1. The smallest part of you
Chapter 3: Cells
Learning Objectives
lymphocyte
what is a cell ?
Know the two general types of cells
Describe endosymbiosis theory
Describe nine organelles in eukaryotic cells.
Differences between plant and animal cells
Yeast cell
The smallest part of you

2. Robert Hooke, a British scientist, mid-1600s All cells contain DNA.
The cell: the smallest unit of life that can function independently and perform all functions of life, including reproducing.
Robert Hooke, a British scientist, mid-1600s
All cells contain DNA.
The only cell which does not contain DNA: ___
So for all practical purposes the statement “all cells contain DNA” is true
The only cell which does not have DNA is Red blood cells. It has a nucleus in the beginning but after maturation it loses its nuclues
Where do we begin if we want to understand how organisms work?
Given their complexity, this task can be daunting. Fortunately, as with most complex things, a strategy of divide-and-conquer comes in handy. In the case of organisms, whether we are studying a creature as small as a flea or as large as an elephant or giant sequoia, they can be broken down into smaller units that are more easily studied and understood (Figure 3-1 What do these diverse organisms have in common? Cells).
The most basic unit of any organism is the cell, the smallest unit of life that can function independently and perform all the necessary functions of life, including reproducing itself. Understanding cell structure and function is the basis for our understanding of how complex organisms are organized.

3. Scanning Electron Micrograph Transmission Electron Micrograph
How to see a cell?
Paramecium
Light Microscope
Light Micrograph
Scanning Electron Micrograph
Transmission Electron Micrograph

4. How to See a Cell Largest Cell: _________
To see a cell, you don’t have to work in a lab or use a microscope: Just open your refrigerator. Chances are you’ve got a dozen or so visible cells in there: eggs.
Although most cells are too small to see with the naked eye, there are a few exceptions, including hens’ eggs from the supermarket, each of which is an individual cell.
The ostrich egg, weighing about three pounds, is the largest of all cells.
In addition to being among the largest cells around, eggs are also the most valuable.
Almas caviar, eggs from the beluga sturgeon, sells for nearly $700 per ounce.
This value is exceeded only by that of human eggs which currently fetch as much as $25,000 for a dozen or so eggs on the open market (Figure 3-2 Not all cells are tiny).  (Human sperm cells command only about a penny per 20,000 cells!)
Most cells are much smaller than hens’ eggs and ostrich eggs. Consider that at this very moment there are probably more than seven billion bacteria in your mouth—even if you just brushed your teeth! This is more than the number of people on earth. It is possible to squeeze so many in there because most cells are really, really tiny—so tiny that 2,000 red blood cells, lined up end to end, would just extend across a dime.
A foot-long egg you say? No way! It’s true, I say!! Big enough to hold 8 ostrich eggs or 180 chicken eggs or 12,000 hummingbird eggs. by Curtis C. Ebbesmeyer
Largest Cell: _________

5. Cell Theory All living organisms are made up of one or more cells.
All cells arise from other pre-existing cells.
By 1830s scientists discovered the central role of cells in biology. The facts that 1) all living organisms are made up of one or more cells, and 2) all cells arise from other pre-existing cells, are the foundations of cell theory, one of the unifying theories in biology, and one that is universally accepted by all biologists.
As we will see in Chapter 10, the origin of life on earth was a one-time deviation from cell theory: the first cells on earth likely originated from free-floating molecules in the oceans early in earth’s history (about three-and-a-half billion years ago). Since that time, however, all cells and thus all life have been produced as a continuous line of cells, originating from these initial cells.
In this chapter, we investigate the two different kinds of cells that make up all of the organisms on earth, the processes by which cells control how materials move into and out of the cell, and how cells communicate with each other. We also explore some of the important landmarks found in many cells. We also look at the specialized roles these structures play in a variety of cellular functions and learn about some of the health consequences that occur when they malfunction.

6. Two types of cells. Prokaryotic cell. Eukaryotic cell Size. Nucleus
Two types of cells Prokaryotic cell Eukaryotic cell Size Nucleus Organelles
Although there are millions of diverse species on earth, billions of unique organisms alive at any time, and trillions of different cells in many of those organisms, every cell on earth falls into one of two basic categories:
A eukaryotic cell (from the Greek for “true nucleus”) has a central control structure called a nucleus, which contains the cell’s DNA. Organisms composed of eukaryotic cells are called eukaryotes.

