Believe
Forum Senior
Topics: 36
Posts: 93
|
Q: A fluorescent molecule of 2000 daltons is microinjected into a single cell of an epithelial layer. When the layer is examined in a fluorescence microscope, the molecule remains confined to that cell. However, when a fluorescent molecule of 800 daltons is injected into a single cell of an epithelial layer, it quickly appears in the adjacent cells. Which of the following is responsible for the spread of the smaller molecule?<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
A) Desmosomes (maculae adherentes)
B) Focal contacts
C) Gap junctions
D) Intermediate junctions
E) Tight junctions (zonulae occludentes)
___________________
Focus on the one step you can take right now. Let go all regrets and resentment about what has already happened.
|
| drk1980
Forum Guru
Topics: 147
Posts: 1,038
|
Gap juntions, this one is probably only 800 daltons wide.
|
| tikka
Forum Elite
Topics: 59
Posts: 138
|
I also go fro gap junctions
|
| roopashri
Forum Elite
Topics: 16
Posts: 190
|
C gap junc
|
| Believe
Forum Senior
Topics: 36
Posts: 93
|
Gap Junctions
Gap junctions are intercellular channels some 1.5–2 nm in diameter. These permit the free passage between the cells of ions and small molecules (up to a molecular weight of about 1000 daltons).
They are constructed from 4 (sometimes 6) copies of one of a family of a transmembrane proteins called connexins.
Because ions can flow through them, gap junctions permit changes in membrane potential to pass from cell to cell.
Examples:
- The action potential in heart (cardiac) muscle flows from cell to cell through the heart providing the rhythmic contraction of the heartbeat. At some synapses in the brain, gap junctions permit the arrival of an action potential at the synaptic terminals to be transmitted across to the postsynaptic cell without the delay needed for release of a neurotransmitter. As the time of birth approaches, gap junctions between the smooth muscle cells of the uterus enable coordinated, powerful contractions to begin.
Several inherited disorders of humans such as
- certain congenital heart defects and certain cases of congenital deafness
have been found to be caused by mutant genes encoding connexins.
___________________
Focus on the one step you can take right now. Let go all regrets and resentment about what has already happened.
|
| reet
Forum Fanatic
Topics: 152
Posts: 1,411
|
wow!!! great pics...
believe thanks alot buddy
___________________
Live as u were to die tommorow. Learn as if u were to live forever.
|
| roopashri
Forum Elite
Topics: 16
Posts: 190
|
believe, awesome pictures
|
| tikka
Forum Elite
Topics: 59
Posts: 138
|
can anyone pl explain the ans of the above q on the basis of the explaination given by beleive ????
acc to the explaination only mol upto 1000 daltons can pass while the mol injected in the q is 2000 daltons in mol wt!!!!
|
| mjl1717
Forum Hero
Topics: 958
Posts: 5,465
|
I do Believe!(with emotion) You are deep. Thank You for everything. Excellent Q and explanation baby!  I noticed the epitaph also.
Edited by mjl1717 on 12/05/05 - 04:30 PM
___________________
Smell the coffee! "Is That an Osler move??"
|
| Believe
Forum Senior
Topics: 36
Posts: 93
|
Tikka, in the qs...
A fluorescent molecule of 2000 daltons is microinjected into a single cell of an epithelial layer. When the layer is examined in a fluorescence microscope, the molecule remains confined to that cell. However, when a fluorescent molecule of 800 daltons is injected into a single cell of an epithelial layer, it quickly appears in the adjacent cells. Which of the following is responsible for the spread of the smaller molecule?
so, ...........molecules with mw smaller than 1000d can pass through GAP JUNCTIONS ....because they permit the free passage between the cells of ions and small molecules (up to a molecular weight of about 1000 daltons)
and... in the qs the molecule is 800d, that's why the answer is Gap J.
___________________
Focus on the one step you can take right now. Let go all regrets and resentment about what has already happened.
|
|
| |
| | | | | | | | | | |
