7th Science Cells and Heredity (Module A) Unit 1: Cells Lesson 1: Characteristics of Cells

Organism - any living thing that carries out its own life processes. 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. Copyright © Houghton Mifflin Harcourt Publishing Company 2

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. Copyright © Houghton Mifflin Harcourt Publishing Company 3

Cell theory 1. All organisms are made up of one or more cells. 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. Copyright © Houghton Mifflin Harcourt Publishing Company 5

Cell Hall of Fame 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 Copyright © Houghton Mifflin Harcourt Publishing Company 6

Cell Hall of Fame (con’t) read pg. 8-9 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 Copyright © Houghton Mifflin Harcourt Publishing Company 7

A few more important cell theory things: 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. Copyright © Houghton Mifflin Harcourt Publishing Company 8

Two types of cells 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, archaea Copyright © Houghton Mifflin Harcourt Publishing Company 9

Bacteria Flagella

Eukaryotes - have DNA in a nucleus 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 Copyright © Houghton Mifflin Harcourt Publishing Company 11

All cells have… cell membrane – protective outer layer Unit 1 Lesson 1 The Characteristics of Cells 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 Copyright © Houghton Mifflin Harcourt Publishing Company 12

What parts do all cells have in common? 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? Copyright © Houghton Mifflin Harcourt Publishing Company 13