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© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko
PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey
Chapter 4 A Tour of the Cell
Plans:
Day 1) Notes: 4.1-4.4/ HW Packet, Assign project and talk about cell cake
Day 2) Cards
Day 3) Cards
Day 4) Review cards
Day 5) Card Matching Game
Day 6) Quiz
Day 7) Cell Cake
Day 8) test
Do Now: What is life? Describe the characteristics of all living things.
1) Nutrition
2) Respiration
3) Regulation
4) Reproduction
5) Synthesis
6) Transport
7) Excretion
8) Growth
Introduction
Cells are the simplest collection of matter that can live.
Cells were first observed by Robert Hooke in 1665.
Working with more refined lenses, Antoni van Leeuwenhoek later described
– blood,
– sperm, and
– organisms living in pond water.
© 2012 Pearson Education, Inc.
Introduction
Since the days of Hooke and Leeuwenhoek, improved microscopes have vastly expanded our view of the cell.
© 2012 Pearson Education, Inc.
Figure 4.0_1
Introduction to the Cell The Nucleus and Ribosomes
The Endomembrane System
Energy-Converting Organelles
The Cytoskeleton and Cell Surfaces
Chapter 4: Big Ideas
The most frequently used
Light passes through a specimen, then through glass lenses, and finally light is projected into the viewer’s eye.
– Magnified up to 1,000 times
Magnification is the increase in the apparent size of an object.
Resolution is a measure of the clarity of an image. In other words, it is the ability of an instrument to show two close objects as separate.
Limited detail
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Figure 4.1B 10 m
1 m
100 mm (10 cm)
10 mm (1 cm)
1 mm
Human height
Length of some nerve and muscle cells
Chicken egg
Frog egg
Human egg Paramecium
100 µm
10 µm
1 µm
100 nm
10 nm
Most plant and animal cells
1 nm
0.1 nm
Nucleus Most bacteria Mitochondrion
Smallest bacteria Viruses
Ribosome
Proteins Lipids
Small molecules
Atoms
Una
ided
eye
Ligh
t mic
rosc
ope
Elec
tron
mic
rosc
ope
2) ELECTRON MICROSCOPE (EM)
How it works?
Maximum magnification?
limitiation?
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1950s, scientists started using them to view the ultrastructure of cells.
– Instead of light, EM uses a beam of electrons.
Electron microscopes can
– resolve biological structures as small as 2 nanometers and
– magnify up to 100,000 times.
– Specimen must be dead
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Scanning electron microscopes (SEM) study the detailed architecture of cell surfaces.
– An electron beam to scan the surface which is usually coated in gold,
– beam excites electrons on the surface
– an image is translated
Transmission electron microscopes (TEM) study the details of internal cell structure.
– Aims an electron beam through a thin section
– Section is stained with heavy metals
– Electrons that scatter create an image
– Uses electromagnets instead of lenses to bend pathway of electron, magnifying specimen
.
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In the 1800s, these studies led to cell theory, which states that
– all living things are composed of cells and
– all cells come from other cells. Cell size must
– be large enough to house DNA, proteins, and structures needed to survive and reproduce, but
– remain small enough to allow for a surface-to-volume ratio that will allow adequate exchange with the environment.
Figure 4.2A
3
3
1
1
Total volume
Total surface area Surface-to- volume ratio
2
54 units2
27 units3 27 units3
162 units2
6
6) PLASMA MEMBRANE (CELL MEMBRANE)
What is the cell membrane like? Where are the proteins?
How does it control the traffic of molecules across it?
What things pass over easily?
What things need help? How are they helped?
The plasma membrane forms a flexible boundary between the living cell and its surroundings.
Phospholipids form a two-layer sheet called a phospholipid bilayer in which
– hydrophilic heads face outward, exposed to water, and
– hydrophobic tails point inward, shielded from water.
Membrane proteins are
– attached to the membrane surface or
– embedded in the phospholipid bilayer.
Some proteins form channels or tunnels that allow ions and other hydrophilic/polar molecules through
O2 and CO2 are nonpolar and pass right over
Other proteins serve as pumps, using energy to actively transport molecules into or out of the cell.
© 2012 Pearson Education, Inc.
Figure 4.2B
Outside cell
Hydrophilic heads
Hydrophobic tails
Phospholipid Inside cell
Channel protein Proteins
Hydrophilic region of a protein
Hydrophobic region of a protein
7) PROKARYOTIC CELL
Types of organisms?
Common with eukaryotic cells?
Different?
What do they have on the outside?
Attach to other things?
