Cells: The Working Units of Life 4

Concept 4.1 Cells Provide Compartments for Biochemical Reactions Most cells are tiny, in order to maintain a good surface area-to- volume ratio. The volume of a cell determines its metabolic activity relative to time. The surface area of a cell determines the number of substances that can enter or leave the cell.

Figure 4.1 The Scale of Life most cells are um 1 um is a millionth of a meter

Concept 4.1 TYPES OF MICROSCOPES nm is a billionth of a m Light microscopes—use glass lenses and light Resolution = 0.2 μm Electron microscopes— electromagnets focus an electron beam Resolution = 2.0 nm

Figure 4.4 Centrifugation Separation of cell components for studystudy Heavier, denser substances sink, lighter ones float. Keep separating until you get to the organelles, structures you wish to study. Cell Fractionation

Figure 4.7 Eukaryotic Cells (Part 1) lysosome

Figure 4.7 Eukaryotic Cells (Part 8)

Concept 4.3 Eukaryotic Cells Have a Nucleus and Other Membrane-Bound Compartments The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, and lysosomes. Tiny, membrane- surrounded vesicles shuttle substances between the various components, as well as to the plasma membrane. ER Golgi Vesicle

Concept 4.4 The Cytoskeleton has 3 components Beads, pipe cleaners & both! Microtubules Microfilaments Intermediate filaments

Concept 4.4 The Cytoskeleton Microtubules Microtubules: Made of protein tubulin. Form rigid, hollow structures. motor proteins move structures in the cell CENTRIOLES, CILIA (9+2) FLAGELLA

Figure 4.12 A Motor Protein Moves Microtubules in Cilia and Flagella

Concept 4.4 The Cytoskeleton Provides Strength and Movement Microfilaments: cell movement cell shape made from protein actin The filaments can shorten or lengthen. Look like twisted ropes for strength -muscle cells also have myosin

Concept 4.4 Intermediate filaments Intermediate filaments: Have tough, super- coiled protein. Anchor cell structures in place Made often of protein keratin, think, hair, nails Resist tension, maintain rigidity

Concept 4.4 The Cytoskeleton Provides Strength and Movement Two methods are used to show links between structure (A) and function (B): Inhibition—use a drug to inhibit A—if B still occurs, then A does not cause B Mutation—if genes for A are missing and B does not occur—A probably causes B

Figure 4.14 The Role of Microfilaments in Cell Movement: Showing Cause and Effect in Biology (Part 1)

Figure 4.14 The Role of Microfilaments in Cell Movement: Showing Cause and Effect in Biology (Part 2)

EXTRA CELLULAR MATRIX exterior of cells

Concept 4.5 Extracellular Structures Allow Cells to Communicate with the External Environment Cell Junctions Tight junctions prevent leakage, no gaps, like rivets on jeans. Think STRUCTURE Gap junctions (channels) think TRANSPORT Small gaps, open allow passage between cells Desmosomes anchor cells, intermediate filaments, larger gap allow materials to move into matrix. Think STRENGTH

Concept 4.5 Extracellular Structures Allow Cells to Communicate with the External Environment Plant cell wall—semi-rigid structure outside the plasma membrane fibrous component is cellulose. Adjacent plant cells connected by plasma membrane-lined channels plasmodesmata. allow movement of water, ions, small molecules, hormones, and some RNA and proteins.