1 Basic Structure of a Cell

2 History of Cells & the Cell Theory Virchow Cell Specialization

3 First to View Cells In 1665, Robert Hooke used a microscope to examine a thin slice of cork (dead plant cells) What he saw looked like small boxes

4 First to View Cells Hooke is responsible for naming cells Hooke called them “CELLS” because they looked like the small rooms that monks lived in called Cells

5 Anton van Leeuwenhoek In 1673, Leeuwenhoek (a Dutch microscope maker), was first to view organisms (living things) Leeuwenhoek used a simple, handheld microscope to view pond water & scrapings from his teeth

6 Robert Brown Discovered & named the nucleus The dark area in the center of the cell

7 Beginning of the Cell Theory In 1838, a German botanist named Matthias Schleiden concluded that all plants were made of cells Schleiden is a cofounder of the cell theory

8 Beginning of the Cell Theory In 1839, a German zoologist named Theodore Schwann concluded that all animals were made of cells Schwann also cofounded the cell theory

9 Beginning of the Cell Theory In 1855, a German medical doctor named Rudolph Virchow observed, under the microscope, cells dividing He reasoned that all cells come from other pre-existing cells by cell division

10 CELL THEORY All living things are made of cells Cells are the basic unit of structure and function in an organism (basic unit of life) Cells come from the reproduction of existing cells (cell division)

11 Cell Size: Surface Area & Volume As cells get larger, their volume increases at a faster rate than their surface area Why is this a problem? –Cells depend on their surfaced area to move needed materials into the cell and waste materials out of the cell –If the surface area decreases, cell cannot move materials fast enough –Therefore, cells must be small to maintain a high surface area to volume ratio

12 Prokaryotic Cells Basic Description: has NO membrane-bound organelles Nucleus? Has NO nucleus Ribosomes? Present Arrangement of Chromosomes? Single chromosome, free-floating in the cytoplasm –May contain plasmids Examples: Bacteria (Bacterium – singular) Sketch a Prokaryotic cell and label it.

13 Eukaryotic Cells Basic Description? Has membrane-bound organelles Nucleus? Has a true nucleus Ribosomes? Present – protein factory Arrangement of Chromosomes? Many linear strands of DNA Examples? Plants, animals, fungi, & protists (everything except for bacteria) –Sketch and label a basic eukaryotic cell and

14 Plant Cell

15 Animal Cell

16 Plant vs. Animal Cells QUESTION?PLANT CELLANIMAL CELL Cell wall and/or cell membrane? Cell Wall AND Cell Membrane Cell Membrane only Chloroplast or no chloroplast? Chloroplast (for photosynthesis) No chloroplast Vacuole or not vacuole? Vacuole (often large to store water) Small vacuole or No vacuole

17 Cell Organization Cells  Tissues  Organs  Organ Systems  Organism

18 CELL SIZE Typical cells range from 5 – 50 micrometers (microns) in diameter

19 How Big is a Micron ( µ ) ? 1 cm = 10,000 microns 1” = 25,000 microns

20 Which Cell Type is Larger? _________ > _____________ > ___________ Plant cellAnimal cellBacteria or Prokaryotes

21 Specialized Animal Cells Muscle cellsRed blood cells Cheek cells Neuron

22 Specialized Plant cells Xylem cells Pollen Guard Cells

What causes a cell to become specialized? Differentiation –Occurs in stem cells –Specific parts of DNA (called genes) are turned on –Once activated or turned on, specific types of cells are made –This is why all cells in an organism have the exact same DNA, but each stem cell may differentiate or become any type of specialized cell. 23

24 Communication Among Cells 1)Types of Chemical Signals A) Hormones  chemical signals made by an endocrine gland and released in to the body

25 Communication Among Cells B)Neurotransmitters  chemical signals released by nerve cells –Used to communicate with other nerve cells or muscle cells

26 Receptor Proteins Proteins of the surface of a cell that “receive” chemical signals A ) Receptor proteins can influence the cell in 3 ways **Receptor chemically changes molecules in the cell’s cytoplasm **Receptor causes a 2 nd signal to form inside the cell **Receptor can open a passageway into the cell.