Post on 29-Dec-2015
Ch 6: Cells
History of Cytology
1665 – Robert Hooke 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 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 cells2) Cells are the basic unit of structure and function3) 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) 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 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