organic and bio chem exam pt 2

During gluconeogenesis the second irreversible step of glycolysis is circumvented by the conversion of ____________ to _____________.

Fructose-1,6-bisphosphate is converted to Fructose-6-phosphate by the enzyme Fructose-1,6-bisphosphatase • Phosphatase enzymes

What is gluconeogenesis and why is it necessary?

Gluconeogenesis ("production of new glucose"): The conversion of pyruvate → glucose. • Glycogen cannot be stored in large enough quantities to fully supply the body's glucose needs during fasting. • Maintaining levels of glucose is important because the brain and red blood cells depend on glucose as their primary fuel!

In the first step of glycogen synthesis, glucose units are _______ by reacting them with ________ to form _________ by the enzyme __________.

Glucose units must be "activated" by the enzyme UDP-glucose pyrophosphorylase. • Glucose-1-phosphate reacts with UTP forming UDP-glucose (UDPG). • Glucose-P + UTP → Glucose-UDP + 2Pi

After periods of vigorous exertion in which oxygen levels are low, pyruvate is reduced by NADH to form _______. This occurs during the process of _______

NADH delivers its electrons to the electron transport chain, reducing O2 to H2O regenerating NAD+ * In the absence of oxygen, NAD+ must be regenerated some other way.

During gluconeogenesis the first irreversible step of glycolysis is circumvented by the conversion of ___________ to _________ which is then converted _________

Oxaloacetate an intermediate • Pyruvate is carboxylated to oxaloacetate by the enzyme Pyruvate carboxylase. • Requires the coenzyme biotin (CO2 carrier) and ATP hydrolysis. Oxaloacetate is converted to PEP Next, oxaloacetate is decarboxylated (loss of CO2 ) and phosphorylated to form PEP by the enzyme Phosphoenolpyruvate kinase. Pyruvate + GTP → Phosphenolpyruvate GDP + Pi

Under aerobic conditions, pyruvate is completely _______ via the __________ and NADH delivers its electrons to the _________ regenerating ________.

Pyruvate (the end product of glycolysis) is completely oxidized via the citric acid cycle • NADH delivers its electrons to the electron transport chain in the mitochondria, reducing O2 to H2O regenerating NAD+ .

Synthesis of glycogen is completed by the ___________ enzyme.

Synthesis is completed by the branching enzyme which adds α(1→6) branches.

How many ATP, NADH, and FADH2 are generated in a single round of the citric acid cycle?

The Citric Acid Cycle generates per glucose molecule. • 2 X 3 = 6 NADH • 2 X 1 = 2 ATP • 2 x 1 = 2 FADH2

Under anaerobic conditions, pyruvate is processed to __________ or ________ via the process of _____________ depending on the organism. This process is required to regenerate ____________ in the absence of oxygen.

(-O2 ), pyruvate is processed to lactate or ethanol via fermentation depending on the organism.

Feedback inhibition is

type of allosteric control inhibition caused by high concentrations of the product of a reaction.

. Fatty acids are metabolized into __________ via ________ which is then completely oxidized via the ___________.

> 90% of ATP in generated by Oxidative phosphorylation. • Oxidative phosphorylation captures the energy of high-energy electrons in the form of NADH and FADH2 to synthesize ATP. • The flow of electrons from NADH and FADH2 to O2 occurs in the electron-transport chain (ETC). • This exergonic set of oxidation-reduction reactions generates a proton gradient. • The proton gradient is used to power the synthesis of ATP.

Complete breakdown of glycogen requires ___________ enzymes.

Complete breakdown requires debranching enzymes to degrade the alpha(1->6) linkages

During gluconeogenesis the third irreversible step of glycolysis is circumvented by the conversion of ___________ to _____________.

Glucose-6-phosphate is converted to glucose by the enzyme Gluocose-6-phosphatase • Glucose is then transported in the blood to other tissues that need glucose (i.e. the brain and red blood cells)

The reactions of the critic acid cycle take place in the __________ of the ________.

In complex organisms, the reactions of the citric acid cycle take place inside the matrix of mitochondria, • in contrast with those of glycolysis, which take place in the cytoplasm

. In the first step of glycogen breakdown, __________ is generated by the enzyme ________

In the first step, glycogen is cleaved by phosphate to give a D-glucose-1-phosphate. This reaction is catalyzed by the enzyme Glycogen phosphorylase. • Cleavage reaction is phosphorlysis and not hydrolysis

. In the second step of glycogen breakdown, the product of step 1 is converted to ________ by the enzyme __________.

In the second reaction, glucose-1-phosphate is isomerized to glucose-6-phosphate which can now enter glycolysis. • This reaction is catalyzed by Phosphoglucomutase

Phosphofructokinase is inhibited by

Inhibited by ATP

Pyruvate kinase is inhibited by

Inhibited by ATP

Hexokinase is inhibited by

Inhibited by Glucose-6-phosphate

Allosteric inhibition is

Inhibition or activation of an enzyme by a small regulatory molecule that interacts with the enzyme at a site other than the active site

Gluconeogenesis is accomplished partly by running glycolysis "backwards." However, during glycolysis some reactions are highly ____________ and irreversible. These reactions include:

It is accomplished partly by running glycolysis "backwards". However, during glycolysis some reactions are highly exergonic and irreversible.

In the second step of glycogen synthesis, the product of step 1 is added to growing chain by the enzyme

UDPG is then added to a growing chain of glycogen, by the enzyme Glycogen synthase.

The citric acid cycle is the final common pathway for the complete oxidation of ,_________ ,and ___________.

Under aerobic conditions, pyruvate is • converted to acetyl CoA • completely oxidized to CO2 via the citric acid cycle in the mitochondria. The citric acid cycle is the final common pathway for the oxidation of fuel molecules - carbohydrates - fatty acids - amino acids

Under aerobic conditions, pyruvate is converted to _________ by the ________ . This reaction results in the transfer of an _______ unit from pyruvate to ___________ forming a high energy ________ bond with loss of ___________. During this process, one molecule of ___________ is reduced, forming __________ .

Under aerobic conditions, pyruvate is converted to acetyl CoA by the Pyruvate dehydrogenase complex

When glucose levels are _________, it can be converted into glycogen and stored in large quantities in the liver and skeletal muscles. Whereas, when glucose levels are ___________, (fasting or exertion), glycogen can be broken down to help maintain the glucose supply.

When glucose is abundant (after a meal), it can be converted into glycogen and stored in large quantities in the liver and skeletal muscles. When glucose levels are low (fasting or exertion), glycogen can be broken down to help maintain glucose supply.