Basic Structure of a Cell

History of Cells & the Cell Theory Cell Specialization Virchow

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

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

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

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

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

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

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

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)

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

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.

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

Plant Cell

Animal Cell

Plant vs. Animal Cells QUESTION? PLANT CELL ANIMAL 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

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

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

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

Which Cell Type is Larger? _________ > _____________ > ___________ Plant cell Animal cell Bacteria or Prokaryotes

Specialized Animal Cells Muscle cells Red blood cells Cheek cells Neuron

Specialized Plant cells Guard Cells Pollen Xylem 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.

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

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

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 2nd signal to form inside the cell **Receptor can open a passageway into the cell.