CH 3 Eukaryotic Cell Structure Photo Credit: © Quest/Science Photo Library/Photo Researchers, Inc.

Eukaryotic Cell Structures Structures within a eukaryotic cell that perform important cellular functions are known as organelles. Cell biologists divide the eukaryotic cell into two major parts: the nucleus and the cytoplasm. The Cytoplasm is the portion of the cell outside the nucleus.

Eukaryotic Cell Structures Plant Cell Nucleolus Nucleus Smooth endoplasmic reticulum Nuclear envelope Ribosome (free) Rough endoplasmic reticulum Ribosome (attached) Cell wall Golgi apparatus Cell membrane Chloroplast Mitochondrion Vacuole

Eukaryotic Cell Structures Animal Cell Smooth endoplasmic reticulum Nucleolus Nucleus Ribosome (free) Nuclear envelope Cell membrane Rough endoplasmic reticulum Ribosome (attached) Centrioles Golgi apparatus Mitochondrion

Comparing the Cell to a Factory

Organelles Specialized structures

Cytoplasm Portion of the cell outside the nucleus Consists mostly of water

Nucleus Main Office Contains nearly all the cell’s DNA & w/ coded instructions for making proteins & other important molecules

The Nucleus Chromatin Nuclear envelope Nucleolus Nuclear pores Nucleus The nucleus controls most cell processes and contains the hereditary information of DNA. The DNA combines with protein to form chromatin, which is found throughout the nucleus. The small, dense region in the nucleus is the nucleolus. Nuclear pores

Nucleus Nuclear Envelope Surrounds the nucleus Composed of two membranes Allows messages to enter & leave the main office

Nucleus Chromatin Granular material seen in the nucleus Consists of DNA bound to protein Condenses to form chromosomes when a cell divides

Nucleus Nucleolus Small, dense region in the nuclei Where assembly of ribosomes begins

Ribosomes Small machine in the factory Proteins are assembled on the ribosomes Small particles of RNA and protein are found throughout the cytoplasm

Endoplasmic Reticulum (ER) The site where lipid components of the cell membrane are assembled, along w/ proteins & other materials that are exported from the cell There are 2 types of ER:

1. Rough Endoplasmic Reticulum Rough ER Portion of ER involved in the synthesis of proteins Named b/c ribosomes attach to it Newly made proteins leave these ribsomes & are inserted into the rough ER, for chemical modification

2. Smooth Endoplasmic Reticulum Contains enzymes that perform specialized tasks

Golgi Apparatus Customization Shop – finishing touches & then shipped Modifies, sorts, & packages proteins & other materials from the ER for storage in the cell or secretion outside the cell

Lysosomes Clean up crew, removes “junk” Small organelles filled w/ enzymes Functions include digestion or breakdown of carbohydrates, lipids & proteins

Vacuoles Storage center Sac-like structure that stores water, salts, proteins & carbohydrates

Vacuoles In many plant cells there is a single, large central vacuole filled with liquid. Vacuole

Vacuoles Contractile vacuole Vacuoles are also found in some unicellular organisms and in some animals. The paramecium contains a contractile vacuole that pumps excess water out of the cell.

Mitochondria & Chloroplasts Power plant Organelles that convert chemical energy stored in food into compounds that are more convenient for the cell to use Chloroplasts Solar power plant Organelles that capture the energy from sunlight & convert it into chemical energy in a process called photosynthesis

Mitochondria & Chloroplasts

Cytoskeleton Support beams Network of protein filaments that helps the cell to maintain its shape Also involved in movement The cytoskeleton is made up of: microfilaments microtubules

Copyright Pearson Prentice Hall Cytoskeleton Cytoskeleton Cell membrane Endoplasmic reticulum Microtubule The cytoskeleton is a network of protein filaments that helps the cell to maintain its shape and is involved in many forms of cell movement. Microtubules are part of the cytoskeleton that help maintain cell shape. Microfilament Ribosomes Mitochondrion Copyright Pearson Prentice Hall

Cell Organelle Interactive Cytoskeleton Centrioles are located near the nucleus and help to organize cell division. Cell Organelle Interactive Plant and Animal Model Interactive

The Cell

Eukaryotic vs. Prokaryotic Has a nucleus Organelles to carry out specialized functions Flagella or cilia Single celled organism Lacks a nucleus & other compartments Can not carry out many specialized functions Flagella

Comparison of Plant and Animal Cells Plant has: Chloroplast Cell Wall Regular/Box-like shape Large Central Vacuole Animal Cell has: Centrioles Irregular shape Small vacuoles called vesicles

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