protein?
Peptide bonds
The function of a protein is determined by?
its shape
What is the secondary structure of a protein?
The folding of the primary structure into alpha helices or beta pleated sheets, held together by hydrogen bonds
What type of bonds hold together the secondary structure of a protein?
Hydrogen bonds
What is a hydrogen bond?
A weak bond between different molecules
What is the tertiary structure of a protein?
The folding of the secondary structures into a precise 3D shape
Which bonds hold together the tertiary structure of proteins?
Disulfide bonds (Very strong), Ionic bonds (Strong), Hydrogen bonds (Weak), Hydrophobic and hydrophilic interactions
What is a disulfide bond?
A strong bond between cysteine amino acids (found in tertiary structure of proteins)
What does hydrophilic mean?
Attracted to water
What does hydrophobic mean?
Repels water
What is the quaternary structure of (some) proteins?
When a protein is made of more than one polypeptide chain bonded together
What is a prosthetic group on a protein?
A chemical group bonded to proteins, but not made of amino acids, such as the iron containing haem group in haemoglobin.
What are globular proteins?
A common type of protein with a spherical shape that is normally soluble in water and has a variety of biological functions (eg enzymes, antibodies, hormones).
What are fibrous proteins?
A common type of protein with a linear structure that is insoluble in water and provides a structural function (eg collagen and keratin)
Describe the structure of haemoglobin
A globular protein with quaternary structure. It is made of four globular polypeptide chains.
Each polypeptide chain has one prosthetic group called haem. The haem contains an iron ion (Fe) which oxygen binds to.
Describe the structure of collagen
It is a fibrous, insoluble protein. The fibrils are rigid/strong because of tightly coiled triple helices.
This gives strength across tissues because these fibrils can form cross-linkages to produce collagen fibres.
Describe the role of haemoglobin
Haemoglobin is found inside red blood cells. It is used to transport oxygen around the body to be used in respiration.
Describe the role of collagen
Collagen is found in large quantities in connective tissue throughout the body. It is very strong and its role is to support organs and bones.