Move?
What do they lack?
Bacteria and archaea
– Prokaryotic and eukaryotic cells have
– a plasma membrane
– chromosomes, ribosomes and cytoplasm
The DNA is coiled into a region called the nucleoid, but no membrane surrounds DNA
The surface of prokaryotic cells may
– be surrounded by a complex cell wall,
– have a capsule surrounding the cell wall,
– have short projections that help attach to other cells or the substrate,
– have longer projections called flagella (swim)
– no true membrane bound organelles.
© 2012 Pearson Education, Inc.
Figure 4.3
Fimbriae Ribosomes
Nucleoid
Plasma membrane
Cell wall
Capsule
Flagella A TEM of the bacterium Bacillus coagulans
Bacterial chromosome
A typical rod-shaped bacterium
Figure 4.3_1 Fimbriae
Ribosome
Nucleoid
Plasma membrane
Cell wall
Capsule
Flagella
Bacterial chromosome
A typical rod-shaped bacterium
Figure 4.3_2
Ribosome
Nucleoid
Plasma membrane
Cell wall
Capsule
A TEM of the bacterium Bacillus coagulans
8) EUKARYOTIC CELL
What does it have that is missing in prokaryotes?
What are the four functions?
How are they achieved?
membrane-bound nucleus and
number of other organelles.
The structures/organelles perform four basic functions.
1. The nucleus and ribosomes are involved in the genetic control of the cell.
2. The endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and peroxisomes are involved in the manufacture, distribution, and breakdown of molecules.
3. Mitochondria in all cells and chloroplasts in plant cells are involved in energy processing.
4. Structural support, movement, and communication between cells are functions of the cytoskeleton, plasma membrane, and cell wall.
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9) Plant and Animal Cell
What does an animal cell have that is missing in a plant?
What does a plant have that is missing in an animal?
What are the chemical reactions in the cell called?
What are the little organs called?
Organelles: are the small structures with specific functions
Cellular metabolism: the many chemical activities of cells, occurs within organelles
Animals only: Lysosomes and centrioles
Plant only: a rigid cell wall, chloroplasts, and a central vacuole.
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Figure 4.4A
Smooth endoplasmic reticulum
Rough endoplasmic reticulum
NUCLEUS: Nuclear envelope Chromatin Nucleolus
Ribosomes
Golgi apparatus
Mitochondrion
Plasma membrane
Peroxisome
CYTOSKELETON: Microtubule Intermediate filament Microfilament
Lysosome Centriole
NOT IN MOST PLANT CELLS:
Figure 4.4B
NUCLEUS: Nuclear envelope Chromatin Nucleolus
Golgi apparatus
Rough endoplasmic reticulum
Ribosomes
Peroxisome
Central vacuole
NOT IN ANIMAL CELLS:
Chloroplast Cell wall Plasmodesma
Mitochondrion
Plasma membrane
Cell wall of adjacent cell
Smooth endoplasmic reticulum
CYTOSKELETON: Microtubule Intermediate filament Microfilament
- contains most of the cell’s DNA and
– controls the cell’s activities by directing protein synthesis by making messenger RNA (mRNA).
DNA is associated with many proteins in structures called chromosomes. (46 for humans) / unorganized chromatin
The nuclear envelope
– is a double membrane
– has pores that allow material in and out
The nuclear envelope is attached to cellular membranes called the endoplasmic reticulum.
The nucleolus is
– a prominent structure in the nucleus
– the site of ribosomal RNA (rRNA) synthesis
© 2012 Pearson Education, Inc.
Figure 4.5
Two membranes of nuclear envelope
Nucleus
Chromatin Nucleolus
Pore
Endoplasmic reticulum
Ribosomes
Ribosomes are involved in the cell’s protein synthesis.
– Ribosomes are synthesized from rRNA produced in the nucleolus.
– Cells that must synthesize large amounts of protein have a large number of ribosomes.
– Free ribosomes are
– suspended in the cytoplasm
– make proteins that function in cytoplasm.
– Bound ribosomes are
– attached to the endoplasmic reticulum (ER)
– associated with proteins packed in organelles or exported
© 2012 Pearson Education, Inc.
Figure 4.6
Ribosomes ER Cytoplasm
Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes
Diagram of a ribosome Protein
mRNA
Colorized TEM showing ER and ribosomes
Many of the membranes within a eukaryotic cell are part of the endomembrane system Some are physically connected and some are
related by the transfer of membrane segments by tiny vesicles (sacs made of membrane). Many of these organelles work together in the
– synthesis, – storage, and – export of molecules.
