cells random cell fact the average human being is composed of around 100 trillion individual...

Random Cell Fact

The average human being is composed of around 100 Trillion individual cells!!!

It would take as many as 50 cells to cover the area of a dot on the letter “i”

WOW!!!!!!!!!!

Discovery of the Cell

In the beginning – Aristotle proposed that living

things could “SPONTANEOUSLY GENERATE” from non-living material


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And that was that for a long time…. Jean-Baptiste van Helmont (1557 – 1644)

performed an experiment that showed that mice could be made from sweaty shirts and grains of wheat!

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Robert Hooke used a compound microscope to look at a piece of cork (plant material). The cork appeared to be made up of tiny empty chambers which Hooke called cells.

Discovery of the cell Anton van Leeuwenhoek – examined pond

water with a single lens microscope he made and saw many organisms. He called them “animalcules”

He also observed blood cells from fish, birds, frogs, dogs, and humans

Therefore, it was known that cells are found in animals as well as plants


But… the idea of spontaneous generation was still hanging on…

Lazzaro Spallanzani designed an experiment to show that when gravy or other infusions were boiled, then sealed, no microorganisms would grow, but he wasn’t taken seriously

Neither was Francesco Redi who did an amazing series of experiments with maggots and meat . . .


Observation: There are flies around meat carcasses at the butcher shop.

Question: Where do the flies come from? Does rotting meat turn into or produce the flies?

Hypothesis: Rotten meat does not turn into flies. Only flies can make more flies.

Prediction: If meat cannot turn into flies, rotting meat in a sealed (fly-proof) container should not produce flies or maggots.

Testing: Wide-mouth jars each containing a piece of meat were subjected to several variations of “openness” while all other variables were kept the same.

Conclusion(s): Only flies can make more flies.


But, people STILL didn’t really believe that spontaneous generation didn’t happen!!

Until … Louis Pasteur came along. His

experiment with swan-necked flasks laid the matter to rest once and for all, mostly because his timing was right.


Around the same time… Robert Brown describes the nucleus of

the cell


Meanwhile, microscopes are getting better, and scientists are getting more and more detailed looks into the structure of life.

Two men take a bold view. 1838 – Matthias Schleiden (botanist) – all

plants are made up of cells 1839 – Theodor Schwaan (zoologist) – all

animals are made up of cells

Development of Cell Theory

1858- Rudolf Virchow, German physician, after extensive study of cells he stated that cells must arise from preexisting cells.

The Cell Theory Complete

3 Basic Components of the Cell Theory – 1. All organisms are composed of one or

more cells. (Schleiden & Schwann)(1838-39) 2. The cell is the basic unit of life in all living

things. (Schleiden & Schwann)(1838-39) 3. All cells are produced by the division of

preexisting cells. (Virchow)(1858)

Prokaryotes vs Eukaryotes

Both have a cell membrane Both contain DNABoth carry out life processes


Prokaryotes Smaller Simpler No internal membrane Genetic material isn’t contained in the nucleus

Bacteria


Eukaryotes Larger More complex Many internal membrane-bound

structures Genetic material is separated from

the rest of the cell in the nucleus (large membrane – enclosed structure that contains the genetic material)

Prokaryotic Cell

Cell membrane

Cell membrane

Cytoplasm

Cytoplasm

Nucleus

Organelles

Eukaryotic Cell

Section 7-1

Prokaryotic and Eukaryotic Cells

Plant Cell

Nuclearenvelope

Ribosome(attached)

Ribosome(free)

Smooth endoplasmicreticulum

Nucleus

Rough endoplasmic reticulum

Nucleolus

Golgi apparatus

Mitochondrion

Cell wall

CellMembrane

Chloroplast

Vacuole

Section 7-2

Figure 7-5 Plant and Animal Cells

Animal Cell

Centrioles

NucleolusNucleus

Nuclearenvelope

Rough endoplasmic reticulum

Golgi apparatus

Smooth endoplasmicreticulum

Mitochondrion

CellMembrane

Ribosome(free)

Ribosome(attached)

Section 7-2

Figure 7-5 Plant and Animal Cells

Prokaryotes Eukaryotes

Cell membraneContain DNA

NucleusEndoplasmic reticulum

Golgi apparatusLysosomesVacuoles

MitochondriaCytoskeleton

Animal Cells Plant Cells

Centrioles

Cell membraneRibosomes

NucleusEndoplasmic reticulum

Golgi apparatusLysosomesVacuoles

MitochondriaCytoskeleton

Cell WallChloroplasts

Section 7-2

Venn Diagrams

Cell Structure

Organelles – specialized internal structure on eukaryotic cells

2 major parts of the cell1)1) NucleusNucleus2)2) CytoplasmCytoplasm

Cell Structure

Cytoplasm – watery material found inside the cell but not in the nucleus!

