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Cells Under the Microscope

Measuring Cell StructuresMeasurements taken by scientists are expressed in _____ units. The official name of the metric system is the ____________ ____________ of Measurements, abbreviated SI. The table below summarizes the SI units used to measure length.

Section 1 Looking at CellsChapter 3





Cells Under the Microscope, continued• Magnification is the ________ of making an image appear

_________ than its actual size.

• Resolution is a measure of the ___________ of an image.

Both high magnification and good resolution are needed to view the ________ of extremely small objects _________.






Cells Under the Microscope, continued__________ microscopes have much higher ___________ and

__________ powers than light microscopes.






Types of Microscopes

Light microscopes form an image when _______ passes through one or more ________ to produce an enlarged image of a specimen.






Types of Microscopes, continuedElectron Microscopes

• Electron microscopes form an image of a specimen using a beam of ____________ rather than light.

• The electron beam and specimen must be in a _________ so that the electron beam will not bounce off of gas molecules.

• ________ organisms ________ be viewed with an electron microscope.






Types of Microscopes, continuedTransmission Electron Microscope• An electron beam is directed at a very thin slice of

a specimen stained with metal ions. Some structures become more ________ stained than others.

• The heavily stained parts _________ electrons, those that are lightly stained allow electrons to pass through.

• The electrons that pass through strike a fluorescent ________, forming an image.






Types of Microscopes, continuedScanning Electron Microscope

• An electron beam is focused on a specimen coated with a very thin layer of _______.

• The electrons that ________ off the specimen form an image on a fluorescent screen.

• The image shows ____________________ details of the surface of a specimen.






Types of Microscopes, continued

Scanning Tunneling Microscope

• A needle-like probe measures differences in ___________ caused by electrons that leak, or tunnel, from the surface of the object being viewed.

• A __________ tracks the movement of the probe across the surface of the object.

• The image shows three-dimensional details of the surface of a specimen.

• ________ specimens and objects as small as ________ can be viewed.






The Cell Theory

The Cell Theory has three parts:

1. All _________ things are made of one or more cells.

2. Cells are the basic units of ________ and ___________ in organisms.

3. All cells arise from _____________ cells.

Section 2 Cell FeaturesChapter 3





The Cell Theory, continued

Cell SizeSmall cells ___________ more ____________ than large cells. If a cell’s surface area–to-volume ratio is too low, substances cannot ________ and _________ the cell well enough to meet the cell’s needs.






The Cell Theory, continued

Common Cell Features

Cells share common structural features, including:

• an outer boundary called the cell ________________,• interior substance called _________________, • structural support called the __________________, • genetic material in the form of _________ • cellular structures that make proteins, called __________






Prokaryotes

Prokaryotes are single-celled organisms that lack a ____________ and other internal compartments. They have a cell wall, may have cilia or flagella, and have a single ___________ molecule of DNA.






Eukaryotic Cells

Eukaryotic cells have:• A ____________ which contains the cell’s DNA• Other internal compartments called ___________.






Eukaryotic Cells, continued

• The cytoskeleton provides the interior _____________ of a cell. There are three basic kinds of cytoskeletal fibers.

1. ________________: long slender filaments made of the protein actin

2. ________________: hollow tubes made of the protein tubulin.

3. Intermediate fibers: thick ropes made of protein.






Eukaryotic Cells, continued

The cytoskeleton’s network of _________ fibers ___________ the cell’s organelles and other components of the cytoplasm.






The Cell Membrane

• The cell membrane is a ______________ permeable barrier that determines which substances enter and leave the cell.

• The ______________ permeability of the cell is mainly caused by the way phospholipids interact with water.

• A phospholipid is a lipid made of a phosphate group and two fatty acids.






The Cell Membrane, continued

Cell membranes are made of a ____________ layer of phospholipids, called a bilayer.






The Nucleus

• The nucleus is an internal compartment that houses the cell’s DNA. Most ____________ of a eukaryotic cell are ______________ by the cell’s nucleus.

• The nucleus is surrounded by a ______________ membrane called the nuclear envelope.

• Scattered over the surface of the nuclear envelope are many small channels called nuclear ________.

Section 3 Cell OrganellesChapter 3





The Nucleus, continued

• Ribosomal proteins and RNA are ______ in the nucleus.

• Ribosomes are partially assembled in a region of the nucleus called the ________________.






Ribosomes and the Endoplasmic Reticulum

• Ribosomes are the cellular structures on which ____________ are made.

• The Endoplasmic Reticulum or ER is an extensive system of internal membranes that ________ proteins and other ____________ through the cell.






Ribosomes and the Endoplasmic Reticulum, continued• The part of the ER with attached ribosomes is

called the ___________ ER.• The rough ER helps transport proteins that are

made by the attached ribosomes.• New proteins enter the ER.• The portion of the ER that contains the completed

protein pinches off to form a ___________.• A vesicle is a small, membrane-bound sac that

transports substances in cells.






Ribosomes and the Endoplasmic Reticulum, continuedThe ____ moves proteins and other substances within

eukaryotic cells.






Ribosomes and the Endoplasmic Reticulum, continuedPackaging and Distribution of Proteins

• Vesicles that contain newly made proteins move through the cytoplasm from the ER to an organelle called the Golgi _________________.

• The ________ apparatus is a set of flattened, membrane-bound sacs that serve as the _______________ and _____________ center of the cell.






Mitochondria

• Mitochondria are organelles that harvest ____________ from organic compounds to make ATP.

• ATP is the main energy currency of cells. Most ATP is made inside the mitochondria.






Mitochondria, continued

• Mitochondria have ____ membranes. The outer membrane is smooth. The inner membrane is greatly folded, and has a large __________ area.

• Mitochondria have their own DNA. Mitochondria reproduce independently of the cell. Mitochondrial DNA is similar to the DNA of prokaryotic cells.

• Mitochondria are thought to be descendents of primitive prokaryotes.






Mitochondria, continued

Mitochondria have an ______ and an _________ membrane.






Structures of Plant Cells

Plants have three unique structures that are not found in animal cells:

• Cell ______

• _______________

• Central __________






Structures of Plant Cells, continued

• The cell membrane of plant cells is surrounded by a thick cell wall, composed of _________ and _____________.

• The cell wall

• helps _____________ and maintain the _________ of the cell

• ____________ the cell from damage

• _______________ the cell with adjacent cells







• Chloroplasts are organelles that use _______ energy to make carbohydrates from carbon dioxide and water.

• Chloroplasts, along with _____________________, supply much of the energy needed to power the activities of plant cells.

• Chloroplasts, like mitochondria, have their own DNA and reproduce independently of the plant cell.

• Chloroplasts, like mitochondria, are thought to be descendents of ancient prokaryotes.







Central Vacuole:

• Most of a plant cell’s __________ is taken up by a large, membrane-bound space called the central vacuole.

• The central vacuole stores ____________ and may contain ions, nutrients, and wastes.


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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter