Metabolic Reactions, Glycolysis, and Cellular Respiration Overview

What are the two main types of metabolic reactions?

Catabolism (degradative reactions) and anabolism (biosynthetic reactions).

What is the primary function of catabolic reactions?

To generate energy and reducing power for cellular processes.

What is the major fuel source for most cells during catabolic reactions?

Glucose.

What is the overall reaction for the complete oxidation of glucose?

Glucose → 6 CO₂ + 6 H₂O, ∆G = -686 kcal/mole.

What is the significance of the stepwise breakdown of glucose?

It allows for a gradual release of energy, facilitating trapping energy in chemical form instead of losing it as heat.

What are the three pathways for the complete breakdown of glucose?

Glycolysis, TCA cycle, and electron transport chain (ETC).

What is the main form of energy currency in cells?

ATP (adenosine triphosphate).

What is the role of NAD+ in metabolic reactions?

NAD+ acts as an electron acceptor in oxidation-reduction reactions, converting to NADH.

What is glycolysis?

A metabolic process that breaks down glucose into pyruvate, generating ATP and NADH.

What are the two stages of glycolysis?

Stage A (energy investment) and Stage B (energy extraction).

What happens during Stage A of glycolysis?

Energy is expended; 2 ATPs are used to convert glucose into a symmetrical hexose that splits into two trioses.

What are the products generated during Stage B of glycolysis?

4 ATPs and 2 NADH are generated through substrate-level phosphorylation.

What is substrate-level phosphorylation?

A process where ATP is generated by transferring a phosphate group directly from a substrate to ADP.

What is the end product of glycolysis?

2 molecules of pyruvate.

What is the fate of pyruvate in anaerobic conditions?

It is converted to lactate during fermentation.

What is the difference between facultative anaerobes and strictly anaerobic cells?

Facultative anaerobes can use both glycolysis and fermentation in the absence of oxygen, while strictly anaerobic cells can only carry out glycolysis and fermentation.

Why is the energy yield of glycolysis considered low?

Only 2 ATP are produced, which is about 2% of the total energy in glucose, as the end products are not completely oxidized.

How do cells regenerate NAD+ from NADH?

Through fermentation or other metabolic processes that convert NADH back to NAD+.

What is the role of enzymes in glycolysis?

Specific enzymes catalyze each step of glycolysis, facilitating the breakdown of glucose.

What is the significance of the movement of electrons in metabolic reactions?

It is crucial for energy production, as one molecule is oxidized (loses electrons) while another is reduced (gains electrons).

What is the importance of understanding glycolysis in cellular metabolism?

It is essential to know what goes into glycolysis and what the products are for understanding energy production in cells.

What is the primary role of NADH in cellular metabolism?

NADH serves as an electron and proton donor for biosynthetic reactions.

What is the purpose of fermentation?

To allow cells to continue glycolysis under anaerobic conditions.

What types of organisms can perform fermentation?

Anaerobes and facultative anaerobes, including some bacteria, yeast, and muscle cells.

What happens to NADH during fermentation?

NADH is converted back to NAD+ without oxygen.

What are the end products of fermentation in muscle cells?

Lactate is produced from pyruvate.

What are the end products of fermentation in yeast?

Ethanol and carbon dioxide are produced from pyruvate.

What problem arises from the production of lactate during vigorous exercise?

It can lead to muscle cramps and interfere with cellular functions.

What is 'oxygen debt' in muscle cells?

The condition where muscle cells require oxygen to convert lactate back to pyruvate after intense exercise.

What are the three main problems associated with glycolysis and fermentation?

1) Low energy efficiency of glucose catabolism, 2) Need to regenerate NAD+, 3) Production of harmful end products.

What is cellular respiration?

A set of oxygen-dependent metabolic processes by which cells derive energy from glucose or other fuel molecules.

What are the main products of the TCA cycle?

1 FADH2, 4 NADH, and 1 GTP (or ATP) per pyruvate.

Where does the TCA cycle occur in eukaryotic cells?

In the mitochondrial matrix.

What is the significance of the TCA cycle in cellular metabolism?

It oxidizes pyruvate to CO2 and produces reducing power in the form of NADH.

How does the TCA cycle relate to glycolysis?

The end product of glycolysis, pyruvate, feeds into the TCA cycle for further oxidation.

What is the main role of NAD+ in cellular metabolism?

To act as an electron acceptor in catabolic reactions.

What is the relationship between NADH and ATP production?

NADH is used in the electron transport chain to generate ATP.

What is the flow of carbon in the TCA cycle?

Reduced carbon compounds are converted to CO2, a highly oxidized and energy-poor compound.

What type of energy is primarily produced by the TCA cycle?

The cycle produces reducing power (NADH and FADH2) rather than direct ATP.

What determines the alcohol level of wine in fermentation?

Most yeast stop glycolysis at approximately 12-13% ethanol due to toxicity.

What is the electron transport chain (ETC)?

A series of protein complexes that transfer electrons and generate ATP using oxygen.

What is the role of oxygen in cellular respiration?

Oxygen is required for the electron transport chain to function and produce ATP.

What happens to pyruvate in the absence of oxygen?

It is converted to lactate or ethanol through fermentation.