7.1 Life is CellularEarly Microscopes

In 1665, Englishman ___________ used an early compound microscope to look at a nonliving thin slice of cork, a plant material.

Under the microscope, cork seemed to be made of thousands of tiny, empty chambers that Hooke called “______”. The term cell is used in biology to this day.

Today we know that living cells are not empty chambers, but contain a huge array of working parts, each with its own function.

In Holland, ______________________ examined pond water and other things, including a sample taken from a human mouth. He drew the organisms he saw in the mouth—which today we call bacteria.

The Cell Theory

Soon after Leeuwenhoek, observations made by other scientists made it clear that __________ _____________________________.

In 1838, German botanist ________________ concluded that all __________________________

The next year, German biologist ________________ stated that _________________________.

In 1855, German physician _______________ concluded that ____________________________ _______________________________, confirming a suggestion made by German Lorenz Oken 50 years earlier.

The cell theory states:

-All living things are made up of __________.

-Cells are the _________________________________________________________.

-New cells _________________________________________________.

• Light Microscopes and Cell Stains

A typical light microscope ____________________________________ and uses two lenses to form an image.

Because light waves are diffracted, or scattered, as they pass through matter, light microscopes can produce clear images of objects only to a ______________________________________

There are 2 functions of microscopes:

1. Magnification: __________________________________________________

2. Resolution: _____________________________________________________

Total Magnification = _________________ x _________________________

Electron Microscopes

Electron microscopes use beams of ___________, not light, that are focused by magnetic fields.

Electron microscopes offer much _________________________ than light microscopes.

This means that electron microscopy can be used to examine only ________________________

There are two major types of electron microscopes: transmission and scanning.

Transmission Electron Microscopes

Transmission electron microscopes magnify up to _______________________

Because beams of electrons can only pass through thin samples, cells and tissues must be cut first into ______________ slices before they can be examined under a transmission electron microscope.

Transmission electron microscopes produce ________________________________________.

Scanning Electron Microscopes

In scanning electron microscopes, a pencil-like beam of electrons is scanned over the surface of a specimen.

Because the ________________________, specimens viewed under a scanning electron microscope do not have to be cut into thin slices to be seen.

Scanning electron microscopes produce _________________________ of the specimen’s surface and produce an image ________________________________________________

Electron Microscopes

Because electrons are easily scattered by molecules in the air, samples examined in both types of electron microscopes must be placed in a vacuum in order to be studied.

Researchers chemically preserve their samples first and then carefully remove all of the water before placing them in the microscope.

This means that electron microscopy can be used to examine ____________________________.

Prokaryotes and Eukaryotes

Although typical cells range from ________ micrometers in diameter, the smallest Mycoplasma bacteria are only 0.2 micrometers across, so small that they are difficult to see under even the best light microscopes.

In contrast, the giant amoeba Chaos chaos may be 1000 micrometers in diameter, large enough to be seen with the unaided eye as a tiny speck in pond water.

Despite their differences, all ______________________________________________________.

In addition, ____________________________________________________________________

All cells contain _________________________________________________________________

Prokaryotes and Eukaryotes

Cells fall into two broad categories, depending on whether they contain a nucleus.

The nucleus is a large membrane-enclosed structure that ___________________________ in the form of DNA. The ___________________________________________.

Prokaryotes vs Eukaryotes

Eukaryotes _____________________________________________________________.

Prokaryotes ____________________________________________________________.

Prokaryotes

Prokaryotic cells are generally __________________________ than eukaryotic cells.

The organisms we call _______________ are prokaryotes.

They have existed _______________________________

They contain ________________________

• Eukaryotes

Eukaryotic cells are generally __________________________________ than prokaryotic cells

Cells are ____________________________________

Most eukaryotic cells contain dozens of ___________________________________________.

They do ________________________________

There are many types of eukaryotes: ________________________________________________ _________________________

7.2 Cell StructureCell Organization

The eukaryotic cell can be divided into two major parts: the ____________________________.

The _________________________ is the fluid portion of the cell _________________________.

Prokaryotic cells have cytoplasm as well, even though they do not have a nucleus.

Many cellular structures act as if they are specialized organs. These structures are known as _______________________, literally “little organs.”

The Nucleus

In the same way that the main office controls a large factory, the nucleus is the _____________ ____________________________

The nucleus ____________________________ and, with it, the coded instructions for _____________________________________________________________________________

The ________________ is dotted with thousands of _______________, which allow material to ________________________________________________.

The nucleus is surrounded by a ___________________________________________________.

Like messages, instructions, and blueprints moving in and out of a main office, a steady stream of ___________________________________________________________________________ to and from the rest of the cell

________________________________ contain the genetic information that is passed from one generation of cells to the next.

Most of the time, the _____________________________ are spread throughout the _________ in the form of ___________________—a complex of DNA bound to proteins.

When a cell divides, its chromosomes condense and can be seen under a microscope

Most nuclei also contain a small, dense region known as the nucleolus.

The nucleolus is ___________________________________________

Vacuoles and Vesicles

Many cells contain _______________________________________________________ calledvacuoles ____________________________________________________________________.

In many ____________, there is a ______________________________ filled with liquid. The ________________________________________________________________, making it possible for plants to support heavy structures such as leaves and flowers.

Vacuoles are also found in some unicellular organisms and in ______________________

Nearly all eukaryotic cells contain smaller membrane-enclosed structures called ____________. Vesicles are used to _______________________________________________________, as well as to and from the cell surface

Lysosomes

Lysosomes are small organelles filled with ___________________________________________. Lysosomes perform the vital function of removing “junk” that might otherwise accumulate and clutter up the cell.

One function of lysosomes is __________________________________________________ into small molecules that can be used by the rest of the cell.

Lysosomes are also involved in ________________________ that have outlived their usefulness.