The endomembrane system includes
– the nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, and the plasma membrane.
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Has ribosomes attached
Rough ER makes
– additional membrane
– ER ribosomes synthesize, modify, and package proteins to be transported to other organelles or secreted by cell
– Steps
1. Polypeptide synthesized by ribosomes according to mRNA, as it enters it takes on its 3D shape
2. Short sugars(address) added creating a glycoprotein
3. Packaged into a vesicle
4. Off to the Golgi
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Figure 4.8B
Transport vesicle buds off
mRNA
Ribosome
Polypeptide Glycoprotein
Rough ER
Sugar chain
Secretory protein inside trans- port vesicle
4
3
2
1
1. Produces enzymes important in the synthesis of lipids, oils, phospholipids, and steroids.
2. Other enzymes help process drugs, alcohol, and other potentially harmful substances.
3. Some smooth ER helps store calcium ions.
© 2012 Pearson Education, Inc.
Serves as a molecular warehouse and finishing factory for products (proteins) manufactured by the ER.
1. Products travel in transport vesicles from the ER to the Golgi apparatus.
2. One side of the Golgi apparatus functions as a receiving dock for the product and the other as a shipping dock.
3. Products are modified by enzymes as they go from one side of the Golgi apparatus to the other and travel in vesicles to other sites.
– Change sugars, add molecular tags like P to help sort proteins
© 2012 Pearson Education, Inc.
Figure 4.9
Golgi apparatus Golgi apparatus
Transport vesicle from the Golgi
“Shipping” side of Golgi apparatus
Transport vesicle from ER
“Receiving” side of Golgi apparatus
1
2
3
4
4
Membranous sac containing digestive enzymes.
– The enzymes and membrane are produced by the ER and transferred to the Golgi apparatus for processing.
– Safely isolate these potent enzymes
Digests food particles engulfed by a cell
1. A food vacuole binds with a lysosome.
2. The enzymes in the lysosome digest the food.
3. The nutrients are then released into the cell.
Remove or recycle damaged parts of a cell.
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Variety of functions.
– Food vacuole
– Some fresh water protists have contractile vacuoles that help to eliminate extra water
– In plants, vacuoles may
– have digestive functions,
– contain pigments, or
– contain poisons that protect the plant
– Large central vacuole
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Do not originate from EM system
Break down fatty acids to be used as fuel
In your liver, they detox alcohol
– an enzyme adds H to oxygen to make H2O2 or hydrogen peroxide
– Other enzymes then convert this toxic substance into a water
4.12 A review of the structures involved in manufacturing and breakdown
The following figure summarizes the relationships among the major organelles of the endomembrane system.
© 2012 Pearson Education, Inc.
Figure 4.12
Smooth ER
Nucleus
Transport vesicle from ER to Golgi
Golgi apparatus
Lysosome Vacuole Plasma membrane
Nuclear membrane
Rough ER
Transport vesicle from Golgi to plasma membrane
Carries out cellular respiration
Converts chemical energy in foods to chemical energy in ATP (adenosine triphosphate).
Mitochondria have two internal compartments.
1. The intermembrane space is the narrow region between the inner and outer membranes.
2. The mitochondrial matrix contains
– the mitochondrial DNA,
– ribosomes,
– many enzymes that catalyze some of the reactions of cellular respiration.
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Photosynthesizing organelles
Photosynthesis is the conversion of light energy from the sun to the chemical energy of sugar molecules.
Compartments.
– Between the outer and inner membrane is a thin intermembrane space.
– Inside the inner membrane is
– a thick fluid called stroma that contains the chloroplast DNA, ribosomes, and many enzymes and
– a network of interconnected sacs called thylakoids.
– In some regions, thylakoids are stacked like poker chips. Each stack is called a granum, where green chlorophyll molecules trap solar energy.
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Mitochondria and chloroplasts have
– DNA and
– ribosomes.
The structure of this DNA and these ribosomes is very similar to that found in prokaryotic cells.
The endosymbiont theory proposes that
– mitochondria and chloroplasts were formerly small prokaryotes and they began living within larger cells.
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Figure 4.15
Mitochondrion Nucleus
Endoplasmic reticulum Engulfing of
photosynthetic prokaryote
Chloroplast
Host cell
Mitochondrion
Host cell Engulfing of oxygen- using prokaryote
Some cells
A network of protein fibers, which functions in structural support and motility.
Motility and cellular regulation result when the cytoskeleton interacts with proteins called motor proteins.
The cytoskeleton is composed of three kinds of fibers.