7. Prokaryotes have four basic structural features:
1) A plasma membrane encompasses the cell. For this reason, anything inside the plasma membrane is referred to as intracellular, while everything outside of the plasma membrane is extracellular.
2) The cytoplasm is the jelly-like fluid that fills the inside of cell.
3) Ribosomes are little granular bodies where proteins are made; thousands of them are scattered throughout the cytoplasm.
4) Each prokaryote has one or more circular loops or linear strands of DNA.
In addition to the characteristics common to all prokaryotes, some prokaryotes have additional unique features. Many have a rigid cell wall, for example, that protects and gives shape to the cell. Some have a slimy, sugary capsule as their outermost layer. This sticky outer coat provides protection and enhances the prokaryotes’ ability to anchor themselves in place when necessary.
Many prokaryotes have a flagellum, a long, thin, whip-like projection that rotates like a propeller and moves the cell through the medium in which it lives. Other appendages include pili, much thinner, hair-like projections that help prokaryotes attach to surfaces.

9. What do all these cells have in common?
have cell membrane
have DNA
have cytoplasm
contain ribosomes

10. Prokaryotes in the News
Escherichia coli
Food poisoning
Salmonella enteritidis
Rod shaped, gram negative

11. Current News: Antibiotic Resistant Bacteria
MRSA: Methicillin Resistant Staphylococcus aureus
National Institute of Health (NIH) Superbug: CRK
These relatively new, highly resistant strains of bacteria—carbapenem resistant Gram negative bacteria as Klebsiella and Acinetobacter—are not just at NIH. This is a widespread problem throughout much of the country
Carbapenem Resistant Klebsiella

12. Beneficial bacteria
You can use your own examples of beneficial bacteria. It is to give the students an idea of the beneficial bacteria as they hear more about the harmful ones
Use a bacterial cell for inserting a foreign gene into a cell

13. Which of the following is NOT found in ALL cell types?
Ribosomes
Mitochondria
DNA
Cytoplasm
Cell Membrane
Ans:B

14. 3.3 Eukaryotic cells have compartments with specialized functions called organelles
In the two billion years that eukaryotes have been on earth, they have evolved into some of the most dramatic and interesting creatures, such as platypuses, dolphins, giant sequoias, and the Venus flytrap. Not all eukaryotes are multicellular, however. Many fungi are unicellular, and the Protista (or protists) are a huge group of eukaryotes, nearly all of which are single-celled organisms visible only with a microscope.
Eukaryotic cells are about 10,000 times larger than prokaryotic cells in volume. They possess numerous structural features that make it easy to distinguish eukaryotes from prokaryotes under a microscope (Figure 3-6). Chief among the distinguishing features of eukaryotic cells is the presence of a nucleus, a membrane enclosed structure that contains linear strands of DNA. In addition to a nucleus, eukaryotic cells usually contain in their cytoplasm several other specialized structures. Many of these structures, called organelles, are enclosed separately by their own lipid membranes.

15. STRUCTURES FOUND IN BOTH CELLS
THE ANIMAL CELL: BASIC STRUCTURE
THE PLANT CELL: BASIC STRUCTURE
STRUCTURES FOUND IN BOTH CELLS
Nucleus
Plasma membrane
Ribosomes
Mitochondria
Rough endoplasmic
reticulum
Smooth endoplasmic
Cytoplasm
Cytoskeleton
Golgi apparatus
Lysosome
STRUCTURE
NOT FOUND
IN PLANT CELLS
Centriole
STRUCTURES
IN ANIMAL CELLS
Chloroplast
Cell wall
Vacuole (occasionally
found in animal cells)
FIGURE 3-6 Structures found in animal and plant cells.
Figure 3-6 (Structures found in animal and plant cells.) illustrates a generalized animal cell and a generalized plant cell.
Because they share a common, eukaryotic ancestor, they have much in common.
Both can have a plasma membrane, nucleus, cytoskeleton, ribosomes, and a host of membrane-bound organelles including rough and smooth endoplasmic membranes, Golgi apparatus, and mitochondria.
Animal cells have centrioles, which are not present in most plant cells.
Plant cells have a rigid cell wall (as do fungi and many protists), and chloroplasts (also found in some protists).
Plants also have a vacuole, a large central chamber (occasionally found in animal cells).
We explore each of these plant and animal organelles in detail later in this chapter.

