The four major classes of biological molecules are carbohydrates, lipids, proteins, and nucleic acids.

The building blocks of carbohydrates are monosaccharides like glucose, fructose, and galactose.

Lipids serve as energy storage molecules, components of cell membranes, and signaling molecules.

The basic structural units of proteins are amino acids linked by peptide bonds.

Nucleic acids store and transmit genetic information (DNA) and are involved in protein synthesis (RNA).

The central dogma states that genetic information flows from DNA to RNA to protein, but not from protein to nucleic acids.

Glycolysis is the metabolic pathway that converts glucose into two pyruvate molecules, generating a small amount of ATP and NADH.

The citric acid cycle is a series of chemical reactions that complete the oxidation of glucose molecules from glycolysis, generating ATP, CO2, and high-energy electron carriers.

The electron transport chain is the final stage of aerobic respiration, where electrons are transferred to oxygen, generating a large amount of ATP through oxidative phosphorylation.

Enzymes are biological catalysts that increase the rate of chemical reactions without being consumed in the process.

Factors that can affect enzyme activity include temperature, pH, enzyme concentration, substrate concentration, and the presence of inhibitors or activators.

The Michaelis-Menten equation describes the rate of enzymatic reactions by relating the reaction rate to the substrate concentration.

The lock-and-key model proposes that the active site of an enzyme has a specific complementary shape to bind the substrate, like a lock and key.

The induced fit model suggests that enzymes and substrates undergo conformational changes upon binding, resulting in a better fit and catalysis.

Competitive inhibitors are molecules that bind to the active site of an enzyme, competing with the substrate and preventing the reaction from occurring.

Non-competitive inhibitors bind to a site other than the active site, altering the enzyme's shape and reducing its activity.

Cofactors are non-protein molecules that assist enzymes in their catalytic activity, often by accepting or donating electrons or chemical groups.

Anabolism refers to metabolic pathways that build larger molecules from smaller ones, while catabolism refers to pathways that break down larger molecules into smaller ones.

ATP (adenosine triphosphate) is the primary energy currency in cells, providing energy for various metabolic processes.

Oxidative phosphorylation is the process by which ATP is synthesized in the mitochondria during aerobic respiration, using the energy released from the electron transport chain.

NADH and FADH2 are electron carriers that transfer electrons from catabolic pathways to the electron transport chain, enabling oxidative phosphorylation.

Cell membranes are composed of a phospholipid bilayer with embedded proteins that regulate the movement of molecules in and out of the cell.

The endoplasmic reticulum is involved in protein synthesis, folding, and transport, as well as lipid synthesis and calcium storage.

The Golgi apparatus modifies, sorts, and packages proteins and lipids for distribution within the cell or for secretion.

Ribosomes are molecular machines made of RNA and protein that serve as the site of protein synthesis, translating mRNA into polypeptide chains.

mRNA (messenger RNA) carries the genetic information from DNA to the ribosomes, tRNA (transfer RNA) brings amino acids to the ribosomes for protein synthesis, and rRNA (ribosomal RNA) is a component of ribosomes.

Transcription is the process by which the genetic information in DNA is copied into RNA molecules, primarily mRNA, in the nucleus.

Translation is the process by which the information in mRNA is used to synthesize a polypeptide chain by ribosomes in the cytoplasm.

The genetic code is the set of rules that govern the translation of nucleotide sequences into amino acid sequences, allowing the synthesis of proteins.

Prokaryotic cells (like bacteria) lack a true nucleus and membrane-bound organelles, while eukaryotic cells (like plant and animal cells) have a nucleus and membrane-bound organelles.

DNA (deoxyribonucleic acid) is the genetic material that carries the instructions for the development, functioning, and reproduction of living organisms, passing traits from one generation to the next.

DNA is a double-stranded molecule composed of nucleotides, with each strand being a linear sequence of deoxyribonucleotides linked by phosphodiester bonds, forming a double helix structure.

Histones are proteins that help package and organize DNA into compact structures called nucleosomes, allowing the long DNA molecules to fit within the nucleus.

DNA replication is the process by which a double-stranded DNA molecule is copied to produce two identical replicas, ensuring the transfer of genetic information during cell division.

Mitosis is the process of cell division that produces two genetically identical daughter cells, while meiosis is a specialized type of cell division that produces four genetically distinct haploid cells from one diploid cell.

Telomeres are repetitive nucleotide sequences at the ends of chromosomes that protect the DNA from degradation during replication, ensuring the complete replication of genetic information.

Gene expression is the process by which the information encoded in a gene is used to synthesize a functional gene product, typically a protein, through transcription and translation.

Promoters are regulatory regions of DNA that initiate transcription, while enhancers are regulatory sequences that can increase or decrease transcription, even from a distance.

Transcription factors are proteins that bind to specific DNA sequences, regulating the transcription of genes by either promoting or inhibiting the binding of RNA polymerase.

Constitutive gene expression refers to genes that are continuously expressed, while regulated gene expression involves genes that are selectively expressed or repressed in response to specific signals or conditions.

Epigenetics refers to heritable changes in gene expression that do not involve changes in the DNA sequence, such as DNA methylation and histone modifications, which can regulate gene activity.

Signal transduction is the process by which cells convert an extracellular signal into a specific cellular response through a series of biochemical reactions involving proteins and other molecules.

Receptors are proteins on the cell surface or within the cell that bind to specific signaling molecules, initiating the signal transduction cascade.

Second messengers are small, diffusible molecules that relay and amplify the signal from the receptor to downstream targets, facilitating the cellular response.

Kinases are enzymes that transfer phosphate groups to other proteins, activating or deactivating them, while phosphatases remove phosphate groups, reversing the effects of kinases.

Protein-protein interactions are crucial for the formation of signaling complexes and the propagation of signals through different components of the signaling pathway.

Metabolic pathways, such as glycolysis, the citric acid cycle, and the electron transport chain, are responsible for breaking down nutrients and generating cellular energy in the form of ATP.

Feedback regulation mechanisms, both positive and negative, help maintain homeostasis and ensure that metabolic pathways are appropriately regulated based on the cell's energy needs and available resources.

Allosteric regulation refers to the modulation of an enzyme's activity by the binding of a molecule (allosteric effector) at a site other than the active site, causing a conformational change that either activates or inhibits the enzyme.

Reversible enzyme inhibition occurs when the inhibitor binds non-covalently to the enzyme, and the inhibition can be reversed by removing the inhibitor, while irreversible inhibition involves the formation of a covalent bond between the inhibitor and the enzyme, making the inhibition permanent.