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Histology Organelles

Organelles in Medical School Histology Course

QuestionAnswer
What are the three major components of the nucleus? Chromitin, Nucleolus, and Nucleoplasm.
What is the Chromatin? DNA of the cell during interphase (the period between cell divisions).
Where are Ribosomal Ribonucleic Acids (rRNA) synthesized? Nucleolus.
What is the Nucleoplasm? A "grab bag" encompassing all non-chromatin and non-nucleolar material. Involved in nuclear maintenance.
The outer membrane of the nuclear envelope is continuous with what structure? The Endoplasmic Reticulum. The outer membrane membrane may also polyribosomes attached and function as a Rough Endoplasmic Reticulum.
What is the Perinuclear Cisterna? The space between the inner and outer membrane of the nucleus which form the nucleur envelope.
Where are nucleur pores formed on the nuclear membrane? Where the inner and outer membrane fuse.
The number of nuclear pores tells us what about the cell? How Active the cell is. More pores = More active
What is the major structure within the nuclear pores? Nucear Pore Complex.
What can pass freely through the nuclear pore complex? Ions and molecules up to 10nm.
Can molecules larger than 10nm pass through the nuclear pore complex? Yes. However the molecules must possess a "signal sequence" of certain amino acids to bind to the receptor site. This process requires enegy (active transport).
Where is the nuclear lamina located? The nucleoplasmic side of the inner membrane.
What are lamins? The fibrous polymers that make up the nuclear lamina.
What are the two functions of the nuclear lamina? Stabilization of the nuclear envelope, and functional organization of the interphase nucleus.
What two forms can chromatin be found in when uncoiled? Euchromatin and Heterochromatin
What is Euchromatin? The active form of chromatin, used for the transcription of the DNA into RNA.
What is Heterochromatin? Relatively "inactive" form of chromatin. The portion of DNA not being transcribed into RNA.
Looking through a Light Microscope, you are able to observe chromatin. What form of chromatin are you looking at? Heterochromatin. Euchromatin is not visible on a light microscope because it is not as condensed.
Dr. Miller uses the phrase "beads on a string" to describe what? Unwound Euchromatin.
What structure makes up the "beads" of the "string"? Nucleosomes
What structure makes up the "string"? Linker DNA
What is a nucleosome? Histone Protein wrapped with Chromatin (DNA).
How many PAIRS of histone proteins are in one nucleosome? 4 pairs.
How many times does the DNA molecule wrap around each nucleosome? 2 times.
What is Linker DNA? Strand of DNA between the nucleosomes?
Where is the heterochromatin located on the chromosome? At the Chromosome tips (near the centromere and telomere).
If the cell would like to inactivate a specific function, it would have to inactivate the gene for that function. How would the cell do this? By translocating the gene to an area adjacent to the heterochromatin since it can silence adjacent genes.
What is a Chromosome Territory? Organized area of the nucleus that possesses an individual chromosome.
Where on the Chromosomal Territory would a very active gene be located? At the border.
What is the name of the narrow areas between chromosomal territories? Interchromosomal domains.
What is the function of the interchromosomal domains? They are conduits (channels) for newly-formed DNA transcripts.
What kind of membrane is around the nucleolus? There is no membrane around the nucleolus!
The nucleolus is present during what phase of mitosis? Interphase
The nucleolus disperses early in mitosis. In what stage of mitosis does it reform? Telophase.
What is the function of the nucleolus? Transcription of genes for rRNA, processing of RNA precursor molecules, assembly of ribosomal subunits, and nuclear export of mRNA.
The size of the nucleoli tells us what information about the cell? How actively the cell is synthesizing proteins. Larger = More protein synthesis.
What are the two major components of the nucleoplasm? Ribonucleoprotein Particles (RNP's) and the Nuclear Matrix.
What are RNP's? RNA sequences complexed with proteins.
