Globular proteins Flashcards
What are the 2 types of proteins?
Globular and Fibrous
Properties of Globular proteins
- Spherical in shape with Hydrophobic R groups on the inside of the Protein and Hydrophilic R groups on the outside
- Hydrophilic groups on the outside means protein is soluble in water as hydrophilic R groups can interact with water
- Have VERY SPECIFIC shapes so they carry out VERY SPECIFIC functions
Protein examples:
- Transport protein
- Hormone
- Enzyme
- Haemoglobin
- Insulin
- Pepsin
Globular protein definition
Globular Proteins are proteins that are usually spherical in shape and are soluble in water, and usually have metabolic roles.
Where is haemoglobin found? What is its main function?
in Red blood cells in the blood
Transport of oxygen from lungs to the body tissues
How many polpeptide chains make up haemoglobin and what structure does it have?
4 POLYPEPTIDE CHAINS
Quaternary structure
What are the names of chains it is made of
2 alpha globin chains and
2 beta globin
Haemoglobin is a _______ protein as it has a _________ group called a ________ group attached to each polypeptide chain/
Conjugated
Prosthetic
Haem
What is a prosthetic group
a non protein component which is bonded to polypeptides and is necessary for proteins to carry out their functions
What does each Haem group have and what does that allow it to do
Each Haem group has 1 Fe 2+ ion and that allows each Haem group to hold an oxygen molecule, and overall a single Haemoglobin protein molecule carries 4 oxygen atoms.
What secretes insulin
the pancreas
What is the role of insulin
maintain blood glucose concentration
Insulin is composed of ________ polypeptide chains, one which is an ________- and the other is a ______________ sheet.
2
alpha helix
beta pleated
How are the 2 polypeptide chains joined in insulin
by disulfide links
The specific ________ of insulin allows it to bond to certain receptors on cell membranes to be able to lower blood glucose concentration
shape
Insulin is soluble in water, why?
Has outer hydrophilic R groups which make it soluble in water
What is the benefit of insulin being soluble
dissolves in blood and easily transported throughout the body
What does pepsin do? Is it a globular protein?
it catalyses breakdown of proteins and yes it is a globlular enzyme
where is pepsin found and what is the nature of its location?
Stomache where there is a very acidic environment with a pH of 2
Why do enzymes denature at low pH and how?
They have amino acids with Basic R groups which accept hydrogen ions, become positively charged, disrupt the bonding between the polypeptide chains in the tertiary structure and the enzyme shape changes and it denatures and can no more carry out its function.
Pepsin is not affected by low ph and why is that?
- Amino acids in pepsin have very few basic R groups and therefore the tertiary structure is not affected by low pH
- Structure is kept stable by disulphide links and hydrogen bonds in the tertiary structure of pepsin
