Introduction to Cells
Objectives <ul><li>State the three parts of the cell theory.  </li></ul><ul><li>Describe the contributions of 17th, 18th, ...
Living Things Are Made of Cells <ul><li>One of the levels of biological organization is the cell. From our studies of the ...
Cell History <ul><li>In 1837, Schleiden discovered that plants were made up of recognizable units, or cells.  </li></ul><u...
Part two of the Cell Theory <ul><li>The second part of the cell theory is pretty hard to argue with: cells are the basic u...
Part two of the Cell Theory <ul><li>Another way that we know that cells are the basic unit of life is that anything less t...
The Cell Theory and Spontaneous Generation <ul><li>Before we consider the origin of cells, let's go back in time again, be...
Part three of the Cell Theory <ul><li>An Italian scientist, Lazzaro Spallanzani, was not convinced. He suggested that perh...
Spontaneous Generation <ul><li>In 1668, an Italian doctor named Francesco Redi showed that maggots come from flies, not fr...
Spontaneous Generation disproved <ul><li>Across the border in France, Louis Pasteur set out to prove that Virchow was righ...
Basic Cell Structures <ul><li>The head of a pin is about 2 millimeters in diameter. Some organisms, such as dust mites, ar...
Cell Structures <ul><li>Plasma membrane - A phospholipid bilayer that surrounds a cell and serves as a barrier between the...
Functions of Proteins in the Plasma Membrane <ul><li>Proteins in the form of enzymes have several functions within the pla...
Prokaryotes vs. Eukaryotes <ul><li>Prokaryotic cells are relatively simple. Bacteria and many unicellular organisms are pr...
Prokaryotes are single-celled organisms, roughly one micrometer in diameter. The cell's genetic material consists of a lar...
Eukaryotes <ul><li>Eukaryotes have membrane bound organelles and a membrane bound nucleus, which contains the DNA (genetic...
<ul><li>The  plasma membrane  serves as the gate of the cell, it determines what enters and exits the cell. </li></ul><ul>...
The most striking differences between eukaryotic cells are between animal cells and plant cells. Plant cells have all of t...
Cell Types <ul><li>Even among the animal cells, a wide range of cell structures are based on the function of each cell typ...
Cell Types <ul><li>Sperm and egg cells are unique because they're haploid, which means they have just 23 chromosomes inste...
Cell Types <ul><li>Red blood cells also show the variety of eukaryotic cells.  </li></ul><ul><li>In mammals, red blood cel...
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Chapter 6 Introduction To Cells

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Chapter 6 Introduction To Cells

  1. 1. Introduction to Cells
  2. 2. Objectives <ul><li>State the three parts of the cell theory. </li></ul><ul><li>Describe the contributions of 17th, 18th, and 19th century biologists to our current understanding of the cell. </li></ul><ul><li>Discuss the theory of spontaneous generation. </li></ul><ul><li>Describe the function of proteins in the plasma membrane. </li></ul><ul><li>Compare and contrast an animal prokaryotes and eukaryotes. </li></ul><ul><li>Explain the ways that genetic information is organized within eukaryotes and within prokaryotes. </li></ul><ul><li>Explain the function of several important cytoplasmic organelles. </li></ul>
  3. 3. Living Things Are Made of Cells <ul><li>One of the levels of biological organization is the cell. From our studies of the characteristics of life, we know that all living things are made of cells. This is the first part of the cell theory. </li></ul><ul><li>We take it for granted now, but the first part of the cell theory was big news when two German scientists, Matthias Schleiden and Theodor Schwann, proposed it more than 150 years ago. </li></ul>
  4. 4. Cell History <ul><li>In 1837, Schleiden discovered that plants were made up of recognizable units, or cells. </li></ul><ul><li>A year after Schleiden published his cell theory on plants, his friend Schwann extended it to animals. </li></ul>
