CHAPTER
Cell Structure and Function GETTING READY TO LEARN Preview Key Concepts 3.1 Cell Theory Cells are the basic unit of life.
3.2 Cell Organelles Eukaryotic cells share many similarities,
3.3 Cell Membrane The cell membrane is a barrier that separates a cell from the external environment.
3.4 Diffusion and Osmosis Materials move across membranes because of concentration differences.
3.5 Active Transport, Endocytosis, and Exocytosis Cells use energy to transport materials that cannot diffuse across a membrane.
Review Biology Vocabulary lipid
protein
enzyme
substrate
1.
: polymer of amino acids
2.
: biological catalysts
34.
: examples include fats and cholesterol : what an enzyme works on
Preview Biology Vocabulary Try to guess the meaning of each boldfaced word from its context. PHRASE 1. The cell membrane, like a tea bag, is characterized by selective permeability. 2. The smell of baking bread spreads throughout your home by diffusion. 3. Cells in your immune system gobble up invading bacteria and recycle old cell parts through phagocytosis.
MY GUESS
Student text pages 70-72
SECTION
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Cell Theory tff\S ^M^^klX*EBT j" II j-L L • KEY CONCEPT Cells are the basic unit of life.
Early studies led to the development of the cell theory. Cells are the very smallest parts of life. All living things are made of cells. However, most cells cannot be seen without a microscope. How did scientists find out about cells when they couldn't see them? Discovery of Cells Over many years, many scientists observed and studied cells under the microscope. As early scientists improved both microscopes and lenses, they could learn more and more about cells. Some of these findings are listed in the table below. SCIENTIST (YEAR)
FINDING
j
Hooke (1665)
identified and named cells
Leeu wenhcHrft (1674) '
QOSfrVt^«I(|ig,f;f$|if
Schleiden (1838)
noted that plants are made of cells
Schwann(1839)
'" .-•''.' ,.-',' . ^-JjjS concluded that atlliving things are made of cells ^"^.,f. >, \'
Virchow (1855)
., a.
proposed that all cells come from other cells
Cell Theory The discoveries of these early scientists came together into the cell theory. Today's scientists agree with this cell theory. It says three things: • All living things are made of cells. • All cells come from other living cells. • The cell is the most basic unit of life. There is nothing living that is smaller than a cell. 'flisTANr^ Underline the part of the cell theory that says where cells come from.
Interactive Reader 37
Prokaryotic cells lack a nucleus and most internal structures of eukaryotic cells. Cells come in different shapes and carry out different jobs. VISUAL VOCAB However, they all share some features. Cells are very small. Prokaryotic cells do not have a They are surrounded by a membrane that controls what nucleus or other membrane-bound organelles. enters and leaves the cell. They have cytoplasm, a jellylike material that contains the building blocks needed for life. cell And they are made of similar molecules. One of these molcytoplasm membrane ecules is DNA, the genetic information. There are two main types of cells, prokaryotic cells and organelle nucleus eukaryotic cells. Prokaryotic cells are extremely small. Their DNA floats in the cytoplasm, and they have no distinct* Eukaryotic cells have a nucleus and other membrane-bound organelles. internal parts. Prokaryotes, such as bacteria, are made of only one cell. Eukaryotic cells have a nucleus, which is a mem"~" brane that separates DNA from the cytoplasm. The nucleus is a type of organelle, a small part that carries out a specific job in a cell. Eukaryotic cells have many types of organelles. Like the nucleus, most organelles are covered by a membrane. Eukaryotes, such as plants and animals, are made of one cell or many cells. V In the text above, circle two things that eukaryotic cells have them that prokaryotic cells do not have. * ACADEMIC VOCABULARY distinct distinguishable as a separate entity
cell theory
eukaryotic cells
cytoplasm
organelle
prokaryotic cells
Go back and highlight each sentence that has a vocabulary word in bold.
1. Name two types of cells.
,_
2. In both types of cells, the jellylike substance is 3. Parts that carry out specific jobs within a cell are The Big Picture 4. List the three parts of the cell theory.
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McDougal Littell Biology
