Breakfast Makes You Hungry
Tauhid Nur Azhar
At one of the legendary restaurants in Bandung, located right next to the Santo Borromeus Hospital, there is a sign near the motorcycle parking area that reads: “Prioritize breakfast, not hope.”
I’m not in a position to agree or disagree with this statement, but if I had to say, it’s probably true that without breakfast, it’s a bit difficult to achieve our hopes, right? Maybe we’ll lack energy, because we’ve always believed that breakfast is the source of strength for our daily activities.
Breakfast in Indonesia is special, isn’t it? At the very least, there’s usually nasi goreng (fried rice), which according to data from the Indonesian Ministry of Health’s Food Composition Database, can have up to 267 kcal.
If we can’t prepare nasi goreng, there’s at least a plate of plain white rice with around 204 kcal, served with crackers and sweet soy sauce.
But how does rice or “kejo” (as the Sundanese people call it) get converted into energy, just like cheese is converted into energy for the Dutch? And if we consume too much of either, it can trigger the emergence of diseases.
It turns out that it’s all related to the work of a small organelle called the mitochondria, which is like the “engine” of the cell. Mitochondria play a crucial role in producing energy through a process called oxidative phosphorylation. Here are some of the main functions of mitochondria:
- Energy Production (ATP): Mitochondria act as the “engine” of the cell by converting nutrients like glucose into energy in the form of Adenosine Triphosphate (ATP) through the Krebs cycle and electron transport chain.
- Regulation of Programmed Cell Death (Apoptosis): Mitochondria have a role in regulating programmed cell death by releasing proteins like cytochrome c, which triggers a series of events leading to cell death.
- Calcium Metabolism Control: Mitochondria help store and release calcium in cells, which is important for various cellular functions, including muscle contraction and cellular signaling.
- Synthesis of Biological Molecules: Mitochondria contribute to the synthesis of molecules like steroids, amino acids, and cell membrane components.
- Free Radical Regulation: Mitochondria produce free radicals during ATP production. They also have a system to control the amount of free radicals and prevent oxidative damage to cells.
- Mitochondrial Genetic Inheritance: Mitochondria have their own genetic material, known as mitochondrial DNA (mtDNA), which is inherited only from the mother. This pattern of inheritance plays a role in various genetically inherited diseases and is also related to certain capacities and competencies that are only inherited through the maternal line.
Let’s focus on our breakfast journey again. If we had a plate of white rice with fried eggs and a piece of grilled fish in green chili sauce for breakfast, how does our body convert that plate of rice into energy that we can accumulate to build our nation?
The rice, eggs, and fish that we ate for breakfast must be converted into energy molecules, specifically ATP (adenosine triphosphate). The process of converting rice into ATP molecules involves a series of complex biochemical steps, starting from digestion to cellular respiration.
Rice is composed of carbohydrates in the form of starch, which is a polysaccharide (a long chain of glucose molecules). The digestion process breaks down starch into glucose through the action of salivary amylase enzymes in the mouth.
The digestion of carbohydrates is temporarily halted when the food enters the stomach, as the acidic environment of the stomach is not suitable for amylase enzymes.
In the small intestine, pancreatic amylase enzymes continue to break down starch into maltose and disaccharides. Other enzymes such as maltase, sucrase, and lactase then convert disaccharides into glucose.
The glucose produced from digestion is absorbed by cells in the small intestine through active transport mechanisms and enters the bloodstream.
The glucose absorbed from the small intestine will enter the bloodstream and be transported to cells throughout the body via the circulatory system. Insulin, a hormone produced by the pancreas, facilitates the uptake of glucose into cells, particularly in muscle and adipose tissue. Glucose then enters cells through glucose transporters (GLUT).
Once inside the cell, glucose undergoes the first stage of cellular respiration, known as glycolysis. This process occurs in the cytoplasm and does not require oxygen (anaerobic). Glycolysis consists of several steps, including the phosphorylation of glucose to form glucose-6-phosphate using one ATP molecule.
The glucose-6-phosphate is then broken down into several steps, resulting in the formation of pyruvate (two pyruvate molecules from one glucose molecule).
The result of glycolysis at this stage is 2 ATP molecules (net), 2 NADH molecules, and 2 pyruvate molecules.
If oxygen is available, the pyruvate produced from glycolysis enters the mitochondria for further oxidation. Pyruvate undergoes oxidative decarboxylation by the pyruvate dehydrogenase enzyme to form acetyl-CoA. This process produces 1 NADH molecule and 1 CO2 molecule (per pyruvate molecule).
Since one glucose molecule produces two pyruvate molecules, the total yield is 2 acetyl-CoA molecules, 2 NADH molecules, and 2 CO2 molecules.
Acetyl-CoA then enters the Krebs cycle, which occurs in the mitochondrial matrix. Each acetyl-CoA molecule will combine with oxaloacetate to form citrate, and through a series of oxidative reactions, carbon is broken down to produce energy.
Each acetyl-CoA molecule produces 3 NADH molecules, 1 FADH2 molecule, 1 GTP molecule (equivalent to ATP), and 2 CO2 molecules.
Since one glucose molecule produces two acetyl-CoA molecules, the Krebs cycle runs twice for each glucose molecule, producing a total of 6 NADH molecules, 2 FADH2 molecules, 2 ATP molecules (from GTP), and 4 CO2 molecules.
