Prokaryotic cells, mitochondria, and chloroplasts have 70S ribosomes, whereas eukaryotic cells have 80S ribosomes. This provides support for the Endosymbiotic Theory, which states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote).

The addition and removal of phosphate groups can serve critical functions in the regulation of protein activity. The binding or uncoupling of phosphate groups frequently serves to activate or deactivate proteins.

A phosphatase removes a phosphate group from its ligand.

A kinase is an enzyme that phosphorylates—or adds a phosphate group to—its ligand.

Several different types of proteins can change the structure of a ligand, such as isomerases, and ubiquitin ligases add ubiquitin to their ligands.

Active transport is the movement of molecules against their concentration gradient (from an area of low concentration to an area of high concentration, requiring energy, usually in the form of ATP. Passive transport is the movement of molecules with their concentration gradient (from an area of high concentration to an area of low concentration), and does not require energy input. Facilitate diffusion is the movement of molecules with their concentration gradient across the cell membrane using transmembrane proteins (carrier proteins or channels), and does not require energy. Osmosis is the movement of a solvent (usually water), from an area with a lower concentration of solute to an area of higher concentration of solute; this process does not require energy.

Prokaryotic cells, mitochondria, and chloroplasts have 70S ribosomes, whereas eukaryotic cells have 80S ribosomes. This provides support for the Endosymbiotic Theory, which states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote).

Histones are proteins found in the nucleus of eukaryotic cells. DNA wraps itself around histones to further condense. Also, depending on how tightly the DNA is wrapped around the histones, it may or may not be availible for activity (e.g. replication or transcription). Cells modify the interaction between DNA and histones around certain genes under certain conditions to make those genes available or unavailable as needed.

The addition and removal of phosphate groups can serve critical functions in the regulation of protein activity. The binding or uncoupling of phosphate groups frequently serves to activate or deactivate proteins.

A phosphatase removes a phosphate group from its ligand.

A kinase is an enzyme that phosphorylates—or adds a phosphate group to—its ligand.

Several different types of proteins can change the structure of a ligand, such as isomerases, and ubiquitin ligases add ubiquitin to their ligands.

Active transport is the movement of molecules against their concentration gradient (from an area of low concentration to an area of high concentration, requiring energy, usually in the form of ATP. Passive transport is the movement of molecules with their concentration gradient (from an area of high concentration to an area of low concentration), and does not require energy input. Facilitate diffusion is the movement of molecules with their concentration gradient across the cell membrane using transmembrane proteins (carrier proteins or channels), and does not require energy. Osmosis is the movement of a solvent (usually water), from an area with a lower concentration of solute to an area of higher concentration of solute; this process does not require energy.

Histones are proteins found in the nucleus of eukaryotic cells. DNA wraps itself around histones to further condense. Also, depending on how tightly the DNA is wrapped around the histones, it may or may not be availible for activity (e.g. replication or transcription). Cells modify the interaction between DNA and histones around certain genes under certain conditions to make those genes available or unavailable as needed.

The Golgi apparatus is a series of flattened membrane sacs found in the cell. It receives vesicles filled with proteins from the rough endoplasmic reticulum. The Golgi apparatus is responsible for recognizing proteins based on their signal sequences and sending concentrations of similar proteins to various parts of the cell. It can also deliver proteins out of the cell using secretory vesicles. The membrane sacs of the Golgi apparatus are constantly used and regenerated to create vesicles of packaged proteins.

The Endosymbiotic Theory states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). This theory explains the origin of eukaryotic cells. Numerous lines of evidence exist, including that mitochondria and chloroplasts have their own circular DNA (prokaryotes also have circular DNA), mitochondria and chloroplasts have a double membrane (the inner membrane would have initially been the ingested prokaryote’s single membrane, and the outer membrane initially would have come from the cell that engulfed it), mitochondria and chloroplasts have 70S ribosomes (prokaryotes 70S have ribosomes, whereas eukaryotes have 80S ribosomes).