Proteins - globular & fibrous Flashcards
What are globular proteins?
Globular proteins are compact, roughly spherical in shape and soluble in water
They play important physiological roles and can be easily transported around organisms.
How do globular proteins achieve their spherical shape?
Their non-polar hydrophobic R-groups are orientated towards the centre and polar hydrophilic R-groups orientate themselves on the outside
This orientation enables solubility in water.
What is the significance of the solubility of globular proteins?
It enables them to play important physiological roles and be involved in metabolic reactions
Their solubility allows easy transport around organisms.
What role do R-groups play in the folding of globular proteins?
Interactions between the R-groups result in specific shapes for globular proteins
This shape allows them to perform specific physiological roles.
What are conjugated proteins?
Proteins that contain a prosthetic group, e.g., haemoglobin which contains haem
Conjugated proteins have additional components that assist in their function.
What was the first protein to have its sequence determined by scientists?
Insulin
Insulin is a globular protein produced in the pancreas.
What is the role of insulin?
It plays an important role in the control of blood glucose concentration
Insulin consists of two polypeptide chains.
How many amino acid residues are in polypeptide A and B of insulin?
Polypeptide A has 21 amino acid residues and polypeptide B has 30 amino acid residues
The two chains are held together by three disulfide bridges.
What are fibrous proteins?
Fibrous proteins are long strands of polypeptide chains with cross-linkages due to hydrogen bonds
They have little or no tertiary structure.
Why are fibrous proteins insoluble in water?
Due to the large number of hydrophobic R-groups
This property makes them suitable for structural roles.
What is the structure of fibrous proteins like?
They have a limited number of amino acids with a highly repetitive sequence
This creates very organised structures that are strong.
What is collagen?
The most common structural protein found in vertebrates
It forms connective tissues such as tendons, cartilage, and ligaments.
What is the structural composition of collagen?
Formed from three polypeptide chains closely held together by hydrogen bonds to form a triple helix
This structure provides great tensile strength.
What are the most common amino acids in collagen?
Glycine, proline, and hydroxyproline
Each polypeptide chain contains about 1000 amino acids.
How do covalent bonds contribute to collagen’s structure?
They form cross-links between R-groups of amino acids in interacting triple helices
These cross-links hold collagen molecules together to form fibrils.
What are collagen fibres and how are they arranged?
They are formed when many fibrils are arranged together and positioned to withstand forces
The staggered ends of fibrils provide additional strength.
