Cells: Basic Structures & Functions

Historical Timeline of The Cell and Development of The Cell Theory

Early 1600’s

1665 1670

1838

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In 1665, Robert Hooke used a microscope to examine a thin slice of cork (dead plant cell walls).

What he saw looked like small boxes.

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) in pond water.

Leeuwenhoek used a simple, handheld microscope to view pond water & scrapings from his teeth

Cell Theory Nearly a century after Hooke’s

findings, several other scientist’s discoveries led to the formation of the cell theory.

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

In 1839, a German zoologist named Theodore Schwann concluded that all animals were made of cells

Schwann also cofounded 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 IS FORMED All living things are made of cells

Cells are the basic unit of structure and function in all living organisms (basic unit of life)

Cells come from the reproduction of existing cells (cell division)

Discoveries Since the Cell Theory

In 1970, American biologist, Lynn Margulis, provided evidence that some organelles within cells were at one time free living cells themselves

Supporting evidence included organelles with their own DNA

Chloroplast and Mitochondria

Simple or Complex Cells

Although ALL living things are made of cells, organisms may be:

Unicellular – composed of one cell Multicellular- composed of many cells

that may organize into tissues, etc.

Types of Cells Living organisms are made of either

prokaryotic or eukaryotic cells – the two major kinds of cells which can be distinguished by structural organization

Prokaryotes – The first Cells Cells that lack a nucleus or membrane-

bound organelles Includes bacteria Simplest type of cell Single, circular chromosome

No nucleus, DNA scattered through center of the cell.

Surrounded by cell membrane & cell wall made of (peptidoglycan)

Contain ribosomes

(no membrane) in their cytoplasm to make proteins

Examples of bacteria:

E.coli, Streptococcus

Eukaryotes Cells that HAVE a true nucleus and

membrane-bound organelles

Includes protists, fungi, plants, and animals

More complex type of cells

Eukaryotes contain 3 basic cell structures:

Nucleus

Cell Membrane

Cytoplasm with organelles

Two Main Types of Eukaryotic Cells

Plant Cell

Animal Cell

Cell Boundaries

Cell Wall Outer boundary in bacteria, plant and

fungi cells NOT found in animal cells Primary function: provide support and

structure

Plasma Membrane

Also call the cell membrane Found in ALL cells Primary function: maintain

homeostatsis Provides protection from environment Regulates exchange with the

environment Selectively permeable

Controls what enters and what does not

Plasma Membrane

Composed of 3 Biomolecules:1. Lipids

Phospholipids make up the phospholipid bilayer Hydrophillic head and hydrophobic tails Two phospholipids orient themselves tail to tail

to form the phospholipid bilayer Cholesterol

Found in plasma membrane of animal cells Provides stabilization

Plasma Membrane

2. Carbohydrates “ID tags” to identify cells

3. Proteins Embedded in the phospholipid bilayer Function: serve as channels and pumps

for transport in and out of cell

Plasma Membrane

Plasma Membrane