C7- A View of the Cell

A View of the Cell  7-1 Discovery of Cells  7-2 Plasma Membrane Plasma MembranePlasma Membrane  7-3

Discovery of Cells  Anton van Leeuwenhoek used the first microscope early in the 1600s.  It revealed the world of microorganisms and cells which are the basic unit of an organism.

Discovery of Cells  Robert Hooke coined the term cell after observing cork under a microscope. Hooke’s illustration of cork

Discovery of Cells  1838 Matthias Schleiden observed plant cells.  Theodor Schwann studied animal cells.  Ideas were summarized in the Cell Theory.

Cell Theory  1. All organisms are made of one or more cells.  2. The cell is the basic unit of structure and organization in organisms.  3. All cells come from preexisting cells.

Electron Microscopes  Light Microscopes 1500X  Dev new EM in 1930s & 40s  Uses beam of electrons to multiply image 500,000X  Lets us see internal cell structure

Scanning vs. Transmission EM  Scan surface of cell for 3D image  Study internal structure of cell

Two Basic Cell Types  All cells contain specialized structures called organelles.  Eukaryotes have membrane-bound organelles  Prokaryotes do not  Some eukaryotes are unicellular like amoebas.

Two Basic Cell Types  Robert Brown observed eukaryotes had a prominent structure.  Rudolf Virchow said it was responsible for cell division.  Eventually the structure was called the nucleus or cell’s control center.

7.2 Plasma Membrane  Responsible for controlling what goes in and out of the cell.

Plasma Membrane  Maintains homeostasis by selective permeability keeping some things in and keeping others out

Plasma Membrane Structure  Phospholipid Bilayer  Glycerol backbone, 2 fatty acids & a phosphate group make a phospholipid.  Water is attracted to the head but not to the lipid fatty acids.

Plasma Membrane Structure  Fluid Mosaic Model because phospholipids ripple like water with the currents.  Protein molecules float like boats on the surface in a mosaic pattern.  Flexible

Other components  Cholesterol stabilizes the phospholipids by keeping the the tails from sticking together  Transport proteins span the membrane to move needed substances in and wastes out of the cell.

7.3 Eukaryotic Cell Structure  Each component has a specific function.  They work together to help the cell survive.  Cell wall fairly rigid part of plant cells, bacteria & protists made of cellulose.

Eukaryotic Cell Structure  Nucleus  Cell Control  Contains directions for making proteins in chromatin.  Strands of genetic material, DNA  Chromatin condenses to chromosomes before cell division

Eukaryotic Cell Structure  Nucleolus  Makes ribosomes  Ribosomes are production site of proteins made by direction of DNA  They’re made of RNA and must travel to the cytoplasm to build proteins.  The nucleolus makes ribosomes which are the site of protein synthesis.  Ribosomes must travel out of the nucleus to the Cytoplasm where they build the proteins according to DNAs direction.

Eukaryotic Cell Structure  Cytoplasm  Clear, gelatinous fluid inside a cell  Ribosomes and RNA pass through nuclear pores in the nuclear envelope to enter the cytoplasm

Eukaryotic Cell Structure  Assembly, transport & storage  Endoplasmic reticulum site of cellular chemical reactions  Highly folded membrane which ribosomes attach to (Rough ER) do protein synthesis

Eukaryotic Cell Structure  Each protein has a specific function.  Smooth ER has no ribosomes but makes and stores lipids.  After proteins are made they’re sent to the Golgi Apparatus

Eukaryotic Cell Structure  Golgi Apparatus  Modifies proteins & sorts them into packages (vesicles) for transport to their destination

Eukaryotic Cell Structure  Vacuoles membrane bound compartment for temporary storage  Stores food, enzymes & other needed materials.  Animal cells may also have vacuoles usually smaller.

Eukaryotic Cell Structure  Lysosomes contain digestive enzymes.  Used to digest worn out organelles, food particles or engulfed viruses or bacteria.  The membrane prevents enzymes from destroying the cell.

Eukaryotic Cell Structure  Energy Transformers  Chloroplasts capture light energy & convert it to chemical energy.

Eukaryotic Cell Structure