Cellular Respiration

Catabolic

A reaction that breaks something down, like cellular respiration destroying glucose to turn it into ATP. The opposite being anabolic, where something is created.

Anabolic

A reaction that builds something up, like photosynthesis creates glucose. The opposite being catabolic, where something is catabolized, or destroyed.

Exergonic

A reaction that releases energy. Cellular respiration is an example of an exergonic reaction.

Endergonic

A reaction that takes in energy. Photosynthesis is an example of an endergonic reaction.

Yeast

A single celled eukaryotic organism that undergoes alcoholic fermentation.

Eukaryotes

All multicellular organisms, and some unicellular (like yeast). These cells are able to undergo aerobic respiration and receive a yield of 36 ATP compared to the measly 4 from anaerobic respiration.

Fermentation

An anaerobic (without oxygen) process that converts NADH back into NAD+ so that glycolysis can occur again. This occurs in many bacteria and yeast as well. Yeast undergo alcoholic fermentation, and human muscles cells undergo lactic acid fermentation when they run out of oxygen.

NAD+

An electron carrier used in cellular respiration who is reduced to NADH after accepting electrons. NAD+ is the oxidized form of NADH.

NADH

An electron carrier who is oxidized to NAD+ after losing electrons in the Electron Transport Chain (ETC).

Prokaryotes

Bacteria and other single celled organisms. These cells cannot undergo aerobic respiration because they do not have mitochondria (a membrane-bound organelle). Instead, they undergo anaerobic fermentation.

Glucose

C6H12O6. The product in photosynthesis, and the reactant in cellular respiration.

Reduction

Gaining electrons. For example, NAD+ is reduced to NADH when it gains electrons from glucose.

Oxidation

Losing electrons. For example, NADH is oxidized to NAD+ when it loses electrons to eventually Oxygen in the Electron Transport Chain (ETC).

Glycolysis

Means "the breakdown of sugar." It is the process by which we turn glucose C6H12O6 into 2 pyruvate, 2 net ATP, and 2 NADH. Occurs in both eukaryotes and prokaryotes in their cytosol (cytoplasm).

Aerobic

Means "with oxygen." This is the more complex fate of glucose where it is broken down into 36 ATP, rather than the 2 net ATP we see in Anaerobic respiration alone.

Anaerobic

Means "without oxygen." This is the less evolved fate of glucose and involves fermentation--either alcoholic (yeast) or lactic acid (muscle cells). The total ATP yield from this process is only 4 (2 net) compared to the 36 of aerobic respiration.

Passive Transport

Movement across the membrane that does not require energy. When the protons (H+) flood ATP synthase, they are going down their concentration gradient and do not require the input of energy.

Active Transport

Movement across the membrane that requires the input of energy. Active transport uses the energy from the electrons in the ETC to move protons (H+) across the membrane to be used to turn ATP synthase later down the line.

Alcoholic Fermentation

NADH is converted back into NAD+ but generates a molecule of CO2 not seen in lactic acid fermentation. Yeast undergo this process to be able to continue using NAD+ in glycolysis in their cytosol.

Electrons

Negatively charged subatomic particles that are passed down between molecules in the electron transport chain. They are removed from glucose in the Krebs Cycle and Glycolysis, whereas the carbons of glucose are all lost as a carbon dioxide (CO2) byproduct.

Coenzyme A

One of the reactants in Acetyl CoA formation that bonds with pyruvate.

Glyco-

Prefix that means "sugar"

ATP synthase

Protein who undergoes a conformational change in the Electron Transport Chain (ETC) after a flood of protons (H+) come down their concentration gradient (passive transport) to cause this protein to rotate. It adds a phosphate to ADP to make ATP.

H+

Protons. These are used to come down their concentration gradient (passive transport) after being pumped across the membrane with the energy from the electrons being passed down the ETC.

Acetyl CoA

Pyruvate is converted into this molecule if oxygen is present for aerobic respiration to occur. This is converted into citric acid in the first step of the Krebs (or Citric Acid) cycle.

Byproduct

Something that is produced in a reaction that is not the intended outcome. For example, O2 is the byproduct of photosynthesis, and CO2 is the byproduct of cellular respiration.

-lysis

Suffix that means "to break." For example, hydrolysis breaks up a macromolecule with the addition of water.

