USMLE Step I 2011 Practice and Orientation materials are available already.

The United States Medical Licencing Examination materials for Step I are already available at the USMLE website.

The materials can be downloaded in pdf format in:

The content outlines for this exam has been updated by a subcommittee of the step I committee.

The updated content can be found in this link:

USMLE committee recommends to students considering to exam Step I after May 2011 to be familiarized with the previous (2010) and the updated content outlines.

In future posts we will discuss the topics associated to the sample questions related to Biochemistry that are included in these materials.


USMLE and the H1N1 Influenza.

N1H1 Virus (CDC Influenza Lab)

N1H1 Virus (CDC Influenza Lab)


USMLE committee has announced that it is allowing that those candidates that are concerned about their ability to test safely, to reschedule USMLE test appointments without paying the additional fees.


If the current threat level continues, the eligibility period that end on July 31, will be extended beyond that date (please, visit the USMLE site for details)


USMLE recommends to monitor the website for updated information.


And of course, if you have flu-like symptoms, or you may have been recently exposed to a Flu patient, you should reschedule your exam.


Read the complete information here.

USMLE Step I, 2009: Important links


Step I Content description on line


Pdf version of Step I content description and sample material 2009


Overview of Step I content in the USMLE Bulletin of Information-2009


2009 Orientation Materials

– Multiple choice tutorial and Practice Test items Version FredV1 (current test delivery software)

– Multiple choice tutorial and Practice Test items Versions FredV2 (test delivery software for 2009)



And of course, review frequently the main link:


List of sites with official USMLE Step I Sample Test material since 2003


I think that this list might be of interest for those medical students and International Medical Graduates that are studying for the USMLE Step I.


If you have any doubt about the answer to questions about Biochemistry topics, please, do not hesitate to write a comment asking about it. Please recall that the questions can not be reproduced because of copyright issues, so you should refer to them as the Question No. X of 200Y material.


USMLE Content test description and sample test materials 2003 Step I


USMLE Content test description and sample test materials 2004 Step I


USMLE Content test description and sample test materials 2005 Step I


USMLE Content test description and sample test materials 2007 Step I


USMLE Step I Content Description and General information 2008




A summary of USMLE announcements for Step I during the first semester of 2008


A summary of official announcements about USMLE Step I posted at the USMLE website during the first semester of 2008



April 14th: About the inclusion of media files in the Step I exam


A small number of multiple choice questions will include audio or video clips


May 09: About number of items in Step I


The number of items on Step I will change from 350 to 336, divided into seven blocks with 48 questions each (the time for each block remains the same: 60 minutes)


June 10th: About the Comprehensive Review of USMLE.


On June 2, it was informed that the Composite Committee, which establishes policy for the US Medical Licensing Examination, concurred with the Committee to evaluate the USMLE Program (CEUP), in the following recommendations:


 1.- The design of assessments to support decisions about a physician readiness to provide patient care:

a)     at the interface between undergraduate and graduate medical education

b)     at the beginning of independent practice.


 2.- USMLE should work in the design of an schema for measuring the general competencies important to medical practice and licensure


3.- The recommendation that the USMLE emphasize the importance of the scientific foundations of medicine in all components of the assessment process. The assessment of these foundations should occur within a clinical context or framework, to the greatest extent possible.


The report emphasize that the process will be evolutionary and that the entire process will take a minimum of four years before it will impact any test-takers.


(An official summary of the  report here)



For reading all the announcements in detail, please click




Calculating calories in meals


Answer to Biochemistry Question N-02: (e) 500 Calories



                                      from zamber on flickr



Since usually we use large amounts of energy compared to the calorie unit used in Physics, the calorie unit used in Nutrition is different to the classical calorie definition used in Physics. While in Physics 1 calorie is defined as the quantity of energy necessary for increasing the temperature of one gram of water 1 Celsius degree at 1 atmosphere of pressure, the nutritional calorie correspond to 1000 this value (in a more accurate way, it correspond to what is called a large calorie, in contrast to the  classical “small” calorie of Physics, and should be abbreviated as Cal). It means, that 1 Nutritional calorie is equivalent to 1 kilocalorie in physics.


In the SI unit 1 physics’ calorie is equivalent to 4.184 joules, so a Nutritional calorie is equivalent to 4 184 Joules.



The body needs energy for:


1.- Mantaining Resting Metabolic Rate (RMR, former BMR)


2.- Heat production  (An important factor in heat production is the thermic effect of food, or diet induced thermogenesis, that may amount 5-10 %  of total energy expenditure/day)


3.- Physical activity



The human body obtain the energy it needs from the foods.


