A. We could look up the chemical composition of Actin to get exactly how many atoms it contains. But let's see how "the estimation game" does instead. Actin is a biological molecule, so it's probably made up of mostly carbon, oxygen, nitrogen, and hydrogen, with a few other stray atoms tossed in. Use an "average sized biological atom" to estimate the number of atoms in Actin. B. Given the radius of an average atom let's consider a simple model of Actin. Suppose Actin is tightly packed into a sphere or cube. For estimation purposes we could model each atom as a cube. If you built up a cube of the total number of atoms you found in A, what would be the dimensions of the cube? C. Look up Actin and find its actual size. How did the really simple model do? Can you draw any conclusions about the structure of Actin from these results?
Nucleotides
It is an organic molecule made up of three basic components- a nitrogenous base, phosphate,and pentose sugar. The nucleotides are important for metabolic reactions andthe formation of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
Nucleic Acids
Nucleic acids are essential biomolecules present in prokaryotic and eukaryotic cells and viruses. They carry the genetic information for the synthesis of proteins and cellular replication. The nucleic acids are of two types: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The structure of all proteins and ultimately every biomolecule and cellular component is a product of information encoded in the sequence of nucleic acids. Parts of a DNA molecule containing the information needed to synthesize a protein or an RNA are genes. Nucleic acids can store and transmit genetic information from one generation to the next, fundamental to any life form.
Often, complex molecules are described in terms of their atomic masses. But what is more
relevant in biology is how they take up space. (For proteins, their shapes are particularly
important.) Let's see if we can get an approximate idea of the physical size of a protein molecule
by doing various estimations.
An important molecule in the internal mechanisms of cells is Actin. This is measured as having
a mass of about 42 kDa (= 42,000 Daltons, where 12 Daltons is defined as the mass of a carbon
atom). Let's see if we can estimate how big it is using very crude estimates. Of course eventually
we will want to know how big it actually is and what its shape is, but getting a scale would help
us determine what measurement tools might be appropriate.
In order to estimate the size of Actin, we'll first make an estimate of how many atoms it has,
then, using the average size of an atom, we'll consider different models of how it might be
arranged to get an idea of its size.
A. We could look up the chemical composition of Actin to get exactly how many atoms it
contains. But let's see how "the estimation game" does instead. Actin is a biological molecule, so
it's probably made up of mostly carbon, oxygen, nitrogen, and hydrogen, with a few other stray
atoms tossed in. Use an "average sized biological atom" to estimate the number of atoms in
Actin.
B. Given the radius of an average atom let's consider a simple model of Actin. Suppose Actin is
tightly packed into a sphere or cube. For estimation purposes we could model each atom as a
cube. If you built up a cube of the total number of atoms you found in A, what would be the
dimensions of the cube?
C. Look up Actin and find its actual size. How did the really simple model do? Can you draw
any conclusions about the structure of Actin from these results?
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