Struktur dan Fungsi Antibodi


Antigen merupakan protein dan permukaan polisakarida berbagaimikroba, jaringan cangkokan yang tidak cocok, ataupun sel-sel darahyang ditransfusikan. Selain itu, antigen dapat pula berwujud proteinasing seperti racun lebah atau serbuk sari yang dapat menyebabkanalergi atau hipersensitivitas.Sebuah antigen mempunyai bagian pada permukaan suatu organismeatau substansi tertentu yang dapat berikatan dengan antibodi.Bagian tersebut dinamakan epitop atau determinan antigenik. Semua
epitop tentu akan berikatan dengan antibodi yang sesuai. Sehingga permukaanbakteri, misalnya, yang berperan sebagai antigen seluruhnyadapat ditutupi oleh banyak jenis antibodi.Antibodi merupakan protein terdiri atas satu atau lebih molekulyang berbentuk huruf Y. Empat rantai proteinnya disusun oleh ikatansulfi da. Dua rantai berat yang identik merupakan batang dan sebagianlengan Y. Sedangkan dua rantai ringan yang identik berada pada bagianlainnya. Pada kedua molekul berbentuk Y terdapat daerah variable (V)rantai berat dan rantai ringan. Dinamakan seperti itu karena pada bagianV memiliki urutan asam amino yang bervariasi dari satu antibodike antibodi lainnya.Umumnya antibodi terdiri atas sekelompok protein yang beradapada fraksi-fraksi globulin serum. Fraksi-fraksi globulin serum inidinamakan imunoglobulin atau disingkat Ig. Imunoglobulin ini bermanfaatapabila di dalam tubuh terjadi reaksi imun.Manusia memiliki beberapa tipe imunoglobulin dengan berbagaistruktur. Adapun tipe-tipe imunoglobulin tersebut meliputi imunoglobinM (IgM), imunoglobulin G (IgG), imunoglobulin A (IgA), imunoglobulinD (IgD), dan imunoglobulin E (IgE).


Read More »

contah Narrative Text


The Prince and His Best Friends
Once upon a time, there lived a kind young prince
named Jonathan. He was loved, and adored by his people.
His two close friends were Peter Piper, the servant of the
palace and Franklin Greedy, the son of an Aristocrat.
One day, The Prince, Peter Piper, and Franklin
Greedy were walking through the forest. Suddenly a
group of bandits attacked the three boys near an old
house. They entered the old house and blockaded the
gate and doors. The three boys were trapped inside
the house.
Franklin was very terri�� ed and asked the Prince
to surrender immediately, but Peter was not afraid.
He urged and supported the Prince not to give up. The
Prince decided not to surrender because he realised
that he would become a hostage for the bandits to
ask for ransom to his father, but Franklin was scared
and wanted to make a deal, it made Peter suspicious
about Franklin’s behaviour. So he quietly made up a
plan for him and the Prince to escape.
Early at dawn, Franklin opened the front gate and
unlocked the doors. The bandits entered the house
in search of the Prince. When they came to the room
where the Prince was supposed to be sleeping, no
one was there. Suddenly they heard a horse running
outside the house and saw over the window that
Peter Piper and the Prince were riding away on one
of the bandit’s horses.
It turns out, Peter Piper sneaked out of the house
and waited in the yard, while the Prince was hiding
behind the house. The bandits were very angry at
Franklin and took him with them while the Prince
and Peter went safely going back to the Capital

sumber
Read More »
Langganan: Postingan (Atom)