Cell Structure and Function

Chapter 4

Initial Question: Describe three key features that all cells have in common.

• OBJECTIVES:

1. Cite the key features of the cell theory.

2. Analyze why all cell’s aren’t the same size

• STANDARDS:

Bio.A.1.2.1

3.1.10.A.1,8

• Mid 1600s - Robert Hooke observed and

described cells in cork

• Late 1600s - Antony van Leeuwenhoek

observed sperm, microorganisms

• 1820s - Robert Brown observed and

named nucleus in plant cells

Early Discoveries

Developing Cell Theory

• Matthias Schleiden

• Theodor Schwann

• Rudolf Virchow

Cell Theory

1) Every organism is composed of one or more

cells

2) Cell is smallest unit having properties of life

3) Continuity of life arises from growth and

division of single cells

• Smallest unit of life

• Can survive on its own or has potential to do so

• Is highly organized for metabolism

• Senses and responds to environment

• Has potential to reproduce

Cell

Structure of Cells

All start out life with:

–Plasma membrane

–Region where DNA

is stored

–Cytoplasm

Two types:

–Prokaryotic

–Eukaryotic

• Main component of cell membranes

• Gives the membrane its fluid properties

• Two layers of phospholipids

Lipid Bilayer

one layer

of lipids

one layer

of lipids Figure 4.3

Page 56

Membrane Proteins

Protein pump across

bilayer

Protein channel

across bilayer

Protein pump

Recognition protein

Receptor protein

extracellular environment

cytoplasm

lipid bilayer

Figure 4.4

Page 57

Why Are Cells So Small?

• Surface-to-volume ratio

• The bigger a cell is, the less surface area there is per unit volume

• Above a certain size, material cannot be moved in or out of cell fast

enough

• Create detailed images of something that is

otherwise too small to see

• Light microscopes

– Simple or compound

• Electron microscopes

– Transmission EM or Scanning EM

Microscopes

Limitations of Light Microscopy

• Wavelengths of light are 400-750 nm

• If a structure is less than one-half of a wavelength long, it will not be visible

• Light microscopes can resolve objects down to about 200 nm in size

Electron Microscopy

• Uses streams of accelerated electrons rather than light

• Electrons are focused by magnets rather than glass lenses

• Can resolve structures down to 0.5 nm

Initial Question: Distinguish between a prokaryotic cell and eukaryotic cell.

OBJECTIVES: 1. Contrast the general features of

prokaryotic and eukaryotic cells

2. Describe the nucleus of eukaryotes

with respect to structure and function.

3. Describe the organelles associated

with the endomembrane system, and tell the

general function of each.

4. Contrast the structure and function of

the mitochondria and chloroplasts.

STANDARDS:

Bio.A.1.2.1

3.1.10.A.1,8

• Archaebacteria and Eubacteria

• DNA is not enclosed in nucleus

• Generally the smallest, simplest cells

• No organelles

Prokaryotic Cells

Prokaryotic Structure

DNA

pilus

flagellum

cytoplasm

with ribosomes

capsule cell

wall

plasma

membrane

Eukaryotic Cells • Have a nucleus and other

organelles

• Eukaryotic organisms

–Plants

–Animals

–Protistans

–Fungi

Animal Cell Features

• Plasma membrane

• Nucleus

• Ribosomes

• Endoplasmic

reticulum

• Golgi body

• Vesicles

• Mitochondria

• Cytoskeleton Figure 4.10b

Page 61

Plant Cell Features

• Cell wall

• Central vacuole

• Chloroplast

• Plasma membrane

• Nucleus

• Ribosomes

• Endoplasmic

reticulum

• Golgi body

• Vesicles

• Mitochondria

• Cytoskeleton Figure 4.10a

Page 61

Initial Question: How do cells move? Explain!

OBJECTIVES: 1. Contrast the general features of

prokaryotic and eukaryotic cells

2. Describe the nucleus of eukaryotes

with respect to structure and function.

3. Describe the organelles associated

with the endomembrane system, and tell the

general function of each.

4. Contrast the structure and function of

the mitochondria and chloroplasts.

