internal membranes and organelles Flashcards
describe the cytoplasm
- makes up most of the mass of the cell
- made of mostly water
- acts as solvent for many intracellular proteins
list some functions of the cytoplasm
metabolism
protein synthesis
molecule storage
covalent modification
what is intermediary metabolism
degradation of small molecules into energy sources all of which occur in the cytoplasm
list examples of intermediary metabolism
glycolysis
gluconeogenesis
biosynthesis of sugars, fatty acids, amino acids
After the release of the spliced mRNA, free ribosome latches on and with the help of tRNAs, it produces a _________
polypeptide
where can protein synthesis occur?
rough endoplasmic reticulum
cytoplasm by free ribosomes
what are some molecules that cytoplasm can store?
glycogen
triglycerides
how do triglycerides appear in cytoplasm?
fat droplets, water-insoluble
how does glycogen appear in the cytoplasm?
granules
what is an example of covalent modification and describe it
phosphorylation- protein kinase uses a phosphate group from ATP to modify a protein, which causes it to become activated or inactivated
describe the structure of the endoplasmic reticulum
membrane bound organelle somewhat continuous with the nuclear envelope, lumen is separated from cytoplasm by these membranes
what is the purpose of endoplasmic reticulums?
makes proteins and lipids that are then sorted and sent to their specific places within the cell or extracellularly
what is the rough ER characterized by?
presence of ribosomes on its membrane (cytoplasmic side)
what is cisternae?
“stacks of flattened sacs” of the rough ER and is prominent in protein production and secretion
example of cisternae
pancreatic acinar cells (secrete pancreatic enzymes)
plasma cells (of immune system and secrete anitbodies)
what are the ribosomes that are present on the rough ER called and what do they do?
membrane-bound ribosomes
- direct their protein synthesis into the ER lumen when there is special signal sequence present in the mRNA
~ tells the ribosome that this protein needs to be transported to specific location via golgi apparatus
describe the structure of the smooth ER
- “meshwork of fine tubules”
- no ribosomes bound
- somewhat continuous with rER
what is the function of the smooth ER
lipid metabolism and detoxification
glycosylation
what are certain cells that will have abundant smooth ER
- hepatocytes
- cells producing steroid hormones
describe glycosylation
- process attaches a specific oligosaccharide to the N-terminus of a protein on the asparagine residue
- then acts as a “tag” and informs the cell that the protein is meant to stay intracellularly
list functions of the golgi apparatus
glycosylation
packaging of proteins
recycling of membrane components
“post office of cell”
describe golgi apparatus’ role in glycosylation
- modifies the residues to create differences in the oligosaccharides so that each type of protein ends up having a distinct tag on it
- core portion of oligosaccharide is added by ER while the terminal portion of the oligosaccharide is modified by the golgi apparatus
describe the golgi apparatus function in secretory cells
Golgi is used to concentrate and store a large number of products in secretory vesicles, which are later used to release the cell’s protein product.
- The vesicles that proteins are packaged into also act as sorting centers for the proteins
- The Golgi sends proteins out to different parts of the cell, but it is also used by the cell to recycle different components
The same transport vesicles that are used to send proteins out from the golgi apparatus are once again recycled by the cell, and being recycled with them are the ____________ that are used to form and fuse the vesicles.
vesicle proteins
what is the main function of lysosomes?
most of intracellular digestion occurs
what are lysosomes
small vesicles filled with hydrolytic enzymes that are used to degrade macromolecules into waste products that are then exocytosed out of the cell
what are acid hydrolases
enzymes in the lysosome that are optimally active at a pH of 5 that tells us the internal environment of the lysosome is acidic in nature
what do the special transport proteins of the lysosome do?
uses ATP to pump H+ ions inside it to create an acidic environment
what are docking markers
helps tag the lysosome so that specific transport vesicles in the cell can fuse with them
what are primary lysosomes?
newly formed and have not come into contact with a substrate
what are secondary lysosomes and how are they created?
those that have substrates and enzymes. They are created when primary lysosomes and membrane-bound substrates fuse together
which tag on a protein would send it to the lysosome?
If a protein has a mannose-6-phosphate (M6P) containing oligosaccharide, it will be sent to the lysosome
what is I-Cell disease?
occurs when the patient lacks the lysosomal enzyme tag mannose-6-P. As a result, the lysosomal enzymes are not present in the lysosome and macromolecules cannot be broken down. There are a variety of mutations that cause lysosomal storage diseases, and some have a much more severe etiology than others
what are some symptoms of I-Cell disease?
coarse facial features, hepatomegaly (enlarged liver), splenomegaly (enlarged spleen), failure to thrive (child does not reach growth milestones), developmental delay (child does not reach developmental milestones), and restricted joint movement
what kind of cells are peroxisomes present in almost all of?
eukaryotic cells
how are peroxisomes formed?
by budding from smooth ER
what is the peroxisome a major site of?
oxygen utilization where the oxygen is used in catabolic reactions
what is the main enzyme found in peroxisomes
catalase
what is catalase?
used to oxidize many different substrates. It uses hydrogen peroxide in this reaction and water is released as the end product
peroxisomes also contain enzymes that catalyze the formation of hydrogen peroxide as a __________.
waste product
what is the purpose of catalase reaction in peroxisomes?
safety mechanism of sorts to prevent the accumulation of hydrogen peroxide in the cell, which is a toxic waste product
