What is Lost When a Calorie is Burned?

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iStock

What is lost when a calorie is burned?

Bart Loews:

According to the laws of thermodynamics, nothing. In terms of your body, it’s not terribly helpful to think in terms of calories, because they’re just a measure of heat.

Let’s drill down to your energy systems and how your muscles work. Your muscles are composed of two strands of proteins: myosin and actin. The myosin has little hooks that grab on to the actin and then pull it in to create a contraction. It does this using ATP.


The myosin head takes on the ATP and shears one of the phosphate molecules off. The remaining ADP binds to the actin and then rotates pulling the actin down. The ADP molecule is then released and a new ATP molecule is taken on. The ADP molecule is then recycled.

This is what is actually happening when your muscles contract. The shearing of the phosphate from the ATP does generate heat and creates a little bit of excess waste, which is where the calorie theory started from, how you heat up when you perform activities.

Okay, so what does that have to do with loss? I’m getting there …

ATP cannot be stored long term. It’s a comparatively large molecule and it is water soluble, so it will break down inside the cells if left unused. Your body has to have a way of creating it on the fly using fuel sources that can be stored long term.

These fuel sources are:

  • Glucose (sugar)
  • Adipose (fat)

Both sugar and fat can be broken down into acetyl CoA in the cell and then turned into ATP using the Krebs (or Citric Acid) cycle.


During this cycle the primary yield is ATP, while the primary byproducts are water and CO2. The CO2 is exhaled while the water is either repurposed in the body or urinated out. This is one of the major reasons why you lose weight: the conversion of sugars and fats into energy.

The other reason is that your body requires a certain amount of glucose to be stored in your liver, kidneys, and muscles for optimal performance. If you don’t have enough glucose through food, your body will synthesize glucose from fats and proteins for storage as well.

This post originally appeared on Quora. Click here to view.

What's the Difference Between Straw and Hay?

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iStock.com/dusipuffi

The words straw and hay are often used interchangeably, and it's easy to see why: They're both dry, grassy, and easy to find on farms in the fall. But the two terms actual describe different materials, and once you know what to look for, it's easy to tell the difference between them.

Hay refers to grasses and some legumes such as alfalfa that are grown for use as animal feed. The full plant is harvested—including the heads, leaves, and stems—dried, and typically stored in bales. Hay is what livestock like cattle eat when there isn't enough pasture to go around, or when the weather gets too cold for them to graze. The baled hay most non-farmers are familiar with is dry and yellow, but high-quality hay has more of a greenish hue.

The biggest difference between straw and hay is that straw is the byproduct of crops, not the crop itself. When a plant, such as wheat or barley, has been stripped of its seeds or grains, the stalk is sometimes saved and dried to make straw. This part of the plant is lacking in nutrients, which means it doesn't make great animal fodder. But farmers have found other uses for the material throughout history: It what's used to weave baskets, thatch roofs, and stuff mattresses.

Today, straw is commonly used to decorate pumpkin-picking farms. It's easy to identify (if it's being used in a way that would be wasteful if it were food, chances are it's straw), but even the farms themselves can confuse the two terms. Every hayride you've ever taken, for example, was most likely a straw-ride.

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How and Why Did Silent Letters Emerge in English?

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iStock/Bychykhin_Olexandr

Kory Stamper:

The easy answer is “"because English can’t leave well enough alone."

When we first started speaking English around 600 AD, it was totally phonetic: every letter had a sound, and we sounded every letter in a word. But English—and England itself—were influenced quite a bit by the French, who conquered the island in 1066 and held it for a long time. And then later by Dutch and Flemish printers, who were basically the main publishers in England for a solid two centuries, and then by further trading contact with just about every continent on the planet. And while we’re shaking hands and stealing language from every single people-group we meet, different parts of the language started changing at uneven rates.

By the 1400s, English started to lose its phonetic-ness: the way we articulated vowels in words like “loud” changed slowly but dramatically, and that had an effect on the rest of the word. (This is called “The Great Vowel Shift,” and it took place over a few hundred years.) Somewhere in the middle of the GVS, though, English spelling became fixed primarily because of the printing press and the easy distribution/availability of printed materials. In short: we have silent letters because the spelling of words stopped changing to match their pronunciations.

This post originally appeared on Quora. Click here to view.

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