Microbial replication question from Kaplan - USMLE Forums
 USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
 Home USMLE Articles USMLE News USMLE Polls USMLE Books USMLE Apps
 USMLE Forums Microbial replication question from Kaplan
 Register FAQs Members List Search Today's Posts Mark Forums Read

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

#1
03-23-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,684 Threads: 213 Thanked 1,600 Times in 660 Posts Reputation: 1610
Microbial replication question from Kaplan

A flask is inoculated to a density of 3x10^3 cells/ml. What will be the density of cells in the culture after 50 minutes if the generation time is 20 mins and the lag time is 10 mins ?

#2
03-23-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,175 Threads: 38 Thanked 854 Times in 478 Posts Reputation: 864

Quote:
 Originally Posted by Hope2Pass A flask is inoculated to a density of 3x10^3 cells/ml. What will be the density of cells in the culture after 50 minutes if the generation time is 20 mins and the lag time is 10 mins ?
You need to know the LESD process in this.

Log / Lag........... 10 minutes
Exponential..........20 min
Stationary.......... 10 min?
Decline / Death....10 min?

Only time they are dividing is in the exponential phase, after which there is no increase in numbers.

Quote:
 and the bacteria has 40 minutes to grow: 50 minutes - lag time (10 minutes) = 40 minutes With the generation time of 20 minutes and 40 minutes to grow, you will have 2 generations. You need to know this equation: b = B x 2^n (This equation is an expression of growth by binary fission) b = number of bacteria at the end of the time interval B = number of bacteria at the beginning of a time interval n = number of generations (number of times the cell population doubles during the time interval) in this case it is 2. b = 3x10^3 cell /ml x 2^ n In this case n = 2 because there are 2 generations during the 40 minutes b = 3x10^3 cell /ml x 2^ 2 b = 3x10^3 cell /ml x 4 b = 12 x 10^3 cel/ml

 Tags Microbiology-, Step-1-Questions

Message:
Options

## Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
User Name:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
 AMG IMG ---
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.

 Not yet Step 1 Only CK Only CS Only 1 + CK 1 + CS 1+CK+CS CK+CS 1+CK+CS+3 ---
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.