The major dietary energy sources:



4 cal/g  (nutritional calorie)


9 cal/g (nutritional calorie)


4 cal/g (nutritional calorie)



As you can see, fat is the most concentrated source of energy – weight for weight it provides just over twice as much as either protein or carbohydrate.


Alcohol provides almost as much energy as fat: 1 gram of alcohol can supply 7 cal/g . For some people alcoholic drinks form a large part of their energy intake. This can be harmful to health since a high alcohol consumption is a risk factor for several diseases.


The energy content of a food or drink depends on how many grams of carbohydrate, fat, protein and/or alcohol are present.


Since the source of energy in the diet has been implicated as a risk factor in certain diseases, it has been described a recommended distribution of calories in diet. The Acceptable Macronutrient Distribution Range (AMDR) has been defined as the range of intake for a particular energy source that is associated with reduced risk of chronic disease while providing intakes of essential nutrients (Dietary Guideline for Americans, Glossary . The caloric composition of diet should be approximately, 45-65 % from carbohydrates, 20-35 percent from fats and 10-35 % from proteins, but there are recommendations for specific groups.


Different websites show the caloric value of thousands of foods. This is one of those sites with several related links:



Anyway, it is important that you know the general principles described above.


USMLE released sample questions, that exemplify contents of the examination, have included questions about caloric calculation in past years (Ex: Question 45 in 2005 USMLE Step I Content Description and Sample Test, that also appears as Question 35 in the 2006 edition). Unfortunately, copyright issues do not allow us to reproduce that question here.



More information can be found in:


A classic:

Merrill, A.L.; Watts, B.K. :Energy values of food: Basis and derivations


Food composition and Nutrition Links from the USDA



Biochemistry and USMLE step I exam (II): My High Yield Topics List about Structure and Function of Proteins


Some introductory warnings:


If you intend to use this post  as a guide for studying Biochemistry for the USMLE Step I, DON’T DO IT! You better go to study your notes and/or some of your review books…


If you already studied Biochemistry for USMLE, and you just want to read some ideas about which topics would be interesting to reinforce, the following topics would be a good guide.


These topics  have relevant medical  importance and have been described and referred in different sources as high yield in this kind of exams.


(Disclaimer:  This post reflect the subjective opinion of the blogger;  the blogger is not responsible of a poor performance of the student in the biochemistry questions in USMLE and do not claim that the student will obtain a good result following the advices in this post and blah, blah, blah, etc).


But of course, do not limit your study to high yield topics. What if you have a “low yield disease” and you are attended by a physician who just studied “high yield topics”?


Certainly, this is a very important exam, but like the name says,..“Step I”, just one step. (I am sure that you realize that when you decided to study Medicine, you also decided to climb a stair with countless steps… “Ars longa, Vita brevis”)


Once passed these philosophical statements, let’s talk about practical issues related to this exam.


I consider (I believe, I think, I suppose, I assume…) that the most relevant High Yield topics in Structure and function of Proteins for USMLE, not including enzymes, are the following:



-Main physiological types of Hb describing their chain composition


– Oxygen affinity and Hb F


-Comparison between the curves of oxygen binding in myoglobin and Hemoglobin and to explain them.


– Allosteric effectors of Hb (special attention to allosterism in the curve of binding of Oxygen to Hb)


 -Bohr Effect in Hb oxygen binding


-Action of 2,3 BPG on T/R Hb equilibrium.


-Role of Hb in Nitric Oxide transport.


-Classification of hemoglobinopathies.


-Diseases caused by defects in Hb synthesis.


-Causes and biochemical characteristics of the Thalassemias.


-Causes and consequences of Sickle cell anemia


-Comparison between Sickle cell anemia, Hemoglobin C disease and Hemoglobin SC disease.


-Clinical importance of glycosylated Hb


-Metahemoglobin main characteristics


-Mechanism of production of CO intoxication.


– Collagen biosynthesis and processing (special attention to the relationship between scurvy and collagen biosynthesis)


-Diseases that are consequence of disorders of collagen synthesis In particular causes and characteristics of Ehler-Danlos Syndrome and Osteogenesis Imperfecta)


– Relationship between elastin in alveolar walls and emphysema


-Biochemical basis of Cystic Fibrosis and clinical consequences.


-Causes of protein misfolding (pay attention to Amyloidoses and protein misfolding)



Final Note (I am sorry, I feel I need to repeat it):


If you intend to use this post as a guide for studying Biochemistry for the USMLE Step I,  DON’T DO IT! You better go to study your notes and/or some of your review books…


If you already studied Biochemistry for USMLE, and you just want to read some ideas about which topics would be interesting to revisit, this post could help you…