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7.2 Cell Structure
Lesson Summary
Cell Organization Eukaryotic cells contain a nucleus and many specialized structures.
Cytoplasm is the fluid portion of a cell. Organelles are structures that have specialized functions in eukaryotic cells. The nucleus contains DNA and controls the activity of a cell.
Organelles That Store, Clean Up, and Support These structures include:
vacuoles: membrane-enclosed saclike structures that store water, salts, and organic molecules lysosomes: small organelles filled with enzymes that break down large molecules and organelles that are no longer useful the cytoskeleton: a network of protein filaments; it helps the cell maintain its shape and is involved in movement centrioles: organelles made from tubulins; they help organize cell division in animal cells
Organelles That Build Proteins Three kinds of organelles work with the nucleus to
make and distribute proteins:
ribosomes: small particles of RNA and protein found throughout the cytoplasm in all cells; they produce proteins by following coded instructions from DNA the endoplasmic reticulum (ER): an internal membrane system where lipid components of the cell membrane are assembled, along with proteins and other materials the Golgi apparatus: an organelle that appears as a stack of flattened membranes; it modifies, sorts, and packages proteins and other materials from the ER for storage in the cell or release outside the cell
Organelles That Capture and Release Energy Two types of organelles act as
power plants of the cells. Both types are surrounded by two membranes.
Chloroplasts capture the energy from sunlight and convert it into food that contains chemical energy in a process called photosynthesis. Cells of plants and some other organisms contain chloroplasts, which contain chlorophyll. Mitochondria are found in nearly all eukaryotic cells; they convert the chemical energy stored in food to a usable form.
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Cellular Boundaries All cells are surrounded by a cell membrane. Many cells also have a
cell wall. Both cell membranes and cell walls separate cells from the environment and provide support.
Cell walls support, shape, and protect the cell. Most prokaryotes and many eukaryotes have them. Animals do not have cell walls. Cell walls lie outside the cell membrane. Most cell walls allow materials to pass through them. A cell membrane consists of a lipid bilayer, a strong but flexible barrier between the cell and its surroundings. The cell membrane regulates what enters and leaves the cell and also protects and supports the cell. Most biological membranes are selectively permeable, allowing some substances, but not others, to pass across them.
Lesson Objectives
Describe the structure and function of the cell nucleus.
Describe the role of vacuoles, lysosomes, and the cytoskeleton.
Identify the role of ribosomes, endoplasmic reticulum, and Golgi apparatus in making proteins.
Describe the function of the chloroplasts and mitochondria in the cell.
Describe the function of the cell membrane.
BUILD Understanding
Venn Diagram A Venn diagram is made up of overlapping circles. It is a useful tool for
comparing two or even three topics.
Use terms from the box to complete the Venn diagram.
cell membrane cytoskeleton mitochondria cell wall DNA found in cytoplasm nucleus containing DNA centriole endoplasmic reticulum ribosome chloroplast Golgi apparatus vacuole cytoplasm lysosome
Prokaryotes Eukaryotes
Both
Cell Organization
An organelle is a specialized cell structure. Each organelle functions in a different way. All of the organelles help the cell carry out life processes.
Use the terms in the box to write the name of the organelle underneath its picture.
Organelle Function
Controls most cell processes and stores genetic material
Where lipid parts of the cell membrane and proteins for export are assembled and stored
Modifies, sorts, and packages materials from the endoplasmic reticulum
Converts the energy stored in food into a more usable form
BUILD Connections
The Cell As a Living Factory An analogy takes two things
that seem to be different and shows how they can be similar.
- If the cell were a factory, what part would serve as the main office?
- Which cell part would provide electricity?
- With a partner, discuss how the actions of the forklifts are related to actions in cells.
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endoplasmic reticulum Golgi apparatus mitochondrion nucleus
