The Cell Theory

Some Random Cell Facts The average human being is composed of around 100 Trillion individual cells!!! It would take as many as 50 cells to cover the area of a dot on the letter “ i ”

Discovery of Cells English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork. He described the cells as tiny boxes or a honeycomb He thought that cells only existed in plants and fungi

Anton van Leuwenhoek Used a handmade microscope to observe pond scum & discovered single-celled organisms He called them “animalcules” He also observed blood cells from fish, birds, frogs, dogs, and humans Therefore, it was known that cells are found in animals as well as plants

1838- German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells German physiologist, Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues are composed of cells.

Development of Cell Theory Rudolf Virchow, German physician, after extensive study, concluded that cells must arise from preexisting cells.

The Cell Theory Complete The 3 Basic Components of the Cell Theory were now complete: 1. All organisms are composed of one or more cells. 2. The cell is the basic unit of life in all living things. 3. All cells are produced by the division of preexisting cells.

2 Basic Types of Cells 1)Prokaryotic examples ??? 2)Eukaroytic examples????

Plasma membrane Structure –Main component is phospholipids that are arranged in a double layer (bilayer) –Has scattered proteins within the phospholipids

Function of the Plasma Membrane Regulate what gets into or leaves the cell

Nucleus Structure –Surrounded by a double membrane –This “nuclear membrane” has pores Function –Holds the chromosomes (DNA) and the nucleolus

Nuclear envelope Double layer of membrane Has pores Surrounds the nucleus Regulates what goes into and out of the nucleus

Chromosomes Structure –String-like structures in the nucleus made of DNA and protein Function –Contain your genes

Nucleolus Structure –Small dark structure in the nucleus Function –Produce ribosomes

Ribosomes Small structures (NOT made of membrane) Make proteins

Central Vacuole Structure –LARGE sac made of membrane –Found in center of plant cells Function –Stores chemicals and water

Smooth Endoplasmic Reticulum Structure –Canals and tubes made of membrane Function –Makes lipids (oils, phospholipids, steroids) –Detoxifies poisons

Rough Endoplasmic Reticulum Structure –Canals and tubes made of membrane –Have ribosomes attached to the outside Function –Transport materials in the cell –Make proteins (those exported from the cell, those found on the plasma membrane, those found in lysosomes)

Golgi Apparatus Structure –Stacks of membrane sacs –has a receiving end (from ER) and a shipping end Function –Chemically modifies substances –Packages material for transport out of the cell or to other locations within the cell

Vesicles Structure –Small membrane “bubbles” that bud off the ER or Golgi Functions –Transport materials to new locations

Lysosomes Structure –Sacs of membrane that contain hydrolytic enzymes –-found mostly in animal cells Function –Use enzymes to break down old organelles –In white blood cells are used to destroy bacteria

Mitochondria Structure –Surrounded by a double membrane Folds found on the inside Function –Cellular Respiration Converts energy in sugars into the energy of ATP molecule

Chloroplasts Structure –Surrounded by a double layer of membrane Disks found inside Function –Convert solar energy into chemical energy (food) –Site of photosynthesis

Perioxisome Structure –Small membranous sac Function –Some reactions occurring here produce H 2 O 2 (toxic) So, it also contains an enzyme (catalase) that converts this to water and oxygen gas

Cell Wall Structure –Found outside the plasma membrane –Plant  made of cellulose Function –Give support to certain cells (plant) –Does NOT determine what can get into/out of the cell

Cytoskeleton Structure Made of protein fibers –Microtubules Hollow tube –Microfilaments Small rods –Intermediate filaments Function –Give the cell shape –Help to move organelles around the cell

Fig Microfilament Actin subunit 7 nm Intermediate filament Fibrous subunits 10 nm Microtubule Tubulin subunit 25 nm Nucleus

Centrioles Structure –Made of rings of microtubules –Found in pairs that lie at right angles Look similar to a pair of barrels Function –Found in animal cells –Help organize the tubulin required for cell division

Cilia Structure –Microtubules that extend from the cell (still covered by the plasma membrane) –Short and many of them Function –In single-celled organisms, they can move the organism from place to place –If anchored in place, can set up a current, moving fluid across the surface of a cell

Fig. 4-1c

Fig. 4-18a Cilia ujIPo&feature=related&safety_mode=true& persist_safety_mode=1

Flagella Structure Same as cilia, but are longer and there are just a few of them Prokaryotes also have them –Not made of microtubules Function Move the cell within its environment

How large can cells get? -depends on how efficiently they can get nutrients in and wastes out 30 µm 10 µm Surface area of one large cube = 5,400 µm 2 Total surface area of 27 small cubes = 16,200 µm 2

Fig EXTRACELLULAR FLUID Microfilaments Collagen fiber Connecting glycoprotein Integrin Plasma membrane Glycoprotein complex with long polysaccharide CYTOPLASM

Fig Tight junctions Anchoring junction Gap junctions Plasma membranes of adjacent cells Extracellular matrix

Fig Vacuole Walls of two adjacent plant cells Cytoplasm Plasma membrane Plasmodesmata cell wall

A BE CD (CONTAINING DIGESTIVE ENZYMES) AC AD C D E AB BD B AE BC

A B C E AB AC AD AE BC BD BE D

A B C D