Intracellular, extracellular enzyme-catalysed reactions

What is the role of enzymes in metabolism?

Enzymes are essential for metabolism, the sum of all chemical reactions in living organisms.

Define intracellular enzymes.

Intracellular enzymes operate within cells, driving pathways such as glycolysis and the Krebs cycle.

What is glycolysis?

The first step of cellular respiration where glucose is broken into pyruvate, producing ATP and NADH.

Where does glycolysis occur?

In the cytoplasm.

What is the role of hexokinase in glycolysis?

Hexokinase phosphorylates glucose to form glucose‑6‑phosphate, trapping it inside the cell.

What are the end products of glycolysis?

Pyruvate, ATP, and NADH.

Is glycolysis aerobic or anaerobic?

Anaerobic; it does not require oxygen.

What is the Krebs cycle?

A stage of aerobic respiration in the mitochondrial matrix that oxidizes acetyl‑CoA into carbon dioxide.

What happens to acetyl-CoA in the Krebs cycle?

It is oxidized to carbon dioxide, producing NADH, FADH₂, and ATP.

What is the role of citrate synthase in the Krebs cycle?

It catalyzes the reaction between acetyl‑CoA and oxaloacetate to form citrate.

What are extracellular enzymes?

Enzymes that function outside cells to break down large molecules into smaller, absorbable units.

Give an example of extracellular enzyme activity.

Chemical digestion in the gut, where enzymes break food macromolecules into monomers.

What is the function of proteases?

Proteases break proteins into amino acids.

What is the role of amylase in digestion?

Amylase breaks starch into maltose, which maltase converts into glucose.

How are extracellular enzymes often secreted?

As inactive precursors (zymogens) to prevent self‑digestion of tissues.

Why are intracellular reactions like glycolysis and the Krebs cycle important?

They produce ATP, the cell’s main energy currency.

What is the significance of extracellular digestion?

It breaks food into absorbable units that supply raw materials for cellular processes.

What is enzyme specificity?

Each enzyme acts on a specific substrate, ensuring precise metabolic control.

What conditions do enzymes require to function optimally?

Optimal temperature and pH.

Give an example of an enzyme adapted to a specific environment.

Pepsin works best in stomach acid; trypsin works in the alkaline small intestine.

How do intracellular and extracellular enzymes illustrate interconnectedness in biological systems?

Both types support metabolism and homeostasis by coordinating internal and external biochemical processes.