Lecture 10 - Glycolysis and Gluconeogenesis
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911 Terms
What is glycolysis?
The metabolic pathway that breaks down glucose into pyruvate.
What is the primary purpose of glycolysis?
To extract energy from glucose and produce metabolic intermediates.
Is glycolysis anabolic or catabolic?
Catabolic.
Why is glucose considered an excellent fuel?
It yields a large amount of energy when oxidized.
What energy-carrying molecules can be generated from glucose metabolism?
ATP, NADH, NADPH, and FADH₂.
Why is glucose widely used as an energy source?
Many organisms and tissues can meet their energy needs using glucose alone.
What makes glucose a highly efficient metabolic fuel?
It can be readily oxidized to release usable cellular energy.
Why is glucose a useful storage molecule?
It can be efficiently stored as polysaccharides.
How is glucose stored in animals?
As glycogen.
How is glucose stored in plants for energy reserves?
As starch.
What structural polysaccharide is made from glucose in plants?
Cellulose.
Match the glucose storage form with the organism.
Animals → Glycogen
Plants (energy storage) → Starch
Plants (structural) → Cellulose
Why is glucose considered a versatile biochemical precursor?
Its metabolites can be used to synthesize many cellular molecules.
What important glycolytic product serves as a precursor for biosynthesis?
Pyruvate.
Why is pyruvate important beyond energy production?
It serves as a precursor for many biosynthetic pathways.
What major classes of molecules can be synthesized from glucose-derived carbon skeletons in bacteria?
Amino acids, membrane lipids, nucleotides, and cofactors.
How do bacteria use glucose besides generating energy?
As a carbon source for biosynthesis.
What molecules can bacteria synthesize using carbon from glucose?
Amino acids
Membrane lipids
dNTPs
rNTPs
Metabolic cofactors
What does dNTP stand for?
Deoxyribonucleoside triphosphate.
What does rNTP stand for?
Ribonucleoside triphosphate.
What important cellular energy molecule is generated during glycolysis?
ATP.
What electron carrier is directly produced during glycolysis?
NADH.
Why is NADH important?
It carries high-energy electrons for ATP production.
Why is glycolysis historically important in biochemistry?
Research on glycolysis helped establish many core biochemical principles.
What major biochemical concepts were discovered through glycolysis research?
Coenzymes
ATP as an energy currency
Enzyme purification methods
How did glycolysis contribute to the development of modern biochemistry?
It served as one of the first thoroughly characterized metabolic pathways.
What is glycolysis?
The breakdown of glucose into pyruvate.
What is the end product of glycolysis?
Pyruvate.
Why is glucose considered an excellent fuel?
It yields substantial energy upon oxidation.
What is the storage form of glucose in animals?
Glycogen.
What is the storage form of glucose in plants?
Starch.
What important biosynthetic precursor is produced by glycolysis?
Pyruvate.
What electron carrier is produced during glycolysis?
NADH.
Why is glucose one of the most important molecules in metabolism?
Glucose is both an excellent fuel and a versatile biosynthetic precursor. Through glycolysis, glucose is broken down into pyruvate, producing ATP and NADH that support cellular energy needs. Glucose can be efficiently stored as glycogen in animals and starch in plants, while cellulose provides structural support in plants. Additionally, glucose-derived intermediates supply carbon skeletons for the synthesis of amino acids, membrane lipids, nucleotides (dNTPs and rNTPs), and metabolic cofactors. The study of glycolysis was foundational to modern biochemistry, leading to discoveries involving ATP, coenzymes, and enzyme purification techniques.
What are feeder pathways for glycolysis?
Metabolic pathways that convert carbohydrates other than free glucose into intermediates that enter glycolysis.
Why are feeder pathways important?
They allow cells to obtain energy from stored carbohydrates and dietary sugars.
Where do feeder pathways for glycolysis occur?
In the cytosol.
What enzyme releases glucose units from glycogen and starch?
Glycogen phosphorylase.
What is the product of glycogen phosphorylase activity?
Glucose 1-phosphate (G1P).
How is glycogen broken down for entry into glycolysis?
Glycogen phosphorylase cleaves glucose residues to form glucose 1-phosphate.
What storage polysaccharides can feed into glycolysis?
Glycogen and starch.
Why is glucose 1-phosphate advantageous compared with free glucose?
It is already phosphorylated, saving the cell ATP.
What must happen to disaccharides before they can enter glycolysis?
They must be hydrolyzed into monosaccharides.
What is hydrolysis?
The cleavage of a molecule using water.
What monosaccharides are produced when lactose is hydrolyzed?
Glucose and galactose.
What two sugars make up lactose?
Glucose and galactose.
What monosaccharides are produced when sucrose is hydrolyzed?
Glucose and fructose.
What two sugars make up sucrose?
Glucose and fructose.
Which monosaccharides can enter glycolysis through feeder pathways?
Fructose, galactose, and mannose.
Do all sugars enter glycolysis at the same point?
No, different sugars enter at different intermediates.
Which sugars enter glycolysis at different points than glucose?
Fructose, galactose, and mannose.
Why are feeder pathways necessary for sugars such as fructose and galactose?
