Metabolism Flashcards
What is a glucose with two phosphate groups attached to it called?
Fructose-1,6 bis-phosphate
Is Fructose-1,6 bis-phosphate stable?
No
What does Fructose-1,6 bis-phosphate split into?
DHAP and glycealdehyde-3-phosphate
What happens to DHAP?
It is converted into glycealdehyde-3-phosphate
How many carbons does pyruvate have?
3
What does phosphofructokinase catalyse?
The formation of fructose-1,6-bisphosphate
Can Phosphofructokinase regulate glycolysis?
Yes, it speeds up or slows down the process depending on what is needed by the cell
What is the enzyme called that converts glucose to glucose-6-phosphate?
Hexokinase
What is the enzyme called that converts glucose-6-phosphate to fructose-6-phosphate?
Phosphoglucose-isomerase
What is the enzyme called that converts fructose-6-phosphate to fructose-1,6-bisphosphate?
Phosphofructokinase
What does DHAP stand for?
Dihydroxyacetonephosphate
What is the enzyme called that converts DHAP to glycealdehyde-3-phosphate?
Triose phosphate isomerase
What is the enzyme called that converts fructose-1,6-bisphosphate to DHAP and glycealdehyde-3-phosphate?
Fructose bisphosphate aldolase
Can glucose with a phosphate attached readily cross the membrane?
No
Is phosphoenolpyruvate (PEP) an unstable molecule?
Yes, it donates its phosphate group to ADP making it ATP
What acts as the source of phosphoryl groups that can be transferred to ADP to
regenerate ATP in mammal’s muscle cells?
1,3-bisphosphoglycerate, phosphoenolpyruvate, creatine phosphate
Metabolic pathways that require energy and are often biosynthetic are called
anabolism
The catalytic mechanism in which an isomerization takes place by a ketose to form an aldos is
via an _____intermediary.
enediol
What common structure is found in ATP, NAD, FAD and CoA-SH?
Adenosine diphosphate (except for the extra phosphate at 3 ́-C)
Why is there a common structure is found in ATP, NAD, FAD and CoA-SH?
These molecules may have evolved from the RNA catalysts in early life
Creatine is available for purchase in health food stores? What could it be good for?
Store chemical energy in the form of creatine-phosphate, ready to make ATP.
In intravenous injection of fructose in the blood of a subject, lactate content in the blood increased significantly more than when the corresponding amount of glucose was injected. How
can this be explained?
The fructose-1-phosphate pathway (see Figure 16.13 in Stryer) forms glyceraldehyde 3-
phosphate in fewer steps. Phosphofructokinase, a key control enzyme, is bypassed. Collectively,
fructose is metabolized more quickly into pyruvate, without being controlled at the PFK step (occurs in glucose catabolism). With oxygen supply limited, the final product pyruvate is reduced to lactate to regenerate NAD+.
Xylose has the same structure as glucose with the exception that C-5 in xylose has a hydrogen
as a substituent where glucose has a hydroxymethyl group. In the presence of xylose, the ATP
hydrolysis in the active site increases in hexokinase. How can this be explained?
Xylose is not a “perfect” substrate and does not induce the same conformational change of
hexokinase. As a result the enzyme active site does not exclude water completely, thereby ATP
hydrolysis increases. Also, xylose does not have the C-6 linked OH group (as in glucose) to
accept phosphate from ATP.
The level of ATP (or rather the cell’s energy status) has an important regulatory function on
metabolism. How does an increased concentration of ATP in the cell affect the activity of the pyruvate kinase?
Inhibits
