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Photosynthesis & Cell Respiration
Transcript of Photosynthesis & Cell Respiration
Life and Energy
Cells are the smallest living organisms. A single cell can be its own living organism--like bacteria--or cells can make up larger and more complex organisms--like humans, plants, and animals.
Energy and Producers
Living organisms use energy to live. Some organisms get their energy from other organisms and some make their own energy. But even organisms that make their own energy need energy to get started. Where do you suppose they get that energy?
All the energy for living organisms starts with the sun. Our sun provides energy in many different forms, but producers--organisms who make their own energy--use the sun's light to help make their energy. Which producers can you name?
Here on Earth, nearly every single plant is a producer. There are some exceptions--venus fly trap, for example--but if it is a plant, chances are it uses sunlight to make its own energy. Other organisms then come along and use that energy for their own. Those organisms are called consumers. Consumers can't make their own energy, so they consume producers to get it.
The Sun and Energy for Life
What do you suppose are the three things a plant needs to make its own energy to live?
Plants need light from the sun, water, and carbon dioxide to produce their own energy. Who can name the chemical formula for carbon dioxide? What about water?
Cell Respiration: Energy for Consumers
When a consumer eats a producer, it begins a process called respiration. In animals, oxygen and glucose (or other sources of energy) are carried to cells by the blood, where they are finally combined together inside structures called mitochondria. Mitochondria perform a similar function as the chloroplasts do in plant cells.
The mitochondria of a cell turn the glucose and oxygen into an easy-to-burn molecule that's called ATP. What makes it easy-to-use? ATP can be easily formed and easily smashed. When we talk about energy for our bodies, we get it from smashing those molecules of ATP, and mitochondria use food to make more ATP to smash for energy. But what about the left over stuff?
There's another part of cell respiration that's important. Remember, when plants go through photosynthesis, they create both glucose for food and oxygen as leftovers, and plants release that oxygen into the atmosphere.
Do you remember the molecule that animals breathe? The very same oxygen our cells need for respiration is the same leftover junk plants release after making their food.
Do you remember one of the compounds we exhale when we breathe? The very same carbon dioxide we release after cell respiration is one of the substances plants use to produce their food.
What connections do you see between photosynthesis and cell respiration? Which do you suppose is more important: the producers or the consumers? If you had too many producers or too many consumers, what impact do you think that might have on the environment? How are humans connected to photosynthesis and cell respiration?
Consumers and Energy
Producers make their own energy to grow and develop, then store the extra to be used later. An apple tree, for example, uses that energy to make apples to help reproduce and spread more apple trees. For some producers, later never comes because a consumer gets to them first. It is important to remember that though apples may be delicious, when we eat them we take energy that was meant for the apple seeds.
We'll talk more about food webs and the interactions between producers, consumers, and the environment later. Let's explore how, exactly, a consumer gets its energy after making a meal of a producer.
Photosynthesis & Cell Respiration
Grade 7 Science
These bacteria do everything a living organism does: eat, breathe, move, and reproduce.
These organisms are all made up of millions of cells and each of those cells helps the chick or rabbit do the same things as a bacterium.
All organisms, no matter the size or shape, all need one thing in order to carry out the functions of life. Do you think you know what that is?
Energy is the one thing that all organisms need. The form the energy takes and how an organism gets that energy are some of the ideas we'll explore here. We're also going to explore food webs and where energy goes as it is used up by some organisms and produced by others.
Do you know the source of all the energy on the planet? How does that source connect to your breakfast this morning?
Keep an eye out for the following vocabulary: producers, photosynthesis, consumer, metabolism, respiration, and organism.
Plants are good examples of producers because they can make their own energy. Some bacteria and other microscopic organisms are also producers.
All animals are consumers--they can't make their own energy, so they rely on the energy that producers make and store. There are different kinds of consumers, depending on what they eat for food and energy.
This dog is another example of a consumer. Some consumers eat only producers and some consumers eat only other consumers. Also, some consumers, like humans, can eat both producers and other consumers. We'll learn more about the different types of consumers later when we study food webs.
Photosynthesis is the process that plant cells use to combine light energy, carbon dioxide, and water to create food in the form of the sugar glucose. Sugars are organic compounds that form crystal shapes, and usually taste sweet to humans. Glucose is the most common sugar found in plants, but there are other types of sugars like fructose, sucrose, and lactose.
Plants absorb sunlight using the chlorophyll found in chloroplasts (remember those?) and break apart water and carbon dioxide molecules, then rearrange them to form sugar. During photosynthesis, carbon from carbon dioxide is used as the backbone for glucose molecules and the extra oxygen, released into the atmosphere, is what animals breathe.
Photosynthesis creates more energy than a plant needs, so the plant stores the extra glucose in vacuoles in plant cells. Fruits, vegetables, and beans contain lots of glucose, which is why animals eat them for energy. Plants also rely on this stored energy to survive unfavorable conditions in the environment, such as winter or drought.
Glucose and other sugars are important products of photosynthesis, but they aren't the only important products. The oxygen molecules that are released, or "exhaled", by plants is also vital to animal life here on Earth.
This is called a chemical equation and it shows us how the atoms rearrange during photosynthesis. If you count carefully, you'll see that we start and end up with exactly the same number of atoms--the only difference is the order the atoms are combined. This is called the Law of Conservation of Matter and it's one of the biggest theories in all of science.
Here is the carbon dioxide the plant absorbs from the air. The coefficient 6 tells us how many molecules of carbon dioxide we begin with. How many atoms of carbon are found in one carbon dioxide molecule?
Here is the water the plant absorbs from the soil using its roots. How many atoms of oxygen are found in one molecule of water? How many atoms of hydrogen? If we have six water molecules, how many oxygen atoms in total? How many hydrogen atoms in total?
Sunlight provide the energy needed to rearrange the water and carbon dioxide into glucose. This formula represents one glucose molecule. How many carbon atoms do you see? How many hydrogen atoms do you see?
The oxygen here is left over after the glucose molecule has formed. Because plants don't need this leftover oxygen, they release it into the air. Where do you suppose this extra oxygen came from? How do you know?
Cell Respiration and Energy
So let's get some vocabulary out of the way.
: the process used by animal cells to combine oxygen and glucose to produce energy, carbon dioxide, and water (in the form of vapor).
: like chloroplasts in plant cells, these are the structures where glucose and oxygen are combined and then broken apart into energy, water, and carbon dioxide.
: the energy molecule that animal cells make from glucose and oxygen. ATP is transported all over an animal's body where cells smash it to release energy plus water vapor and carbon dioxide.
We won't get much deeper into the chemistry of cells except to say the following. First, animals also absorb minerals and other materials from the plants they eat, and those other materials are used to help animals grow and develop. Plants also use some of the same minerals, but most of the mass of a plant comes from the carbon they use to build stems and leaves and cellulose and roots and so on.
Hey, who wants to watch another video?
Cell respiration is pretty much the same as photosynthesis, with just a few differences. Plant cells use sunlight to kick start their energy process by using it combine water and carbon dioxide together inside the chloroplasts in their cells to make glucose and oxygen. Animal cells take that same glucose and oxygen and combine it in the mitochondria in their cells to get energy (that's the ATP) and release water and carbon dioxide.