Flashcards in Proteins 2 Deck (28):
what are the general functions of proteins? (9)
- control gene expression
what are glycoproteins?
compounds composed of protein and carbohydrate
how are glycoproteins formed?
through post translational modification (glycosylation)
- a sugar molecule attaches to an amino acid
give an example of an amino acid that attaches a sugar group to the - N (amine) group (i.e forms a glycoprotein)
give an example of an amino acid that attaches a sugar group to a O atom (i.e forms a glycoprotein)
hydroxylysine, serine. threonine
give an example of a glycoprotein
where does glycosylation occur?
in the endoplasmic reticulum and golgi apparatus
what are the roles of glycoproteins? (5)
- protein stability
- increased solubility
- protein orientation
- cell signalling
- cell recognition
what is HbA1C?
a type of glycoprotein (glucose attaching to red blood cells) that helps to show control of blood gluocse in diabetics over a longer period of time (2-3 months)
what are lipoproteins?
protein and lipid molecules that are joined either covalently or non-covalently
what is the function of lipoproteins?
transport water insoluble fats and cholesterol in the blood
give an example of a lipoprotein
HDL, LDL, Cryoglobulins
what is an LDL receptor?
a glycoprotein present on the surface of all body cells that binds to apoB on LDLs
what is the function of LDL receptors?
to bind to apoB on LDLs leading to the internalisation of LDL and its breakdown which signals the body to stop producing cholesterol
what is familial hypercholesterolemia?
an inheirited autosomnal dominant disorder in which faulty LDL receptors are produced
whata re the symptoms of FH?
often no symptoms are present and only blood tests highlight abnormal LDL levels. In some cases cholesterol is deposited in tendons, skin and arteries.
what are metalloproteins?
a protein molecule with a bound metal ion
what are the functions of metalloproteins?
what is the function of globular proteins?
have varied functions
- can act as hormones, enzymes or transporters
what is the function of fibrous proteins?
are structural proteins e.g bone matrices, muscle fibre, connective tissue
what is the structure of haemoglobin?
four polypeptides held toether in a quarternary structure with a haem group at the centre of each polypeptide
what is co-operative binding?
a process in which oxygen binds to one subunit which alters the shape of the other subunits making it easier for more oxygen to bind
what causes sickle cell anaemia?
a single base change which results in valine being coded for instead of glutmic acid
- valine is hydrophobic and glutamic acid is hydrophilic and so different interactions form
what are the features of sickle cells?
- have a crescent shape (sickle shape)
- insoluble and at low concentrations of oxygen form crystals (leading to infarction)
- give up oxygen to tissues more easily than normal red blood cells
what is the repeating subunit in collagen?
- (glycine - X - proline) -
* X is either alanine, hydroxyproline or lysine
how do collagen fibres form?
polypeptide coils to form a helix ---> 3 polypeptides then coil round each other (triple helix) ---> hydrogen bonds hold the helices together forming microfibrils which then form fibrils and then fibres
what causes scurvy?
lack of vitamin C
- vitamin C needed to convert proline to hydroxyproline and lysine to hydroxylysine
- both of these forms need to make hydrogen bonds and so lack of them forms weaker collagen fibres