The final step in ATP production occurs in the electron transport chain (ETC) and oxidative phosphorylation, which takes place in the inner mitochondrial membrane. NADH and FADH2 molecules produced from glycolysis, pyruvate decarboxylation, and the Krebs cycle will donate their electrons to the electron transport chain. The following steps occur:
NADH and FADH2 molecules release their electrons to protein complexes in the electron transport chain.
The electrons then move through the complexes, releasing energy that is used to pump protons (H+) from the mitochondrial matrix to the intermembrane space, creating a proton gradient.
Protons then return to the matrix through the ATP synthase enzyme, which uses the energy from the proton flow to synthesize ATP from ADP and inorganic phosphate (Pi).
Let’s talk about the contribution of ATP molecules from the rice we ate for breakfast. Can we calculate and quantify the ATP from the rice? Let’s try.
The energy released by 1 molecule of ATP when hydrolyzed into ADP (adenosine diphosphate) and inorganic phosphate (Pi) is typically around 7.3 kilocalories per mole ATP (kcal/mol ATP) under standard physiological conditions (pH 7, temperature 25°C, pressure 1 atm).
To determine the energy produced by 1 molecule of ATP, we need to convert this value to a suitable unit.
Conversion of Energy from Kilocalories to Calories 1 kilocalorie (kcal) = 1000 calories (cal).
So, the energy per mole ATP is: 7.3 kcal/mol x 100 = 730 cal/mol
Calculating Energy per Molecule ATP One mole of ATP contains 6.022 x 10²³ molecules (Avogadro’s number). Therefore, the energy produced by 1 molecule of ATP is: [7300 cal/mol] / [6.022 x 10²³ molecules/mol] = 1.2 x 10^-20 cal
The energy produced by 1 molecule of ATP is approximately 1.21 x 10^-20 calories. This amount is very small because one calorie is a large unit of energy compared to the energy produced by a single molecule.
But that’s the energy of a single ATP molecule, and we ate a plate of rice. According to literature, a plate of rice is equivalent to 150–200 calories. We can see this in the following quote:
“A plate of cooked white rice contains approximately 204 kcal. This energy comes from: 2% fat, 89% carbohydrates, 9% protein, 577 milligrams of sodium, and 55 milligrams of potassium.”
In addition, white rice also contains 44.08 grams of carbohydrates, 4.2 grams of protein, and 0.08 grams of sugar.
However, I think I made a mistake in my calculation or used the wrong formula, or maybe the calorie content of white rice in various literature is calculated with the completeness of side dishes, because my calculation of the number of calories that can be produced by a plate of white rice is lower than the data available. Why is that?
Let’s calculate the number of ATP molecules and energy that can be produced by 1 plate of rice, based on the carbohydrate content (glucose) in it.
First, let’s calculate the amount of glucose in 1 plate of rice, assuming 1 plate of rice contains approximately 150 grams of cooked rice. Regardless of the type of rice, from previous data, we know that 100 grams of cooked rice contains approximately 28 grams of carbohydrates.
So, 150 grams of cooked rice contains: [28 grams/100 grams] x 150 grams = 42 grams of carbohydrates.
Carbohydrates in rice are mostly starch, which is broken down into glucose in the body.
Next, let’s calculate the number of moles of glucose in 42 grams of carbohydrates. The molecular weight of glucose (C6H12O6) is 180 grams/mol.
The number of moles of glucose in 42 grams of carbohydrates (glucose) is: [42 grams/180 grams/mol] = 0.233 mol
Then, let’s calculate the number of glucose molecules in 1 plate of rice. One mole of glucose contains 6.022 x 10²³ molecules (Avogadro’s number).
The number of glucose molecules in 1 plate of rice (0.233 mol) is: 0.233 x 6.022 x 10²³ molecules/mol
Next, let’s calculate the number of ATP molecules produced from 150 grams of rice in 1 plate. One molecule of glucose produces approximately 30 molecules of ATP through cellular respiration.
The number of ATP molecules produced by 1 plate of rice is: 1.40 x 10²³ molecules of glucose x 30 molecules of ATP
Then, let’s calculate the energy in calories. The energy produced by 1 molecule of ATP is approximately 1.21 x 10^-20 calories.
So, the total energy produced by ATP from 1 plate of rice is: 4.20 x 10²⁴ molecules of ATP x 1.21 x 10^-20 = 50,800 cal or 50.8 kcal.
The number of ATP molecules produced by 1 plate of rice (150 grams) is approximately 4.20 x 10²⁴ molecules of ATP.
The energy produced by 1 plate of rice is approximately 50.8 kilocalories (kcal).
After re-examining the data, I found that according to several literature sources, the carbohydrate content of rice is actually around 89–90 grams/100 grams, not 42 grams/100 grams. Therefore, my final calculation of the energy contribution from 1 plate of rice is around 109–110 kcal, which is closer to the data available.
Actually, the calculation above is an example or illustration of how we, through cellular activity and the mitochondria organelle, can convert biological energy sources into energy and calories that are then used for kinetic energy, biolistrik in neurophysiology, and as a power source for various physiological and biochemical mechanisms in our body. That’s the true story of how a grain of rice becomes ATP and gives us the energy to move the world.
Thank you, breakfast, you have truly enabled me to learn about hope, until I realized that thinking too much about hope will only make us hungrier.