What is the function of Heterogenous RNP's (hnRNP)? Condense RNA
What is the function of Small Nuclear RNP's (snRNP)? RNA splicing of introns.
What is the nuclear matrix? The space between the chromatin and nucleoli, including the nuclear lamina and portions of nuclear pore complex. It forms a nuclear structural support system.
Why do hormones such as steroid have a long-term effect? Because the hormone binds to a receptor on the nuclear matrix. This interaction initiates a change in nuclear gene transcription.
What are the two functions of the mitochondria? Produce ATP and regulate Apoptosis
By what process does mitochondria make ATP? Oxidative Phosphorylation
Describe the outer and inner membrane of a mitochondrion. The outer membrane is smooth. The inner membrane is folded. Both are typical lipid bilayers.
What is the major protein present in the outer membrane and what is its function? Porin: forms large channel to allow passage of molecules up to 10kD. When Apoptosis occurs, porin inverts and aligns with inner membrane proteins.
What is the major protein present in the inner membrane and what is its function? ATP Synthase: Forms ATP from ADP and phosphate.
Does the Electron Transport Chain function on the inner or outer membrane of the mitochondria? Inner membrane
Which direction do the proton pumps on the electron transport chain pump protons? What is the result? Protons are pumped from the Matrix to the Intermembrane Space. The only way back into the matrix (down the concentration gradient) is through the ATP Synthase.
What is the Cristae? How does it incrase energy-producing ability? Cristae are the folds on the inner membrane which give the inner membrane more surface area. This allows for more ATPase to be present.
What structure makes the inner membrane of the mitochondria virtually impermeable to ions, electrons, and protons? How does it do this? Cardiolipin. It does this by having four fatty acid chains per molecule instead of two.
What structure is the "inner membrane marker" for the mitochondria? Cardiolipin.
Where in the mitochondria are proteins synthesized? How do you know? In the Matrix since it is filled with ribosomes, DNA and RNA.
What do Matrix Granules do? Store Ca++ and Mg++
True or False: Mitochondrial DNA is circular and their duplication is dependent on the nuclear DNA. False. Mitochrondrial DNA is circular like bacteria but they duplicate independently of nuclear DNA. They do not follow Mendelian Genetics.
True or False: Mitochondrial proteins are coded by nuclear DNA, synthesized by ribosomes, then transferred to the mitochondria. True
What happens when the Mitochondrial Permeability Transition pore is open? Apoptotic factors escape from the mitochondria into the cell. Dissipation of proton gradient
What protein codes for the Mitochondrial Permeability Transition pore to open and how? Porin by inverting and aligning itself with the inner membrane of the mitochondria.
What is a polyribosome? Cluster of ribosomes held together by a strand of mRNA.
True or False: A bound ribosome is one that is permanently bound to the RER. False. A bound ribosome is only temporarily bound to the RER.
The endoplasmic reticulum is derived from what other intracellular structure? Nuclear envelope.
Proteins synthesized in the RER are destined for one of two paths. What are they? To be stuck in a membrane (Integral Membrane Protein) or be stuck in a vesicle.
What information do we know about a cell that has a high number of RER? It is actively exporting proteins.
True or False: The RER consists of tubules. False. The RER of flattened cisternae.
True or False: The SER consists of tubules. True.
What is the function of the SER? Lipid and Cholesterol synthesis.
Proteins enter the Golgi Apparatus at which side? At the Cis face
Proteins that enter the Golgi Apparatus are coming from where? The RER.
Proteins exit the Golgi Apparatus at which side? At the Trans face.
What is the name of the structure between the Cis and Trans face on the Golgi Apparatus? The medial compartment.
What are the two functions of the Golgi Apparatus? 1- Phosphorylation and glycosylation of proteins. 2- Protein sorting.
Proteins leaving the Golgi Apparatus have 1 of 4 fates. What are they? 1- Become integral membrane protein. 2- Release into extracellular space. 3- Intracellular storage within secretory vesicles.
Created by: pa0246ph