rEVISION Flashcards
Which forces predominantly keep the structure of an alpha-helix protein stable
Hydrogen bonds between the C=O of one residue and the N-H of another residue, 4 amino acids along the helix, stabilise the entire structure.
What is the optimum pH for the enzyme lysozyme?
at pH 5.0, Asp52 is ionised and Glu35 is unionised, allowing for lysis between the NAG and NAM units of polymers in bacterial cell walls.
is glucose always converted to glucose-6-phosphate by hexokinase
No
This reaction can also be catalysed by a slightly different enzyme, glucokinase, in the liver
Why is regeneration of NAD + essential?
Because otherwise the dehydrogenation of glyceraldehyde-3-phosphate cannot occur
Why is regeneration of NAD + essential?
Because otherwise the dehydrogenation of glyceraldehyde-3-phosphate cannot occur
A deficiency in which option affects the Link reaction from pyruvate to acetyl coenzyme A?
Thiamine, or B1, is needed to form Thiamine pyrophosphate, which is a prosthetic group in the Pyruvate Dehydrogenase complex. A deficiency in B1 leads to Beri-Beri
Where in the cell does the TCA cycle occur?
The mitochondrial matrix
Which TCA participant is linked with malate on an antiporter in the malate-aspartate shuttle?
The malate-aspartate shuttle system uses two membrane carriers and four enzymes. Hydrogen is transferred from cytoplasmic NADH to oxaloacetate to give malate, a reaction catalysed by cytosolic malate dehydrogenase (MDH). Malate is transported into the mitochondria where it is rapidly re-oxidised by NAD+ to give oxaloacetate and NADH (catalysed by mitochondrial MDH). Oxaloacetate and glutmate then undergo transamination to give the pair alpha-ketoglutarate and aspartate, which can exit the mitochondrial matrix via specific transporters in exchange for malate and glutamate respectively
: Which option best applies to ATP synthase?
the active site of the beta subunit has 3 states
As the discs of the c subunits rotate, the attached gamma subunit also rotates, but it is asymmetrical. This forces structural changes in the beta subunit between 3 states: open, loose binding and tight binding. ADP could be produced if ATP synthase rotates in the opposite direction.
In the first step of fatty acid biosynthesis, the production of malonyl CoA is catalysed by which enzyme and coenzyme combination?
Acetyl CoA carboxylase with biotin
At which Carbon is cholesterol acylated in its storage form?
3
At which Carbon is cholesterol acylated in its storage form?
3
In the first step of fatty acid biosynthesis, the production of malonyl CoA is catalysed by which enzyme and coenzyme combination?
Acetyl CoA carboxylase with biotin/vitamin b7
Which of the following is a function of cholesterol?
Cholesterol is a precursor of steroid hormones, not peptide hormones. High concentration of cholesterol cause low membrane fluidity. It cannot be metabolised to palmitate.
Cholesterol becomes the steroid hormone precursor pregnenolone via which enzyme?
cholesterol desmolase
Which of the following components would be found in the core of a lipoprotein?
triacylglycerol
Apart from triglycerols, cholesterol esters could also be found at the core of a lipoprotein.
About the other options: Free cholesterols, phospholipids and proteins are in the surface layer.
Haem group is found at the core of erythrocytes.
Which of the following components would be found in the core of a lipoprotein?
triacylglycerol
Apart from triglycerols, cholesterol esters could also be found at the core of a lipoprotein.
About the other options: Free cholesterols, phospholipids and proteins are in the surface layer.
Haem group is found at the core of erythrocytes.
Which enzyme catalyses the regulated step of cholesterol synthesis?
The formation of mevalonate is the regulated step and is catalysed by HMG CoA reductase- i.e the step is the slowest
During cholesterol synthesis, how many molecules of Isopentenyl pyrophosphate are used to form one molecule of squalene?
6
Which of the following is usually ABSENT from Low-Density Lipoproteins?
Free fatty acid
Fats are transported as triacylglycerol and not as free fatty acid.
Where are lipoprotein lipase found?
Lipoprotein lipase is found on CAPILLARY endothelial cells.
Chylomicrons travel from the lacteals to enter the blood stream at the left subclavian vein
Lacteals are part of the lymphatic system. The lymphatic system drains into the thoracic duct which deposits into the blood stream at the LEFT subclavian vein.
what activates lipoprotein lipase?
APOPROTEIN C-II pays a key role in activating lipoprotein lipase.
how many steps are required to convert lanosterol to cholestrol
19
Where in the cell does protein modification and quality control generally occur?
Modification of proteins occurs in the rough ER, of lipids, generally in the smooth ER. The ribosomes are the site of translation and the Golgi apparati of packaging
Which statement most accurately describes to constitutive secretion?
Secretion in this case is continuous regardless of environmental factors
give an example of golgi apparatus function
- Protein transport occurs in both directions between ER/ribosomes and the apparati.
- Folding of protein chains generally occurs in the rough ER
- An example of Golgi apparatus function is the phosphorylation of mannose on lysosomal proteins
what does gluconeogenesis use at its starting point
-oxaloacetate
Which reacts in the presence of malate dehydrogenase to form malate in the malate-aspartate shuttle?
Oxaloacetate
Which donates an electron to another of the options to produce cytosolic glycerol-3-phosphate?
NADH
Which is linked to malate on an antiporter?
In the malate-aspartate shuttle, malate is pumped into the matrix and alpha-ketogluterate out
Which reacts to form aspartate inside the mitochondrial matrix?
Oxaloacetate
Which produces glucocorticoids?
the adrenals
what body parts do gluconeogenesis?
the liver and the kidneys
Which is the main glycogen store for maintenance of blood glucose?
The liver
Though skeletal muscle normally stores in total more glycogen, this is predominantly for its own metabolism
