7th Science
Cells and Heredity (Module A)
Unit 1: Cells
Lesson 1: Characteristics
of Cells
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What is a cell?
• A cell is the smallest functional and structural unit of all living organisms.
• Organism - any living thing that carries out its own life processes.
Unit 1 Lesson 1 The Characteristics of Cells
Cell size
All cells are small - size is limited by their outer surface area.
• If too large, can’t take in enough nutrients or get rid of enough wastes.
• The surface area-to-volume ratio: ratio of the outer surface to the cell’s volume. • The smaller the cell, the greater this ratio.
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Unit 1 Lesson 1 The Characteristics of Cells
Cell theoryThree basic components:
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Unit 1 Lesson 1 The Characteristics of Cells
1. All organisms are made up of one or more cells.
2. The cell is the basic unit of all organisms.
3. All cells come from existing cells.
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Unit 1 Lesson 1 The Characteristics of Cells
•Robert Hooke (1665) - first to describe cells. He looked at the bark of a cork tree under a microscope (that he built).
• Thought that cork cells looked like cells in monastery
Cell Hall of Fame
• Anton van Leeuwenhoek (1673) made first microscope, described “wee beasties” in pond water.
• Matthias Schleiden (1838) said all plants are made of cells.
• Theodor Schwann (1839) said all animalstissues are made of cells.
• Rudolf Virchow (1858) said cells divide to form new cells
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Unit 1 Lesson 1 The Characteristics of Cells
Cell Hall of Fame (con’t) read pg. 8-9
A few more important cell theory things:
• Unicellular organisms: Organisms made up of just
one cell
• One cell has to carry out ALLlife functions.
• multicellular organisms: Organisms made up of more than one cell
• Cells have specialized functions.
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Unit 1 Lesson 1 The Characteristics of Cells
• Prokaryotes - No nucleus or membrane-bound
organelles
• All are single-celled
• DNA is in the cytoplasm
• Have ribosomes to make proteins
• Some have flagella to help move
• Smaller than eukaryotes
• Examples: bacteria, archaeaCopyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 1 The Characteristics of CellsTwo types of cells
Bacteria Flagella
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Unit 1 Lesson 1 The Characteristics of Cells
• Eukaryotes - have DNA in a nucleus
• Have other membrane-bound organelles
• Most are multicellular
• Also have ribosomes (not membrane bound)
• Examples: animals, plants, protists, fungi
• Do page 11
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• cell membrane – protective outer layer • controls materials moving into and out of the cell.
• cytoplasm - region inside the cell that includes the fluid and all the organelles except for the nucleus.• organelle - small body in the cytoplasm
• specialized to perform a specific function
• DNA (deoxyribonucleic acid)- genetic material that provides instructions for all cell processes
Do page 10
Unit 1 Lesson 1 The Characteristics of CellsAll cells have…
What parts do all cells have in common?
• How many parts of a cell can you name?
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Unit 1 Lesson 1 The Characteristics of Cells
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