Cell Structure

Nucleus Control center of the cell Contains the cell’s DNA Nuclear envelope – two membranes

that suround the nucleus Nuclear pores – small holes found in

the envelope that allow material to move into and out of the nucleus

Cell Structure

Nucleus cont’d Nucleoplasm – cytoplasm found

inside the nucleus Nucleolus – small darkened dense

region where ribosomes are made Chromatin – DNA bound to proteins Chromosomes – when a cell divides,

the chromatin condenses to form chromosomes

Cell Structure

Ribosomes Made up of RNA Can be free or attached If free – chilling in the cytoplasm If attached – sit on the endoplasmic

reticulum Necessary for protein synthesis Just look like little dots Made up of two different subunits

Cell Structure

Endoplasmic Reticulum – internal membrane system made up of fluid filled canals Smooth ER

No ribosomes attached to it Contains enzymes that help with the synthesis

of lipids and detoxification of drugs Rough ER

Ribosomes are attached So proteins made on the ribosomes enter here

to be chemically modified

Cell Structure

Golgi Apparatus Proteins from the rough ER come

here next Here the proteins are modified,

sorted and packaged for either storage in the cell or secretion out of the cell

Looks like a sac of membranes

Cell Structure

Lysosomes Small bubble-like organelles filled with enzymes

Help to breakdown lipids, carbs and proteins

Also breakdown worn out organelles

Cell Structure

Vacuoles Sac-like structures Stores materials – water salts, proteins, carbs

Plants – have a central vacuole which helps to make the plant turgid

Animals – have food and contractile vacuoles

Cell Structure

Mitochondria Converts chemical energy stored in food

into compounds that are convenient for the cells to use

Cellular respiration happens here Contains both an outer and inner

membrane Inner membrane is folded forming cristae Inherited from the cytoplasm of the female

egg

Cell Structure

Chloroplast Helps to capture energy from the sun and

convert it into chemical energy by photosynthesis

Contains chlorophyll (pigment that helps to capture energy from the sun)

Has a double membrane Stroma – liquid found here Grana – stacks of membranes

Importance of Mitochondria and Chloroplast Both have their own DNA Believe they are descendents of ancient

prokaryotes Endosymbiotic theory – both formed a

symbiotic relationship with early eukaryotes and actually lived within the cell.

Cell Structure

Cytoskeleton Protein filaments that helps the cell

maintain its shape Helps with movements Microfilaments

Threadlike structures made up of the protein actin

Framework to support the cell Help with movement by assembling and

disassembling

Cell Structure

Cytoskeleton cont’d Microtubules

Hollow structures made up of the protein tubulin Helps with cell shape and cell division (form the

mitotic spindle) Centrioles –

Made from tubulin Found near the nucleus Help with cell division Not found in plants Made up of 9 groups of 3 microtubules

Cell Structure

Cytoskeleton cont’d Microtubules cont’d

Cilia and flagella Hair-like organelles that help with movement Flagella – longer; usually a cell only has a

few Cilia – can cover the whole cell; usually

move substances across the cell Made from structures called basal bodies Made up of 9 pairs of microtubules plus a

pair in the middle

Cell membrane

Endoplasmicreticulum

Microtubule

Microfilament

Ribosomes Mitochondrion

Section 7-2

Figure 7-11 Cytoskeleton

Cell Structure

Cell membrane Controls what enters and leaves

the cell Provides protection and support Separates cell from its

surroundings Lipid bilayer – made up of 2 layers

of phospholipids

Cell Structure

Cell membrane cont’d Also contains proteins which help with

transport or act as receptorsIntegral proteins – span the length of

the membranePeripheral proteins – attached to only

one side of the membrane Contains carbs which link to either the

lipids of the proteins. These carbs help to identify the cells.

Cell Structure

Cell wall Found in plants and most bacteria Surrounds the cell membrane Provides shape and protection In plants, the cell wall is made up

mostly of cellulose