Cell Biology: ATP and Mitochondria Function

Adenosine triphosphate (ATP) is the main energy currency for eukaryotic cells. It stores energy in the bonds connecting its phosphate groups.

The breakdown of ATP releases energy. This happens when a phosphate group is removed from ATP, forming ADP (adenosine diphosphate) and a free phosphate group.

The synthesis of ATP requires energy input. This energy comes from breaking down nutrients (carbohydrates, lipids and amino acids) and oxidizing them. Oxidation means stripping them of electrons.

Substrate-level phosphorylation is a process where a high-energy molecule directly donates a phosphate group to ADP to make ATP. It doesn't require oxygen (anaerobic).

Oxidative phosphorylation is a process where electrons are transferred from nutrients to high-energy intermediate molecules. These intermediates then power the electron transport chain and ATP synthase in mitochondria. It requires oxygen (aerobic).

F-class proton pumps are protein complexes that move protons down their concentration gradient. The energy released from this movement is used to make ATP.

LEO says GER. Loss of electrons = Oxidation; Gain of electrons = Reduction. Oxidation is the loss of electrons, often resulting in a more positive charge.

LEO says GER. Loss of electrons = Oxidation; Gain of electrons = Reduction. Reduction is the gain of electrons, often resulting in a more negative charge.

Mitochondria are organelles in eukaryotic cells where oxidative phosphorylation occurs. They have their own DNA and ribosomes.

V-class proton pumps are protein complexes that move protons against their concentration gradient. They require energy to do this.

The outer mitochondrial membrane is permeable to ions and most small molecules. It uses channel proteins known as porins.

The inner mitochondrial membrane requires protein transporters to move most molecules. It folds inwards to form cristae, increasing surface area. It contains proteins involved in energy production, including transport proteins, electron transport system components, and ATP synthase.

The space between the inner and outer mitochondrial membranes. It accumulates protons during oxidative phosphorylation.

The innermost region of the mitochondrion, surrounded by the inner mitochondrial membrane. It's where pyruvate decarboxylation, the citric acid cycle, and β-oxidation occur.

A series of enzymatic reactions that occur in the cytosol of the cell. It breaks down glucose into pyruvate and produces a net gain of 2 ATP molecules.

High energy electrons from NADH, produced in the cytosol, are transported into the mitochondrial matrix using electron shuttles.

A process that generates ATP using the energy stored in a proton gradient across the inner mitochondrial membrane.

The inner mitochondrial membrane is impermeable to NADH. To overcome this, the cell uses electron shuttles to transport NADH's high-energy electrons into the mitochondrial matrix.

Cancer cells often rely heavily on glycolysis for energy production, even in the presence of oxygen.

A protein embedded in the inner mitochondrial membrane that uses the proton gradient to synthesize ATP.

The malate-aspartate shuttle is a mechanism used by cells to transport electrons from NADH in the cytosol to the mitochondrial matrix for oxidative phosphorylation. It involves a series of reactions that transfer electrons from NADH to malate, which is then transported to the mitochondrial matrix. In the matrix, malate is oxidized back to oxaloacetate, regenerating NADH and allowing the electrons to enter the electron transport chain.

Cells can adjust their rate of energy production through glycolysis to meet their energy needs. This regulation happens through negative feedback mechanisms, where the products of reactions inhibit the enzymes that catalyze those reactions.

In the absence of oxygen, cells can't use oxidative phosphorylation, so they rely on anaerobic respiration. In this process, NAD+ is regenerated from NADH by reducing pyruvate. This produces lactic acid in animal cells and ethanol in yeast.

The citric acid cycle, or Krebs cycle, is a series of reactions that occur in the mitochondrial matrix. It breaks down acetyl-CoA into CO2, producing reduced electron carriers (NADH and FADH2), which power ATP synthesis.

Succinate dehydrogenase, an enzyme in the citric acid cycle, is directly attached to the inner mitochondrial membrane. This allows the FADH2 it produces to directly enter the electron transport chain without diffusing through the matrix.

The electron transport chain uses the energy from electrons carried by NADH and FADH2 to pump protons (H+) across the inner mitochondrial membrane, creating an electrochemical gradient, known as the proton motive force.

ATP synthase utilizes the energy stored in the proton motive force to synthesize ATP. Protons flow through ATP synthase down their concentration gradient, releasing energy to drive ATP production.

Fatty acids can be used as energy sources by the cell. They are first converted to fatty acyl-CoA and then transported into the mitochondrial matrix, where they are broken down through β-oxidation.

β-oxidation is a process that breaks down fatty acyl-CoA into 2-carbon acetyl-CoA units, releasing energy stored in the fatty acid. This generates FADH2 and NADH, which donate electrons to the electron transport chain to produce ATP.

ATP produced in the mitochondrial matrix needs to be transported to the cytosol for use by the cell. This is done through the ATP/ADP antiporter, which exchanges ADP with ATP through the inner mitochondrial membrane.