7-1 Life Is Cellular Copyright Pearson Prentice Hall.

7-1 Life Is Cellular

Copyright Pearson Prentice Hall

Figure 7.0 Fluorescent stain of cell

The Discovery of the Cell

Early MicroscopesIn 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.”Cells are the basic units of life.



Hooke’s Drawing of Cork Cells



The Cell TheoryIn 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.



Prokaryotes and Eukaryotes

Prokaryotes and EukaryotesCells come in a variety of shapes and sizes.All cells:

– are surrounded by a barrier called a cell membrane.

– at some point contain DNA.


Figure 7.4 A prokaryotic cell

Figure 7.4x1 Bacillus polymyxa

Figure 7.4x2 E. coli


Cells are classified into two 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.



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 prokaryotes.



– Eukaryotic cells contain a nucleus in which their genetic material is separated 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 eukaryotes.


7-1

The cell theory states that new cells are produced from

• nonliving material.• existing cells.• cytoplasm.• animals.


7-1

The person who first used the term cell was• Matthias Schleiden.• Lynn Margulis.• Anton van Leeuwenhoek.• Robert Hooke.


7-1

Which organism listed is a prokaryote? • protist• bacterium• fungus• plant


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One way prokaryotes differ from eukaryotes is that they

• contain DNA, which carries biological information.• have a surrounding barrier called a cell membrane.• do not have a membrane separating DNA from the rest of the cell.

• are usually larger and more complex.


Eukaryotic Cell Structures

Eukaryotic Cell StructuresStructures within a eukaryotic cell that perform important cellular functions are known as organelles.

Cell biologists divide the eukaryotic cell into two major parts: the nucleus and the cytoplasm.

The Cytoplasm is the portion of the cell outside the nucleus.


Eukaryotic Cell StructuresPlant Cell


Nuclear envelope

Ribosome (free)

Ribosome (attached)

Mitochondrion

Golgi apparatus

Vacuole

Nucleolus

NucleusSmooth endoplasmic reticulum

Rough endoplasmic reticulum

Cell wall

Cell membrane

Chloroplast

Eukaryotic Cell Structures


Smooth endoplasmic reticulum

Ribosome (free)

Ribosome (attached)

Golgi apparatus

Mitochondrion

Rough endoplasmic reticulum

Cell membrane

Nucleus

Nuclear envelope

Nucleolus

Centrioles

Animal Cell

Nucleus

Nucleus

The nucleus is the control center of the cell.

The nucleus contains nearly all the cell's DNA and with it the coded instructions for making proteins and other important molecules.


Nucleus

The Nucleus


Nucleolus Nuclear envelope

Nuclear pores

Chromatin

Ribosomes

RibosomesOne of the most important jobs carried out in the cell is making proteins.Proteins are assembled on ribosomes.Ribosomes are small particles of RNA and protein found throughout the cytoplasm.


Endoplasmic Reticulum


Ribosomes

Endoplasmic Endoplasmic ReticulumReticulum

There are two types of ER—rough and smooth.There are two types of ER—rough and smooth.

Golgi Apparatus

The Golgi apparatus appears as a stack of closely opposed membranes.


Vacuoles

In many plant cells there is a single, large central vacuole filled with liquid.


Vacuole

Vacuoles

Vacuoles are also found in some unicellular organisms and in some animals. The paramecium contains a contractile vacuole that pumps excess water out of the cell.


Contractile vacuole

Mitochondria and Chloroplasts

Mitochondria Nearly all eukaryotic cells contain mitochondria.Mitochondria convert the chemical energy stored in food into compounds that are more convenient for the cell to use.


Mitochondrion


Chloroplasts Plants and some other organisms contain chloroplasts.Chloroplasts capture energy from sunlight and convert it into chemical energy in a process called photosynthesis.


Chloroplast



Cytoskeleton

The cytoskeleton is a network of protein filaments that helps the cell to maintain its shape. The cytoskeleton is also involved in movement. The cytoskeleton is made up of:

• microfilaments• microtubules


CytoskeletonCytoskeleton


Ribosomes Mitochondrion

Endoplasmic reticulum

Cell membrane

Microtubule

Microfilament

Centrioles are located near the nucleus and help to organize cell division.


Cell Organelle Interactive

Plant and Animal Model Interactive

http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=cbd&wcsuffix=3072

7-2

In the nucleus of a cell, the DNA is usually visible as

• a dense region called the nucleolus.• the nuclear envelope.• granular material called chromatin.• condensed bodies called chloroplasts.


7-2

Two functions of vacuoles are storing materials and helping to

• break down organelles.• assemble proteins.• maintain homeostasis.• make new organelles.


7-2

Chloroplasts are found in the cells of • plants only.• plants and some other organisms.• all eukaryotes.• most prokaryotes.


7-2

Which of the following is NOT a function of the Golgi apparatus?

• synthesize proteins. • modify proteins.• sort proteins.• package proteins.


7-2

Which of the following is a function of the cytoskeleton?

• manufactures new cell organelles• assists in movement of some cells from one place to another

• releases energy in cells• modifies, sorts, and packages proteins


Unicellular Organisms: One cell carries out all life functions.


Colonial Organisms: Groups of single celled organisms live together. Larger size makes it harder for organisms to eat. All/most cells do most functions.


• Multicellular Organisms: Groups of specialized cells working together. The simplest multicellular organism:



But what is a slime mold?



Organization Within An Organism

• Nature has levels of organization

• Unique properties emerge at successively higher levels • Atoms are organized into molecules

• In multicelled species, cells are organized into tissues, organs, and organ systems

• All organisms consist of one or more cells

• Emergent properties: Life emerges at the cellular level

Levels of Organization

Levels of Organization

Microscopes

MicroscopesMicroscopes are devices that produce magnified images of structures that are too small to see with the unaided eye.


Microscopes

Light MicroscopesThe most commonly used microscope is the light

microscope.Light microscopes produce clear images of objects at a magnification of about 1000 times.



Microscopes

Compound light microscopes allow light to pass through the specimen and use two lenses to form an image.


Microscopes

Electron MicroscopesTo study even smaller objects, scientists use electron

microscopes.


Exploring the Cell

Electron MicroscopesElectron microscopes reveal details 1000 times smaller than those visible in light microscopes.

Electron microscopy can be used to visualize only nonliving, preserved cells and tissues.


Exploring the Cell

Transmission electron microscopes (TEMs)• Used to study cell structures and large protein molecules

• Specimens must be cut into ultra-thin slices


Exploring the Cell

Scanning electron microscopes (SEMs)• Produce three-dimensional images of cells• Specimens do not have to be cut into thin slices


Exploring the Cell


Scanning Electron Micrograph of Neurons

7-1

Electron microscopes are capable of revealing more details than light microscopes because

• electron microscopes can be used with live organisms.• light microscopes cannot be used to examine thin tissues.

• the wavelengths of electrons are longer than those of light.

• the wavelengths of electrons are shorter than those of light.


Estimating Field Diameter of a Microscope

(2) Line up major division

on opposite edge

(1) Set up so that the finely divided part overlaps one edge of the field

Field diameter= 0.52 mm

Estimating Field Diameter of a Microscope

(2) Line up major division

on opposite edge

(1) Set up so that the finely divided part overlaps one edge of the field

Field diameter= 0.52 mm

7-1 Life Is Cellular Copyright Pearson Prentice Hall.

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