cell structuresection 1 section 1: introduction to cells preview bellringer key ideas the discovery...

Cell Structure Section 1

Section 1: Introduction to Cells

Preview• Bellringer• Key Ideas• The Discovery of Cells• Looking at Cells• Cell Features• Summary

Cell Structure Section 1

Bellringer

After viewing the list of items on the board, work with a partner and make two new lists: those items on the list comprised of cells and those items not comprised of cells.

Give a rationale for each answer.

Cell Structure Section 1

Key Ideas

• How were cells discovered?

• Why does cell shape vary?

• What enables eukaryotes to perform more specialized functions than prokaryotes?

Cell Structure Section 1

The Discovery of Cells

• Microscope observations of organisms led to the discovery of the basic characteristics common to all living things.

• Scientists first discovered cells in the 1600s using crude microscopes.

• Observations made by scientists using more powerful microscopes in the 1800s led to the formation of the cell theory.

Cell Structure Section 1

Visual Concept: Cell Theory

Cell Structure Section 1

Looking at Cells

• Cells vary greatly in their size and shape.

• A cell’s shape reflects its function. Cell size is limited by a cell’s surface area-to-volume ratio.

• Cells can be branched, flat, round, or rectangular.

Cell Structure Section 1

Looking at Cells, continued

• All substances that enter or leave a cell must cross the surface of the cell.

• A cell’s ability to move substances across its surface can be estimated by finding its surface area-to-volume ratio.

• Cells with greater surface area-to-volume ratios can exchange substances more efficiently.

Cell Structure Section 1

Relationship between Surface Area and Volume

Cell Structure Section 1

Looking at Cells, continued

• When comparing cells of the same shape, small cells have greater surface area-to-volume ratios than large cells.

• So, small cells function more efficiently than large cells.

Cell Structure Section 1

Cell Features

• All cells share common structural features, including a cell membrane, cytoplasm, ribosomes, and DNA.

• The cell membrane is the outer layer that covers a cell’s surface and acts as a barrier between the outside environment and the inside of the cell.

• The cytoplasm is the region of the cell within the cell membrane. The cytoplasm includes the fluid inside the cell called the cytosol.

Cell Structure Section 1

Cell Features, continued

• A ribosome is a cellular structure that makes proteins.

• The DNA of a cell provides instructions for making proteins, regulates cellular activities, and enables cells to reproduce.

Cell Structure Section 1

Features of Prokaryotic and Eukaryotic Cells

Cell Structure Section 1

Cell Features, continued

Features of Prokaryotic Cells

• A prokaryote is an organism made of a single prokaryotic cell.

• Prokaryotic cells do not have a nucleus or other internal compartments. The genetic material of a prokaryotic cell is a single loop of DNA.

• For millions of years, prokaryotes were the only organisms on Earth.

Cell Structure Section 1

Cell Features, continued

Features of Eukaryotic Cells

• A eukaryote is an organism made up of one or more eukaryotic cells. All multicellular organisms are made of eukaryotic cells.

• The DNA of a eukaryotic cell is found in an internal compartment of the cell called the nucleus.

• All eukaryotic cells have membrane-bound organelles. An organelle is a small structure found in the cytoplasm that carries out specific activities inside the cell.

Cell Structure Section 1

Cell Features, continued

• Each organelle in a eukaryotic cell performs distinct functions.

• The complex organization of eukaryotic cells enables them to carry out more specialized functions than prokaryotic cells.

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Visual Concept: Comparing Prokaryotes and Eukaryotes

Cell Structure Section 1

Comparing Prokaryotes and Eukaryotes

Cell Structure Section 1

Summary

• Microscope observations of organisms led to the discovery of the basic characteristics common to all living things.

• A cell’s shape reflects its function. Cell size is limited by a cell’s surface area-to-volume ratio.

• The complex organization of eukaryotic cells enable them to carry out more specialized functions than prokaryotic cells.