  5. 5. Part two of the Cell Theory <ul><li>The second part of the cell theory is pretty hard to argue with: cells are the basic unit of life. </li></ul><ul><li>The best evidence we have for part two of the cell theory is that there are many different unicellular, or one-celled, organisms. </li></ul><ul><li>These can be relatively simple cells like bacteria, or they can be more complex cells like paramecium. They're definitely alive, even though they have just one cell. </li></ul>
  6. 6. Part two of the Cell Theory <ul><li>Another way that we know that cells are the basic unit of life is that anything less than a whole cell isn't alive. A part of a cell can't reproduce or respond to its environment like a whole cell can. </li></ul><ul><li>Viruses aren't alive either, because they depend on the cell they're in for the energy and they reproduce only because the cell reproduces. </li></ul>
  7. 7. The Cell Theory and Spontaneous Generation <ul><li>Before we consider the origin of cells, let's go back in time again, before Schleiden and Schwann proposed the first part of the cell theory. </li></ul><ul><li>One idea that was popular up until the mid-nineteenth century was the theory of spontaneous generation: living organisms can come from non-living things. </li></ul>
  8. 8. Part three of the Cell Theory <ul><li>An Italian scientist, Lazzaro Spallanzani, was not convinced. He suggested that perhaps the microorganisms had entered the broth from the air after the broth was boiled, but before it was sealed. </li></ul><ul><li>Another German, Rudolph Virchow, was a doctor who studied how wounds heal after an injury. After observing that new skin grew where skin had been injured, he proposed what has become the third part of the cell theory : cells come from pre-existing cells. </li></ul>
  9. 9. Spontaneous Generation <ul><li>In 1668, an Italian doctor named Francesco Redi showed that maggots come from flies, not from rotting meat. </li></ul><ul><li>Few scientists were ready to give up on the theory of spontaneous generation in spite of the evidence. </li></ul><ul><li>In 1745, John Needham boiled chicken broth, put it into a flask, sealed it, and waited - sure enough, microorganisms grew. Needham claimed victory for spontaneous generation. </li></ul>
  10. 10. Spontaneous Generation disproved <ul><li>Across the border in France, Louis Pasteur set out to prove that Virchow was right. If cells come from pre-existing cells, then spontaneous generation doesn't happen. </li></ul><ul><li>Pasteur boiled meat broth in a flask and bent the neck of the flask into an S shape. Air could enter the flask, but airborne microorganisms could not – they would settle by gravity in the neck. </li></ul><ul><li>As Pasteur predicted, no microorganisms grew, he had disproved spontaneous generation. </li></ul>
  11. 11. Basic Cell Structures <ul><li>The head of a pin is about 2 millimeters in diameter. Some organisms, such as dust mites, are much smaller than that, but they're huge compared to human cells. Yet, bacterial cells are much smaller than human cells </li></ul>
  12. 12. Cell Structures <ul><li>Plasma membrane - A phospholipid bilayer that surrounds a cell and serves as a barrier between the cell and its surroundings. </li></ul><ul><li>The inside of a human cell is between 70% and 90% water. The water is the solvent, or liquid part, of a complex solution called cytosol. Cytosol contains dissolved ions, small molecules, and large molecules like enzymes that are soluble in water.  </li></ul><ul><li>A key function of the plasma membrane is to maintain stability within the cell. A cell needs to keep substances on the inside from leaving and substances on the outside from coming in, until the cell needs for them to move in or out in order to maintain a stable environment. </li></ul>
  13. 13. Functions of Proteins in the Plasma Membrane <ul><li>Proteins in the form of enzymes have several functions within the plasma membrane: </li></ul><ul><ul><li>They bind to molecules and send messages to the inside of the cell telling it that it's time to do something: produce ATP, contract, or begin to divide. </li></ul></ul><ul><ul><li>They catalyze reactions </li></ul></ul><ul><ul><li>They activate an organism’s immune system </li></ul></ul>
