Section 2 Eukaryotic CellsChapter 4Bellringer

What are three differences between prokaryotic and eukaryotic cells?

Write your answer in your science journal.

Chapter 4What You Will Learn

• Eukaryotic cells have many parts--such as cell membranes, a nucleus, and ribosomes--in common.

• Plant cells and animal cells have some cell parts that are different.

Section 2 Eukaryotic Cells

Chapter 4Cell Wall

• Eukaryotic cells have many organelles in common to carry out important functions.

• Plants are eukaryotes that have some structures and organelles not seen in animal cells.

• Plant cells have a rigid structure that surrounds the cell membrane called the cell wall. Animal cells lack a cell wall.

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Chapter 4Cell Membrane

• All cells have a cell membrane made up of proteins and phospholipids.

• A phospholipid has a water-loving, or hydrophillic, head and a water-fearing, or hydrophobic, tail.

• The phospholipids form a two-layer protective membrane.

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Chapter 4Cell Membrane, continued

• The two-layer membrane makes it difficult for materials to pass into or out of the cell.

• Some materials, like nutrients and wastes, move through the membrane using protein passageways within the membrane.

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Chapter 4Cytoskeleton

• The cytoskeleton is a web of proteins in the cytoplasm of some cells. It plays a key role in cell movement, shape, and division.

• Different cells have different shapes because of the arrangement of their cytoskeletons.

Section 2 Eukaryotic Cells

Chapter 4Nucleus

• All eukaryotic cells have a nucleus. The nucleus is the large organelle that contains the cell’s DNA.

• The DNA provides messages for making proteins. The messages are sent out of the nucleus through pores in the nucleus membrane.

• Some cells have a dark area within the nucleus called the nucleolus. Ribosome assembly begins here.

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Chapter 4Ribosomes

• Ribosomes are small organelles that make proteins. There are more ribosomes than any other organelle in the cell.

• Because all cells need to make proteins, all cells have ribosomes.

• Unlike most organelles, ribosomes are not covered by a membrane.

Section 2 Eukaryotic Cells

Chapter 4Endoplasmic Reticulum

• The endoplasmic reticulum, or ER, is a system of folded membranes in which proteins, lipids, and other materials are made.

• Rough ER is covered with ribosomes that make proteins near the nucleus. Smooth ER lacks ribosomes.

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Chapter 4Endoplasmic Reticulum, continued

• Smooth ER makes lipids and breaks down toxic materials. The ER also functions as a delivery system for the cell.

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Chapter 4Mitochondria

• A mitochondrion is the main power source of a cell. Mitochondria are organelles in which sugar is broken down to release energy.

• Mitochondria have two membranes. The folded inner membrane of a mitochondrion is where ATP is made.

• ATP is the energy storing molecule used by the cell to carry out its functions.

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Chapter 4Mitochondria, continued

• Most eukaryotic cells have mitochondria. They are unusual organelles in that they have their own DNA and divide on their own, like bacteria.

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Chapter 4Chloroplasts

• Chloroplasts are organelles in which photosynthesis takes place. Plants, algae, and some prokaryotes have cells with chloroplasts.

• Chloroplasts are green because they contain chlorophyll, the pigment that traps the energy of sunlight.

• This energy is used to make sugar during photosynthesis.

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Chapter 4Chloroplasts, continued

• Chloroplasts, like mitochondria, have their own DNA and two membranes. Photosynthesis takes place in the inner membrane.

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Chapter 4Golgi Complex

• The Golgi complex packages and distributes proteins and lipids. The materials may be taken to other parts of the cell or may exit the cell.

• Materials may be modified in the Golgi complex to do different jobs before they are sent off.

• The Golgi complex pinches off portions of its membrane to create bubbles. The bubbles contain the materials to be transported.

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Chapter 4Golgi Complex, continued

• The Golgi complex looks much like the smooth ER.

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Chapter 4Cell Compartments

• The bubble that forms from the Gogi complex’s membrane is an example of a vesicle.

• A vesicle is a small sac that surrounds materials to be moved into or out of the cell. Vesicles also move materials within the cell.

• All eukaryotic cells have vesicles.

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Chapter 4Lysosomes

• Lysosomes are vesicles that contain digestive enzymes. They carry out digestion inside a cell.

• Lysosomes destroy worn-out organelles, engulf foreign invaders, and get rid of wastes.

• Lysosomes are found mainly in animal cells.

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Chapter 4Vacuoles

• A vacuole is another type of vesicle found in cells. They play an important role in plants.

• Vacuoles in plants and fungi may act like lysosomes. The large central vacuole in a plant cell stores water and other liquids.

• Some plants wilt when their large central vacuoles lose water.

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