Cell Structure

Microscopes Reveal Cell Structure 1. Most cells are too small to see with the naked eye 2. Scientists became aware of cells only after microscopes were invented in the 1600’s. 3. Robert Hooke in 1665 saw, “a lot of little boxes” from a thin slice of cork. The boxes reminded him of small rooms in which monks lived, so he called them cells.

Cell Features A. The three parts of the cell theory are: 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.

B. Cells Must be Small 1. Small cells function more efficiently than large cells 2. What is the advantage of having so many cells instead of fewer large ones? a. Small cells can exchange substances more readily than large cells because small objects have a higher surface-area-to-volume ratio than larger objects. b. As a result, substances do not need to travel as far to reach the center of the cell.

C. Common Features of Cells 1. Cell Membrane 2. Cytosol 3. Cytoskeleton 4. Ribosomes

Prokaryotes Do Not Contain Internal Compartments A. Prokaryote is a single celled organism that lacks a nucleus and other internal compartments B. Characteristics of prokaryotes: 1. for nearly 2 million years prokaryotes were the only organisms on Earth 2. the genetic material is a single, circular molecule found in an area called nucleoid region

C. Characteristics of Bacteria 1. Can exist in a broad range of environments 2. Cell wall surrounding the cell membrane that provides structure and support 3. Some bacterial cell walls are surrounded by a capsule which enables it to cling to almost anything. 4. Flagella- which are threadlike structures that protrude from the cell’s surface and enable movement

D. Characteristics of Viruses 1. Not living 2. Smaller than bacteria 3. Possesses an envelope on the outside outside a. helps the virus enter the host cell b. Made up of proteins, lipids, and glycoproteins (proteins & carbohydrates from host cell) 4. Do not grow, maintain homeostasis, or metabolize. 5. CAUSE DISEASE

ProkaryotesEukaryotesViruses Outer Covering Cell Wall surrounding cell membrane Cell Membrane Protein Coat /Capsid / Envelope Internal Compartments NoneOrganellesNone Uses Host Cell to Metabolize DNA Nucleoid Region Nucleus DNA or RNA not Both Other Characteristics * Single Celled *Capsule*Flagella*Pathogenic*Compartmentalized *Possesses Organelles *Single celled & multicellular *Cilia & Flagella Not Living (Needs Host to Survive) Pathogenic Smaller than bacteria

Plant Cell Vs. Animal Cell

Plant Cell Plasmodesmata: open channel in a cell wall of a plant cell through which strands of cytoplasm connect. Cell-Cell communication. Animal Cell Chromatin: Complex of DNA and proteins that make up eukaryotic cells. Long thin fibers.