Cells

Robert Hooke -1665• In his book, entitled

Micrographia, Hooke was the first to use the term cell

• From the Latin “cella” meaning “small chamber”

Anton van Leeuwenhoek-1675

• A Dutch cloth merchant who became interested in studying cells

• Was the first to see and describe bacteria, sperm cells and protista

• Theodor Schwann (1838) – all animals are composed of cells

• Matthias Schleiden (1838) – all plants are composed of cells

• Rudolf Virchow (1856) “Omnis cellula e cellula”

• “where a cell arises, there a cell must previously have existed”

Modern Cell Theory

• All organisms are composed of cells.

• Cell come from other cells.

• Cells are the smallest unit of structure and function in living organisms.

Prokaryotic Cells

• Lack a true nucleus

• Size: 1-10 microns• Include bacteria

Basic Bacterial Cell

Examples of Prokaryotes

Eukaryotic Cells

• Have a true nucleus

• Size: 10-100+ microns

• Include plants, animals, fungi and protista

• Cell Membrane – surrounds the cell• Cytosol – “cell liquid”• Organelles – “little organs”• Nucleus- control center

Cell Membrane• Regulates the

passage into and out of the cell

• Provides protection

• Helps in cellular recognition of molecules

Cytosol/Cytoplasm• Cytosol: the liquid

portion inside the cell membrane

• Cytoplasm: the cytosol and organelles, but not the nucleus

Nucleus

Nucleus

• Contains DNA • The cell’s “brain” or

CPU• DNA codes for

protein production• Surrounded by the

nuclear envelope

Cytoplasm• Contains the cytosol and organelles

• Ribosomes• Endoplasmic reticulum• Golgi bodies or complex• Lysosomes• Mitochondria• Chloroplasts

Ribosomes

Ribosomes• Are the cell’s

protein factories• Read mRNA code

as seen on the right• Maybe free in the

cytoplasm• Or bound to the ER

Endoplasmic Reticulum• Comes from the Greek Endo =

“within” Latin reticulum = “network.” • A membrane network within the

cytoplasm• Two types: Rough – with ribosomes

attached (RER)• Or Smooth – with no ribosomes (SER)

Rough ER

• Helps the ribosomes in the formation of proteins

• Used to transport proteins to other parts of the cell

Smooth ER

• Functions include synthesis of membrane lipids & detoxification of drugs

• Liver cells contain large amounts of smooth ER

Golgi Body

Golgi Body

• Modify, sort, and package proteins from the ER for storage in the cell & secretion out of the cell

Lysosomes

Lysosomes• Digestive sacs filled with

enzymes

• Breakdown lipids, carbohydrates, and proteins into a form that can be used by the cell

• Digest worn out organelles

• Helps to recycle cellular structures

• Sometimes called “suicide sacs”

• Involved in rheumatoid arthritis

• Example…

Mitochondria

• Converts chemical energy stored in food into compounds that the cell can use (cellular respiration)

• Contain their own DNA

Chloroplasts

• Site of photosynthesis• Contains the green pigment chlorophyll• Helps to convert light energy, water, and carbon

dioxide into sugars• Also contain genetic information

Endosymbiotic Theory

• States mitochondria and chloroplasts were once free living prokaryotic cells

• First proposed in the 1890s, but not supported until 1981 with the discovery of mitochondrial DNA

• Explanation…

Vacuole

• Storage area for water, salts, proteins, and carbohydrates

• Many plants have a large central vacuole filled with liquid to support the plant

Cell Wall• The cell wall is a

rigid structure that is found in plants, fungi, and bacteria cells

• It supports and maintains the shape of the cell. It is extremely strong.