CellsThe smallest unit of life

Which of these is the smallest object?

1 2 3 4 5

20% 20% 20%20%20%

1. Human cell2. Protein molecule3. Virus4. Bacteria5. Amino acid

Prokaryotic organisms lack a nucleus in their cells. Which of these organisms is prokaryotic?

1 2 3 4

25% 25%25%25%

1. Plants2. Fungi3. Protists (such as

Amoeba and Paramecium)

4. Bacteria

Which of these objects can be seen with the aid of an ordinary student microscope?

1 2 3 4

25% 25%25%25%

1. Human cell2. Virus3. Protein molecule4. Oxygen atom

Which of these is made up of cells?

1 2 3 4 5 6

17% 17% 17%17%17%17%1. Animals2. Plants3. Fungi4. Bacteria5. Only animals and

plants6. All of these

Discovering the Cell

1665 - Robert Hooke

Anton van Leeuwenhoek - late

17th, early 18th centuries

• 1839 – Cell Theory is proposed independently by Theodore Schwann and Matthias Jakob Schleiden.

• Cell Theory:

• The cell is the fundamental structure of all living things.

• All living things are made of cells.

• Cells arise from pre-existing cells through cell division.

Ernst Ruska - 1938

Light micrograph

Scanning electron micrograph

Paramecium

Cell Membrane

Transmission electron micrograph

Scanning electron micrograph

Which of these can be seen with an electron microscope but not a light microscope?

1 2 3 4

25% 25%25%25%

1. Human cells2. Bacteria3. Protein

molecules4. Amino acids

• Discuss and write down your ideas:

• How did the invention of the microscope change the human view of the world?

• How did the invention of the electron microscope change our understanding of cells?

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TOGETHER

Prokaryotic Cells

Prokaryotic Features

• No membrane-bound organelles, such as a nucleus.

• DNA in one large ring-shaped chromosome

• An enormous variety of metabolic pathways.

• Highly successful and adaptable.

External structure

Coccus (spherical)

Spirillus (spiral) Bacillus (rod-shaped)

Internal Structurechromosome(nucleoid region)

plasmid (DNA)cytosol

plasma membrane

cell wall

capsule orslime layer

prokaryoticflagellum

food granule

ribosomes

pili

True or False: A virus is a kind of bacteria.

1 2

50%50%1. True2. False

Viruses• A virus is usually

not considered living.

• A virus consists only of a protein coat (sometimes with a lipid outer layer) and a piece of genetic material (DNA or RNA).

Bacteria vs. Virus

FeaturesBacteri

aVirus

Reproduces independently?

Has genetic material?

Has cell membrane?

Has metabolism?

Living?

Yes No

Yes

Yes

Yes

Yes

No

No

No

Yes

Which of these does a bacteria NOT have?

1 2 3 4

25% 25%25%25%1. DNA2. Cell membrane3. Nucleus4. Bacteria have

none of these.

Eukaryotic Cells

Eukaryotic Features

• Cells contain membrane-bound organelles.

• Nucleus holds multiple strands of DNA, which condense into chromosomes during cell division.

• May be single-celled or multi-cellular organisms.

Figure 4-3 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

smoothendoplasmicreticulum

mitochondrion

cytosol

lysosome

ribosomes onrough ER

centriole

Golgi apparatus

vesicle

nuclear pore

nuclear envelope

chromatin (DNA)

nucleolus

plasmamembrane

rough endoplasmicreticulum

free ribosome

nucleus

Animal cell

Figure 4-9a Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

nuclearpores

nuclearenvelope

chromatin

nucleolus

Nucleus

vesicles

rough ER

smooth ER

ribosomes

Endoplasmic Reticulum

Figure 4-13 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

Protein-carryingvesicles from ERmerge with Golgiapparatus

Golgiapparatus

Vesicles carryingmodified proteinleave Golgi apparatus

Golgi Apparatus

Figure 4-14 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

1 A protein issynthesized in the rough ER.

5 Vesicles merge with theplasma membrane andrelease protein byexocytosis.

4 Completed proteinis packaged intovesicles.

3 Vesicles fuse with Golgi. The protein may be altered and finished.

2 Protein is packagedinto vesicles and travelsto Golgi apparatus.

ER and Golgi function

A cell that produces a lot of protein must have an

extensive:

1 2 3 4

25% 25%25%25%

1. Nucleus2. Rough ER3. Smooth ER4. Golgi apparatus

Proteins are packaged for delivery by the:

1 2 3

33% 33%33%

1. Nucleus2. Rough ER3. Golgi apparatus

• Discuss and summarize in your own words the roles of:

• the cell nucleus

• the rough ER

• the Golgi complex

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Lysosomes

ER, Golgi, & Lysosome Function after Phagocytosis

Figure 4-15 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

1 Enzymes aresynthesized in ER.

plasmamembrane waste

ERERdigestiveenzymes

foodvacuole

lysosome

Golgi

nucleus

4 Lysosome fuses withfood vacuole andenzymes digest food.

3 Lysosomes budfrom Golgi.

2 Golgi modifiesenzymes.

Mitochondrion

cristae

outermembrane

innermembrane

intermembranecompartment

0.2 micrometer

matrix

White blood cells must locate, engulf, and destroy many foreign particles. Which organelle

will help them most in this task?

1 2 3 4

25% 25%25%25%

1. Nucleus2. Lysosome3. Endoplasmic

reticulum4. Golgi bodies

• Discuss and summarize in your own words the roles of the lysosome and the mitochondrion in animal cell nutrition.

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TOGETHER

Figure 4-3 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

smoothendoplasmicreticulum

mitochondrion

cytosol

lysosome

ribosomes onrough ER

centriole

Golgi apparatus

vesicle

nuclear pore

nuclear envelope

chromatin (DNA)

nucleolus

plasmamembrane

rough endoplasmicreticulum

free ribosome

nucleus

Animal cell

True or false: Plant cells are much more primitive than animal cells and have far fewer types of

organelles.

1 2

50%50%

1. True2. False

Plant cells are:

1 2

50%50%

1. Eukaryotic2. Prokaryotic

Plant Cell - same organelles as an animal cell, plus a few more

ribosomes free ribosome

nuclear pore

nuclear envelope

chromatin (DNA)

nucleolusnucleus

smoothendoplasmicreticulum

vesicle

roughendoplasmicreticulum

Golgi apparatus

choloroplastmitochondrionplastid

plasmamembrane

plasmodesma

cell wall

central vacuole

cytosol

Cell Wall

secondarycell wall

middlelamella

plasmamembrane

primarycell wall

• How is the cell wall of plant cells similar to an animal’s skeleton? How is it different?

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Chloroplast

thylakoid

outermembrane

innermembrane

channelinterconnecting

thylakoids

1 micrometer

stroma

granum(stack of thylakoids)

Leucoplasts and other plastids

starchglobules

0.5 micrometer

plastid

What do chloroplasts do?

1 2 3

33% 33%33%

1. Make energy2. Use energy to

make molecules.3. Break sugar

down to release energy.

• Chloroplasts carry out photosynthesis to make sugars and other monomers. What does the plant use these monomers for?

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One-celled Eukaryotic organisms have unique challenges.

A Paramecium must:

ingest food

excrete waste

sense and respond to the environment

(a) Cilium

(b) Flagellum

propulsion of fluid

return strokepower strokeplasma membrane

direction of locomotion propulsion of fluid

continuous propulsion

ciliumParamecium0.1 micrometer

protein"arms"

central pair ofmicrotubules

section of cilium(transmission EM)

basal body

plasma membrane

contractilevacuole

full reservoir

contracted reservoir

pore

collectingducts

centralreservoir

Reservoir contracts, expellingwater through pore.

Water enters collecting ducts,fills central reservoir.

• In a one-celled organism, which organelle is most like:

• A stomach (assists with digestion)?

• A kidney (removes excess water)?

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Recap

• Prokaryotic cells have no membrane-bound organelles.

• Eukaryotic cells have membrane-bound organelles, which compartmentalize processes for better efficiency.

• ALL cells have a cell membrane and DNA.