Electron Transport Chain (ETC)

Taking place on the cristae of the mitochondria, this takes the electrons from NADH and FADH2 and uses them to drive the creation of ATP by means of a proton (H+) gradient that uses the energy from the electrons to pump protons out of the mitochondrial matrix, who then return to the matrix by means of passive transport and turn ATP synthase to generate 36 ATP.

Pyruvate

The 3-carbon molecule produced at the end of glycolysis. There are 2 of these produced because glucose has 6 carbons total. These will be converted into acetyl coA in aerobic respiration, or used to convert NADH back to NAD+ in fermentation.

Carbon Dioxide (CO2)

The byproduct of aerobic respiration and alcoholic fermentation. All 6 of glucose's carbons are lost as molecules of CO2 gas. This is one of the products of cellular respiration, and one of the reactants in photosynthesis.

Conformational Change

The change in a protein's shape. Often this prevents a protein from working, but in regards to ATP Synthase, it is used to generate ATP from ADP.

3.5%

The efficiency of glycolysis alone. This is why large eukaryotic cells require aerobic respiration to generate 36 ATP rather than the 4 total seen in anaerobic respiration.

Adenosine TriPhosphate (ATP)

The energy currency of the cell that is created during the process of cellular respiration. Glucose goes in, and ATP comes out. In aerobic (with oxygen) respiration, a 36 ATP yield is possible, whereas in anaerobic (without oxygen) respiration, 4 total (2 net) is possible.

Oxygen (O2)

The final electron acceptor during aerobic respiration, and thus why aerobic respiration (which means with oxygen) requires oxygen. We inhale this gas which is released as a byproduct during photosynthesis, and is a reactant during cellular respiration.

Cristae

The folds of the inner membrane of the mitochondria. This is where ATP synthase is using the concentration gradients of protons (H+) to cause a conformational change in ATP synthase that leads to the creation of 36 ATP.

Mitochondrial Matrix

The inner core of this organelle is where the Krebs Cycle occurs.

Cell Membrane

The location of aerobic respiration in SOME prokaryotes. These prokaryotes are believed to be the ancestors who were engulfed and turned into mitochondria according to the endosymbiont theory.

36-38

The net yield of ATP at the end of aerobic respiration.

2

The net yield of ATP at the end of glycolysis alone.

Citric Acid Cycle

The other name for the Krebs Cycle that occurs in the mitochondrial matrix which converts Acetyl CoA into first citric acid, and then eventually all the carbons are released as a CO2 byproduct.

Cellular Respiration

The process by which cells catabolize (break down) complex molecules into ATP. There is aerobic (with oxygen, 36 ATP yield) and anaerobic (without oxygen, 4 ATP yield). It consists of steps like glycolysis acetyl coA formation, the Krebs Cycle, and the Electron Transport Chain.

Photosynthesis

The process by which plants convert sunlight into glucose. The reaction is the inverse (reverse/opposite) of cellular respiration.

H2O

The product at the end of cellular respiration made after O2 (oxygen) is the final electron acceptor. One of the reactants during photosynthesis.

Lactic Acid

The product produced when cells undergo fermentation to return NADH back to NAD+. This occurs in the muscle cells of humans.

Cytosol

The site of glycolysis in both eukaryotes and prokaryotes. May also be called the cytoplasm.

Mitochondria

The site of of aerobic (with oxygen) respiration. This is where Acetyl coA goes to eventually be converted into ATP in the matrix of this organelle found only in eukaryotes.

Muscle Cells

These cells of the human body will undergo lactic acid fermentation once oxygen has been depleted (lost) creating an anaerobic environment. This allows for 4 ATP to be made BACK in continuing glycolysis, but no new ATP is made during fermentation, it only returns NADH to NAD+.

Krebs Cycle

This converts Acetyl CoA (what was pyruvate after glycolysis) into 6 NADH, 2 FADH2, 2 ATP, and 4 CO2. After this step there are no more carbons remaining, they have all been lost as a carbon dioxide byproduct. It takes place in the mitochondrial matrix.

Total/gross

This means the full amount produced, ignoring the amount consumed. For example, a total/gross gain of 4 ATP from glycolysis, but only a net gain of 2 because 2 ATP were consumed.

Net

This means the result after calculating for expenses. If 4 ATP are created, but 2 are used up, then you have a net gain of 2, and a total or gross gain of 4.