Biochemistry: Enzymes and Cofactors

The smooth endoplasmic reticulum (ER) in liver cells is responsible for detoxifying harmful substances like toxins, drugs, and metabolic byproducts.

Cytosol refers to the fluid component of the cytoplasm, while cytoplasm encompasses both the cytosol and all the organelles and other components suspended within it.

A holoenzyme refers to the active form of an enzyme, formed when a cofactor binds to it.

Lysosomes, commonly known as the 'suicide bags' of the cell, are responsible for breaking down waste materials, such as nutrients, bacteria, and cellular debris.

The Golgi apparatus acts as a processing center for proteins, modifying and packaging them for distribution within and outside the cell.

Hydrogen bonds play a crucial role in forming the secondary structure of a protein, shaping it into various arrangements like alpha-helices and beta-sheets.

Peroxisomes in liver cells are tasked with breaking down various substances including fatty acids, amino acids, and toxic compounds, producing hydrogen peroxide as a byproduct.

The hydrophobic effect, a non-covalent interaction, contributes to the tertiary structure of a protein by allowing hydrophobic groups (water-fearing) to cluster together, excluding water.

The quaternary structure of a protein refers to the three-dimensional shape formed by the association of two or more separate peptide chains.

Enzymes escaping from lysosomes become inactive because the neutral pH of the cytosol is not conducive to their optimal function.

Oxygen, the final electron acceptor in the Electron Transport Chain (ETC), receives electrons from the chain and binds with protons (H+) to form water.

Denaturation occurs when a protein loses its natural shape due to unfavorable conditions such as extreme temperature, pH, or solvent changes.

A prosthetic group is a non-protein cofactor that is covalently bound to an enzyme, becoming an integral part of its structure and function.

Oxidative phosphorylation, the process of generating ATP from ADP, takes place within the Electron Transport Chain (ETC), driven by a proton gradient.

Coenzyme Q (CoQ) or Ubiquinone, a mobile carrier molecule in the Electron Transport Chain (ETC), accepts electrons from both NADH and FADH2, shuttling them through the chain.

Each NADH molecule yields a theoretical 3 ATP molecules, whereas each FADH2 molecule produces 2 ATP molecules.

Cytochrome C, a protein in the Electron Transport Chain (ETC), plays a key role in electron transfer by undergoing redox reactions, accepting and donating electrons.

The Electron Transport Chain (ETC) is located within the inner mitochondrial membrane of eukaryotic cells, specifically on its cristae.

C4 photosynthesis provides a significant advantage in hot and dry climates by enabling a faster fixation rate of carbon dioxide, making it more efficient.

In CAM photosynthesis, PEP carboxylase acts as a primary enzyme, fixing CO2 into oxaloacetate (OAA), which then forms malic acid.

C4 plants exhibit a characteristic leaf structure called Kranz anatomy, characterized by a ring of mesophyll cells surrounding bundle sheath cells.

The Calvin cycle, shared by both C3 and C4 plants, plays a vital role in regenerating RuBP, the initial carbon acceptor, after the fixation of CO2.

The fundamental difference between C4 and CAM photosynthesis lies in the timing of carbon dioxide fixation and the enzymes used. C4 uses PEP carboxylase in the initial fixation, while CAM uses RuBisCO.

C4 photosynthesis requires an additional ATP molecule for every CO2 molecule fixed, utilizing ATP to convert AMP back to ADP.

The main difference in ATP totals between eukaryotes and prokaryotes arises from the transport of NADH across the mitochondrial membrane in eukaryotes. Prokaryotes lack this step, resulting in higher ATP yields.

The proton concentration gradient established across the mitochondrial membrane is crucial for ATP generation in chemiosmosis, as protons flow from high concentration to low, driving ATP synthase.

In eukaryotic cells, transferring two NADH molecules from the cytosol to the mitochondrial matrix requires a cost of 2 ATP molecules.

The oxidation of NADH and FADH2 in the Electron Transport Chain (ETC) results in the release of protons (H+), which contribute to the proton gradient across the mitochondrial membrane.

The inner mitochondrial membrane serves as the site for ATP production through chemiosmosis, housing the Electron Transport Chain (ETC) and ATP synthase.

Protons (H+) are transported from the mitochondrial matrix to the intermembrane space during chemiosmosis, creating a concentration gradient that drives ATP synthesis.