Glycolysis Overview and Tissue Functions

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Questions and Answers

What is the main end product of glycolysis in the presence of oxygen?

Acetyl-CoA

Glucose

Pyruvate (correct)

Lactate

Which type of glycolysis occurs in the absence of oxygen?

Fermentative glycolysis

Anaerobic glycolysis (correct)

Aerobic glycolysis

Oxidative glycolysis

Which enzyme is responsible for converting fructose-6-phosphate to fructose-1,6-bisphosphate?

Phosphofructokinase (correct)

Aldolase

Glyceraldehyde-3-phosphate dehydrogenase

Hexokinase

In glycolysis, how many ATP molecules are net produced during anaerobic conditions?

2 ATP Signup and view all the answers

What key role does glycolysis serve in red blood cells (RBCs)?

Providing energy exclusively Signup and view all the answers

Which compound is produced from glyceraldehyde-3-phosphate in glycolysis?

1,3-phosphoglycerate Signup and view all the answers

What is one physiological importance of glycolysis in skeletal muscle tissue?

Energy source during high-intensity exercise Signup and view all the answers

What is the primary end product of aerobic glycolysis?

Pyruvate Signup and view all the answers

Which of the following statements is true regarding the ATP production from glucose during aerobic glycolysis?

Net gain of 8 ATP Signup and view all the answers

Which enzyme is exclusively found in the liver that converts glucose?

Glucokinase Signup and view all the answers

What is the fate of pyruvate in anaerobic glycolysis?

Converted to ethanol or lactate Signup and view all the answers

How many ATP are generally produced from anaerobic glycolysis?

2 ATP Signup and view all the answers

What is a biological importance of glycolysis in relation to oxygenation of tissues?

Formation of 2,3 bisphosphoglycerate Signup and view all the answers

Which statement about hexokinase is correct?

It is inhibited by glucose-6-phosphate. Signup and view all the answers

What is the role of NAD+ in glycolysis?

It acts as an electron acceptor. Signup and view all the answers

Which glycolytic pathway yields the highest energy output?

Aerobic glycolysis Signup and view all the answers

What process must occur to reoxidize NADH during fermentation?

Conversion of pyruvate to lactate Signup and view all the answers

Which enzyme is responsible for the conversion of pyruvate to lactate?

Lactate Dehydrogenase Signup and view all the answers

Which of the following statements about lactate is true?

Lactate can serve as a fuel source for some tissues Signup and view all the answers

What role do astrocytes play in lactate metabolism?

They facilitate lactate transport to neurons Signup and view all the answers

During intense exercise, what compound do skeletal muscles primarily produce?

Lactate Signup and view all the answers

What is one possible fate of lactate after being released into the blood?

It can be converted back to pyruvate in other tissues Signup and view all the answers

What is required for the Glyceraldehyde-3-phosphate Dehydrogenase reaction to occur?

NAD+ Signup and view all the answers

Which of the following statements best describes lactate's role in cellular metabolism?

Lactate is a mobile form of nutrient energy and may signal other cells Signup and view all the answers

What is the role of Alcohol Dehydrogenase in pyruvate metabolism?

Converts NADH to NAD+ Signup and view all the answers

Which of the following enzymes is NOT one of the key regulators of glycolysis?

Citrate lyase Signup and view all the answers

How does high ATP concentration affect glycolysis?

Inhibits phosphofructokinase and pyruvate kinase Signup and view all the answers

Which substrate is known to inhibit hexokinase?

Glucose-6-phosphate Signup and view all the answers

During brief and intense exercise, which pathway do skeletal muscles primarily utilize?

Fermentation to lactate Signup and view all the answers

What is the function of lactate in the body?

Mobilizes energy for other tissues Signup and view all the answers

Which hormone stimulates the biosynthesis of glycolytic enzymes?

Insulin Signup and view all the answers

What happens to lactate produced in exercising muscles after exercise?

It is transformed back into pyruvate Signup and view all the answers

Study Notes

Intended Learning Outcomes

Students should be able to understand the key aspects of glycolysis by the end of the lecture.

Glycolysis

Glycolysis is the oxidation of glucose to pyruvate, occurring in the presence of oxygen or resulting in lactate production in the absence of oxygen.
The process occurs in the cytoplasm of all tissue cells.
Glycolysis is crucial for tissues lacking mitochondria, such as mature Red Blood Cells (RBCs).

