Quick Answer
Glucose, also known as C6H12O6, has a molecular weight of about 180 Daltons. This means that one molecule of glucose has a mass of around 180 Daltons.
What is Glucose?
Glucose is a simple sugar and carbohydrate that serves as the most important source of energy for living organisms. It is a monosaccharide, meaning it is made up of only one sugar unit.
Glucose is vital for many processes in the body and is the primary fuel used by cells. It circulates in the blood to supply tissues and organs with energy. The human brain relies on glucose as its main source of energy.
The chemical formula for glucose is C6H12O6. It has six carbon atoms, twelve hydrogen atoms, and six oxygen atoms. Glucose has an aldehyde group and is known chemically as an aldohexose.
Glucose is a product of photosynthesis in plants and is also produced in animals from the breakdown of glycogen and some amino acids. It is stored in the body as glycogen, with the majority of glycogen being stored in the liver and muscles.
When glucose levels fall, glycogen can be broken down into glucose through a process known as glycogenolysis. The hormone glucagon triggers glycogenolysis when glucose needs to be released into the bloodstream.
What is a Dalton?
A Dalton (Da) is a unit that is used to measure atomic and molecular mass. One Dalton is defined as being precisely 1/12 the mass of a single atom of the isotope carbon-12.
The carbon-12 isotope by definition has 6 protons and 6 neutrons, giving it an atomic mass of 12 Da. So, one Dalton is equivalent to 1.660 538 782 × 10-27 kg. This is an extremely small unit of mass.
Daltons provide a convenient scale for expressing atomic and molecular weights. The molar mass of a compound in grams per mole is numerically equal to the compound’s molecular weight in Daltons.
Daltons allow us to easily compare the masses of atoms and molecules on the atomic scale. Heavier atoms and molecules will have a higher number of Daltons.
For example, one water molecule has an atomic mass of about 18 Da (the sum of oxygen’s ~16 Da and two hydrogen atoms at ~1 Da each). A uranium atom weighs around 238 Da.
Molecular Weight of Glucose
As mentioned earlier, glucose has the chemical formula C6H12O6. This tells us it contains:
– 6 carbon atoms
– 12 hydrogen atoms
– 6 oxygen atoms
To calculate its molecular weight in Daltons, we need to add up the atomic weights of these constituent atoms:
– Carbon (C): 12 Da
– Hydrogen (H): 1 Da
– Oxygen (O): 16 Da
There are 6 carbons (6 x 12 Da = 72 Da)
12 hydrogens (12 x 1 Da = 12 Da)
6 oxygens (6 x 16 Da = 96 Da)
So the total molecular weight of glucose adds up to:
– 72 Da (from 6 C)
– 12 Da (from 12 H)
– 96 Da (from 6 O)
This gives glucose a molecular weight of around **180 Daltons.**
Therefore, we can say that one molecule of glucose weighs approximately 180 Daltons.
Converting Grams to Daltons
Since 180 Daltons is equal to 180 grams per mole, we can use the molecular weight of glucose in Daltons to convert between grams and moles.
For example, to find out how many Daltons are in 5 grams of glucose:
– Molecular weight of glucose = 180 Daltons
– 5 grams glucose x (1 mole glucose / 180 grams glucose) = 0.0278 moles glucose
– 0.0278 moles glucose x 180 Daltons/mole = 5 Daltons
So 5 grams of glucose contains around 5 Daltons.
We can also go the other way, from Daltons to grams. Let’s say we want to find out how many grams 100 Daltons of glucose is equivalent to:
– Molecular weight of glucose = 180 Daltons/mole
– 100 Daltons glucose x (1 mole glucose / 180 Daltons glucose) = 0.556 moles glucose
– 0.556 moles glucose x 180 grams glucose/mole = 100 grams
Therefore, 100 Daltons of glucose is equal to 100 grams of glucose. Converting between the two units is straightforward using the molar mass.
Why Glucose has a Weight of 180 Daltons
Glucose has a molecular weight of around 180 Daltons for a few key reasons:
1. It contains 6 carbon atoms
Carbon has an atomic weight of 12 Daltons. With 6 carbon atoms, this contributes 72 Daltons (6 x 12 Da) to glucose’s overall 180 Daltons molecular weight.
2. It contains 12 hydrogen atoms
Hydrogen is very light with an atomic weight of just 1 Dalton. The 12 hydrogen atoms account for 12 Daltons (12 x 1 Da) of glucose’s weight.
3. It contains 6 oxygen atoms
With an atomic weight of 16 Daltons, the 6 oxygen atoms add 96 Daltons (6 x 16 Da) to the total molecular weight.
4. The atomic weights of C, H and O sum to 180 Da
Adding up the contributions from the elemental atoms gives:
– Carbon = 72 Daltons
– Hydrogen = 12 Daltons
– Oxygen = 96 Daltons
Total = 72 + 12 + 96 = 180 Daltons
So the number and types of atoms contained in glucose ultimately give it a molecular weight of around 180 Da.
Molecular Weight and Chemical Formulas
Looking at the molecular formula of a compound lets us easily determine its molecular weight in Daltons.
For example, water with the formula H2O:
– 2 hydrogen atoms (2 x 1 Da) = 2 Da
– 1 oxygen atom (1 x 16 Da) = 16 Da
– Total molecular weight = 18 Daltons
Methane CH4:
– 1 carbon atom (1 x 12 Da) = 12 Da
– 4 hydrogen atoms (4 x 1 Da) = 4 Da
– Total molecular weight = 16 Daltons
This demonstrates how molecular weights in Daltons can be derived simply from chemical formulas, based on the atomic weights of the constituent elements.
Other Units for Molecular Weight
While Daltons are commonly used, molecular weight can also be expressed in other units:
| Unit | Definition |
|---|---|
| g/mol | Grams per mole – numerically equal to Daltons |
| kg/mol | Kilograms per mole |
| u | Atomic mass unit, equivalent to Daltons |
So glucose could also be said to have a molecular weight of:
– 180 g/mol
– 1.80 x 10-4 kg/mol
– 180 atomic mass units (amu)
But Daltons (Da) remain the most widely used unit when stating molecular weights.
Molecular Weights of Other Carbohydrates
While glucose has a molecular weight of 180 Daltons, other carbohydrates have different molecular weights based on their chemical makeup:
| Carbohydrate | Molecular Formula | Molecular Weight (Daltons) |
|---|---|---|
| Galactose | C6H12O6 | 180 |
| Fructose | C6H12O6 | 180 |
| Sucrose | C12H22O11 | 342 |
| Lactose | C12H22O11 | 342 |
| Maltose | C12H22O11 | 342 |
| Cellulose | (C6H10O5)n | Varies |
Both galactose and fructose are monosaccharides like glucose with the same chemical formula, giving them equal 180 Da molecular weights.
Disaccharides like sucrose, lactose and maltose consist of two joined monosaccharides, so they have about twice the molecular weight at 342 Da.
Polysaccharides like cellulose consist of long chains of glucose units, so their molecular weights are much higher and variable.
Conclusion
In summary:
– Glucose (C6H12O6) has a molecular weight of around 180 Daltons
– One Dalton is defined as 1/12 the mass of a carbon-12 atom
– The molecular weight in Daltons is calculated by adding the atomic weights of the constituent atoms
– Glucose weighs 180 Da because it contains 6 carbon, 12 hydrogen and 6 oxygen atoms
– The molecular weight allows conversion between mass units like grams and Daltons
– Chemical formulas indicate molecular weights based on the atoms present
– Other carbohydrates have different molecular weights depending on their composition
So when asked ‘How many Daltons is glucose?’ we can definitively state that glucose weighs approximately 180 Daltons, owing to its chemical formula containing 6 carbons, 12 hydrogens and 6 oxygens. The Dalton is a handy unit for comparing the molecular weights of molecules on the atomic scale.
