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Flashcards in Proteins 2 Deck (28):

what are the general functions of proteins? (9)

- movement
- enzyme
- structural
- protection
- storage
- receptors
- transport
- hormones
- 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?

- enzymes
- storage
- signalling
- transport


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


what cause osteogenesis imperfecta (brittle bone disease)

glysine substituted for a larger amino acid which prevents the polypeptides from packing together to form tight helices and so weaker interactions form better fibres
- secondary and tertiary structure lost