Glycolysis: Specific Tissue Functions

RBCs: Exclusively rely on glycolysis for energy production.
Skeletal Muscle: A primary energy source during high-intensity exercise.
Adipose Tissue: Produces glycerol-P for Triglyceride (TG) synthesis and acetyl-CoA for Fatty Acid (FA) synthesis.
Liver: Involved in acetyl-CoA production for FA synthesis and glycerol-P for TG synthesis.

ATP Yield in Glycolysis

ATP calculation is based on ATP generated minus ATP utilized.
Anaerobic glycolysis produces a net gain of 2 ATP.
Aerobic glycolysis yields 8 ATP.

Glycolysis Pathway

(Diagram needed here for accurate notes, but the provided text outlines the steps and enzymes involved.)*
Glucose is phosphorylated to glucose-6-phosphate.
Fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate.
The 6-carbon molecule fructose-1,6-bisphosphate is split into two 3-carbon molecules (glyceraldehyde-3-phosphate(G3P) and dihydroxyacetone phosphate(DHAP)).
G3P is further metabolized to produce ATP and NADH.
After a series of enzymatic reactions, pyruvate is formed.

Differences between Glucokinase and Hexokinase

Feature	Glucokinase	Hexokinase
Site	Liver cells only	All tissues
Substrate	Glucose only	Hexoses
Insulin	Stimulated	No effect
Affinity	Low (high Km)	High (low Km)
G-6-P	No effect	Inhibited
Glucose levels	Acts over 100 mg%	Acts on low glucose levels

Difference between Aerobic and Anaerobic Glycolysis

Feature	Aerobic Glycolysis	Anaerobic Glycolysis
End Product	Pyruvate	Lactate
Energy	8 ATP	2 ATP
NAD+ Regeneration	Through respiratory chain in mitochondria	Through lactate formation

Biological Importance of Glycolysis

Energy Production: Anaerobic glycolysis generates 2 ATP, while aerobic glycolysis yields 8 ATP.
Oxygenation of Tissues: Formation of 2,3-bisphosphoglycerate decreases hemoglobin's affinity for oxygen.
Intermediate Production: 3-phosphoglycerate is an intermediate, forming amino acid serine.
Mitochondrial Fuel Source: Aerobic glycolysis provides pyruvate to the Krebs Cycle via the formation of acetyl CoA.

Fate of Pyruvate

Anaerobic glycolysis: Pyruvate is reduced to lactate.
Alcoholic fermentation: Pyruvate is converted to ethanol.
Aerobic respiration: Pyruvate enters the Citric Acid Cycle (Krebs Cycle).

Fermentation

Anaerobic organisms lack a respiratory chain.
They oxidize NADH by reducing pyruvate to lactate or other more reduced compounds.
Fermentation includes glycolysis plus the reoxidation of NADH.
The process is needed to oxidize NADH in the absence of an electron transport chain.
Pyruvate is the product in this process.

Lactate Dehydrogenase

Lactate Dehydrogenase (LDH) catalyzes the reduction of pyruvate to lactate, oxidizing NADH to NAD+.
Lactate is a mobile nutrient energy source and potential signaling molecule in mammals.
Cells have carrier proteins to facilitate lactate transport.

Lactate Metabolism

Lactate produced in active skeletal muscles can be released into the bloodstream and taken up by other tissues.
Lactate can be converted back into pyruvate by LDH.
Pyruvate can then enter the Krebs Cycle or be converted to glucose via gluconeogenesis in the liver.

Regulation of Glycolysis

Glycolysis is controlled by 3 irreversible enzymes:
Glucokinase/hexokinase
Phosphofructokinase-1
Pyruvate kinase.
Insulin stimulates the last 3 enzymes, boosting glycolysis.
Adrenaline and glucagon inhibit pyruvate kinase, limiting the process.
G-6-P inhibits hexokinase(not glucokinase) while citrate inhibits phosphofructokinase.
High/low levels of ATP,ADP and AMP can regulate the process.

Sources of Lactate

Skeletal muscles, during high-intensity exercise which produces lactate,
Astrocytes, which produce and release lactate in the brain. In RBCs, NAD+ regeneration converts pyruvate into lactate.

Lactate's Function

Lactate is an end-product of fermentation.
It's a mobile form of energy.
Cell membranes contain carriers for lactate transport.
Lactate in blood can be used by other cells or converted back to pyruvate.

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Description

This quiz covers key aspects of glycolysis, including its process of converting glucose to pyruvate and its importance in different tissues such as RBCs, skeletal muscle, and liver. Understand how ATP yield varies in aerobic and anaerobic conditions and the role of glycolysis in energy production.