LS1.2 - Inside a Cell

Have you ever felt tired during exercise? The more we exercise, the more we are able to do, but even the most fit athletes experience muscle fatigue eventually. Working muscles require ATP (cellular energy) in order to move our body during exercise. In the mitochondria of muscle cells, oxygen (O₂ ) is used to break down and harness the chemical potential energy stored in glucose molecules. This process, called aerobic cellular respiration, produces a great deal of ATP, and generates carbon dioxide (CO₂ ) and water (H₂O) as a waste products.

As muscle cells work and deplete their oxygen reserves over time, muscle cells are able to continue to generate ATP through a process called anaerobic cellular respiration, inside the cytoplasm of the cell. It does not require oxygen, and it produces much less ATP than aerobic respiration. Anaerobic respiration releases an additional waste product called lactic acid.

As lactic acid builds up in muscles, the muscles become fatigued. Additionally, muscle cells may use up most of their glucose stores, which slows down the process of generating ATP. The circulatory and respiratory systems must work faster to clear away the waste products of cellular respiration from the muscle cells, and to bring in new oxygen and glucose. In addition to having more muscle tissue, athletes often have more mitochondria in their muscle cells and more efficient circulatory and respiratory systems in order to meet the demands of extensive exercise

The glucose required for ATP generation comes from the food that we eat. It may appear that we can never have too much sugar, but excess sugars in the blood cause damage to tissues. Therefore, the body must regulate, or balance, the amount of sugar that is present in the blood.

Adapted from: https://www.rd.com/health/diet-weight-loss/where-fat-goes-lose-weight/

Weight loss happens when you burn more calories for energy than you take in. But after you shed them, what exactly happens to all those extra pounds of fat?

Seems like everyone wants to trim the fat, which is why it’s nice to know you can lose fat in a single day. And when you do slim down, it might seem like fat has evaporated into thin air and well, it kind of has. “Your body’s’ primary source of energy is glucose, which is stored as glycogen in two places: liver and muscles,” explains Tanya Zuckerbrot, a NYC-based registered dietician. “When your body uses up its glycogen stores it turns to fat for fuel. Fat from food is stored in our body as triglycerides, which are made up of atoms.” When we start shedding pounds these atoms form into carbon dioxide (CO₂) and water (H₂O).

Physicist Ruben Meerman and Professor Andrew Brown, from the University of New South Wales, published their research on “Where does fat go?” in the British Medical Journal in 2014. Through their novel calculations they concluded that “our lungs are the primary excretory organ for weight loss,” says Zuckerbrot. “Meaning when you lose weight you breathe out most of the broken down fat as carbon dioxide and lose a small percentage as water in sweat, urine, and tears.”

Maria Bella, a nutrition expert, adds that exercise, an activity that increases our breaths per minute, therefore aides in weight loss. “It’s important to remember, however, that diet remains the most important factor for weight loss, something made clear in the British Medical Journal study. Take for example a relatively sedentary 150-pound person who sleeps for eight hours, rests for eight hours, and is active for eight hours, this person will exhale about 1.5 pounds of CO₂ per day. If this same person was to replace an hour of rest with an hour of jogging this would only raise this number by one-third pound of CO₂ a day—and to lose two pounds of fat, that person would need to exhale about six pounds of CO₂. In other words, it’s hard to work off a bad diet.

According to Zuckebrot, the best route to maximize fat loss is to follow a high-fiber, lower-carb diet. “By following a high-fiber, low-net carb diet, you give your body the carbohydrates needed for energy, without going overboard on carbohydrates, which eating an excess of leads to weight gain.”