Glycolysis and Gluconeogenesis Flashcards

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Questions and Answers

What is the function of glycolysis?

To convert glucose to three carbon compounds with the formation of ATP.

Where does glycolysis occur?

In all cells and in the cytosol.

How many reactions are in glycolysis?

Ten.

What does glycolysis do?

Turn glucose into pyruvate. Signup and view all the answers

Do you lose ATP in glycolysis?

False Signup and view all the answers

How many oxidative steps are there in glycolysis, and what happens in this step?

One, and NAD is reduced to NADH. Signup and view all the answers

What are the several metabolic fates of pyruvate?

Could be catalyzed by lactate dehydrogenase to make lactate under anaerobic conditions, could lose a CO2 molecule and get converted into ethanol, could be acted upon by pyruvate dehydrogenase to form acetyl coA, or could be acted upon by pyruvate carboxylase to form oxaloacetate. Signup and view all the answers

What is the regulation of glycolysis exerted on?

The three essentially irreversible reactions that use hexokinase, phosphofructokinase, and pyruvate kinase. Signup and view all the answers

What is the most important rate limiting step in glycolysis?

Where you use phosphofructokinase. Signup and view all the answers

What happens to pyruvate under aerobic and anaerobic conditions?

Under anaerobic conditions, pyruvate is reduced to lactate, while under aerobic conditions, it is oxidized to form acetyl coenzyme A. Signup and view all the answers

What are the two big organs for gluconeogenesis?

Liver and kidney. Signup and view all the answers

In regards to ATP, what is the difference between glycolysis and gluconeogenesis?

Glycolysis is an ATP reducing system, while gluconeogenesis is an ATP requiring system. Signup and view all the answers

Why can't we reverse all of glycolysis?

Those reactions between kinases are one-way reactions, so we need enzyme reactions that bypass those steps. Signup and view all the answers

What is known as the synthesis of glucose from 3-carbon molecules such as pyruvate, lactate, and glycol?

Gluconeogenesis. Signup and view all the answers

Where does gluconeogenesis occur?

Kidney and liver. Signup and view all the answers

How many reactions does it take to convert pyruvate to glucose?

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How many reactions of gluconeogenesis are catalyzed by the same enzymes as glycolysis?

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In glycolysis, what enzyme is used to catalyze pyruvate to phosphoenol, and how is this different from gluconeogenesis?

Kinase; in gluconeogenesis, the conversion of pyruvate to phosphoenol pyruvate occurs in two steps catalyzed by pyruvate carboxylase and phosphoenol pyruvate carboxykinase. Signup and view all the answers

Hormonal and dietary regulation is exerted on which enzymes?

Hormonal and dietary regulation is exerted on the enzymes restricted to gluconeogenesis: pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose 1,6-bisphosphate, and glucose 6-phosphatase. Signup and view all the answers

How does activation of pyruvate carboxylase occur?

By acetyl coenzyme A. Signup and view all the answers

Pyruvate to oxaloacetic acid is regulated by which enzyme?

Pyruvate carboxylase. Signup and view all the answers

The conversion of two moles of pyruvate to one mole of glucose requires how many moles of ATP and NADH?

6 moles of ATP and 2 NADH. Signup and view all the answers

What are usually the substrates used in gluconeogenesis?

Lactate, pyruvate, glycerol. Signup and view all the answers

Liver can oxidize lactate to form what?

Pyruvate. Signup and view all the answers

Describe the cori cycle.

Glucose in muscle can make pyruvate in glycolysis; during early exercise, lactate travels to the liver and is oxidized to form pyruvate, which can then be utilized in gluconeogenesis. Signup and view all the answers

Insulin increases glycolysis and decreases gluconeogenesis.

True Signup and view all the answers

What are the levels of glucocorticosteroids and glucagon in the two cycles?

Glucocorticoids and glucagon increase gluconeogenesis and decrease glycolysis. Signup and view all the answers

Several hours after a meal, there is a switch from glycolysis to gluconeogenesis. How is this regulated?

Hormone levels such as glucocorticoids, insulin, glucagon, etc.; the switch is mediated by phosphorylation of proteins. Signup and view all the answers

Study Notes

Glycolysis Overview

Glycolysis transforms glucose into three-carbon compounds, producing ATP.
Occurs in all cells within the cytosol.
Comprises ten reactions, ultimately converting glucose into pyruvate.
No ATP is lost; there is a net production of ATP.
One oxidative step takes place, where NAD is reduced to NADH.

Metabolic Fate of Pyruvate

Pyruvate can be converted to lactate under anaerobic conditions by lactate dehydrogenase.
It can lose a CO2 molecule to become ethanol.
Under aerobic conditions, pyruvate forms acetyl coenzyme A through pyruvate dehydrogenase.
Alternatively, pyruvate can form oxaloacetate via pyruvate carboxylase.

Regulation of Glycolysis

Regulated at three irreversible steps involving hexokinase, phosphofructokinase, and pyruvate kinase.
Phosphofructokinase is crucial as the rate-limiting step; influenced by ATP concentrations.

Aerobic vs Anaerobic Conditions

Anaerobic conditions convert pyruvate to lactate, regenerating NAD from NADH.
Aerobic conditions oxidize pyruvate to acetyl CoA, which enters the citric acid cycle.

Gluconeogenesis Basics

Primarily occurs in the liver and kidneys.
ATP-consuming process to synthesize glucose from three-carbon precursors like pyruvate and lactate.
Transformation of pyruvate to glucose uses eleven reactions, with seven shared with glycolysis.

Key Enzymes in Gluconeogenesis

Enzymes specific to gluconeogenesis include pyruvate carboxylase, phosphoenolpyruvate carboxykinase, and fructose-1,6-bisphosphate, among others.
Pyruvate carboxylase activation requires acetyl CoA.

Energy Requirements

Converting two moles of pyruvate to one mole of glucose consumes six ATP molecules and two NADH.
Lactate, pyruvate, and glycerol are common substrates in gluconeogenesis.

Further Insights

The Cori cycle connects muscle and liver metabolism; lactate produced in muscles during exercise is transported to the liver, where it is converted back to pyruvate.
Insulin facilitates glycolysis, while gluconeogenesis is promoted by glucocorticoids and glucagon.

Hormonal Regulation

Glucagon increases gluconeogenesis and decreases glycolysis.
After meals, there's a regulatory switch from glycolysis to gluconeogenesis facilitated by hormonal changes, particularly glucagon and insulin, through protein phosphorylation.

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Description

Test your knowledge on glycolysis and gluconeogenesis with these flashcards. Each card provides essential functions, locations, and processes involved in glycolysis. Ideal for students looking to strengthen their understanding of carbohydrate metabolism.