Cell Structure Section 2

Section 2: Inside the Eukaryotic Cell

Preview• Bellringer• Key Ideas• The Framework of the Cell• Directing Cellular Activity• Protein Processing• Storage and Maintenance• Energy Production• Summary

Cell Structure Section 2

Bellringer

Use a light microscope to view a slide of a eukaryotic cell. Try to find the nucleus of the cell and give your reason why you identified the structure as the nucleus.

Cell Structure Section 2

Key Ideas

• What does the cytoskeleton do?

• How does DNA direct activity in the cytoplasm?

• What organelles are involved in protein production?

• What are vesicles and vacuoles?

• How does the cell get energy?

Cell Structure Section 2

The Framework of the Cell

• The cytoskeleton helps the cell move, keep its shape, and organize its parts.– Like a human’s skeleton

• There are three different kinds of cytoskeleton fibers: microfilaments, microtubules, and intermediate fibers.

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Directing Cellular Activity

• DNA contains instructions for making proteins which control most of the activity of the cell.

• The DNA of eukaryotic cells is stored in the nucleus.

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Directing Cellular Activity, continuedNucleus• The nuclear envelope surrounds the nucleus.

• Nuclear pores located on the nuclear envelope act as channels to allow certain molecules to move in and out of the nucleus.

• The nucleolus is a structure within the nucleus where ribosomes are made.

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The Nucleus

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Click to animate the image.

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Directing Cellular Activity, continued

Ribosomes

• Each ribosome in a cell is made of RNA and many different proteins.

• Free ribosomes make proteins that remain inside the cell.

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Protein Processing

• Proteins that are sent outside the cell are packaged in vesicles. Vesicles are small, membrane-bound sacs that enclose the proteins.– Like sending mail (need to put mail in an envelope)

• The endoplasmic reticulum and Golgi apparatus are organelles involved in preparing proteins for extracellular export.

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Protein Processing, continued

Endoplasmic Reticulum

• The endoplasmic reticulum, or ER, is a system of internal membranes that moves proteins and other substances through the cell.

• The endoplasmic reticulum is divided into two portions: rough ER and smooth ER.

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Endoplasmic Reticulum (ER)

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Protein Processing, continued

Endoplasmic Reticulum

• The portion of the ER with attached ribosomes is called rough ER because it has a rough appearance

• The portion of the ER with no attached ribosomes is called smooth ER because it has a smooth appearance

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Visual Concept: Endoplasmic Reticulum (ER) and Ribosomes

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Protein Processing, continued

Golgi Apparatus

• The Golgi apparatus is a set of flattened, membrane-bound sacs.

• The Golgi apparatus helps modify, sort, and package cell products for distribution.

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Golgi apparatus

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Storage and Maintenance

Lysosomes

• A lysosome is a vesicle produced by the Golgi apparatus that contains enzymes that break down large molecules.

• Lysosomes recycle old or damaged organelles and digest food particles to provide nutrients for the cell.(the “stomach” of a cell)

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Visual Concept: Lysosomes

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Storage and Maintenance, continued

Vacuoles

• A vacuole is a fluid-filled vesicle found in the cytoplasm of many plant cells.

• Plant cells contain a large compartment called the central vacuole, which stores water, ions, nutrients, and wastes.

• When water fills the central vacuole, the cell becomes rigid, allowing the plant to stand up. When the vacuole loses water, the cell shrinks, and the plant wilts.

Cell Structure Section 2

Visual Concept: Vacuoles

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Energy Production, continued

Chloroplasts

• A chloroplast is an organelle found in plant and algae cells that uses light energy to make carbohydrates from carbon dioxide and water.

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Energy Production, continued

Mitochondria

• Mitochondria are cell organelles that use energy from organic compounds to make ATP (Adenosine Triphosphate – the main energy source for cells).

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Mitochondrion

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Summary

• The cytoskeleton helps the cell move, keep its shape, and organize its parts

• In the cytoplasm, ribosomes use the RNA messages to assemble proteins.

• The endoplasmic reticulum and Golgi apparatus are organelles involved in preparing proteins for extracellular export.

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Summary, continued

• Vesicles help maintain homeostasis by storing and releasing a variety of substances as the cell needs them.

• The energy for cellular functions is produced by chemical reactions that occur in the mitochondria and chloroplasts.