November 29, 2017

A magnesium atom that loses two electrons becomes a

(1) positive ion with a smaller radius

(2) negative ion with a smaller radius

(3) positive ion with a larger radius

(4) negative ion with a larger radius 

Answer and Explanation:

To answer this question we first must think what charge an electron has. Electrons are negatively charged. Therefore, losing two electrons will make magnesium a positively charged ion. You can also...

November 27, 2017

Reverse transcriptase is an enzyme whose function is to create single stranded DNA  (cDNA) from RNA template (hence it's name "reverse"). This enzyme is found primarily in retroviruses. One significant example of such retrovirus is HIV. This virus contains the reverse transcriptase that allows it to produce complementary DNA and start creating it's own proteins and multiply, generating new viruses. Drugs, known as rever...

November 24, 2017

Membrane serves an essential function of choosing to let all the necessary molecules in and wastes out. It is composed of two layers of phospholipids as well as proteins, carbohydrates and lipids.  Phospholipids move freely on the membrane giving it the "fluid" term. Different proteins are embedded into the membrane in a nonuniform fashion. Therefore, membrane looks like a mosaic.

It's worth noting that the upper an...

November 21, 2017

Exothermic reactions are reactions that release energy. An example of exothermic reactions is combustion or burning. Endothermic reactions on the other hand absorb energy. An example of an endothermic reaction is melting of ice.

For exothermic reactions, since the heat is released, we see heat on the product side of the equation. Also, change in enthalpy will have a negative sign.

For endothermic reactions, since the heat...

November 18, 2017

Both kinases and phosphatase are enzymes that are essential to many reactions in our body. MCAT loves enzymes and asks plenty of questions about them!

Kinase is an enzyme whose function is to add a phosphate group from ATP to other organic molecules in a process called phosphorylation. Phosphatase, on the other hand, does the opposite of kinase. It cleaves phosphate groups using water.

Where do we see these enzymes in act...

November 15, 2017

An energy-rich organic compound needed by organisms is

(1) water

(2) salt

(3) oxygen

(4) glucose 

Answer and Explanation:

In order for a compound to be organic it must contain a very important element: Carbon. This can eliminate choices 1 and 3 since the formula for water is H2O and oxygen is O2. A compound that is rich in energy is glucose, choice 4. The formula for glucose is C6H12O6. Animal bodies break down glucose in a...

November 12, 2017

What is the oxidation number of manganese in KMnO4? 

(1) +7

(2) +2

(3) +3

(4) +4 

Answer and Explanation:

We can figure out the oxidation number of Manganese by making a simple equation. First, we need to see what are the oxidation numbers of all of the other elements. We can find these numbers on the periodic table. We can see that K has +1 number while oxygen is -2. Therefore, we can now make our equation.

All the oxidation...

November 10, 2017

Proteins, starch, and DNA are similar in that they are all

(1) organic compounds

(2) parts of genes

(3) made of amino acids

(4) made of simple sugars 

Answer and Explanation:

Proteins, starch and DNA are all important molecules in our body. What do they have in common? Well let's take a look at the answer choices and figure out. Only starch is made of simple sugars, while proteins are made of amino acids, and DNA contain gen...

November 7, 2017

A solid sample of a compound and a liquid sample of the same compound are each tested for electrical conductivity. Which test conclusion indicates that the compound is ionic?

(1)  Both the solid and the liquid are good conductors.

(2)  Both the solid and the liquid are poor conductors.

(3)  The solid is a good conductor, and the liquid is a poor conductor.

(4)  The solid is a poor conductor, and the liquid is a good conduct...

November 2, 2017

Medicine and science are advancing. The idea of pig organs for humans transplants was tested in 1990s when it was discovered that hidden in pig DNA were genes for viruses that resembled those causing leukemia in monkeys. Thus, pig cells grown next to human cells infected human cells with their retroviruses and posed a great danger to the humans.

A major breakthrough has been done in the experiments, reported in the journ...

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