Oxygen Transporters And Protein Secretion Flashcards
How is the harm group bound to the polypeptide chain?
Histidine residue
What type of dependence des oxygen binding to myoglobin show and what does his imply?
Hyperbolic
Constant affinity for oxygen
What type of curve dos oxygen binding in haemoglobin show?
What does this imply
Sigmoidal binding curve
This implies that the affinity for oxygen. Increases with the partial pressure for oxygen
What ensure oxygen transport by haemoglobin?
Coopertaivity enhances it as the binding of oxygen promotes the transistion from a low affinity -T state to a high affinity r state
Haemoglobin has a high affinity for oxygen i. The lungs and a low afffinity in the tissues
How does BPG regulate oxygen binding
It is an allosteric effector
It lowers the affinity of Hb for oxygen so stabilises the T state
Shifts curve to right
BPG interacts wit positively charged reissues on beta units
How does CO2 act as a allosteric effector
Binding of CO2 nd H+ lowers the affinity
Stabilises t state
Allows delivery of oxygen at metabolically active tissues that produce CO2 and H+
How is carbon monoxide regulate oxygen binding
It binds to haemoglobin 250x more regularly than O2
Blocks further oxygen binding
Stabilises R state in unaffected subunits which prevents dissociation at tissues
Shits curve to the left meaning they are less likely to dissociate
What causes sickle cells disease
Mutation of glutamate to valine in beta haem group
Haemoglobin stick together and aggregate
Valine residue lies on the surface in the t state
This causes the cells to be more prone to lose- anaemia
More rigid- block microvasculatue
How are proteins destined for the cytosol or post translational import into organless synthesised?
Free ribosomes
How are proteins destined for membranes or secretory pathways via co-translational insertion synthesised by?
Synthesised by ribosomes on the RER
What is constiuitive secretion?
Secreted with no regulation
What is regulated secretion?
Controlled
E.g.
endocrine cells- secreting hormones
Exocrine cells- secreting digestive juices
Neurocrine cells- secreting neurotransmitters
What does the pre part of a protein represent?
Defines the signal sequence which is removed during processing
What are the functions of the endoplasmic reticulum?
. Insertion of proteins into membranes • Specific proteolytic cleavage • Glycosylation • Formation of S-S bonds • Proper folding of proteins • Assembly of multisubunit proteins • Hydroxylation of selected Lys and Pro residues
Where does posttranslational modifiction occur?
Endoplasmic reticulum
Function of Golgi apparatus
Movement of proteins to the cis-Golgi through budding
• Further protein modifications
• Release through trans-Golgi
to membrane/organelles
What produces collagen?
Fibroblasts
Structure of collagen
Basic unit- tropocollagen
Collagen is formed of thee polypeptide chains that form a right handed helix structure
The triple helical structure allows strength
H bonds between polypeptide chains
Every third amino acid is glycine
What causes scurvy?
Enzyme prolyl hydroxylase requires vitamin C and fe2+ ions for its activity to catalyse the hydroxylation of proline and lysine residues.
Vitamin C deficiency causes reduced activity of the enzyme which results in reduced stabilisation of the triple helical structure of collagen
Abnormal collagen leads to defective connective. Tissue
Leads to easy bruising tiredness irritability swollen and painful joints and swelled and bleeding gums
