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Science WorkbookCell Structure Lesson

Day 1Cells Day 1

Inquiry Lab: Is It Alive?Sometimes, it is difficult to tell living things from nonliving things. To be considered alive, something must have all of the characteristics of life.

Procedure1. With your group, discuss some characteristics you could look for to tell whether

something is living or nonliving.2. Examine an assortment of objects given to you by your teacher.3. Make a table that has three columns. In the first column, describe each of the

objects. In the second column, state whether each object is living or nonliving.4. In the third column, write down the characteristics of life that you observed in

each object.

Analysis1. Identify characteristics of life that are difficult to see during a brief observation

like this one.________________________________________________________________________________________________________________________________________________________________________________________________

2. Identify an object or material (not necessarily among your samples) that undergoes growth but that has never been alive.________________________________________________________________________________________________________________________________

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Introduction to CellsAfter reviewing the list of objects you compiled in the Is It Alive? Lab, work with a partner and make two new lists: those items comprised of cells and those items not comprised of cells. Give a rationale for each answer.

Cells No Cells

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Reference: Units of length

Reference: Cell size

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BIG IDEAS READING

The Discovery of CellsIn 1665, Robert Hooke, an English scientist, used a simple microscope to look at a thin piece of a cork. His microscope could only magnify objects 30 times their normal size. Hooke saw many “little boxes” in the cork. They reminded him of the small rooms in which monks lived, so he called them cells. Hooke later discovered cells in the stems and roots of plants. Ten years later, Anton

van Leeuwenhoek, a Dutch scientist, used a more powerful microscope that could magnify objects 300-fold. He discovered many living creatures in pond water. He named them animalcules, or “tiny animals.” Today, we know that they were not animals. They were single-celled organisms.

Cell Theory It took more than 150 years for scientists to fully appreciate the discoveries of Hooke and Leeuwenhoek. By the 1830s, microscopes were powerful enough to resolve structures only 1 µm apart. In 1838, Matthias Schleiden, a German botanist, concluded that cells make up every part of a plant. A year later, Theodor Schwann, a German zoologist, discovered that animals are also made up of cells. In 1858, Rudolph Virchow, a German physician, proposed that cells come only from the division of existing cells. The observations of Schleiden, Schwann, and Virchow form the cell theory:

• All living things are made up of one or more cells.

• Cells are the basic units of structure and function in organisms.

• All cells arise from existing cells.

The cell theory has withstood the rigorous examination of cells by scientists equipped with today’s high-powered microscopes. As new tools and techniques are invented, scientists will learn more about the characteristics of cells.

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What they are REALLY saying is ___?Use the space below to provide a short description of what each of the sections from the Big Ideas Reading is REALLY saying. Please write these summaries in your own words.

Section # What they are REALLY saying…in your words

1: The Discovery of

Cells

2: Cell Theory

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BIG IDEAS READING

Cell Features All cells—from bacteria to those in a berry, bug, or bunny—share common structural features. All cells have an outer barrier, cell fluid, protein factories, and genetic codes. The outer barrier of a cell acts as a gateway between the outside environment and the inside of the cell. The fluid inside the cell is full of dissolved particles. Also suspended in this fluid are structures vital to the functioning of the cell. This includes protein factories where proteins are made. Proteins are required for the structure, function, and regulation of cells. How are these proteins made? Cells contain genetic codes that provide instructions for making proteins. These codes also provide instructions for regulating cellular activities and enabling cells to reproduce.

Features of Simple Cells The bacterium shown in the figure below is an example of an organism made of a single simple cell. Such cells have a very simple organization. The genetic material looks like a tangled string and usually lies near the center of the cell. Both the genetic material and protein factories lie in the simple cell’s fluid.

Image Caption: The internal fluid of a simple cell is made up of everything that is inside the cell barrier, including sites for protein production and a loop of genetic material.

Simple cells have a cell wall that surrounds the cell barrier and that provides structure and support. Some simple cell walls are surrounded by a structure that enables simple cells to cling to surfaces, including teeth, skin, and food. Scientists think that the first simple cells may have lived 3.5 billion years ago or more. For millions of years, simple cells were the only organisms on Earth. They were very simple and small (1 to 2 µm in diameter). Like their ancestors, modern simple cells are also very small (1 to 15 µm), and they live in a wide range of habitats. Simple cells make up a very large and diverse group of cells.

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Features of Complex Cells All multicellular organisms are made up of complex cells. Because of their complex organization, complex cells can carry out more specialized functions than simple cells can.

Primitive complex cells first appeared about 1.5 billion years ago. As shown in the animal cell in the figure below, a complex cell contains compartments that are separated by barriers. The cell’s genetic material is housed in a central internal compartment.

Image Caption: The inner fluid of a complex cell is made up of many different structures that are surrounded by barriers.

In addition to having a barrier, cell fluid, protein factories, and a central internal compartment, all complex cells have barrier-bound parts. These parts to the cell carry out specific activities inside the cell. The animal cell in the figure above shows many of the cell parts found in complex cells. Each cell part performs distinct functions. Many cell parts are surrounded by a barrier. Some of the barriers are connected by channels that help move substances within the cell.

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What they are REALLY saying is ___?Use the space below to provide a short description of what each of the sections from the Big Ideas Reading is REALLY saying. Please write these summaries in your own words.

Section # What they are REALLY saying…in your words

1: Cell Features

2: Features of Prokaryotic

Cells

3: Features of Eukaryotic

Cells

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BIG IDEAS LECTUREAs the teacher lectures, use the space below to take notes. Pay careful attention to the new scientific terms that are used by scientists to communicate the BIG IDEAS you just read about.

Questions(write down any questions you may

have here)

Notes(Place your notes here)

CELL MEMBRANE (barrier) =

CYTOPLASM (cell fluid) =

RIBOSOME (protein factory) =

PROKARYOTE (organism made of a simple cell) =

EUKARYOTE (organism made of complex cells) =

NUCLEUS (central internal compartment) =

ORGANELLE (cell part) =

DNA (genetic material) =

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Day 1 ReviewUsing what you have written in your notebook today, answer the following review questions in the space provided…

1. List the three parts of cell theory.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. Describe the importance of a cell’s surface area-to-volume ratio.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

3. Compare the structure of a eukaryotic (complex) cell with that of a prokaryotic (cell) cell. Try to use all of the scientific terms introduced in the BIG IDEAS Lecture.

________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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Cells Day 1

Homework

Section: Introduction to CellsIn the space provided, write the letter of the description that best matches each term.

______ 1. cell membrane

______ 2. cytoplasm

______ 3. nucleus

______ 4. ribosome

Write ct next to all of the statements that are part of the cell theory. Leave the other statements blank.

______ 5. Cells come in many different sizes.

______ 6. All cells arise from existing cells.

______ 7. A cell’s shape reflects its function.

______ 8. All living things are made up of one or more cells.

______ 9. Cells are the basic units of structure and function in organisms.

In the space provided, write the letter of the phrase that best answers each question.

______10. Who first discovered cells?a. scientists who wanted to confirm the cell theoryb. scientists looking at skin cells through microscopes c. scientists looking at living plants through microscopesd. scientists looking at cork and pond water through microscopes

______11. Why can eukaryotes carry out more specialized functions than prokaryotes can?a. Eukaryotes have more organelles.b. Prokaryotes have more organelles.c. Eukaryotes are bigger.d. Prokaryotes are bigger.

a. cell structure with its own membrane that stores the cell’s genetic material

b. cell structure where proteins are madec. layer that forms the boundary between the

inside and outside of a celld. the fluid inside a cell and all of the structures

within the fluid

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