Chapter 5: Lesson 14: Understanding Cells

You can understand more about cells by studying their basic structures and functions.cell- the basic unit of life; all living things are made of cells.From the tiniest bacteria to the biggest whale, all living things are made of cells. A cellis the basic unit of life. Each cell contains structures that help the cell to function and stay alive.The picture below shows an animal cell. The outside of the cell is called the cell membrane. The cell membrane holds the cell together. It also controls what enters or exits the cell. Waste material goes out through the cell membrane. Food, oxygen, and water go in.The inside of the animal cell is full of cytoplasm. Cytoplasm is a thick liquid that contains chemicals needed by the cell. It also surrounds and protects the structures inside the cell. One of the most important of these structures is the nucleus. The nucleus controls all the activities in the cell. It is held together by a nuclear membrane.Mitochondriaare structures that break down sugars to provide energy for the cell. Vacuoles are spaces that store food, water, or waste inside the cell. A membrane surrounds each vacuole and keeps its contents separate from the cytoplasm.Plant cells are similar to animal cells, but they have a few extra structures. Each plant cell has a cell membrane to hold it together. But the plant cell also has a stiff cell wall that surrounds the membrane. The cell wall helps the plant to hold its shape.Inside the plant cell, the cytoplasm surrounds the nucleus, mitochondria, and vacuoles. But the plant cell also has chloroplasts. Chloroplasts are green structures that can use light and carbon dioxide to make food for the plant. Animal cells cannot make their own food.Another difference between animal and plant cells is in the vacuole. Vacuoles inside plant cells are large enough and do not just store substances. They also help the plant to keep its shape. Water flows into plants and fills each vacuole. When a vacuole is full, it presses against the cell wall. This allows the plant to stand up. When a plant does not have enough water, vacuoles get smaller and the inside of each cell shrinks. This shrinking makes a plant wilt.Single-celled organisms are made of one cell. Bacteria, amoebas, and some types of algae are common single-celled organisms. Many-celled organisms are made of more than one cell. Snails, some algae, grass, dogs, and humans are all many-celled organisms. Larger plants and animals can be made of trillions of cells.The cells in a many-celled organism can look different from each other. Their special shapes and structures help them to perform different functions. In a human, flat skin cells cover and protect the outside of the body. Long, branching nerve cells carry signals in the brain and the rest of the body. Tough bone cells give your body structure. Strong, fibrous muscle cells help you move. They also allow your heart to pump blood. Smooth, round red blood cells carry oxygen to other cells.These amoebas are examples of single-celled organisms.This algae is an example of a many-celled organism.These long, branching nerve cells carry signals throughout the body. Is a tree made of cells? Explain. What does the cell membrane do? List the 3 structures in the animal cell that are surrounded by cytoplasm. What surrounds the outside of a plant cell? What are chloroplasts? Is a cat a single-celled or many-celled organism? Name 2 types of cells in the human body. What is a cell? The nucleus is an important structure in both the plant and animal cells. What does the nucleus do? How do vacuoles in plant cells help a plant keep its shape? Cells are so tiny that you cannot see them without a microscope. To look at individual cells, you first need to take a small sample of material from a plant or animal. To observe plant cells, you can cut a very thin slice of leaf or stem. To observe animal cells, you can take a scraping from the inside of your cheek. Put the sample on a microscope slide and add a drop of water to it. Drop a cover slip onto the water to hold the sample in place. Then add stain to the side of the cover slip. The stain will color some structures within each cell and make them easier to see. Use your knowledge of plant and animal cells to label the structure below. Use the words below to help you (spelling counts!):vacuole nucleus cell membrane chloroplast cell wall cytoplasm cytoplasm nucleus cell membrane cell wall vacuole chloroplast What kind of cell is shown in the diagram above? Explain. The arrow in the picture below points to a structure inside an animal cell. What does the structure do? it stores food or waste it controls all cell activities it holds the cell together it provides energy for the cell Food, oxygen, and water enter a cell through the - mitochondria nucleus cell wall cell membrane Which of the following is not found in an animal cell? nucleus vacuole cytoplasm chloroplast Which of the following is not a many-celled organism? amoeba snake mushroom jellyfish Which structures help a plant to hold its shape? cell wall and cell membrane vacuole and cell wall cytoplasm and vacuole cell membrane and nucleus What does a chloroplast do inside a plant cell? it makes food it stores food it creates energy it protects the cell