Main content
Course: Middle school biology - NGSS > Unit 3
Lesson 2: Food and energy in organismsCellular respiration
Cellular respiration is the process by which the body gets energy from food. It is a series of chemical reactions that happen in our cells, converting glucose from our food and oxygen from the air we breathe into carbon dioxide, water, and usable energy. Created by Khan Academy.
Want to join the conversation?
- Does anyone know a clear definition of "cells"(13 votes)
- Cells are the smallest unit that can live on its own and that makes up all living organisms and the tissues of our body
-hope this helps 👾(25 votes)
- I was eating while watching this lol(17 votes)
- thank you mitochondria =)(18 votes)
- how does calories work?(4 votes)
- The calories in food provide the energy that our body needs to perform these functions. When we consume more calories than our body needs, the excess energy is stored as fat, leading to weight gain. Conversely, when we consume fewer calories than our body needs, our body will start to use its stored energy (fat) to make up the deficit, leading to weight loss.
Therefore, understanding the number of calories in the foods we eat is essential for maintaining a healthy diet. By knowing the calorie content of different foods, we can make informed decisions about what to eat and how much to eat, which is particularly important when trying to lose weight. For example, if we consume more calories than we need, we may want to reduce our intake of high-calorie foods such as fast food, sugary drinks, and snacks, and focus instead on low-calorie, nutrient-dense foods such as fruits, vegetables, lean protein, and whole grains.(26 votes)
- How much energy does a woodchuck need to chuck all the wood it could chuck?(10 votes)
- Estimates vary, but the average beaver/woodchuck probably uses around 6547 kilojoules of energy per day. Since beavers live an average of 11 or so years, a beaver will use around 26 million kilojoules of energy in its life.(13 votes)
- How does the body use the energy that is released? How does it take it in?(4 votes)
- The body uses the energy that is released as fuel so that our organs and tissues can function. The energy is taken in when food is broken down and mitochondria converts chemical energy into a type of energy that we can use. This is called oxidative phosphorylation(14 votes)
- No wonder I am so energised after eating a bowl of noodles(10 votes)
- If our cells produces water, why do we have to drink? Where do produced water goes?(7 votes)
- The body obtains water primarily by absorbing it from the digestive tract. Additionally, a small amount of water is produced when the body processes (metabolizes) certain nutrients. The body loses water primarily by excreting it in urine from the kidneys.(5 votes)
- 2:13"You're not throwing away any of the bricks".
There are less bricks in the bridge than in the house.
This is why I have trust issues.(5 votes)- I noticed that too... But maybe that brick that was in the house but not in the bridge was just carved into a nice decoration in the center of the bridge she forgot to draw?(5 votes)
- Me after the ten-thousandth mitochondria comment:(7 votes)
Video transcript
- [Instructor] So let's
say I was preparing to go on a long hike. Besides packing water,
dressing for the weather and mapping my route, I'd probably also want to eat a snack before leaving to make
sure I have enough energy for the hike. We as humans need food
to nourish our bodies. But how exactly does
that food give us energy? How does something like an
apple or a piece of chocolate get converted into something
our bodies can use? The answer to this question can be found in a process called cellular respiration. Which is how organisms get
their energy from food. In other words, cellular respiration
helps make life possible. It's happening right now in your cells and in mine, in my little brothers pet hamster cells and in the cells of the
tree outside the window. It's providing all of us with the energy that we need to function. So let's dive into this process to find out more about how it works. Cellular respiration is a
series of chemical reactions that happen in an organized
way inside our cells. It's these chemical reactions that result in an overall release of
energy that our bodies can use. Although cellular respiration involves many chemical
reactions, this entire process for plants and animals
can be summarized here by this equation. On the left side of this
equation are the inputs; Glucose, which is a type of sugar, and oxygen. Glucose comes from our
food and oxygen comes from the air we breathe. The right side of this
equation shows the outputs, carbon dioxide and water. The air in the middle shows
that during the process of cellular respiration, glucose and oxygen molecules
are are broken apart and their atoms are rearranged to eventually form
carbon dioxide and water. This whole process releases energy, similar to how firewood
releases energy as it burns. Also, no atoms are lost
during cellular respiration. You can see the same
number of each type of atom on both sides of the arrow, for example, six carbon atoms on both sides. It's similar to how you could
take apart a brick house and use those bricks to build
something else, like a bridge. You're not throwing
away any of the bricks, but instead you're creating
something new out of them. So we know that cellular
respiration involves a series of chemical reactions, but where in the cell
do these steps happen? To find out, let's walk
through the process together. After eating, your food is broken down into small molecules during digestion. These small molecules
which include glucose can enter your cells. Then cellular respiration can begin. The first set of chemical
reactions happen in the cytosol, which is the jelly-like
fluid containing all of the cells organelles, and they involve glucose as an input. The rest of the reactions
happen in mitochondria, with oxygen as an input and carbon dioxide and water as outputs. Together, these chemical reactions result in an overall release of energy. It might be a little mind boggling for you to think about how
the food we eat provides the energy our bodies need to carry out all of lives processes. And I know it was for me. After all, it's not every day
you take a bite of an apple and wonder how that apple's molecules are rearranged inside your body. What's important to know though, is that cellular respiration is the way our cells get usable energy. Through cellular respiration, you and I get the energy that we need to do the things we want to do, including accomplishing our goals. So, the next time you feel
proud of your yourself for finishing a big hike
or acing your biology quiz, make sure to thank your mitochondria.