Chapter 3 Cell Structure

I. History of Cells Cells were first observed only after microscopes were invented in the 1600s Robert Hooks, “The Cell Guy” used a microscope to observe a thick slice of cork in 1665 - He saw a lot of little boxes that reminded him of the small cells in which monks lived, so he called them cells

Anton van Leeuwenhoek used a microscope to view water from a pond - discovered many living creatures; first single-celled organisms Ameoba Yeast Bacteria http://www.youtube.com/watch?v=t4Tst9DZFPI

II. The Cell Theory 3 parts 1. All living things are made of one or more cells 2. Cells are the basic units of structure and function in organisms 3. All cells arise from existing cells

A. Cell size Small cells function more efficiently than large cells because of the higher surface are-to volume ratio - substances do not need to travel as far to reach the center of a small cell, therefore they can enter and leave the cell in numbers large enough to meet the cell’s needs

B. Common Features of Cells 1. Cell membrane: outer boundary Encloses the cell and separates the cell interior from its surrounding Regulates what enters and leaves a cell 2. Cytoplasm: cell interior 3. Cytoskeleton Microscopic fibers that support a cells structures in the cytoplasm Outside of Cell Inside of Cell Cytoplasm http://www.youtube.com/watch?v=Rl5EmUQdkuI&feature=fvwrel

4. DNA Provides instructions for making proteins Regulates cellular activities Enables cells to reproduce 5. Ribosomes: one type of cellular structure Makes proteins

III. Prokaryotes Single-celled organisms that lack a nucleus and other internal compartments Characteristics of Prokaryotes A prokaryote’s enzymes and ribosomes are free to move around in the cytoplasm because there are no internal structures that divide the cell into compartments

Genetic material is a single, circular molecule of DNA, often located near the center of the cell Prokaryotic cells have a cell wall surrounding their cell membrane that provides structure and support Some prokaryotic cell walls are surrounded by a capsule Many have flagella, which are long, threadlike structures that enable movement

IV. Eukaryotic Cells Eukaryotes are organisms whose cells have a nucleus The nucleus houses the cell’s DNA Organelles are structures that carry out specific activities allowing eukaryotic cells to function in ways different from prokaryotes

Some eukaryotic cells have hair like structures called cilia that help some cells propel them through their environment and others move substances across their surfaces Concept Map Prokaryotes vs. Eukaryotes

V. The Cytoskeleton Provides the internal framework and the shape of an animal cell Composed of an intricate network of protein fibers anchored to the inside of the plasma membrane Some fibers attach the nucleus and other organelles to fixed locations in the cell

A. Microfilaments (Actin Fibers) Three types A. Microfilaments (Actin Fibers) Form a network just beneath the cell surface attached to membrane proteins embedded within the cell membrane By contracting or expanding, actin fibers control the shape of animal cells Cell membrane Microfilaments

B. Microtubules Hollow tubes made of the protein tubulin Act as “rails” for motor proteins to move along that carry RNA molecules

C. Intermediate Fibers Thick ropes that anchor particular enzymes and ribosomes near one another

VI. The Cell Membrane Cell membranes are fluid because of the lipids that form them The cell membrane only allows certain substances in the cell’s environment to pass through; it is selectively permeable

The Cell Membrane as a Barrier The cell membrane has a double layer of phospholipids called a lipid bilayer - a phospholipid is made of a phosphate group and two fatty acids

the phosphate group acts as a polar “head,” it is attracted to water, or hydrophilic the fatty acids act as nonpolar “tails,” they are repelled by water, or hydrophobic

B. Membrane Proteins Some proteins are located in the lipid bilayer to indicate cell type, bind specific substance, and move substances into and out of the cell with the help of enzymes

Proteins are made of amino acids that anchor the proteins in the bilayer - polar amino acids are attracted to the polar “head” groups and water on either side of the cell membrane - nonpolar amino acids are attracted to the nonpolar “tail” groups on the inside of the lipid bilayer

Nuclear pores are scattered over the surface of the nuclear envelope VII. Nucleus The nucleus is surrounded by two lipid bilayers called the nuclear membrane, or nuclear envelope Nuclear pores are scattered over the surface of the nuclear envelope Ribosomes are assembled in a region of the nucleus, called the nucleolus Eukaryotic Organelle Concept Map during lecture

Ribosomes and RNA are moved out of the nucleus to the cytoplasm through the nuclear pores Hereditary information is coded in the cell’s DNA which is stored in the nucleus

VIII. Ribosomes and the Endoplasmic Reticulum Ribosomes make proteins Ribosomes themselves are made of proteins as well as RNA Production of Proteins 1. Some ribosomes are suspended in the cytosol and make proteins that remain inside the cell

2. Other ribosomes are attached to the endoplasmic reticulum and make proteins that are exported from the cell The endoplasmic reticulum, or ER, helps move proteins and other substances through the cell - it too is made of a lipid bilayer

ER with ribosomes attached to its surface is called rough ER Helps transport proteins that are made by the attached ribosomes by pinching them off into vesicles and moving them to the Golgi apparatus b. ER without ribosomes is called smooth ER Helps make lipids and break down toxic substances

B. Packaging and Distribution of Proteins 1 B. Packaging and Distribution of Proteins 1. Ribosomes make proteins on the rough ER; the proteins are packaged into vesicles 2. The vesicles transport the newly make proteins from the rough ER to the Golgi apparatus

3. In the Golgi apparatus, proteins are processed and then packaged into new vesicles Many of these vesicles move to the cell membrane and release their contents outside the cell Other vesicles, including lysosomes, remain within the cytoplasm; Lysosomes digest and recycle the cell’s used component by breaking down proteins, nucleic acids, lipids, and carbohydrates http://www.youtube.com/watch?v=ekdIEpSf-1I

IX. Mitochondria Mitochondria harvests energy to make ATP, the main energy of cells Mitochondria has two membranes 1. an outer, smooth membrane 2. an inner, folded membrane Chemical reactions occur in between the two membranes that produce ATP

Mitochondrial DNA Mitochondria has its own DNA and ribosomes that make their own proteins Mitochondrial DNA comes from your mother

X. Structures of Plant Cells A. Unique Features of Plant Cells 1. Cell Wall Composed of proteins and carbohydrates, including the polysaccharide cellulose Helps support and maintain the shape of the cell Plant Specific Organelles Concept Map during lecture

2. Chloroplasts Use light energy to make carbohydrates from carbon dioxide and water Found in a variety of eukaryotic algae Also contain two membranes, supply energy to the cell, and contain their own DNA like mitochondria

3. Central Vacuole Stores water and can contain other substances including ions, nutrients, and wastes When full, it makes the cell rigid allowing for the plant to stand upright http://www.youtube.com/watch?v=wJyUtbn0O5Y&feature=related