Globular Proteins Flashcards
What does the overall 3D structure of the protein determine?
Which type of protein is formed
What are the 2 types of proteins that can be formed?
Fibrous
Globular
What are the important properties of globular proteins?
3
Roughly spherical in shape
Soluble in water
Very specific shapes
What do the roughly spherical shape of the globular have on the inside and outside?
Hydrophobic R groups on the inside
Hydrophilic R groups on the outside
What do the very specific shapes allow?
It allows them to carry out very specific functions
What are 3 roles of globular proteins?
Transport proteins
Hormones
Enzymes
What is an example of a transport protein?
Haemoglobin
What is an example of a hormone?
Insulin
What is an example of an enzyme?
Pepsin
What is the definition of a globular protein?
A protein with a spherical shape that is soluble in water. Globular proteins typically have metabolic roles
Haemoglobin
Where is haemoglobin found?
In red blood cells
Haemoglobin
What does haemoglobin have an important role in?
The transportation of oxygen from the lungs to the body tissues
Haemoglobin
What is haemoglobin made up of?
What does this mean?
4 polypeptide chains meaning that the protein has a quaternary structure
Haemoglobin
What other protein is haemoglobin also?
Why?
A conjugated protein
As it has a prosthetic group attached to each polypeptide chain
Haemoglobin
What is the definition of a prosthetic group?
A non-protein component that is necessary for the protein to carry out its function
Haemoglobin
What are the 4 prosthetic groups in haemoglobin called?
What do they contain?
Haem groups
They contain an iron ion (Fe2-)
Haemoglobin
How many oxygen molecules bind to each haem group?
What does this allow?
One oxygen molecule
Allowing each haemoglobin to transport 4 oxygen molecules
Insulin
What is insulin secreted by?
The pancreas
Insulin
What is the important role of insulin?
Maintaining blood glucose concentration
Insulin
What is insulin composed of?
(2)
2 polypeptide chains
An a-helix
A ß-pleated sheet
Insulin
How are the 2 polypeptide chains joined together?
By disulphide links
Insulin
What does the shape of insulin allow?
It to specifically bind to receptors on cell membranes to help lower blood glucose concentrations
Insulin
What makes insulin soluble in water?
It has hydrophilic R groups on the outside
Insulin
What does insulin being soluble allow?
It allows insulin to dissolve in the blood and be easily transported around the body
Pepsin
What does pepsin do?
Catalysts the digestion of proteins
Pepsin
Where is pepsin found?
In the stomach
Pepsin
What kind of environment is the stomach?
An acidic environment
One with a low pH
Pepsin
What kind of pH do many enzymes become denatured at?
(high/low)
At a low pH
Pepsin
Why do many enzymes become denatured at a low pH?
Because they contain amino acids with basic R groups
Pepsin
Why do enzymes that contain amino acids with basic R groups denature?
Basic R groups accept hydrogen ions (H+) and become positively charged
The positively charged R groups can affect the ionic bonds + hydrogen bonds in the protein - this denatures the enzyme and therefore alters its function
Pepsin
What prevents the tertiary structure of the pepsin being affected by low pH?
The primary structure of pepsin has very few basic R groups
Pepsin
How is the tertiary structure of pepsin kept stable?
(2)
By hydrogen bonds and disulphide links
