TEKS 7.12Ddifferentiate Between Structure and Function in Plant and Animal Cell Organelles

Name ______Class ______Date ______

TEKS 7.12DDifferentiate between structure and function in plant and animal cell organelles, including cell membrane, cell wall, nucleus, cytoplasm, mitochondrion, chloroplast, and vacuole.TEKS 7.12ECompare the functions of a cell to the functions of organisms such as waste removal.

Looking Inside Cells

Cells are too small to see without a microscope. When you look at a cell through a microscope, you can usually see the outer edge of the cell. Sometimes you can also see smaller structures within the cell. Each kind of cell structure has a different function within its cell.

OrganellesIn the picture, you can see many
of the tiny cell structures inside a cell. These structures are called organelles. Each organelle carries out specific functions within its cell. In this lesson, you will read about the structures that plant and animal cells have in common. You will also read about some differences between plant and animal cells.

What makes up the outside of a cell?

Cell WallThe cell wall is a rigid layer that surrounds the cells of plants and some other organisms. The cells of animals, in contrast, do not have cell walls. A plant’s cell wall helps protect and support the cell. The cell wall is made mostly of a strong material called cellulose. Still, many materials, including water and oxygen, can pass through the cell wall easily.

Cell MembraneThink about how a window screen allows air to enter and leave a room but keeps insects out. One of the functions of the cell membrane is something like that of a screen. The cell membrane controls what substances pass into and out of a cell. Everything a cell needs, such as food particles, water, and oxygen, enters through the cell membrane. Waste products leave the same way. In addition, the cell membrane prevents harmful materials from entering the cell. Figure 1 above shows an animal cell, with the cell membrane around it.

All cells have cell membranes. In plant cells, the cell membrane is just inside the cell wall. In cells without cell walls, the cell membrane forms the border between the cell and its environment.

What is the nucleus?

A cell doesn’t have a brain, but it has something that functions in a similar way.
A large oval structure called the nucleus (NOO klee us) acts as a cell’s control center, directing all of the cell’s activities. The nucleus is the largest of the cell’s organelles. Notice in Figure 2 that the nucleus is surrounded by a membrane, called the nuclear envelope. Materials pass in and out of the nucleus through pores in the nuclear envelope.

Chromatin and RibosomesYou may wonder how the nucleus “knows” how to direct the cell. Chromatin, thin strands of material that fill the nucleus, contains information for directing a cell’s functions. For example, the instructions in the chromatin ensure that leaf cells grow and divide to form more leaf cells. Notice the small, round structure in the nucleus. This structure, the nucleolus, is where ribosomes
(RY buh zohmz) are made. Ribosomes are small grain-shaped organelles that produce proteins. Proteins are important substances in cells.

What is in the cytoplasm?

CytoplasmMost of a cell consists of a thick, clear, gel-like fluid. This cytoplasm fills the region between the cell membrane and the nucleus. The fluid of the cytoplasm moves constantly within a cell, carrying along the nucleus and other organelles that have specific jobs.

MitochondriaFloating in the cytoplasm are rod-shaped structures that are nicknamed the “powerhouses” of a cell. You can see them in Figure 3 – Animal Cell. Mitochondria (myt oh KAHN dree uh; singular: mitochondrion) convert energy stored in food to energy the cell can use to live and function.

VacuolesPlant cells often have one or more large, water-filled sacs floating in the cytoplasm. This type of sac, called a vacuole (VAK yoo ohl), stores water, food, or other materials needed by the cell. Vacuoles can also store waste products until the wastes are removed. Some animal cells do not have vacuoles.

ChloroplastsA typical plant cell contains green structures—called chloroplasts—in the cytoplasm. A chloroplast captures energy from sunlight and changes it to a form of energy that cells can use in making food. Animal cells don’t have chloroplasts, but the cells of plants and some other organisms do. Chloroplasts make leaves green because leaf cells contain many chloroplasts.Figure 4. Plant Cell

Do Cells Function Like Organisms?

You have read about the functions of cells. Those functions may have sounded familiar. Cells are living things, and they carry out many of the same life processes as complex organisms. Just as your body is protected by your skin, a cell has a cell membrane to control which substances pass in and out of it. You need to eat and drink to live. Animal cells take in food particles through their cell membranes, and plant cells produce food through a chemical reaction to sunlight. Water passes through the cell membranes of both plants and animals.

After you eat, your body changes the food into a form that it can use for energy. In a cell, the organelles convert the energy stored in food to energy the cell can use to live and function. You have to breathe—or exchange gases—to live, and so does a cell. Oxygen and carbon dioxide pass easily through the cell wall and cell membrane. Cells also eliminate waste products, just as humans do. Those waste products pass out of the cell through the cell membrane. Cells are the basic units of structure and function in living things, and their structures let them meet all their basic life needs.

Cell Organelle Structure and Function

1. DifferentiateHow are the outsides of plant and animal cells different in their structure and function, and how are they the same?

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2. DifferentiateName an organelle that all plant cells have but only some animal cells have. Explain what the organelle does.

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3.CompareCompare the vacuoles in the plant cell shown above and the animal cell shown on the previous page. Explain how they are the same and different.

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4. Compare Cell Functions to Organism FunctionsPlant cells produce their own food using sunlight. What does an animal do that serves a similar function?

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Lesson Check

1. Differentiate For each cell function listed in the chart below, write in the name of the matching structure. If the particular structure is not found in a cell, write “none.”

Function / Structure in Animal Cells / Structure in Plant Cells
a. controls substances passing into and out of the cell
b. rigidly protects and supports the cell
c. directs all of the cell’s activities
d. fills the cell with fluid and holds the organelles
e. converts food energy to energy the cell can use
f. captures energy from sunlight for the cell to make food
g. stores water, food, and other materials

2. CompareCompare how a human cell exchanges oxygen and carbon dioxide with how the human as an organism does so.

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3. Differentiate How are the structure and function of cytoplasm different from those of mitochondria?

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4. Differentiate How do plant and animal organelle structures differ with respect to the function of obtaining food?

AAnimals have a nucleus.BAnimals have cytoplasm.

CPlants have vacuoles.DPlants have chloroplasts.

TEKS Review

1. DifferentiateFor each structure listed below, record the function of that cell part and identify whether it is found in plants, animals, or both plants and animals.

Structure / Function / Plant, Animal, or Both
a. cytoplasm
b. chloroplast
c. cell membrane
d. nucleus
e. vacuole
f. cell wall
g. mitochondrion

2. CompareComplete the analogy.

Bark is to tree as ______is to plant cell.

3. CompareConsider the functions of an animal cell’s nucleus. Compare how it functions like an animal’s brain.

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4. ContrastDescribe the difference in structure and function between how plant and animal cells obtain food.

a. plant cells______

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b. animal cells______

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5. DistinguishDescribe the structure and function of the nucleus and of a mitochondrion. How is the functioning of the nucleus dependent on mitochondria?

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