Cell Theory 2012-13

History Cells were unknown until the invention of microscopes in the 1650’s two scientists working independently built the first microscopes Anton von Leeuwenhoek in Holland Robert Hooke in England

Anton von Leeuwenhoek Studied pondwater, sour milk, and semen named moving organisms “animalcules”

Anton von Leeuwenhoek People thought human sperm cells contained tiny human beings called a homunculus

Robert Hooke Studied cork - a kind of tree bark named the structures he saw “cells” because they reminded him of the small rooms monks slept in.

The cell theory has three parts: All living things contain at least one cell Cells are the smallest living units of matter Cells can only come from pre-existing cells

All living things contain at least one cell Many scientists have observed different plants and animals Each of them noted that no matter what they observed, if it was alive it had cells.

Cells are the smallest living units of matter scientists realized that when cells were dissected or broken open they died This meant that whatever “life” is, it is something that happens inside cells

Cells can only come from pre-existing cells Except the first cell has not been disproved yet- no scientist has ever built a living cell from nonliving molecules

Spontaneous Generation Until 1850, most people believed that living things could spontaneously appear from non-living material

Spontaneous generation People believed that mice could be “created” spontaneously by putting grain in dark, quiet place and leaving it for a few weeks. Scientists sought to disprove it

Francesco Redi First to challenge spontaneous generation Did not accept that flies appeared from rotting meat

Redi’s Experiment IV= cover DV= presence of flies Hypothesis: If a jar containing rotting meat is covered, then it will produce no flies

Redi’s Conclusions Flies lay eggs, grow into maggots, grow into flies If flies can’t lay eggs, then no new flies

Objections to Redi “sealing the jar closed kept a magical essence from entering the rotting meat and bringing it to life” “Scientists seek only to challenge belief systems and stir things up”

Lazzaro Spallanzani microbes that spoil food come from the air and can be killed by boiling IV= air, DV= food spoilage Hypothesis: If air is allowed to reach food, then microbes will get in and cause it to spoil

Spallanzani’s Experiment Flask 1: boiled broth, open Flask 2: boiled broth, sealed shut Results Flask 1 spoiled Flask 2 did not spoil

Objections to Spallanzani Sealing the flask blocked the magical life force in the air from getting to the broth.

Louis Pasteur 1822. France Supported that spontaneous generation is a myth Invented pasteurization (sterilization by heat)

Pasteur’s Experiment Used special “swan-neck flasks” that allowed air in but kept bacteria out

Pasteur’s Experiment IV= bacteria, DV= spoiling broth Hypothesis; If boiled broth is kept free of bacteria, then it will not spoil even if air can reach it.

Spontaneous generation is dead! Redi didn’t believe in it, and did an experiment using flies Spallanzani didn’t believe in it, and experimented with broth Pasteur disproved it conclusively with his open-air yet spoilage free flasks.

Pasteur is the father of modern microbiology supported the last part of the cell theory: cells only come from pre-existing cells showed that heat can be used to sterilize foods and preserve them

As a result… in the late 1870’s, doctors start to wash their hands and instruments before operating...some even start wearing gloves

Organelles are membrane-bound cell parts Mini “organs” that have unique functions Located in cytoplasm (everything inside the cell membrane)

Cells have evolved two different architectures: Prokaryote Eukaryote

Prokaryote cells are smaller and simpler Commonly known as bacteria Single-celled (unicellular) or Filamentous (strings of single cells)

Prokaryote cells These are prokaryote E. coli bacteria on the head of a steel pin.

Prokaryote Cells cytoplasm: inner liquid filling DNA in one big loop

ribosomes: for building proteins Prokaryote Cells ribosomes: for building proteins

Endosymbiont theory: a prokaryote ancestor “eats” a smaller prokaryote They join forces and become more complex

Eukaryotes Bigger and more complex Have organelles Have chromosomes can be multicellular include animal, plant, fungal, and protist cells

Cell Structures Cell membrane delicate phospholipid and protein skin around cytoplasm found in all cells

Nucleus a membrane-bound sac evolved to store the cell’s chromosomes-DNA has pores: holes

Nucleolus inside nucleus location of ribosome factory made of RNA

mitochondrion makes the cell’s energy the more energy the cell needs, the more mitochondria it has

Ribosomes build proteins from amino acids in cytoplasm may be free-floating, or may be attached to ER made of RNA

Endoplasmic reticulum may be smooth: builds lipids and carbohydrates may be rough: stores proteins made by attached ribosomes

Golgi Complex takes in sacs of raw material from ER sends out sacs containing finished cell products

Lysosomes sacs filled with digestive enzymes digest worn out cell parts digest food absorbed by cell

Centrioles pair of bundled tubes (microtubules) organize cell division

Cytoskeleton found throughout cytoplasm gives shape to cell & moves organelles around.

Structures found in plant cells Cell wall very strong made of cellulose protects cell from rupturing

Vacuole huge water-filled sac keeps cell pressurized stores starch

Chloroplasts filled with chlorophyll turn solar energy into food energy

Eukaryote cells can be multicellular The whole cell can be specialized for one job cells can work together as tissues Tissues can work together as organs

Label the cells