16. Endosymbiosis Theory Explains the
presence of chloroplasts in plants and algae, and
Presence of mitochondria in plants and animals.
When you compare a complex eukaryotic cell to the structurally simple prokaryotic cell, it’s hard not to wonder how eukaryotic cells came about. How did they get filled up with so many organelles?
We can’t go back two billion years to watch the initial evolution of eukaryotic cells, but we can speculate about how it might have occurred.
One very appealing idea, called the endosymbiosis theory, has been developed to explain the presence of two organelles in eukaryotes, chloroplasts in plants and algae and mitochondria in plants and animals. Chloroplasts help plants and algae convert sunlight into a more usable form of energy. Mitochondria help plants and animals to harness the energy stored in food molecules.
According to the theory of endosymbiosis, two different types of prokaryotes may have come to have close partnerships with each other.
For example, some small prokaryotes capable of performing photosynthesis (the process by which plant cells capture the light energy from the sun and transform it into the chemical energy stored in food molecules) may have come to live inside a larger “host” prokaryote.
The photosynthetic “boarder” may have made some of the energy from its photosynthesis available to the host.
Chloroplast came from cyanobacteria
Mitochondria came from aerobic bacteria

17.  ENDOSYMBIOSIS INVAGINATION Organelles may have developed
ANCESTRAL EUKARYOTE
ANCESTRAL
EUKARYOTE
ANCESTRAL
PROKARYOTE
proficient at converting
food and oxygen into
energy
DNA
Plasma membrane 1
Plasma membrane
folds in on itself.
Inner compartments
(organelles) are
formed. 1
Ancestral eukaryote
engulfs prokaryote.
And prokaryote
merge.
Over time, the engulfed
prokaryote evolves into
an organelle, such as a
mitochondrion or a
chloroplast.
Nucleus
Rough
endoplasmic
reticulum 2 2
Mitochondrion
FIGURE 3-7 How did eukaryotic cells become so structurally complex? Two theories.
After a long while, the two cells may have become more and more dependent on each other until neither cell could live without the other, and they became a single, more complex organism.
Eventually, the photosynthetic prokaryote evolved into a chloroplast, the organelle in plant cells in which photosynthesis occurs.
A similar scenario might explain how a prokaryote unusually efficient at converting food and oxygen into easily usable energy might take up residence in another prokaryote and evolve into a mitochondrion, the organelle in plant and animal cells that converts the energy stored in food into a form usable by the cell (Figure 3-7 How did eukaryotic cells become so structurally complex?). 
The idea of endosymbiosis is supported by several observations.
Chloroplasts and mitochondria are similar in size to prokaryotic cells.
Chloroplasts and mitochondria have small amounts of circular DNA, similar to the organization of DNA in prokaryotes and in contrast to the linear DNA strands found in the eukaryote’s nucleus.
Chloroplasts and mitochondria divide by splitting, just like prokaryotes.
Chloroplasts and mitochondria have internal structures called ribosomes, which are similar to those found in bacteria.
In addition to the theory of endosymbiosis as an explanation for the existence of chloroplasts and mitochondria, another theory about the origin of organelles in eukaryotes is the idea that the plasma membrane around the cell may have just folded in on itself (a process called invagination) to create the inner compartments, which subsequently became modified and specialized (see Fig. 3-7). It may turn out that organelles arose from both processes. Perhaps mitochondria and chloroplasts originated from endosymbiosis, while all of the other organelles arose from plasma membrane invagination. We just don’t know. 3 
Organelles may have developed
by endosymbiosis or invagination
or a combination of the two.

18. 3.13 The nucleus is the cell’s genetic control center.
The nucleus—the largest and most prominent organelle in most eukaryotic cells.
The nucleus has two primary functions:
genetic control center
storehouse for hereditary information
 The nucleus is the largest and most prominent organelle in most eukaryotic cells. In fact, the nucleus is generally larger than any prokaryotic cell.
If a cell were the size of a large lecture hall or movie theater, the nucleus would be the size of a big rig 18-wheeler truck parked in the front rows.
The nucleus has two primary functions, both related to the fact that most of the cell’s DNA resides in the nucleus. First, the nucleus is the genetic control center, directing most cellular activities by controlling which molecules are produced and in what quantity they are produced. Second, the nucleus is the storehouse for hereditary information. 18

