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th
7
Science
Cells and Heredity (Module A)
Unit 1: Cells
Lesson 1: Characteristics
of Cells
Unit 1 Lesson 1 The Characteristics of Cells
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.
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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 theory
Three basic components:
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
Characteristics of Cells
Cell
Hall 1ofTheFame
•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
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 1 The Characteristics of Cells
Cell Hall of Fame
(con’t) read pg. 8-9
• 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 animals
tissues are made of cells.
• Rudolf Virchow (1858) said cells divide to form
new cells
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 1 The Characteristics of Cells
A few more important cell theory things:
• Unicellular organisms: Organisms made up of just
one cell
• One cell has to carry out ALL
life functions.
• multicellular organisms: Organisms made up of more
than one cell
• Cells have specialized functions.
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Unit 1 Lesson
1 Theof
Characteristics
Two
types
cells 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, archaea
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Bacteria Flagella
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
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 1 The Characteristics of Cells
All
cells have…
• 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
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Unit 1 Lesson 1 The Characteristics of Cells
What parts do all cells have in
common?
• How many parts of a cell can you name?
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