STANDARDS:

Bio.A.1.2.1

3.1.10.A.1,8

• Keeps the DNA molecules of eukaryotic cells separated from metabolic machinery of cytoplasm

• Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells

Functions of Nucleus

Components of Nucleus

nuclear envelope

nucleoplasm

nucleolus

chromatin

Figure 4.11b

Page 62

Nuclear Envelope

• Two outer membranes (lipid bilayers)

• Innermost surface has DNA attachment sites

Nuclear pore bilayer facing cytoplasm Nuclear envelope

bilayer facing nucleoplasm

Figure 4.12b

Page 63

• Group of related organelles in which lipids are assembled and new polypeptide chains are modified

• Products are sorted and shipped to various destinations

Cytomembrane System

Components of Cytomembrane System

Endoplasmic reticulum

Golgi bodies

Vesicles

Endoplasmic Reticulum

• In animal cells, continuous with nuclear

membrane

• Extends throughout cytoplasm

• Two regions - rough and smooth

Golgi Body • Puts finishing touches on proteins and

lipids that arrive from ER

• Packages finished material for shipment to final destinations

• Material arrives and leaves in vesicles

budding vesicle

Figure 4.15

Page 65

Vesicles

• Membranous sacs that

move through cytoplasm

• Lysosomes

• Peroxisomes

• ATP-producing powerhouses

• Membranes form two distinct

compartments

• ATP-making machinery embedded in

inner mitochondrial membrane

Mitochondria

Mitochondrial Origins

• Mitochondria resemble bacteria

–Have own DNA, ribosomes

–Divide on their own

• May have evolved from ancient bacteria that were engulfed but not digested

Ticket Out the Door

• Briefly characterize the structure and function of the nucleus, nuclear envelope, and nucleolus.

Initial Question: Why does the mitochondria have its own DNA? Put the answer in the tray.

OBJECTIVES: 1. Contrast the structure and function of the

mitochondria and chloroplasts.

2. Describe the cytoskeleton of eukaryotes

and distinguish it from the endomembrane

system.

STANDARDS:

Bio.A.1.2.1

3.1.10.A.1,8

• Plastids

• Central Vacuole

Specialized Plant Organelles

Chloroplasts

Convert sunlight energy to ATP through photosynthesis

Other Plastids

• Chromoplasts

–No chlorophyll

–Abundance of carotenoids

–Color fruits and flowers red to yellow

• Amyloplasts

–No pigments

– Store starch

• Present in all eukaryotic cells

• Basis for cell shape and internal organization

• Allows organelle movement within cells and, in some cases, cell motility

Cytoskeleton

Cytoskeletal Elements

microtubule

microfilament

intermediate filament

Microtubules

• Largest elements

• Composed of tubulin

• Arise from microtubule

organizing centers (MTOCs)

• Involved in shape, motility, cell

division

Figure 4.21

Page 71

tubulin subunit

Microfilaments

• Thinnest elements

• Composed of actin

• Take part in movement,

formation, and

maintenance of cell shape actin subunit

Figure 4.21

Page 71

Intermediate Filaments

• Only in animal cells

of certain tissues

• Most stable

cytoskeletal

elements

• Six known groups

one polypeptide chain

Figure 4.21

Page 71

Motor Proteins

• Kinesins and dyneins move along

microtubules

• Myosins move along microfilaments

kinesin

microtubule

Figure 4.24b, Page 72

Initial Question: What is ATP and why do cells (especially your muscle cells) need ATP? Put your answer in the tray.

OBJECTIVES: 1. Describe the cytoskeleton of eukaryotes and

distinguish it from the endomembrane

system.

2. Describe several surface structures of cells

and tell how they help cells to survive.

STANDARDS:

Bio.A.1.2.1

3.1.10.A.1,8

Flagella and Cilia

• Structures for cell

motility

• 9 + 2 internal

structure

dynein

microtubule

Figure 4.25

Page 73

Plant Cell Walls

Primary cell wall

Secondary cell wall

(3 layers)

Plant Cuticle

• Cell secretions and waxes accumulate at plant cell surface

• Semitransparent

• Restricts water loss

Matrixes between Animal Cells

• Animal cells have no cell walls

• Some are surrounded by a matrix of cell

secretions and other material

Cell-to-Cell Junctions

• Plants

–Plasmodesmata • Animals

– Tight junctions

–Adhering junctions

–Gap junctions

plasmodesma

Animal Cell Junctions

tight

junctions

adhering

junction

gap

junction

Fishbowl

• Write down one question about a concept that you are unsure of or don’t understand.

Initial Questions:

• What is tubulin ?

• Name the cytoskeleton component that is made of tubulin.

• What is the function of the ER?

OBJECTIVES: 1. Describe the cytoskeleton of eukaryotes and distinguish it from the

endomembrane system.

2. Describe several surface structures of cells and tell how they help cells to survive.

3. Contrast the structure and function of the mitochondria and chloroplasts.

4. Contrast the general features of prokaryotic and eukaryotic cells

5. Describe the nucleus of eukaryotes with respect to structure and function.

6. Describe the organelles associated with the endomembrane system, and tell the general function of each.

7. Contrast the general features of prokaryotic and eukaryotic cells

8. Describe the nucleus of eukaryotes with respect to structure and function.

9. Describe the organelles associated with the endomembrane system, and tell the general function of each.

STANDARDS: Bio.A.1.2.1 3.1.10.A.1,8

Ticket Out the Door

• Write down one item that you learned from the video.