3.7 Types of proteins Flashcards
What are the characteristics of globular proteins?
- Compact
- Water soluble
- Spherical
- Hydrophilic R-groups on the outside - this makes these proteins soluble
What roles is a globular protein involved in?
- Chemical reactions
- Immunity
- Muscle contraction
What type of protein is insulin?
Globular
Explain what insulin is
Elaborate on hormones
- A hormone involved in regulation of blood glucose concentration
- Hormones are transported via bloodstream so need to be soluble
- Hormones need to fit into specific receptors on plasma membranes to have their effect so need to have a precise shape
What are conjugated proteins?
Globular proteins containing a non-protein component called a prosthetic group
What are simple proteins?
Proteins without prosthetic groups
Elaborate on prosthetic groups
- Different types
- Lipids can mix with proteins forming lipoproteins
- Carbohydrates can mix with proteins forming glycoproteins
- Metal ions + molecules from vitamins form prosthetic groups
- These are called cofactors when they’re needed for the protein to carry out its function
- Haem groups (containing an iron II ion) are an example of prosthetic groups
Spare
spare
spare
spare
spare
spare
What is haemoglobin?
Red, oxygen-carrying pigment founds in erythrocytes (red blood cells)
What type of protein is haemoglobin?
Quaternary protein
Describe and elaborate on the structure of haemoglobin
- Made from 4 polypeptides, 2 alpha subunits and 2 beta subunits
- Each subunit contains a prosthetic haem group
- Iron ions in haem group can combine reversibly with an oxygen molecule - this enables haemoglobin to transport oxygen
as
as
as
as
as
as
as
as
What is catalase? What type of protein is catalase?
- Enzyme
2. Quaternary protein
What is catalase made up of?
4 haem prosthetic groups
What does the presence of iron II ions allow catalase to do?
Allows catalase to interact with hydrogen peroxide and speed up its breakdown
What is hydrogen peroxide?
A common byproduct of metabolism
Damaging to cells if it accumulates - catalase prevents this from happening
What do fibrous proteins tend to make?
Strong, long molecules NOT folded into 3-D shapes like globular proteins
What are fibrous proteins made from? Explain why.
Long, insoluble molecules - due to the presence of a high proportion of amino acids with hydrophobic R-groups in their primary structures
What do fibrous proteins contain?
Limited range of amino acids with small R-groups
Describe the amino acid sequence in the primary structure of fibrous proteins. What does this lead to?
- Repetitive
2. Leads to very organised structures
Give examples of fibrous proteins
- Keratin
- Elastin
- Collagen
What is keratin?
Hair
Skin
Nails
What does keratin contain? What does this result in?
- A high proportion of the sulfur-containing amino acid, cysteine
- Many strong disulfide bridges forming strong, inflexible and insoluble materials
