Chapter 7 Cell Structure and Function 7 1

Chapter 7 Cell Structure and Function

7 -1 Life is Cellular The Discovery of the Cell • Because there were no instruments to make cells visible, the existence of cells was unknown for most of human history. • This changed with the invention of the microscope.

Early Microscopes • In 1665, Robert Hooke used an early compound microscope to look at a thin slice of cork, a plant material. • Cork looked like thousands of tiny, empty chambers. • Hooke called these chambers “cells” after tiny rooms called cells. • Cells are the basic units of life and contain living matter.

Hooke’s Drawing of Cork Cells

• Around the same time, Anton van Leeuwenhoek used a single-lens microscope to observe pond water and other things. • The microscope revealed a world of tiny living organisms.

The Cell Theory • In 1838, Matthias Schleiden concluded that all plants were made of cells. • In 1839, Theodor Schwann stated that all animals were made of cells. • In 1855, Rudolph Virchow concluded that new cells were created only from division of existing cells. • These discoveries led to the cell theory.

The cell theory states: • All living things are composed of cells. • Cells are the basic units of structure and function in living things. • New cells are produced from existing cells.

Exploring the Cell • New technologies allow researchers to study the structure and movement of living cells in great detail.

Prokaryotes and Eukaryotes • Cells come in a variety of shapes and sizes. • All cells have 2 characteristics in common 1. They are surrounded by a barrier called a cell membrane. 2. At some point they contain the molecule that carries biological information- DNA.

• Cells are classified into 2 categories, depending on whether they contain a nucleus. • The nucleus is a large membrane-enclosed structure that contains the cell's genetic material in the form of DNA. • The nucleus controls many of the cell's activities (nucleus = the brain of the cell) *Eukaryotes are cells that contain nuclei. *Prokaryotes are cells that do not contain nuclei. (nuclei is plural form of nucleus)

What are the characteristics of prokaryotes and eukaryotes?

Prokaryotes • Prokaryotic cells have genetic material that is not contained in a nucleus. • Prokaryotes do not have membrane-bound organelles. • Prokaryotic cells are generally smaller and simpler than eukaryotic cells. • Bacteria are examples of prokaryotes.

Eukaryotes • Eukaryotic cells contain a nucleus in which their genetic material is separate from the rest of the cell. • Eukaryotic cells are generally larger and more complex than prokaryotic cells. • Eukaryotic cells generally contain dozens of structures and internal membranes. • Many eukaryotic cells are highly specialized. • Plants, animals, fungi, and protists are all examples of eukaryotes.

7 -4 The Diversity of Cellular Life

• The ____________among living things arise from the ways in which cells are specialized to perform certain tasks and the ways in which cells associate with one another to form ___________organisms.

Unicellular Organisms • Unicellular organisms are made up of only one cell. (prefix uni- means one) • Unicellular organisms dominate life on Earth. • Unicellular organisms include some fungi and protozoans, fungi, and bacteria. • They do grow, respond to their environment, transform energy, and reproduce.

Amoeba Bacteria (bacillus) Fungi Bacteria (cocci) Paramecium

Multicellular Organisms • Organisms that are made up of many cells are called multicellular. (prefix multi- means many) • There is a great variety among multicellular organisms • Multicellular organisms depend on communication of specialized cells.

• Cells throughout an organism can develop in different ways to perform different tasks. • This process is called cell specialization.

Specialized Animal Cells • Animal cells are specialized in many ways. • Red blood cells transport oxygen.

Cells in the pancreas produce proteins.

Muscle cells allow movement.

Specialized Plant Cells • Plants exchange carbon dioxide, oxygen, water vapor, and other gases through tiny openings called stomata on the undersides of leaves. • Highly specialized cells, known as guard cells, regulate this exchange.

Stomata enclosed by guard cells.

Levels of Organization • The levels of organization in a multicellular organism from smallest to largest are: • individual cells • tissues • organ systems

In multicellular organisms, cells are the first level of organization.

Tissues • Similar cells are grouped into units called tissues. • A tissue is a group of similar cells that perform a particular function.

• Most animals have four main types of tissue: • muscle • epithelial • nervous • connective

Organs • Organs are groups of tissues that work together to perform a specific function.

Organ Systems • In most cases, an organ completes a series of important tasks. • A group of organs that work together to perform a specific function is called an organ system.