Open questions Flashcards
Compare tight and gap junctions
Tight junctions
- hold cells together
- diffusion barrier
- prevents flow of materials between cells
Where is it found?
- Kidney
- Intestine
- Plasma membrane
What is the main protein component?
- Zona occludin
Gap junction
- Communication between cells
Where is it found?
- heart
- neuron
- cardiac muscle
What is the main protein component?
- 2 connexon channels
Which 2 RNA processing steps occur on transcripts destined to become mRNA?
What is the significance of these modifications?
Where do these steps happen in the cell?
1) 5’ end capping (cotrancriptional modification)
Adding methyl guanine cap to the 5’
2) 3’end tailing (post transcriptional modification)
Adding poly A tail to 3’
3) Splicing (co trancsriptional modifications) by shRNA
Cutting out the introns and binding the exons
The process regulate and stabilize mRNA synthesis
Happens in the nucleus
By which mechanism do water molecules pass the plasma membrane?
What are the similarities and the differences between them?
- The water can be transferred inside the cell by simple or facilitated diffusion
- Similarities: They both don’t require energy (ATP)
Differences: Simple diffusion happens through membrane, facilitated uses aquaporins (channel proteins)
Where are the mitochondrial proteins synthesized?
How are they targeted and transported to their destination?
Mitochondrial proteins are synthesized in the cytosol on free ribosomes.
They have mitochondrial localisation signal on their N-terminus. This binds to the outer membrane receptor.
The two membranes (outer and inner) are temporarily linked forming a mebrane contact site.
These sites are the translocon molecules TIM and TOM which form the tunnel for proteins to enter the mitochondria.
TOM is in action to enter for outer membrane protein,
Tim is in action for inner membrane protein.
What do you know about the location, the structure and the function of the nuclear lamina?
The nuclear lamina is located under the inner face of the bilayer nuclear envelope. Nuclear lamina is composed of a meshwork of intermediate filaments.
The proteins of this filament are Lamin A, B and C.
The nuclear lamina binds to chromatin of nuclear lamina associated proteins.
It provides structural support for the nuclear envelope and involves in many cytological processes like replication, transctiption, nuclear organization etc.
What is the anaphase?
What happens in this phase?
Anaphase is triggered by APC. How does it act?
- The sister chromatids now separate to form two new daughter chromosomes and eacah is pulled slowly towards the poled. Kinetochore microtubules become shorter and the spindle poles move apart.
APC is an E3 ubiquitin ligase that marks target cell cycle proteins for degradation by the 26S proteosome.
List the main steps of microscopic microtechniques.
Give the name of the substrances or instruments that is commonly used in a given step.
1) Sample collection
2) Fixation
- Physical : freeze, microwave
- Chemical: salt, acids, alcohols, aldehyde(formaldehyde and glutheraldehyde)
3) Paraffin embedding: dehydration of tissue by alcohol.
- Xylene
- Paraffin
4) Sectioning: Microtone sectioning.
5) Staining:
- deparafinization by xylene
- rehydration
- dying
List all the possible sites of protein synthesis in a eukaryotic cell.
What can be the destination of the proteins synthesized at different locations?
Free ribosomes in cytosol
Destination of protein:
- Nucleus/peroxisome
- Mitochondria
Ribosomes on the rER membrane
- rER, golgi, plasma membrane, lysosome, secreory vessicles, mitochondria
What are the compartments of the nucleolus and what are their functions?
List the type of membrane receptor through which extracellular signals can influence the function of cells whose type (chemically) of ligands have membrane receptors?
Hydrophilic signals can effect:
- Ion channel linked receptors
- Enzyme-linked receptor
- G- protein linked receptor
Draw the ultrastructure of the nucleus.
Label and name different parts of it.
