Eukaryotic Cells Think back to Schwann and Schleiden. It wasn t until that fateful lunch that Schwann realized he was seeing cells. After that moment cell biology knowledge exploded (just a saying; it didn t really blow up). Once they started piecing together the Cell Theory suddenly all living things were made of cells. Even then, neither of these scientists realized how complex these cells really are. As modern scientists would eventually discover, there are even smaller parts to this puzzle than just the cell. As we discussed in class, the most common cell on earth is prokaryotic. The one you are most familiar with though is eukaryotic. It s most familiar because it s what you are. Everything we see and interact with on a daily basis is eukaryotic from fish to humans to dogs and cats and birds and even mosquitoes. They all have eukaryotic cells in their bodies. Organelles Within every eukaryotic cell are small organs called organelles. Organelles carry out many of the same functions that your organs carry out. These structures perform various life processes that keep both the cell and you alive. Interestingly, they complete many of the same process that your organs carry out such as digestion, circulation, and even reproduction. The following is a basic list of many of the organelles in both plants and animals. Cell Wall Even though there are only two different cells on earth, there are still differences between the same types of cell. For example, prokaryotes have both eubacteria and archeabacteria. These two are as different as 6 th graders are to 8 th graders (except for not having a nucleus. For eukaryotes though, the differences are more subtle. To help show these differences within eukaryotes, let s look at the two types of cells that we have been exploring in class, animal cells and plant cells. Let s start with the outside of a eukaryotic cell. Some eukaryotic cells have a stiff outside structure called a cell wall. The cell wall acts like the bricks on the outside of our school providing extra support and helping everything stay upright. Where all plants have a cell wall, no animal cells have one. As for their job, cell walls help a plant keep its shape. If they don t hold enough water, the cell wall weakens making a plant droop. While they do add some protection, the cell wall allows plants to grow to great heights.
Cell Membrane Regardless of plant cell or animal cell, they all have a cell membrane. For plant cells, the cell membrane is just inside the cell wall, but for animal cells the cell membrane is the outer most covering. Remember, animal cells do not have a cell wall. The cell membrane is a soft protective layer that controls what comes in and out of the cell. It s kind of like the needle location on a soccer ball or a basketball. If nothing pokes into it, the air is trapped inside. If you poke a needle into it, air can be pumped inside. The cell membrane is very similar to this opening. The role of the cell membrane is to hold all of the organelles and fluids (cytoplasm) inside the cell and keep some nasty things such as bacteria outside the cell. 1. What is the purpose of the cell wall? a. To make a plant droop. b. To support the cell c. To carry DNA d. To digest cellulose. 2. What is the purpose of a cell membrane? a. To make lipids b. To make phospholipids c. To protect the cell d. To support the cell wall Cytoplasm Inside the nucleus is a fluid called the cytoplasm (siet oh plas um) that keeps all the organelles from bumping into each other. (Think of a swimming pool filled with children during summer. The water is the cytoplasm and the children are the cell organelles). The cytoplasm also helps the cell membrane keep its shape (kind of like water inside a water balloon). Nucleus All Eukaryotic cells have a nucleus. Remember looking at the onion and cheek cells and seeing the darker spot inside the cell, well that is the nucleus. The nucleus is like the brain of the cell, it controls all cell activities. Inside the nucleus are the Chromosomes or genetic material. The chromosomes contain information for the cell s job or function. Chromosomes are made up of DNA which stands for Deoxyribonucleic acid (Wow what a mouth full). The chromosomes send out messages to other organelles in the cell, telling them what to do. Without your chromosomes, you wouldn t have hair color, eye color, a nose, mouth, well you get the picture.
