Endomembrane System Flashcards
(25 cards)
What is the endomembrane system?
The endomembrane system is a network of interconnected membranes and organelles in eukaryotic cells that work together to modify, package, and transport proteins and lipids.
What does the endomembrane system include?
The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, cell membrane, and vesicles.
How are the membranes of separate organelles in the endomembrane system connected?
The membranes of separate organelles are physically connected via membrane ‘bridges’ or transiently connected by vesicles.
What are vesicles?
Vesicles are small membrane-enclosed sacs that transport substances within a cell or from the interior to the exterior of the cell.
What is the role of vesicles in the endomembrane system?
Vesicles bud off from organelles, taking internal contents and a piece of the membrane, and then fuse with other organelles or the cell membrane.
What does the endomembrane system divide the interior of the cell into?
The endomembrane system divides the interior of the cell into two spaces: one inside the compartments defined by membranes, and another in the cytosol.
What happens in exocytosis?
In exocytosis, a vesicle from the cytoplasm fuses with the cell membrane and empties its contents into the extracellular space or delivers proteins to the cell membrane.
What happens in endocytosis?
In endocytosis, a vesicle buds off from the cell membrane, bringing material from outside the cell into the vesicle, which can then fuse with other membranes inside the cell.
What is the nuclear envelope?
The nuclear envelope is the cell structure composed of two lipid bilayer membranes that defines the boundary of the nucleus.
What are nuclear pores?
Nuclear pores are protein channels in the nuclear envelope that allow molecules to move into and out of the nucleus, essential for communication between the nucleus and the rest of the cell.
What is the role of nuclear pores in the nucleus?
Nuclear pores regulate the movement of mRNA out of the nucleus to the cytoplasm through these channels.
What are ribosomes and their function?
Ribosomes are a complex structure of RNA and protein that synthesize proteins from amino acids as directed by mRNA. They are the site of protein synthesis.
Where are ribosomes located?
Ribosomes are located in the cytosol (free ribosomes) and associated with the endoplasmic reticulum (rough ER).
What is the endoplasmic reticulum?
The endoplasmic reticulum is an organelle composed of a network of membranes involved in protein and lipid synthesis, bounded by a single membrane.
What is the lumen of the endoplasmic reticulum?
The lumen is the continuous interior of the endoplasmic reticulum, where molecules are processed and transported.
What is the rough endoplasmic reticulum?
The rough endoplasmic reticulum (Rough ER) is the part of the ER with attached ribosomes, responsible for synthesizing transmembrane proteins, proteins for organelles, and proteins for secretion.
What is the smooth endoplasmic reticulum?
The smooth endoplasmic reticulum (Smooth ER) lacks ribosomes and is involved in fatty acid and phospholipid biosynthesis, conversion of cholesterol to steroid hormones, and detoxification of lipid-soluble drugs.
What is the function of the Golgi apparatus?
The Golgi apparatus modifies proteins and lipids produced by the ER, acting as a sorting station for them as they move to their final destinations.
What are the three primary roles of the Golgi apparatus?
The three primary roles of the Golgi apparatus are to modify proteins and lipids produced by the ER, to act as a sorting station, and to add carbohydrates to proteins and lipids.
What is glycosylation?
Glycosylation is the process where sugars are covalently linked to lipids or specific amino acids of proteins, forming glycoproteins, which can protect proteins from enzyme digestion.
What is the reverse pathway from the Golgi apparatus to the ER?
The reverse pathway from the Golgi to the ER retrieves proteins from the ER and recycles membrane components.
What are lysosomes?
Lysosomes are specialized vesicles derived from the Golgi apparatus that degrade damaged or unneeded macromolecules and are involved in apoptosis.
What do lysosomes contain?
Lysosomes contain hydrolytic enzymes, which are packaged in the lysosome by the Golgi apparatus, and sometimes contain proton pumps to maintain an optimal pH for enzyme activity.
Why do lysosomes have a pH of 5?
Lysosomes have a pH of 5 to optimize enzyme activity, while the rest of the cell maintains a pH of 7.
