Organelles Flashcards
Name 3 components of the cytoplasm :
- Organelles
- Cytosol
- Inclusions
Name 3 nonmembrane bound organelles
- Centrioles
- Microtubules
- Nucleoli
What are inclusions bodies ?
Something that the cell could not digest..
Insuluble substances such as glycogen, lipid droplets
even ribosomes can be considered inclusion bodies..?
Mitochondria are _____ membrane bound organelles. They provide energy to the cell and are most abundant in cells that generate and expand energy such as _____.
double membrane
heart muscle, liver cell, some cells of the kidney.
Mitochondria is absent in what kind of cells ?
Erythrocytes
Terminal keratinocytes/corneocytes
What is the role of the cytoskeleton?
Organize the organelles and provide structure to the cell
Mitochondrial are _____ structures that would stain as the colour ____ on LM
Pink
The mitochondrial’s ____ membrane contains large _____ which permit ions and small molecules to enter the intermembrane space.
Outer
Channels
In which part of the mitochondria can you find cytochrome C and what is his role?
The intermembrane contains specific enzymes like cytochrome C.
When cytochrome C is discharged into the cell cytoplasm it initiates apoptosis.
Regarding the mitochondria : The matrix surrounded by the _____ membrane contains :
The matrix is surrounded by the inner mitochondrial membrane
Contains : Soluble enzymes of the kreb’s cycle Electron dense matrix granules (store Ca) Mitochondrial DNA, ribosomes, rRNA.
The mitochondrial innermembrane folds into structures called _____ which can be tubularvesicular or ______.
Cristae
Plate-like
The mitochondrial enzymes system is responsible for generation of ____ in a variety of metabolic pathways (oxidative phosphorylation, citric acid cycle, glycolysis, beta oxidation of fatty acids)
ATP
The ER is organized into a mesh like interconnected maze of branching tubes and flattened lamellae. What are the two types and their difference:
Rough ER : ribosomes attached to their outer surface
Smooth ER : ribosomes-free outer surface
The ER has how many membrane (s) ?
1
What is the main role of the rER
Protein synthesis & post translational modifcations of newly synthesized proteins (proper folding, initial glycolysation)
With TEM ; rER appears as series of membrane limited flattened sacs called ____.
Cisternae
What is the role of ribosomes ?
Syntesis of different classes of proteins.
Note that in the cytosol, many ribosomes are connected by one strand of mRNA which are referred to as polysomes. Polysomes can be found in 2 forms : free polysomes and bound polysomes.
Free polysomes are free in the cytosol
Bound polysomes are attached to the outer surface of the rER cisternae
Ribosomes stain ___ in LM. Why ?
Purple
Basophilic - because they contain a lot of RNA which is acidic
Describe the Golgi apparatus and its role.
Group of flattened sacs with vesicles around the margins.
We can find from 1-100 golgi in every cell.
The role : factory in which protein from the ER are further processed and matured and then put into vesicles so they can be carried to their target destination.
They are prominent in protein-secreting cells.
At the TEM level, they appear to consist of 3 different regions.
What are the 3 defined regions of the golgi apparatus on TEM ?
Cis (Vesicles loaded with proteins leave the rER and fuse with the cis region)
Medial (the process of concentration and maturation involves mvmt of the proteins from the cis to the medial to the trans regions)
Trans (Where mature proteins exit in the form of smaller detached vesicles)
Each region contains different enzymes involved in protein maturation.,
Is it possible to visualize the Golgi with LM ?
Yes.
It appears as a lightly stained area in the cytoplasm of protein-producing cells (e.g. plasma cells).
What is the role of sER and it what kind of cells is it well developed?
Participates in biosynthesis of steroid hormones and membrane lipids
Breakdown of toxins and drugs
Synthesis of TG in the intestinal epithelium
Sequestering of calcium in striated muscle
Smoot ER in striated muscle fibers is called ______.
Sarcoplasmic reticulum.
Responsible for storage of Ca ions / trigger contraction of myofibrils
What are lysosomes ?
Membrane bound cell organelle that contain a large variety of acid hydrolases.
Lysosomes function as the digestive system of the cell, serving both to degrade material taken up from outside the cell and to digest obsolete components of the cell itself. They may be used to destroy invading viruses and bacteria.
They are found in all cell types.
Profound in neutrophils and macrophages.
Lysosomal enzymes are synthesized in the ____ and sorted in the ____.
rER
Golgi
How is material brought to the lysosome ?
By heterophagy (endocytosis or phagocytosis) if the material is coming from outside the cell
Or autophagy, if the material comes from the cell itself.
Lysosomes degrade cytoplasmic proteins and organelles by autophagy. What are the three autophagic pathways are involved in degradation of cytoplasmic constituents?
- Macroautophagy
- Microautophagy
- Chaperone mediated autophagy
Describe the proteasome mediated protein degradation
Process in which lysosome are NOT involved
Occurs within proteasomes
It is a process used by cells to destroy proteins (misfolded, cell cycle progressive proteins…)
Proteasomes ‘’chew up’’ proteins which need to be destoyed. In order to be brought to the proteaseome, these proteins must be tagged with ____.
Ubiquitin
Malfunction of proteasome mediated protein degradation leads to what ?