  14. 14. Prokaryotes vs. Eukaryotes <ul><li>Prokaryotic cells are relatively simple. Bacteria and many unicellular organisms are prokaryotes. They don't have membrane-enclosed internal compartments. </li></ul><ul><li>Cells that do have membrane-enclosed compartments are called eukaryotic cells.  </li></ul><ul><li>The most important difference between eukaryotes and prokaryotes is how their DNA is organized. In eukaryotes, the DNA is enclosed in a membrane-covered compartment called the nucleus, the DNA in prokaryotes is not membrane-bound. </li></ul><ul><li>Eukaryotic cells also contain other membrane-enclosed compartments that carry out specific functions. These compartments are called organelles. </li></ul>
  15. 15. Prokaryotes are single-celled organisms, roughly one micrometer in diameter. The cell's genetic material consists of a large DNA molecule concentrated in an area called the nucleoid region , so it’s not membrane-bound. The plasma membrane encases the cytosol and its contents. Some prokaryotes have a cell wall surrounding the plasma membrane. Not all prokaryotes can move, but those that can often use a flagellum to propel them through the environment. Prokaryotes
  16. 16. Eukaryotes <ul><li>Eukaryotes have membrane bound organelles and a membrane bound nucleus, which contains the DNA (genetic information). </li></ul><ul><li>There are two main types: </li></ul><ul><ul><li>Plant cells </li></ul></ul><ul><ul><li>Animal Cells </li></ul></ul>
  17. 17. <ul><li>The plasma membrane serves as the gate of the cell, it determines what enters and exits the cell. </li></ul><ul><li>The ER is a supply convoy; it moves materials from one place to another. (Involved in Protein Synthesis) </li></ul><ul><li>The Golgi apparatus can be thought of as the cell's packing and shipping center. (Involved in Protein Synthesis) </li></ul><ul><li>Mitochondria are the main sites of energy conversion in eukaryotic cells. Think of them as the cell's powerplant! </li></ul><ul><li>(Think ATP!) </li></ul><ul><li>Lysosomes are the cell's recycling center. These are membrane-enclosed sacs that break down carbohydrates, fats, and proteins using digestive enzymes. </li></ul><ul><li>Eukaryotic cells have their own command post: the nucleus . </li></ul><ul><li>(Involved in Protein Synthesis and Cell Division/Reproduction) </li></ul><ul><li>Vacuoles are storage areas within the cell. </li></ul>Animal Cell
  18. 18. The most striking differences between eukaryotic cells are between animal cells and plant cells. Plant cells have all of the organelles listed on the previous slide plus three more. The plasma membrane of a plant cell is surrounded by a rigid cell wall . It protects the cell and maintains its shape. Plants have a second power plant in addition to mitochondria. Organelles called chloroplasts convert the sun's energy to chemical energy during photosynthesis. While the large central vacuole is the third distinguishing feature of plant cells. They store chemicals, including large molecules and toxic substances. PLANT CELL
  19. 19. Cell Types <ul><li>Even among the animal cells, a wide range of cell structures are based on the function of each cell type. </li></ul><ul><li>Nerve cells, or neurons, have many projections, some of which may be several meters long. They need to be that length in order to transmit information from one part of the body to another. </li></ul>
  20. 20. Cell Types <ul><li>Sperm and egg cells are unique because they're haploid, which means they have just 23 chromosomes instead of 46. Sperm also have a long tail so they can travel to reach an egg cell. </li></ul>
  21. 21. Cell Types <ul><li>Red blood cells also show the variety of eukaryotic cells. </li></ul><ul><li>In mammals, red blood cells do not have nuclei. They do not reproduce, so storage of genetic information is not necessary. </li></ul><ul><li>They also don't have mitochondria because they don't use oxygen to produce energy. Their purpose is to carry oxygen through the body, and they could not do this job very well if they used oxygen just to function. </li></ul>
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