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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. As food digests, a consumer's body will break down and absorb organic compounds such as carbohydrates, proteins, and fats. Ultimately, these compounds--including glucose--enter the consumer's cells where they are combined with oxygen the consumer breathes to make energy. Which organelle is the powerhouse of an animal's cells?
The mitochondria of a cell turn the glucose 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.
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 and store the extra to be used later. For some producers, later never comes because a consumer gets to them first.
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.
Let's start by seeing what you remember about animal and plant cells. What organelles are responsible for producing energy in animal cells? What about plant cells? What organic compounds do animal cells use for energy?
Keep an eye out for the following vocabulary: producers, photosynthesis, consumer, metabolism, respiration
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 remember Dalton's Atomic theory, matter can't be created or destroyed. 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. Dalton would call this the Law of Conservation of Matter.
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?