The darker spot inside the nucleus is the nucleolus. If we had a more powerful microscope it would kind of look like an eye inside the nucleus. This organelle is responsible for making ribosomes, but we will discuss those next. 3. What is the genetic material inside a cell s nucleus? a. Protein b. Lipids (fats) c. Chromosomes (DNA) d. Nucleolus Ribosomes Cells need to make proteins. Those proteins are used to fix and repair muscles and other organs. The teeny tiny round Ribosomes are the assembly line for proteins. There are more ribosomes inside a cell than any other organelle. Some ribosomes are floating in the cytoplasm while others are attached to the endoplasmic reticulum. Endoplasmic Reticulum The endoplasmic reticulum (en doh plaz mick re tick yoo lum) sounds like a Harry Potter spell, but it is the name for a series of tubes located next to the nucleus. These tubes are folded and bunched together so it almost looks like a bunch of spaghetti. The endoplasmic reticulum is the internal delivery system for the cell (think of someone delivering your mail). Its job is to transport materials to different parts of the cell. 4. What do all ribosome do? a. Make proteins b. Float in cytoplasm c. Attach themselves to membranes d. Make organelles 5. What does the endoplasmic reticulum look like? a. Oval, with small pores like a sponge b. Small and round like a golf ball c. Long tubes with many folds like spaghetti d. A bubble full of liquid like soap 6. Which phrase best describes the job of the endoplasmic reticulum? a. Internal delivery system b. Protein factory c. DNA storage d. Web of proteins
Mitochondria Just like Westerville has a power plant that supplies electricity, every eukaryotic cell has an organelle that provides energy. The energy provider inside the cell is a peanut shaped organelle called the mitochondrion (mite oh kahn dree uhn). Since cells have more than one mitochondrion, you might see them called mitochondria (many mitochondrions). The mitochondria break down sugar from our food to make a special type of cell energy called ATP (that s short for Adenosintriphosphate). Mitochondria are the entire reason we inhale oxygen. If the mitochondria in our cells didn t need oxygen, we wouldn t need to breath. The organelles in the cell use the ATP to carry out their jobs. Without the mitochondria breaking down the sugar for energy, our cells couldn t survive. Chloroplasts Animal cells cannot make their own food; they have to eat food to get energy. Plant cells are different; they can make food through a process called photosynthesis. Remember that photosynthesis is where plants take in sunlight, water, and carbon dioxide and turn them into sugar (glucose), water, and oxygen. Photosynthesis happens inside the chloroplast (ch lor o plasts). The Elodea leafs had hundreds of chloroplasts in each cell. The chloroplasts almost looked like tiny green skittles inside the cell. Why are plants green? The chloroplasts inside the cell have a green pigment called chlorophyll. (ch lor o fill). The chlorophyll traps the sunlight as energy for photosynthesis. An easy way to remember this is the chlorophyll fills up the chloroplasts giving it the green color. 7. What are the peanut shaped organelles that break down sugar and provide energy to the cell? a. Golgi complex b. Cell membranes c. Ribosome d. Mitochondria 8. Which process happens inside a chloroplast? a. Making ATP b. Making DNA c. Photosynthesis d. Formation of animal cells Golgi Body The golgi is one of those organelles that people keep changing its name. It has been called the golgi body, golgi complex, and the golgi apparatus. It was named after Camillo Golgi, an Italian biologist. It is pronounced GOL JI in the same way you would say squee gie, as soft a "G" sound. While layers of the golgi may look like the endoplasmic reticulum, they have a very different job. The golgi body is a series of tubes that package material for transport around the cell. So the golgi body is like a gift wrapping shop for proteins.
Lysosomes Ever wonder what happens to organelles that are not working properly or extra material that the cell do not need, well that is a job for the lysosomes. They keep the inside of the cell clean, like custodians clean the school (kind of sounds like Lysol). The lysosomes are full of digestive chemicals that can break down worn out or damaged organelles. They also help to get rid of waste and bad things that might get into the cell. Vacuoles Besides the cell wall and chloroplasts another difference between plant and animal cells is the vacuoles. Although both cells have them, plant cells have one big vacuole that takes up most of the cell where as animal cell have many smaller vacuoles spread throughout the cell. The vacuole stores water and other material for the cell. It s kind of like your refrigerator. The cell on the left is a plant cell and the cell on the right is an animal cell. Notice how the plant cell has a vacuole that takes up most of the cell. 9. What long folded cell part serves to package and distribute proteins? a. Golgi complex b. Cell membrane c. Endoplasmic reticulum d. Cytoplasm 10. What do lysosomes do? a. Make new proteins b. Move material around c. Get rid of waste and digest food d. Copy DNA 11. What is the function of most vacuoles? a. To make proteins b. To store water c. To make sugar d. To protect the cell 12. Identify 3 differences from the reading between plant and animal cells.