Glycolysis Flashcards
Where does glycolysis occur?
In the cytoplasm
What is glycolysis? (What happens to glucose in glycolysis?)
The process where glucose (a 6-carbon molecule) is broken down into two 3-carbon molecules of pyruvate.
What are two phases of glycolysis?
- Energy investment phase (ATP consumed) 5 steps
- Energy payoff phase (ATP and NADH produced) 5 steps
What is the net gain of glycolysis?
2 ATP and 2 NADH (from 1 glucose molecule)
What is pyruvate and what does this molecule do in different cycles?
The 3-carbon molecule formed after glycolysis. It can go into the Krebs cycle (in the mitochondria) or undergo fermentation in anaerobic conditions.
True/False
Glycolysis is an aerobic process.
False
It is anaerobic, meaning it does not require any oxygen.
How many ATP molecules are produced in glycolysis?
2
What role does NAD+ play in glycolysis?
NAD+ → NADH
(reduction of NAD+ to NADH)
During oxidation, NAD+ accepts two electrons and one proton to become NADH, which is the reduced form of NAD+.
For glycolysis to continue, NAD+ must be regenerated. This is typically achieved through either the reduction of pyruvate to lactate (in anaerobic conditions) or the transfer of electrons from NADH to the electron transport chain (in aerobic conditions).
The role of NAD+ (glycolysis)
NAD+ is essential for facilitating the oxidation reactions in glycolysis and is recycled to ensure that glycolysis can continue producing ATP efficiently.
What is glucose transformed into?
Glucose → Pyruvate
(2 molecules of 3 carbons)
Importance of glycolysis
Glycolysis is a central metabolic pathway that plays a critical role in cellular energy production and is important for several reasons:
Glycolysis is one of the primary pathways for generating ATP, the energy currency of the cell. Although it produces only a small amount of ATP (2 ATP molecules per molecule of glucose), it provides quick energy, especially in cells with high energy demands or in anaerobic conditions where other energy-generating pathways (like oxidative phosphorylation) are unavailable.
Glycolysis produces NADH, which can be used in the electron transport chain (in aerobic conditions) to generate much more ATP through oxidative phosphorylation. In anaerobic conditions, NADH is used to reduce pyruvate to lactate, ensuring that NAD+ is regenerated, allowing glycolysis to continue.
The intermediates produced in glycolysis, particularly pyruvate and certain triose phosphates, serve as precursors for several other metabolic pathways:
- Pyruvate can be converted into Acetyl-CoA, which enters the citric acid cycle (Krebs cycle) for further energy production.
- Triose phosphates (such as dihydroxyacetone phosphate) can be used in biosynthetic pathways to form amino acids, lipids, and other essential molecules.
Glycolysis can occur in the absence of oxygen (anaerobic conditions), providing energy to cells when oxygen is scarce, such as in muscle cells during intense exercise or in some microorganisms. In these conditions, the conversion of pyruvate to lactate (in mammals) or ethanol (in yeast) regenerates NAD+, ensuring continued glycolysis and energy production.
Glycolysis can operate in both aerobic and anaerobic conditions, making it a flexible and vital pathway for cells under various metabolic states. This adaptability allows cells to switch between aerobic respiration and anaerobic fermentation, depending on the oxygen availability.
Since glycolysis occurs in the cytoplasm and involves relatively few enzymatic steps, it can be quickly activated to meet sudden energy demands, such as during periods of exercise or stress. This makes glycolysis a fast and efficient energy-producing pathway.
Glycolysis is a fundamental metabolic pathway that provides energy (ATP), intermediates for biosynthesis, and the flexibility to operate under both aerobic and anaerobic conditions. It ensures that cells can maintain energy homeostasis and continue to function even under varying environmental and physiological conditions.
What is the connection between glycolysis and photosynthesis?
Glucose that is produced in photosynthesis can later be used in glycolysis for ATP production.
Which enzyme catalyzes the conversion of glucose to glucose-6-phosphate?
Hexokinase
What is the end product of glycolysis?
Pyruvate
