Antibody Antigen Question - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 07-16-2010
USMLE Forums Veteran
 
Steps History: 1 + CS
Posts: 209
Threads: 34
Thanked 92 Times in 30 Posts
Reputation: 122
Immunology Antibody Antigen Question

The amounts of protein precipitated in a series of tubes containing a constant amount of antibody and varying amounts of antigen are presented below. In which tube is antigen-antibody equivalence obtained?
Tube Antigen Precipitated (mg) Protein (mg)
A 0.02 1.1
B 0.08 2.1
C 0.32 3.1
D 1.0 3.7
E 2.0 2.9

A. A
B. B
C. C
D. D
E. E
Reply With Quote Quick reply to this message
The above post was thanked by:
Pixie (07-16-2010), Zagaris (07-16-2010)



  #2  
Old 07-16-2010
doctorF's Avatar
USMLE Forums Guru
 
Steps History: Not yet
Posts: 316
Threads: 68
Thanked 408 Times in 110 Posts
Reputation: 428
Default

i think A... may be i m wrong but i thought this way... antibody which is a protein should be constant... the lowest amount shows more antibody has consumed and antigen and antibody are now in equilibrium
__________________
Why does Good luck often carries more weightage than hard work in successes???
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message
  #3  
Old 07-16-2010
USMLE Forums Veteran
 
Steps History: 1 + CS
Posts: 209
Threads: 34
Thanked 92 Times in 30 Posts
Reputation: 122
Default

In tube d in the question presented, the maximum protein precipitate is observed. According to the rules governing precipitin reactions, maximum precipitation occurs at approximately antigen-antibody equivalence. In tubes a through c, antibody excess occurs; in tube e, antigen excess occurs


this is the explanation they gave but i didnt get the explanati0on can anyone explaina it if u understand the concept
Reply With Quote Quick reply to this message
 
  #4  
Old 07-16-2010
doctorF's Avatar
USMLE Forums Guru
 
Steps History: Not yet
Posts: 316
Threads: 68
Thanked 408 Times in 110 Posts
Reputation: 428
Default

o... if they say so then it must be it... but if somebody xplains it more clearly it will be better otherwise its confusing
__________________
Why does Good luck often carries more weightage than hard work in successes???
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message
  #5  
Old 07-17-2010
Kabutar111's Avatar
USMLE Forums Guru
 
Steps History: Not yet
Posts: 414
Threads: 30
Thanked 87 Times in 70 Posts
Reputation: 97
Send a message via Skype™ to Kabutar111
Listening

i used the same equilance basis.
E--as the amount of antigen ppt and protein are most equal to each other.
E--also there hhigest ppt in E it means more Ag-Ab equivalence.

is it not right please do correct me.:sorry:
Quote:
Originally Posted by ecgram View Post
In tube d in the question presented, the maximum protein precipitate is observed. According to the rules governing precipitin reactions, maximum precipitation occurs at approximately antigen-antibody equivalence. In tubes a through c, antibody excess occurs; in tube e, antigen excess occurs


this is the explanation they gave but i didnt get the explanati0on can anyone explaina it if u understand the concept
__________________
There is no shortcut to SUCCESS ,and there is no excuse for FALIURE - by Kabutar111
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message
  #6  
Old 07-17-2010
USMLE Forums Veteran
 
Steps History: 1 + CS
Posts: 209
Threads: 34
Thanked 92 Times in 30 Posts
Reputation: 122
Default

@kabutar actually i answered E but i dont no why the answer says D
but i still think its E
Reply With Quote Quick reply to this message
  #7  
Old 07-17-2010
Kabutar111's Avatar
USMLE Forums Guru
 
Steps History: Not yet
Posts: 414
Threads: 30
Thanked 87 Times in 70 Posts
Reputation: 97
Send a message via Skype™ to Kabutar111
Unhappy

someone should explain this
__________________
There is no shortcut to SUCCESS ,and there is no excuse for FALIURE - by Kabutar111
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message
  #8  
Old 11-20-2011
dr.muhamad's Avatar
USMLE Forums Guru
 
Steps History: 1 + CS
Posts: 300
Threads: 22
Thanked 97 Times in 62 Posts
Reputation: 107
Default

this is really tough question
Reply With Quote Quick reply to this message
  #9  
Old 11-20-2011
USMLE Forums Guru
 
Steps History: Step 1 Only
Posts: 342
Threads: 50
Thanked 197 Times in 103 Posts
Reputation: 207
Default

it's D
explanation given is right and i can't explain in a better way,,,see the graph given in immuno Kaplan . .

zone of equivalence = max amount of precipitate also known as window phase . .
Reply With Quote Quick reply to this message
  #10  
Old 11-20-2011
USMLE Forums Addict
 
Steps History: Step 1 Only
Posts: 154
Threads: 8
Thanked 134 Times in 62 Posts
Reputation: 144
Default

Quote:
Originally Posted by zohaib View Post
it's D
explanation given is right and i can't explain in a better way,,,see the graph given in immuno Kaplan . .

zone of equivalence = max amount of precipitate also known as window phase . .
Hey Zohaib, i get the principle but the numbers are not clear to me. It D there is 1 mg precip. meaning 1 mg of ag bound to AB. What does the other number mean? is it the rest amount of AB?
Reply With Quote Quick reply to this message
  #11  
Old 12-16-2012
USMLE Forums Newbie
 
Steps History: Not yet
Posts: 1
Threads: 0
Thanked 0 Times in 0 Posts
Reputation: 10
Default Answer

It's an old question but thought it could use an explanation:

SUBTRACT!!!!!
3.1 - 0.32 = 2.78 anti-body complex
3.7 -1.0 = 2.7 anti-body complex

JUST after 3.1 with anti-body complex 2.78 we begin to see a decrease in complex and a rise in antigen precipitation meaning excess antigen - meaning we have passed maximum equivalence, so like from old chemistry be have just hit the titration point

Quote:
Originally Posted by ecgram View Post
The amounts of protein precipitated in a series of tubes containing a constant amount of antibody and varying amounts of antigen are presented below. In which tube is antigen-antibody equivalence obtained?
Tube Antigen Precipitated (mg) Protein (mg)
A 0.02 1.1
B 0.08 2.1
C 0.32 3.1
D 1.0 3.7
E 2.0 2.9

A. A
B. B
C. C
D. D
E. E
Reply With Quote Quick reply to this message



Reply

Tags
Immunology-, Step-1-Questions

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
Where you live. Leave blank if you don't want to tell.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Hepatitis Antibody Profile; Carrier State versus Immunized State USDreamer USMLE Step 2 CK Forum 9 10-09-2012 06:14 AM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)