proteins part 2 Flashcards
What are the different types of proteins?
structural e.g. keratin
enzymatic e.g. digestive enzymes
contractile e.g. myosin
receptor e.g. g proteins
defensive e.g. immunoglobulins
hormonal e.g. insulin
storage
transport e.g. haemoglobin
What is post translational modification?
subsequent modification after protein been transcribed
What is co translational modification?
modification at same time as translation
What are the three types of conjugated proteins?
glycoproteins
lipoproteins
metalloproteins
What are glycoproteins?
Proteins with ≥1 carbohydrate molecule(s) covalently attached
Co-translational or post-translational
modification where oligosaccharide chains are attached to a protein
Effects of glycosylation?
1.Stability
2.Solubility
3.Cell signalling
4.Orientation
How is blood transfusion compatibility achieved?
The immune system recognizes the combo of carbs present upon or absent from the surface of an erythrocyte
if deemed by immune system to be foreign, immune system secretes particular antibodies to effectively clump the foreign red blood cells together
Why can we use glycoproteins for diagnostic purposes?
patients with undiagnosed diabetes mellitus have high levels of glucose in blood
excess glucose binds to haemoglobin within erythrocytes forming glyco proteins
can detect the concentration of these glycoproteins in a patient’s blood
and since erythrocytes only stay in circulation for 100 days , conc will correlate with patients blood sugar levels occurring over that period of time
therefore patients with diabetes or suspected allow clinicians to obtain a useful snapshot of average blood glucose control
HbA1C?
pathological glycoprotein
What are lipoproteins?
proteins combined with lipids
Where are lipoproteins found?
In cell membranes and transporting hydrophobic molecules around aqueous bloodstream
What are apolipoproteins?
lipoproteins with other lipoproteins
What do apolipoproteins do?
transport fat, fat soluble vitamins and fat soluble hormones around the body within blood and cerebral spine fluid
What are metalloproteins?
Protein molecules with a metal ions within
their structures (co-factors)
Various functions (e.g. enzymatic, signal
transduction, storage and transport
Describe structure of haemoglobin?
large quaternary structure, four polypeptide chains , two alpha subunits and two beta subunits.
The interfaces where subunits meet are usually non polar and this plays important role in transmitting information
Each subunit contains an organic molecule called heme and inside heme molecule sits an atom of iron
What allows haemoglobin to transport one mol of oxygen?
Interaction between iron, heme and polypeptide subunit. Each haemoglobin mol with four subunits can carry four mols of oxygen
What does the amount of oxygen that can be dissolved in blood depend on?
partial pressure of oxygen within lung alveoli.
How much oxygen does plasma in working normally lungs have?
plasma leaving lungs has almost as much dissolved oxygen as is possible
plasma can only carry a max of 3ml oxygen per l
What are the effects of sickle cell blood disease?
sickle cells struggle to pass through capillaries and inefficient in delivery oxygen to end tissues
How does sickle cell disease arise?
GAG in normal beta chain changes to GTG, changes tertiary and quaternary.
Polar glutamine becomes non polar valine
What are the the types of protein based on structure?
globular
fibrous
membranous
What are the functions of globular Proteins?
storage
enzymes
hormones
transporters
structural
What is myeloma?
antibody-producing white blood cells secrete abnormally large amounts of immunoglobulins
Give examples of where fibrous proteins are commonly found ?
muscle fibre and connective tissue
What is the cause of scurvy?
body unable to produce twisted collagen fibres- important in maintaining structural integrity.
Result of a deficiency in vitamin C
Why is scurvy a result of vitamin C deficiency?
vitamin c is an essential co factor in the production of collagen.
Without vitamin C, post translational modification of amino acids proline and lysine cannot occur and cannot be converted to hydroxyproline and hydroxylysine.
What other conditions are a result of disorders of collagen synthesis ?
osteogenesis imperfecta - DNA mutation results in the substitution of the small amino acid glycine for a different larger amino acid
Substitution results in weak collagen produced- brittle bones and sclera of eyes easily damaged
What are membraneous proteins?
proteins that are embedded within cell membranes
What is function of membraneous proteins?
important role in transporting substances into and out of cells
also play important role in signalling
What features of familial hypercholesterolemia?
high levels of LDL cholesterol circulate due to genetic disposition
symptoms of FH?
excess cholesterol can be deposited around the eyes (xanthelasma)
and around tendons known as xanthoma
How does FH exert its effects?
FH most commonly affects the LDL receptor protein
which sits within the cell membranes of many cells
depending on the specific mutation that causes FH
could be that no LDL receptor protein can be manufactured
or receptor never emerges from cell membrane
or receptor unable to bind to LDL cholesterol
or receptors can’t internalize LDL cholesterol
can’t release LDL after internalized
