Ch 6: Cells

History of Cytology 1665 – Robert Hooke 1673 – Anton van Leeuwenhoek Viewed cork Named “cells” 1673 – Anton van Leeuwenhoek Unicellular pond organisms – named “animalcules” First to see bacteria and yeast 1833 – Robert Brown discovered nucleus

Cell Theory 1838 – Matthias Schleiden 1839 – THeodor Schwann All plant parts are composed of cells 1839 – THeodor Schwann All animal tissues are composed of cells 1858 – Rudolph Virchow All cells come from other cells Cell Theory: 1) All living things are composed of 1 or more cells 2) Cells are the basic unit of structure and function 3) All cells are produced from existing cells

Cells All cells have: Plasma membrane (cell membrane) regulates materials in/out of cell Composed of phospholipid bilayer Contains different proteins Cytoplasm everything inside the cell membrane Medium for chemical rxns Cytosol – fluid portion Chromosomes (Genes) - DNA Ribosomes –site of protein synthesis

Cell Size – must be small To efficiently exchange materials in/out of cell membrane Cell surface is the only area of interaction w/ environment To transport materials inside of cell Efficiency depends on surface area to volume ratio Small cells function more efficiently than larger cells!

Surface Area to Volume Ratio

Prokaryotic Cells DNA is located in nucloid region (NO NUCLEUS) Does not contain membrane bound organelles Only Eubacteria and Archeabacteria Kingdoms

Prokaryotic Cell

Evolution of Eukaryotic Cells Theory of Endosymbiosis – one prokaryotic cell engulfed another and did not digest it, :. Forming a double membrane… successful relationship Evidence: Chloroplasts and mitochondria each have their own separate DNA and can reproduce on their own, and are similar to prokaryotic cells

Endosymbiosis

Eukaryotic Organelles Nucleus – contains chromosomes Nucleolus contain materials for RNA Makes ribosomes Nuclear Membrane w/ nuclear pores Nucleoplasm – jelly like material w/in nucleus Mitochondria Powerhouse of the cell Releases E stored in food Produces ATP

Eukaryotic Transport System Ribosomes – site of protein synthesis Free floating in cytoplasm (free) Attached to ER (bound) Endoplasmic Reticulum (ER) An internal channel system Rough ER – has ribosomes on surface, aids in transporting proteins Smooth ER – involved in making lipids and breaking down toxic substances

Eukaryotic Transport System Vesicles – membrane buds off ER w/ proteins or lipids enclosed Lysosome – contains digestive enzymes to break down macromolecules and worn out cell parts Peroxisome - contains enzymes that converts fat to carbohydrates (from smooth ER) Golgi body (complex/apparatus) – packaging and distribution center of the cell Cis golgi – arrival side Trans golgi – departure side

Cytoskeleton Cytoskeleton – internal framework Mesh-like network of protein fibers Supports cell shape and anchors organelles Microtubules – hollow tubes move chromosomes during cell division by forming centrioles (animal cells only) Actin – long intertwined microfilaments that contract or expand to determine shape Intermediate fibers – fibrous protein cables that anchor ribosomes and enzymes

Cytoskeleton

Cellular Movement Flagella – long threadlike microtubules (whip-like tail) Cilia – numerous short and tightly packed microtubules

Intercellular Junctions Plants Plasmodesmata – perforated channels in plant cell wall allowing cytosol, water and small solutes to pass freely Animals Tight junctions – forms tight seal between cells Desmosomes – anchor cells together in strong sheets Gap junctions – cytoplasmic channels between adjacent cells allowing communication

Animal Cells only Extracellular Matrix (ECM) Centrioles Collagen – strong glycoprotein fibers Proteoglycans – network of glycoproteins Fibronectin – attaches ECM to Integrins Integrins – membrane proteins bound to ECM and interior microfilaments Centrioles composed of microtubules Aid in moving chromosomes during cell division Centrosome – 2 centrioles

Plant Cells Only Cell Wall Central Vacuole Chloroplast Extra protective layer Cellulose - maintains structure Central Vacuole Stores water, ions, nutrients, and waste materials Controls pressure w/in cell Tonoplast – membrane surrounding vacoule Chloroplast Contains chlorophyll – photosynthetic pigment Uses water, carbon dioxide and sunlight to make food in the form of glucose