History of Cell Discovery Chapter 4

Microscope view of cells Robert Hooke – first to see cells! designed microscope that he was able to view cork cells with (1665). Named “Cells” because they look like monk quarters Cells with stone beds

Microscope view of cells Anton Van Leeuwenhoek – first to see living cells. improved design, and was able to view red blood cells and bacteria. Called them "animalicules"

Scientists of Cell Theory Theodore Schwann – zoologist who observed that the tissues of animals had cells (1839)

Scientists of Cell Theory Mattias Schleiden – botanist who observed that the tissues of plants had cells (1845)

Scientists of Cell Theory Rudolf Virchow – reported that every living thing is made up of cells, and that these cells must come from other cells.

Cell Theory All living things are made of one or more cells. 2. Cells are the basic unit of structure and function in organisms. (the smallest unit that can perform life functions) 3. All cells come from pre - existing cells.

Terms Cell – the smallest unit that can carry on the processes of life. Unicellular – consists of only one cell Multicellular – consists of more than one cell

Basic cell Structures Cell Membrane – outer boundary Nucleus – control center Cytoplasm – stuff between membrane & nucleus

Two Basic Cell Types Prokaryotic – lacks internal organelles. Has a cell membrane & a cell wall Has NO nucleus. Means “before the nucleus” Usually Unicellular organisms Ex: Bacteria

Two Basic Cell Types Eukaryotic – contains organelles. Has a nucleus Has a cell membrane Usually multicellular organisms Ex: Plants, animals, and protists

The First Cells & Their Environment

The First Cells Environment during time of first cells: No oxygen The first cells were: Anaerobic (Does not use oxygen) Prokaryotic (Cells that have no nucleus) Heterotrophic (Consumers)

The First Cells The first autotrophs (make own food) used chemosynthesis (gives off CO2). Around 3 billion years ago, photosynthetic life had began (gives off O2). This production of oxygen was the start of aerobic organisms (use O2 to produce energy

Endosymbiosis Eukaryotes evolved from a mutually beneficial relationship with prokaryotes. Endosymbiosis – Eukaryotic cells engulf prokaryotic cells. Prokaryotic cells then performed beneficial actions inside the eukaryotes while eukaryotes provided a safe environment for the prokaryotes.

Spontaneous Generation Before the 17th century, people believed that living things could come from nonliving things. The Cell Theory has not been written. Example: Rotting meat Maggot Biogenesis – Living things come from other living things

Redi’s Experiment Control group – Uncovered jar that contained meat Experimental group – Netting-covered jar Allowed air to enter and prevented flies from landing on meat Results: Maggots seen in jar without netting, but not seen in jar with netting

Pasteur’s Experiment The invention of microscopes allowed people to discover microorganisms. People believed these microorganisms developed spontaneously from the air. Louis Pasteur created an experiment where broth from boiled meat was placed in a curve-necked flask. Air could enter through the neck, but solid particles could not.

Pasteur’s Experiment: Cont’d Results Broth boiled inside the flask remained clear for one year. After necks were broken off, broth became cloudy and contaminated with microorganisms after one day. Conclusion Microorganisms come from other microorganisms (NO SPONTANEOUS GENERATION)