History of the cell:*CELLS

The development and refinement of magnifying lenses and light microscopes made the observation and description of microscopic organisms and living cells possible.

* Early scientists contributions to the cell theory:

*Leeuwenhoek – developed and improved simple microscopes; he saw small living things in a drop of pond water and called them “animalcules”.

*Robert Hooke*He studied cork with a microscope and described the small boxes he decided to call cells after rooms in monasteries.*He named the cell a “cell”.

*Schleiden*A German botanist who concluded that all plants are made of cells.

*Schwann

*A German zoologist who concluded that all animals are made of cells.

*Virchow concluded that all cells come from pre-existing cells.

*The Cell Theory *All living things are made of cells.*The cell is the basic unit of structure and function

in all living things.*All cells come from pre-existing cells.*MODERN CELL THEORY ADDS:*Energy flow occurs within cells.*Cells contain hereditary information that is passed

from cell to cell during cell division.*All cells are basically the same in chemical

composition in organisms of similar species.

*Continued advancements in microscopy allowed the observation of cell organelles and internal structure.

*Electron Microscopes*Two types were developed in the mid 1900’s.

*The scanning electron microscope (SEM) uses a beam of electrons to scan the surface of a cell.

* The transmission electron microscope (TEM) uses a beam of electrons to study structures within a cell.

*There are two basic cell types:

*Prokaryotes are cells that do not contain a nucleus or other membrane-bound organelles.*They are much smaller that

eukaryotes.*Bacteria are prokaryotes.

* Eukaryotes are cells that contain a nucleus and other membrane-bound organelles.Protists, fungi, plants, and animals are all eukaryotes.

*Organelles*Organelles are membrane-bound structures in a eukaryotic cell.*Each organelle has a specific function for cell survival.

*The plasma membrane

• All cells, prokaryotic and eukaryotic, have a plasma membrane.

• It is a phospholipid bilayer.

• It is selectively permeable as it regulates what goes in and out of the cell.

*Nucleus

*The nucleus controls all cellular functions.*It contains chromatin which is made up of DNA and proteins.*DNA is the blueprint for all cellular activity.

*Nucleolus

• The nucleolus is found in the nucleus.

• It produces ribosomes.• It is the dark, dense regions of the

nucleus.

*Ribosomes

*Ribosomes are where proteins are made.*Some are free in the cytoplasm and some

are bound to the endoplasmic reticulum.*Ribosomes are NOT membrane-bound and

are found in both eukaryotes and prokaryotes.

*Cytoplasm

*The cytoplasm is all cellular contents outside the nucleus in eukaryotic cells.

*Endoplasmic Reticulum

*The ER is a series of membranous canals for the transport of materials.*They are the sites of chemical reactions.*Rough ER – ribosomes are attached that are

producing proteins*Smooth ER – no ribosomes attached; involved in

production and storage of lipids

*Golgi Apparatus*Also called the Golgi bodies or Golgi complex*It receives proteins from the ER.*It modifies, packages, and ships the proteins.

*Flow of materials

*Vacuoles

*Vacuoles are membrane-bound sacs for temporary storage.

*Lysosomes

*They are the cell’s recyclers.*Lysosomes contain digestive enzymes to digest worn out organelles, food particles, or viruses.

*Chloroplasts*These are the sites for photosynthesis.*They capture light energy and convert it to chemical energy.*The chemical energy is stored in food molecules.

*Mitochondria

*These are the sites for cellular respiration.*They are called the “powerhouse of the

cell”.*They break down food molecules and

release energy.

*Cytoskeleton

*This support structure in the cytoplasm is composed of microtubules and microfilaments.

*Centrioles

*Centrioles are involved in cell division. They are found only in animal cells.

*Cilia

*These are short, numerous hair-like projections on the cell surface for locomotion or feeding.

*Flagella

*Flagella are longer projections on the cell surface that move with a whip-like motion.*They are primarily used for locomotion.

*Cell Wall*The cell wall is an inflexible barrier that protects the cell and gives it support.*They are found in prokaryotes, fungi, plants, and in plant-like protists.

*Plant Cells vs. Animal Cells

*Plant cells have a cell wall as well as a plasma membrane.*Animal cells only have a plasma membrane.

*Energy Organelles

*Plant cells have chloroplasts and mitochondria.*Animal cells only have mitochondria.

*Plant cells have a large central vacuole for water storage.*Animal cells only have small, temporary vacuoles.

*And lastly,*Animal cells have centrioles. Plant cells do not.