They must first be converted into glycolytic intermediates.
What is G1P?
Glucose 1-phosphate, a product of glycogen and starch breakdown.
What role does glucose 1-phosphate play in metabolism?
It is converted into glycolytic intermediates for energy production.
What enzyme cleaves glucose from glycogen and starch?
Glycogen phosphorylase.
What product is generated by glycogen phosphorylase?
Glucose 1-phosphate.
What are the products of lactose hydrolysis?
Glucose and galactose.
What are the products of sucrose hydrolysis?
Glucose and fructose.
Which sugars enter glycolysis through feeder pathways?
Fructose, galactose, and mannose.
Where do feeder pathways for glycolysis occur?
In the cytosol.
Describe how feeder pathways supply substrates to glycolysis.
Feeder pathways allow stored and dietary carbohydrates to enter glycolysis. Glycogen and starch are degraded by glycogen phosphorylase, producing glucose 1-phosphate (G1P). Disaccharides are hydrolyzed into monosaccharides: lactose yields glucose and galactose, while sucrose yields glucose and fructose. Monosaccharides such as fructose, galactose, and mannose are converted into glycolytic intermediates and enter glycolysis at different points. These processes occur in the cytosol and ensure that a variety of carbohydrate sources can be used for energy production.
Why is glycolysis considered one of the earliest metabolic pathways?
It likely evolved before photosynthesis and provided an early method of energy production.
Did glycolysis evolve before or after photosynthesis?
Before photosynthesis.
What was Earth's atmosphere like when glycolysis evolved?
Anaerobic (little or no oxygen).
Why was glycolysis useful to early organisms?
It allowed them to extract energy from glucose without oxygen.
What major evolutionary advantage did glycolysis provide?
Anaerobic ATP production.
How did early organisms begin extracting energy from glucose?
By phosphorylating glucose and harvesting energy from high-energy intermediates.
Why is glucose phosphorylated during glycolysis?
To activate it for subsequent reactions.
What is the overall end product of glycolysis?
Pyruvate.
Why is pyruvate considered an important metabolic intermediate?
It can enter many different metabolic pathways.
Which cells rely entirely on glycolysis for ATP production?
Red blood cells (RBCs).
Why do red blood cells depend completely on glycolysis?
They lack mitochondria.
When do muscle cells rely heavily on glycolysis?
During short bursts of intense activity.
Why is glycolysis important during intense exercise?
It can rapidly generate ATP without requiring oxygen.
What are the two major phases of glycolysis?
The preparatory phase and the payoff phase.
What occurs during the preparatory phase of glycolysis?
Glucose is phosphorylated and converted into glyceraldehyde 3-phosphate.
Why is the preparatory phase called the energy investment phase?
ATP is consumed to activate glucose.
What is the first major event in glycolysis?
Phosphorylation of glucose.
What is the purpose of the first priming reaction?
To activate glucose by phosphorylation.
What is the purpose of the second priming reaction?
To further activate the sugar for cleavage.
What happens after the priming reactions?
The 6-carbon sugar phosphate is cleaved into two 3-carbon sugar phosphates.
What is produced when the 6-carbon sugar is split?
Two 3-carbon sugar phosphates.
What molecule is ultimately formed during the preparatory phase?
Glyceraldehyde 3-phosphate (G3P).
What occurs during the payoff phase of glycolysis?
Glyceraldehyde 3-phosphate is oxidized to pyruvate while ATP and NADH are produced.
Why is the payoff phase called the energy generation phase?
ATP and NADH are generated.
What happens to glyceraldehyde 3-phosphate during the payoff phase?
It undergoes oxidation and phosphorylation.
What electron carrier is produced during the oxidation of G3P?
NADH.
What is substrate-level phosphorylation?
Direct formation of ATP by transferring a phosphate group from a metabolic intermediate to ADP.
How many substrate-level phosphorylation reactions occur in glycolysis?
Two.
What is the first ATP-forming reaction in glycolysis?
The first substrate-level phosphorylation step during the payoff phase.
What is the second ATP-forming reaction in glycolysis?
The second substrate-level phosphorylation step that produces ATP and pyruvate.
List the major events of glycolysis in order.
First priming reaction (phosphorylation)
Second priming reaction (phosphorylation)
Cleavage of 6-carbon sugar into two 3-carbon sugars
Oxidation and phosphorylation of G3P
First substrate-level phosphorylation (ATP formation)
Second substrate-level phosphorylation (ATP formation)
Formation of pyruvate
Which phase uses ATP?
Preparatory phase.
Which phase produces ATP and NADH?
Payoff phase.
Compare the preparatory and payoff phases of glycolysis.
The preparatory phase consumes ATP to phosphorylate and split glucose into two G3P molecules, while the payoff phase oxidizes G3P to pyruvate and generates ATP and NADH.
What is the final product of glycolysis?
Pyruvate.
What are the two phases of glycolysis?
Preparatory phase and payoff phase.
Which phase of glycolysis consumes ATP?
Preparatory phase.
Which phase produces ATP and NADH?
Payoff phase.
What cells depend entirely on glycolysis for ATP production?
Red blood cells.