A View of the CellA View of the Cell

Unit #2Unit #2

The History of the Cell The History of the Cell TheoryTheory

Light microscopesLight microscopes Anton van Leeuwenhoek created Anton van Leeuwenhoek created

and used first simple light and used first simple light microscopemicroscope

Compound light microscope uses a Compound light microscope uses a series of lenses to magnify objectsseries of lenses to magnify objects

The History of the Cell The History of the Cell Theory (cont)Theory (cont)

Robert Hooke – used a compound Robert Hooke – used a compound light microscope to study cork; light microscope to study cork; looked like empty boxes or rooms looked like empty boxes or rooms so he called them cells after a so he called them cells after a monk’s roommonk’s room

The History of the Cell The History of the Cell Theory (cont)Theory (cont)

Matthias Schleiden observed plants; Matthias Schleiden observed plants; concluded that all plants are concluded that all plants are composed of cellscomposed of cells

Theodor Schwann observed Theodor Schwann observed different animal tissues; concluded different animal tissues; concluded that all animals are made of cellsthat all animals are made of cells

The Cell Theory of Modern The Cell Theory of Modern BiologyBiology

All organisms are made up of one All organisms are made up of one or more cells.or more cells.

The cell is the basic unit of The cell is the basic unit of structure, organization, and structure, organization, and function in an organism.function in an organism.

All cells come from preexisting All cells come from preexisting cells. (refers to life comes from life)cells. (refers to life comes from life)

Electron microscopesElectron microscopes

uses a beam of electrons instead of uses a beam of electrons instead of light to magnify structures light to magnify structures

specimens must be examined in a specimens must be examined in a vacuum because electrons will vacuum because electrons will collide/react with other atoms in the collide/react with other atoms in the airair

Electron microscopesElectron microscopes

Scanning Electron Microscope (SEM) Scanning Electron Microscope (SEM) used for 3D images of outside used for 3D images of outside structuresstructures

Transmission Electron microscope Transmission Electron microscope (TEM) used for images of inside (TEM) used for images of inside structures in the cellstructures in the cell

Two Basic Cell TypesTwo Basic Cell Types

Cells can be divided into two broad Cells can be divided into two broad groups based on whether or not groups based on whether or not they contain organelles.they contain organelles.

Organelles are specialized, Organelles are specialized, membrane-bound structures within membrane-bound structures within the cellthe cell

Two Basic Cell TypesTwo Basic Cell Types

Prokaryotic cells (prokaryotes) do Prokaryotic cells (prokaryotes) do not have organellesnot have organelles

Eukaryotic cells (eukaryotes) do Eukaryotic cells (eukaryotes) do have organelleshave organelles

The Plasma MembraneThe Plasma Membrane Homeostasis – maintaining stable Homeostasis – maintaining stable

conditions regardless of external or conditions regardless of external or internal factorsinternal factors

Plasma membrane is a flexible, Plasma membrane is a flexible, selectively permeable boundary selectively permeable boundary between the cell and its external between the cell and its external environmentenvironment

Selective permeability – allowing Selective permeability – allowing some materials to pass while some materials to pass while keeping others outkeeping others out

Structure of the Plasma Structure of the Plasma MembraneMembrane

Phospholipid bilayerPhospholipid bilayer Other components of the plasma Other components of the plasma

membrane aremembrane are

Phospholipid bilayerPhospholipid bilayer

Lipids, triglycerides, are composed Lipids, triglycerides, are composed of 3 fatty acid “tails” attached to of 3 fatty acid “tails” attached to Phospholipids Phospholipids

Phospholipid bilayerPhospholipid bilayer

Phospholipid divided into two areas: Phospholipid divided into two areas: the backbone or head is polar and the backbone or head is polar and “likes water”, the fatty acids are “likes water”, the fatty acids are nonpolar and are hydrophobic (fear nonpolar and are hydrophobic (fear water)water)

Polar ends face the outside and Polar ends face the outside and inside of the membraneinside of the membrane

Nonpolar tails face in like a Nonpolar tails face in like a sandwich sandwich

Fluid Mosaic ModelFluid Mosaic Model

the membrane is fluid because the the membrane is fluid because the phospholipids can move within the phospholipids can move within the membrane just as water moves membrane just as water moves with the currentwith the current

protein components are also protein components are also embedded in the membrane and embedded in the membrane and move, creating a pattern or mosaicmove, creating a pattern or mosaic

Other components of the Other components of the plasma membraneplasma membrane

Cholesterol – steroid – stabilizes Cholesterol – steroid – stabilizes membrane by keeping the fatty acids membrane by keeping the fatty acids from sticking togetherfrom sticking together

Transport proteins or membrane-Transport proteins or membrane-spanning proteins – span entire spanning proteins – span entire membrane and create channels or membrane and create channels or carrier molecules for certain substances carrier molecules for certain substances to enter and leave the cellto enter and leave the cell

Integral proteins – are embedded in Integral proteins – are embedded in either the inside layer or the outside either the inside layer or the outside layer; they play a role in cell layer; they play a role in cell identification and attaching structures identification and attaching structures to the cell membraneto the cell membrane

Plasma MembranePlasma Membrane