19. Mitochondria (singular: mitochondrion) are the cell’s all-purpose energy converters, and they are present in virtually all plant cells, animal cells, and every other eukaryotic cells.
Although we consume a variety of foods, our mitochondria allow us to convert the energy contained within the chemical bonds of the carbohydrates, fats, and proteins in food into carbon dioxide, water, and ATP, the molecule that is the energy source all cells use to fuel all their functions and activities.
Because this energy conversion requires a significant amount of oxygen, organisms’ mitochondria consume most of the oxygen used by each cell. In humans, for example, our mitochondria consume as much as 80% of the oxygen we breathe. They give a significant return on this investment by producing about 90% of the energy our cells use to function. 19

20. Did you know that we all have more DNA from one parent than the other?
Who is the bigger contributor:
mom or dad?
Why?
We’re always taught that our mothers and fathers contribute equally to our genetic composition, but this isn’t quite true because the mitochondria in every one of your cells (and the DNA that comes with them) come from the mitochondria that are initially present in your mother’s egg, which, when fertilized by your father’s sperm, developed into you. In other words: all of your mitochondria came from your mother.
The tiny sperm contributes DNA, but no cytoplasm and hence, no mitochondria. Consequently, mitochondrial DNA is something that we inherit exclusively from our mothers. 20

21. Lysosomes
round, membrane-enclosed, acid-filled vesicles that function as garbage disposals
Lysosomes are round, membrane-enclosed, acid-filled vesicles that function as garbage disposals. Lysosomes are filled with about 50 different digestive enzymes and a super-acidic fluid, a corrosive broth so powerful that if a lysosome were to burst, it would almost immediately kill the cell by rapidly digesting all of its component parts.
The selection of enzymes represents a broad spectrum of chemicals designed for dismantling macromolecules no longer needed by cells or generated as by-products of cellular metabolism.
Some of the enzymes break down lipids, others carbohydrates, others proteins, and still others nucleic acids.
Consequently, lysosomes are frequently also a first step when, via phagocytosis, a cell consumes and begins digesting a particle of food or even an invading bacterium. And, ever the efficient system, most of the component parts of molecules that are digested, such as amino acids, are released back into the cell where they can be re-used by the cell as raw materials. 21

22. Lysosomal Diseases Tay Sach’s Disease: Undigested lipids
(affects nerve cells)
Pompe’s disease:
Undigested glycogen
(muscle cells)
With 50 different enzymes necessary for lysosomes to carry out their metabolic salvaging act, malfunctions sometimes occur. A common genetic disorder called Tay-Sachs disease is the result of just such a genetic mishap.
In Tay-Sachs disease, an individual inherits an inability to produce a critical lipid-digesting enzyme. Because the lysosomes cannot digest certain lipids, they continue to be sent to the lysosome where they accumulate, undigested.

23. 3.18 In the Endoplasmic reticulum, cells build proteins and disarm toxins
The information for how to construct the molecules essential to a cell’s smooth functioning and survival is stored on the DNA found in the cell’s nucleus. The energy used to construct these molecules and to run cellular functions comes primarily from the mitochondria. The actual production and modification of biological molecules, however, occurs in a system of organelles called the endomembrane system (Figure The endomembrane system: the smooth endoplasmic reticulum, rough endoplasmic reticulum, and Golgi apparatus).
This mass of interrelated membranes spreads out from and surrounds the nucleus, forming chambers within the cell that contain their own mixture of chemicals. The endomembrane system takes up as much as one-fifth of the cell’s volume and is responsible for many of the fundamental functions of the cell. Lipids are produced within these membranes, products for export to other parts of the body are modified and packaged here, and polypeptide chains are assembled into functional proteins here, and many of the toxic chemicals that find their way into our bodies—from recreational drugs to antibiotics—are broken down and neutralized in the endomembrane system.
Because the process of protein production follows a somewhat linear path, we explore the endomembrane system sequentially, beginning just outside the nucleus with the endoplasmic reticulum. 23