Biologists once thought that lysosomes were only found in ______________, but it is now clear that lysosomes are also found in a few specialized types of ______________________ as well.

The Cytoskeleton

______________________ and __________________ are two of the principal protein filaments that make up the ________________

Microfilaments are __________ structures made up of a protein called __________

They form extensive networks in some cells and produce a tough, flexible framework that ____________________________________.

Microfilaments also ______________________.

Microfilament assembly and disassembly is responsible for the cytoplasmic movements that allow cells, such as amoebas, to crawl along surfaces

Microtubules

Microtubules are hollow structures made up of proteins known as ______________

They play critical roles in maintaining _______________

Microtubules are also important in _________, where they form a structure known as the mitotic spindle, which helps ______________________________

In animal cells, structures known as _________ are also formed from tubulins.

Centrioles are located near the nucleus and help to organize _______________________

Centrioles are ____________________________-.

Microtubules help to build projections from the cell surface, which are known as _______ and __________, that enable cells to swim rapidly through liquids.

Microtubules are arranged in a “9 + 2” pattern.

Small cross-bridges between the microtubules in these organelles use chemical energy to pull on, or slide along, the microtubules, allowing cells to produce controlled movements.

Ribosomes

Ribosomes are small particles of ________________ found throughout the cytoplasm in _____.

Ribosomes _______________ by following coded instructions that come from _________

Each ribosome is like a small machine in a factory, turning out proteins on orders that come from its DNA “boss.”

Endoplasmic Reticulum

Eukaryotic cells contain an internal membrane system known as the endoplasmic reticulum, or ER.

The endoplasmic reticulum is where ______ components of the cell membrane are __________, along with _________ and other materials that are ________ from the cell.

The portion of the ER involved in the synthesis of proteins is called _______________________ _________, or rough ER. It is given this name because of the ____________________________.

Newly made proteins leave these ribosomes and are inserted into the rough ER, where they may be chemically modified.

The other portion of the ER is known as smooth endoplasmic reticulum (_______________) because ___________________________________________________.

In many cells, the smooth ER contains collections of enzymes that perform specialized tasks, including the _______________________________________________________________.

Golgi Apparatus

Proteins produced in the rough ER move next into the Golgi apparatus, which appears as a stack of flattened membranes.

The proteins are bundled into tiny vesicles that bud from the ER and carry them to the Golgi apparatus.

The Golgi apparatus ______________________________________________________ and other materials from the ER for storage in the cell or release outside the cell. It is somewhat like a customization shop, where the finishing touches are put on proteins before they are ready to leave the “factory.”

Organelles That Capture and Release Energy

All living things require a _____________________. Most cells are powered by food molecules that are built using energy from the sun.

_________________________ are both involved in energy conversion processes within the cell.

Chloroplasts

_______________ and some other organisms contain chloroplasts.

Chloroplasts are the biological equivalents of _______________. They capture ____________ __________________________ that contains chemical energy in a process called __________________________________

Two membranes surround chloroplasts.

Inside the organelle are large stacks of other membranes, which contain the green pigment chlorophyll.

Mitochondria

Nearly all eukaryotic cells, including plants, contain mitochondria.

Mitochondria are the __________________________. They _____________________________ ______________________________________________________________________________

Two membranes—an outer membrane and an inner membrane—enclose mitochondria. The inner membrane is folded up inside the organelle.

In humans, all or nearly all of our mitochondria come from the cytoplasm of the ovum, or egg cell. You get your mitochondria from Mom!

Chloroplasts and mitochondria contain their ________________________ in the form of small DNA molecules.

The _____________ theory suggests that chloroplasts and mitochondria may have _________ from independent microorganisms

Cellular Boundaries

Similarly, cells are surrounded by a barrier known as the cell membrane.

Many cells, including most prokaryotes, also produce a strong supporting layer around the membrane known as a cell wall.

The main function of the cell wall is to provide ________________________________________.

Prokaryotes, plants, algae, fungi, and many prokaryotes have cell walls. ____________________ cell walls.

Cell walls ______________________________ and most are porous enough to allow water, oxygen, carbon dioxide, and certain other substances to pass through easily.

Cell Membranes

All cells contain a cell membrane that _______________________________________________ and also protects and supports the cell

The composition of nearly all cell membranes is _______________________________________, which gives cell membranes a flexible structure and forms a strong barrier between the cell and its surroundings.

The Properties of Lipids

Many lipids have oily fatty acid chains attached to chemical groups that interact strongly with water.

The _________________ of such a lipid are hydrophobic, or “____________,” while the ____________________________________ is hydrophilic, or “_______________.”

When such lipids are mixed with water, their hydrophobic fatty acid “tails” cluster together while their hydrophilic “heads” are attracted to water. A lipid bilayer is the result

The _____ groups of lipids in a bilayer are ______________, while the _________________ form an oily layer inside the membrane from which _____________________________.

The Fluid Mosaic Model

Most cell membranes contain __________ molecules that are embedded in the lipid bilayer. Carbohydrate molecules are attached to many of these proteins.

__________ embedded in the lipid bilayer can ______________ and “float” among the lipids, and because so many different kinds of molecules make up the cell membrane, scientists describe the cell membrane as a “___________________.”

Some of the proteins form _______________________________ that help to move material across the cell membrane.

Many of ________________________ molecules act like ____________________________, allowing individual cells to identify one another

The Fluid Mosaic Model

Although many substances can cross biological membranes, some are too large or too strongly charged to cross the lipid bilayer.

If a substance is able to cross a membrane, the membrane is said to be ________________to it.

A membrane is impermeable to substances that ________________________________.

Most biological membranes are selectively permeable, meaning that ______________________ __________________________________. Selectively permeable membranes are also called ____________________________________________.