Redox Reactions and Calories
The formal name for a redox reaction is "oxidation reduction reaction," and you can see that "redox" is just shorthand for the words reduction and oxidation.
Thus, in a redox reaction, two things happen. You guessed it -- oxidation and reduction. These two have to happen together. You cannot have an oxidation
reaction without a corresponding reduction reaction. It’s a bit like the idea behind a blood transfusion or an organ transplant. You cannot have a recipient unless
you have a donor, and it does not make any sense to be a donor unless there is a recipient.
You may have noticed that "oxidation" starts with the same prefix as oxygen, suggesting that oxygen may be somehow involved in this process. Indeed, one
definition of oxidation states that: Oxidation is the gaining of bonds to oxygen Organic fuel substances (such as wood, coal or gas) are examples of compounds
that can be oxidized. In the process of burning, the carbon in these substances becomes bonded with oxygen, while some of the oxygen used to "burn" the fuel
bonds to the hydrogen atoms from the fuel. Thus, one of the definitions of reduction states that: Reduction is the gaining of hydrogen
Therefore, combustion reactions are good examples of redox reactions where one molecule gains oxygen (is oxidized) and one molecule gains hydrogen (is
reduced). For example, let’s look at what happens when gasoline in your car is burned as you drive around town (heptane is a common hydrocarbon component
of gasoline):
C7H12
heptane
+
11 O2
7 CO2
oxygen
carbon dioxide
+
8 H2O
water
Note how the carbon atoms in heptane are oxidized (because the carbon atoms in heptane become bonded with oxygen
atoms), while the oxygen is reduced (becomes bonded with hydrogen atoms).
These definitions of oxidation and reduction are useful. However, more general definitions of oxidation and reduction involve the
movement of electrons between the compounds involved in the redox reaction. In the most broad definition of redox reactions:
Oxidation is the loss of electrons; Reduction is the gain of electrons
Because electrons are negatively charged, an increase in electrons means a decrease in overall charge (the compound becomes
more negatively charged). On the other hand, an atom that is oxidized has given up some of those negatively charged electrons,
which will increase its overall charge (the compound becomes more positively charged). Notice that these definitions do not
involve oxygen and hydrogen. Thus, redox reactions can occur with compounds that do not contain oxygen or hydrogen atoms.An
everyday example of a redox reaction that we are all familiar with is the process of rusting. Rust is the flaky brown substance that
forms on iron objects left exposed to the elements for too long, especially if the objects get wet. Rust doesn’t just form on the iron
object, the iron actually turns into rust (rust is actually a form of oxidized iron).
Because it is difficult to remember the definitions of oxidation and reduction that involve the movement of electrons, a common
mnemonic that can help you keep these rules in mind is “OIL RIG.” This is an especially appropriate mnemonic for remembering
redox reactions because the burning of oil (a hydrocarbon fuel) is a redox reaction!
Questions:
1.
Give two different definitions for oxidation?
2. Give two different definitions for reduction?
3. True or False: Every time one molecule is oxidized, another molecule must be reduced?
4. True or False: Oxidation – Reduction equations can only occur in molecules that contain oxygen and hydrogen.
5. Fossil Fuels made of carbon and hydrogen such as coal is burned in large factories to provide energy. As a result carbon dioxide, water, and impurities in
the coal are given off as smoke.
a. Is the coal being oxidized or reduced? How can you tell?
b. Explain why coal cannot be burned in the absence of oxygen.
6. Below are familiar reactions that occur during photosynthesis.
a. In the photosynthesis equation identify the molecule the is oxidized and the molecule that is reduced.
b. In the chemical reaction that converts NADP+ into NADPH which molecule is oxidized are
which is reduced.
7. When a molecule is oxidized, does it gain or lose energy. Give an example to support your answer.
1. How many calories come from fat?
1. How many calories come from fat?
1. How many calories come from fat?
2. How many calories come from
carbohydrates?
2. How many calories come from
carbohydrates?
2. How many calories come from
carbohydrates?
3. How many calories come from proteins?
3. How many calories come from proteins?
3. How many calories come from proteins?
4. How many calories are in a single serving?
4. How many calories are in a single serving?
4. How many calories are in a single serving?
5. How many grams are in a single serving?
5. How many grams are in a single serving?
5. How many grams are in a single serving?
6. Calculate the calories per gram in
marshmallow.
6. Calculate the calories per gram in corn
chips.
6. Calculate the calories per gram in eggs.
1. Which food can be completely broken down into ATP through cellular respiration?
2. The carbohydrates in corn chips come from polysaccharides such as starch. Explain how the explain amylase helps in the digestion of the corn chips.
3. Which food contained the most calories per gram. Why did this food have more energy per gram compared to the other two types of food?
4. Which food will supply you with the most immediate supply of energy? Explain.
5. Which food will help your body build muscle, hair, and enzymes? Explain.