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