Decrease in protein degradation
Loss of proteasome function due to mutation of genes encoding for uniquitin leads to deseases such as :
Alzheimer’s and Angelman syndrome.
Give an exemple of consequence of overexpression proteasome-mediated pathway:
HPV
Here is what a phagosome looks like in TEM
Digested materials inside the lysosomes are recycled or released to the outside. Indigestible compounds stored in the lysosomes are called _____. In LM, they appear as yellowish, brownish pigments around the nucleus (Lipofuscins). The unreleased indigestible compounds in long-living cells are called _____ (found in neurons and cardiac muscle cells).
Residual bodies
Aging pigments
Absence of certain lysosomal enzymes leads to pathological condition termed _______. This occurs due to mutations in a gene that encodes for _______.
Lysosomal storage disease
Lysosomal proteins
Lysosomal storage diseases results in accumulation of undigested products. What is an example of disease that results from accumulation of these undigested products :
Tay Sachs disease
(Absence of lysosomal galactoside in neurons which produces concentric lamellar structures in the lysosomes and interfere with normal neuronal function.
Gaucher , Pompe’s, Niemann-Pick disease are other examples.
Peroxisomes (aka microbodies) are membrane bound spherical or slightly ovoid structures (0.3-0.5 um) that regulate_____ levels in the cells.
Hydrogen peroxide levels
Peroxisomes differ from lysosomes by their ________ ability. They reveal electron dense matrix which consist of _____ enzyme (breakdown H2O2). The are abundant in ______.
Self replicating
catalase
Heptocytes
Peroxisomes look like lysosomes, but have a dark spot in the middle which represents _____.
Catalase
A malfunction in peroxisome leads to ______ syndrome.
Zellweger’s
Autosomal recessive diosorder which affects brain, liver and kidneys,
Compare the different organelles visualized by TEM and LM
How does chromatin gives rise to a chromosome ?
At its simplest level, chromatin is a double stranded helical structure of DNA…..
https://www.youtube.com/watch?v=LaStQqqnkyU&list=PL9jo2wQj1WCNqh2v1ejc5vDzh8dfeAFeL
What can we find inside the nucleolus ?
DNA, RNA, regulatory cell cycle proteins
The nuclear envelope has an inner and an outer membrane that is perforated with _______. The outer membrane is continuous with the ______.
Nuclear pores
rER
A chromatosome consists of a _____ and a ______histone.
nucleosome + H1 histone
Distinguish Euchromatin from Heterochromatin
Heterochromatin is the part of the chromosome in which the DNA does not have coding genes. These regions appear dark on microscopy due to compact arrangement of chromatin. These parts are inactive, as they are not involved in transcription, and thus coding for proteins.
Euchromatin is the part of the chromosome in which the coding DNA sequences are present. These parts appear lighter on microscopy, as the chromatin is loosly packed. It is streched out so that transcription can take place. It is prominent in active cells, like liver cells.
What is a barr body ?
A barr body represents the inactive X chromosome in a cell with more than one X chromosome.
Females have only one of there chromosomes that is expressed, so the other one is maintained as facultative heterochromatine.
Barr bodies thus can be used to identify the sex of a fetus.
What is the role of the nucleolus ?
Surrounds transcriptionally active rRNA genes.
It is the primary site of ribosomal production and assembly.
It can vary in size and number across different cell types, but it is usually very visible in cells that are active in protein synthesis.
In what process are p53 proteins (nuclostemin) involved ? What can it cause if defective ?
Regulates cell cycle and differentiation
Its regulation involves autophagy and apoptosis
Too much of this protein has been linked with cancer
Inactivation of p53 gene is involved in 50% of cancers
How many membranes does a nucleus have ? What is their respectives names and what are they directly in contact with?
2 membranes : outer nuclear membrane (ONM) continuous with the rER and an inner nuclear membrane (INM) attached to the inner fibrous lamina.
What is the space between the inner and outer membrane called ?
Perinuclear space
The ________ mediates the transport of cellular material between the nucleus and the cytoplasm.
Nuclear pore complex (NPC) which is embedded in the membrane
Impairment of nuclear laminin structure or function can cause tissue specific diseases (e.g. nerve and skeletal development issues, premature aging..). Mutations in laminin or laminin receptors are associated with __________.
Emery-Dreifuss muscular dystrophy
About 50 proteins make up the nuclear pore complexe (NPC). These proteins are also know as ____.
Nucleoporins (or Nup proteins)
The NPC acts as a close-fitting diaphragm or gated channel and allows for transport of small molecules. A central framework, surrounding the central pore is inserted between the ____ ring and the _____ ring. This last complex anchors a ‘’nuclear basket’’. This complex acts as a gated channel and allows for transport of small molecules.
cytoplasmic
nuclear
Any protein that needs to get in the nucleus has a ______. This binds to the nucleor import receptor Imp aka ______ thus the protein is transported to the NPC. A GTP dependant mechanism then transports them to the pore and recycles the Imp protein.
Ribosomal proteins that need to leave the nucleus have a ________ (NLS) that binds to a protein called _____ and then the protein is directed to the nuclear pore complex.
Nuclear localization signal
Importin (Imp)
True or false. Ions and water soluble molecules less than 9 Da in size can cross the nuclear membrane by simple diffusion.
True
True or false. Transport of molecules across the NPC is energy independant.
False