1. Microfilaments (actin filaments) support the cell’s shape and are involved in motility.
2. Intermediate filaments reinforce cell shape and anchor organelles.
3. Microtubules (made of tubulin) give the cell rigidity and act as tracks for organelle movement.
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Figure 4.16
Actin subunit
Nucleus Nucleus
Microfilament Intermediate filament
Fibrous subunits
7 nm 10 nm
Tubulin subunits
Microtubule
25 nm
22)Cilia and Flagella
Function in multicellular organisms
Function in single celled eukaryotes (protists) and prokaryotes
Structure
multicellular organisms
– Cells that sweep mucus out of our lungs have cilia and animal sperm are flagellated
Protists and Prokaryotes
A flagellum, longer than cilia, propels a cell by an undulating, whiplike motion.
Cilia work more like the oars of a crew boat.
Structure
Both are made of microtubules wrapped in an extension of the plasma membrane.
A ring of nine microtubule doublets surrounds a central pair of microtubules. This arrangement is
– called the 9 + 2 pattern
– anchored in a basal body with nine microtubule triplets arranged in a ring.
Cilia and flagella move by bending motor proteins called dynein feet.
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Figure 4.17C
Outer microtubule doublet
Central microtubules
Radial spoke
Dynein proteins
Plasma membrane
4.18 CONNECTION: Problems with sperm motility may be environmental or genetic
In developed countries over the last 50 years, there has been a decline in sperm quality.
The causes of this decline may be
– environmental chemicals or
– genetic disorders that interfere with the movement of sperm and cilia. Primary ciliary dyskinesia (PCD) is a rare disease characterized by recurrent infections of the respiratory tract and immotile sperm.
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Animal cells synthesize and secrete an elaborate extracellular matrix (ECM) that
– helps hold cells together in tissues and
– protects and supports the plasma membrane.
The ECM may attach to a cell through glycoproteins that then bind to membrane proteins called integrins. Integrins span the plasma membrane and connect to microfilaments of the cytoskeleton.
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Figure 4.19
EXTRACELLULAR FLUID
CYTOPLASM Microfilaments of cytoskelton
Plasma membrane
Integrin
Connecting glycoprotein
Glycoprotein complex with long polysaccharide
Collagen fiber
Adjacent cells communicate, interact, and adhere through specialized junctions between them.
– Tight junctions prevent leakage of extracellular fluid across a layer of epithelial cells.
– Anchoring junctions fasten cells together into sheets.
– Gap junctions are channels that allow molecules to flow between cells.
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Figure 4.20 Tight junctions prevent fluid from moving between cells
Tight junction
Anchoring junction
Gap junction
Plasma membranes of adjacent cells
Extracellular matrix
A plant cell has a rigid cell wall that
– protects and provides skeletal support that helps keep the plant upright against gravity and
– is primarily composed of cellulose.
Plant cells have cell junctions called plasmodesmata that serve in communication between cells.
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Figure 4.21
Vacuole
Plant cell walls
Plasmodesmata
Cytoplasm
Primary cell wall Secondary cell wall Plasma membrane
4.22 Review: Eukaryotic cell structures can be grouped on the basis of four basic functions
Eukaryotic cell structures can be grouped on the basis of four functions:
1. genetic control,
2. manufacturing, distribution, and breakdown,
3. energy processing, and
4. structural support, movement, and communication between cells.
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You should now be able to
1. Describe the importance of microscopes in understanding cell structure and function.
2. Describe the two parts of cell theory.
3. Distinguish between the structures of prokaryotic and eukaryotic cells.
4. Explain how cell size is limited.
5. Describe the structure and functions of cell membranes.
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You should now be able to
6. Explain why compartmentalization is important in eukaryotic cells.
7. Compare the structures of plant and animal cells. Note the function of each cell part.
8. Compare the structures and functions of chloroplasts and mitochondria.
9. Describe the evidence that suggests that mitochondria and chloroplasts evolved by endosymbiosis.
© 2012 Pearson Education, Inc.
You should now be able to
10. Compare the structures and functions of microfilaments, intermediate filaments, and microtubules.
11. Relate the structure of cilia and flagella to their functions.
12. Relate the structure of the extracellular matrix to its functions.
13. Compare the structures and functions of tight junctions, anchoring junctions, and gap junctions.
© 2012 Pearson Education, Inc.
You should now be able to
14. Relate the structures of plant cell walls and plasmodesmata to their functions.
15. Describe the four functional categories of organelles in eukaryotic cells.
© 2012 Pearson Education, Inc.