1. Cell components Flashcards
What are Lamins?
Lamins attach chromatin to the inner membrane of the nuclear envelope and participate in the breakdown and reformation of the nuclear envelope during the cell cycle. Phosphorylation of the lamina (by lamin kinase) during prophase of mitosis initiates nuclear dissassembly into small vesicles.
What are the 3 distinct morphological zones of the nucleolus and what does each do?
I. Granular zone: found at the periphery, contains ribosomal precursor particles in various stages of assembly. II. Fibrillar zone: centrally located; contains ribonuclear protein fibrils. III. Fibrillar center: contains DNA that is not being transcribed.
What are the 2 positively charged proteins found in the histone protein?
Lysine and Arginine.
What are nucleosomes?
They are the basic repeating units of the chromatin fiber; they have a diameter of approximately 10nm.
What are euchromatins?
Thye are a more extended form of DNA, which is potentially transcriptionally active. In a typical cell, euchromatin accounts for 90% of the total chromatin, although only about 10% is being actively transcribed in the 10-nm fiber of nucleosomes. Heterochromatin are the highly condesed part that are not being transcribed (30-nm).
What does the rough endoplasmic reticulum do? (RER)
RER is a single, lipid bilayer continous with the outer nuclear membrane. It is organized into stacks of large flattened sacs called cisternae that are studded with ribosomes on the cytoplasmic side. They synthesize proteins that are destined for the Golgi apparatus, secretion, the plasma membrane, and lysosomes. RER is very important in cells that are specialized in the synthesis of proteins destined for secretion (e.g., pancreatic acinar cells).
What does the smooth endoplasmic retuculum do?
SER contains enzymes involved in the biosynthesis of phospholipids, triglycerides, and sterols. It is the center for detoxification reactions, glycogen degradation and gluneogenesis, the site where lipolysis begins, and sequestration and release of calcium ions (in striated muscle it is known as sarcoplasmic reticulum).
What does the Golgi apparatus do?
The golgi apparatus is involved in the posttranslational modification and sorting of newly synthesized proteins and lipids and glycoproteins.
What is the cause of hyperproinsulinemia?
It is characterized by elevated levels of proinsulin in the serum resulting from the failure of a peptidase to cleave proinsulin to insulin and C-peptide in the Golgi apparatus. Clinical manifestations are similar to those seen in patients with noninsulin dependent diabetes.
What is the cause of I-cell disease?
Deficiency of N-acetylglucosamine-phosphotransferase; phosphorylation of mannose in glycoproteins targets proteins to lysosomes. Phosphate is added in 1a 2-step sequence of reactions that are catalyzed by N-acetylglucosamine-phosphotransferase and N-acetylglucosaminidases. With the enzyme missing, a whole family of enzymes is sent to the wrong direction, which accumulate in cells and makes them sick. The missing enzymes are found in the plasma and other body fluids, where they have normal levels of activity. The absence of the mannose-6-phospate on the hydrolases results in their secretion rather than their incorporation into lysosomes.
What is another name for I-cell disease?
Mucolipidosis II
What do peroxisomes do?
They synthesize and degrade hydrogen peroxide, Beta-oxydation of very long fatty acids (>C24) from head to leaving the last 10 carbons where the remaining is destroyed in the mitochondria, phospholypid exchange and bile acid synthesis.
What are 4 diseases associated with peroxisome deficiency?
Zellweger (cerebrohepatorenal) syndrome, neonatal adrenoleukodystrophy, infantile Refsum disease, hyperpipecolatemia.
What do tubulins do?
A major component of microtubules, they are involved in chromosomal movement during meiosis and mitosis (spindle formation), intracellular vesicle and organelle transport, and ciliary and flagellar movement.
What is the cause of Chediak-Higashi syndrome?
A defect in microtubule polymerization; it causes delayed fusion of phagosomes w/ lysosomes in leukocytes (preventing phagocytosis of bacteria), increased fusion of melanosomes in melanocytes (causing albanism), and granular defects in natural killer cells and platelets.
