Krebs Cycle

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Krebs Cycle Noun

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[krebz sy-kuhl]

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Krebs Cycle

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A sequence of chemical reactions in aerobic organisms that generates energy-storing molecules as part of cellular respiration.

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Example: This diagram shows the Krebs Cycle, a key step in cellular respiration. Acetyl-CoA enters the cycle, releasing CO2 and producing energy molecules like ATP.

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Cellular Respiration Noun

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[sel-yuh-ler res-puh-rey-shuhn]

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Cellular Respiration

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The metabolic process in which cells produce energy in the form of ATP from nutrients like glucose.

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Example: This diagram shows how plants use photosynthesis to create oxygen and glucose, which animals then use for cellular respiration, releasing carbon dioxide and water.

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Mitochondrion Noun

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[my-toh-kon-dree-uhn]

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Mitochondrion

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The organelle in eukaryotic cells where the Krebs cycle and electron transport chain occur, producing most of the cell's ATP.

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Example: This image shows a mitochondrion taking in food (like rice) and converting it into usable energy (ATP) for the cell's activities.

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Mitochondrial Matrix Noun

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[my-toh-kon-dree-uhl mey-triks]

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Mitochondrial Matrix

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The innermost compartment of the mitochondrion, which is the specific site of the Krebs cycle and pyruvate oxidation reactions.

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Example: This diagram shows the mitochondrion and provides a magnified view of the mitochondrial matrix, the inner gel-like substance where the Krebs cycle reactions occur.

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Pyruvate Noun

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[pahy-roo-veyt]

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Pyruvate

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A three-carbon molecule that is the end product of glycolysis and serves as the starting material for pyruvate oxidation.

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Example: This diagram shows that pyruvate is a molecule made from glucose, which then enters the mitochondrion to fuel the Krebs cycle and produce energy (ATP).

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Pyruvate Oxidation Noun

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[pahy-roo-veyt ok-si-dey-shuhn]

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Pyruvate Oxidation

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The preparatory step where pyruvate is converted into acetyl CoA before entering the Krebs cycle, also called the link reaction.

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Example: A three-carbon pyruvate molecule is changed into a two-carbon acetyl CoA, releasing one carbon atom as carbon dioxide (CO2).

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Acetyl CoA Noun

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[uh-see-til koh-ey]

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Acetyl CoA

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A two-carbon molecule (acetyl coenzyme A) that enters the Krebs cycle by combining with oxaloacetate to form citrate.

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Example: This image shows two chemical pathways that create Acetyl-CoA, a key molecule that enters the Krebs cycle for energy production.

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Oxaloacetate Noun

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[ok-suh-loh-as-i-teyt]

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Oxaloacetate

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A four-carbon compound that combines with acetyl CoA to start the Krebs cycle and is regenerated at the cycle's end.

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Example: This image displays the skeletal structure of oxaloacetate, a key molecule in the Krebs cycle, showing how its atoms are arranged.

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Citrate Noun

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[si-treyt]

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Citrate

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The six-carbon molecule formed in the first step of the Krebs cycle when acetyl CoA joins with oxaloacetate.

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Example: This image shows the arrangement of atoms (carbon, oxygen, hydrogen) that make up a citrate molecule, a key substance in the Krebs cycle.

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ATP (Adenosine Triphosphate) Noun

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[ey-tee-pee (uh-den-uh-seen trahy-fos-feyt)]

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ATP (Adenosine Triphosphate)

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The primary energy-carrying molecule used to power most cellular activities, produced in small amounts during the Krebs cycle.

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Example: This diagram shows the structure of an ATP molecule, made of adenine, ribose, and a triphosphate group, highlighting the high-energy bonds that store cellular energy.