24. Rough Endoplasmic Reticulum modifies proteins
Perhaps the organelle with the most cumbersome name, the rough endoplasmic reticulum or rough ER (from the Greek words for a “within-cell network”), is a large series of interconnected, flattened sacs (they look like a stack of pancakes) that are connected directly to the nuclear envelope. In most eukaryotic cells, the rough ER almost completely surrounds the nucleus (Figure The rough endoplasmic reticulum is studded with ribosomes).  It is called “rough” because its surface is studded with little bumps. These bumps are protein-making machines called ribosomes, and generally cells with high rates of protein production have large numbers of ribosomes. We cover the details of ribosome structure and protein production in Chapter 5.
The primary function of the rough ER is to fold and package proteins that will be shipped elsewhere in the organism. Poisonous frogs, for example, package their poison in rough ER of the cells in which it is produced before transporting it to the poison glands on their skin. Proteins that are used within the cell itself are generally produced on free-floating ribosomes in the cytoplasm. 24

25. The Smooth Endoplasmic Reticulum Lipid synthesis, detoxification25

26. The Golgi apparatus, which is not connected to the endoplasmic reticulum, is a flattened stack of membranes (each of which is called a Golgi body) that are not interconnected.
(Figure Golgi apparatus: processing of molecules synthesized in the cell and packaging of those molecules destined for use elsewhere in the body.)
After transport vesicles bud from the endoplasmic reticulum, they move through the cytoplasm until they reach the Golgi apparatus. There, the vesicles fuse with the Golgi apparatus and dump their contents into a Golgi body.
There are about four successive Golgi body chambers to be visited and the molecules get passed from one to the next. In each Golgi body, enzymes make slight modifications to the molecule (such as the addition or removal of phosphate groups or sugars). The processing that occurs in the Golgi apparatus often involves tagging molecules (much like adding a postal address or tracking number) to direct them to some other part of the organism. After they are processed, the molecules then bud off from the Golgi apparatus in a vesicle which then moves into the cytoplasm. If the molecule is destined for delivery and used elsewhere in the body, the transport vesicle eventually fuses with the cell’s plasma membrane and dumps the molecule into the bloodstream via exocytosis. 26

27. Prokaryotic cells are ______ than eukaryotic cells
A. Structurally simpler
B. Functionally simpler
C. More ancient
D. Both A and B
E. Both A and C
Ans: E

28. A student is examining different samples with a microscope
A student is examining different samples with a microscope. She discovers a single-celled organism swimming in a freshwater pond sample (shown here).What type of cell is this?
Prokaryotic
Eukaryotic
Animal cell
Bacterial cell
Ans: B

29. Waste accumulates in cells due to an abnormal ____
A. Mitochondria
B. Lysosome
C. Rough endoplasmic reticulum
D. Golgi bodies
Ans: B

30. THE ENDOMEMBRANE SYSTEM AT WORK1
Transport vesicle buds from the
smooth or rough ER.
Transport vesicle fuses with Golgi apparatus, dumping contents inside.
Golgi apparatus modifies the molecules as they move through its successive chambers.
Modified molecules bud off from the Golgi apparatus as a
Transport vesicle.
Smooth ER
Rough ER 2
Transport
vesicle
Transport
vesicle 3
Golgi
apparatus
Plasma
membrane 4
Transport
vesicle
FIGURE 3-35 The endomembrane system: producing, packaging, and transporting molecules.
Figure 3-35 (The endomembrane system: producing, packaging, and transporting molecules.) shows how the various parts of the endomembrane system work to produce, modify, and package molecules within a cell. 5
Vesicle fuses with the plasmamembrane, dumping contents outside the cell for delivery elsewhere in the organism.

31. The cell wall provides additional protection and support for plant cells31

32. Vacuoles: multipurpose storage sacs for plant cells
Functions of vacuole
Nutrient storage
Waste management
Predator deterrence
Physical support
Sexual reproduction 32

33. 3.21 Chloroplasts: the plant cell’s power plant
Chloroplasts resemble photosynthetic bacteria.
Have Circular DNA
Dual outer membrane 33

34. Which of the following does NOT contain DNA?
Which of the following does NOT contain DNA?
Ribosomes
Nucleus
Mitochondria
Chloroplasts
Ans: A

35. Cytoskeleton 35

36. Cilia and Flagellum
The cytoskeleton also plays a more direct and obvious role in helping some cells to move.
Cilia are short projections that often occur in large numbers on a single cell (Figure 3-30 Cilia and flagella assist the cell with movement). Cilia beat swiftly, often in unison and in ways that resemble blades of grass in a field blowing in the wind. Cilia can move fluid along and past a cell. This movement can accomplish many important tasks, including sweeping the airways to our lungs clean of debris (such as dust) from the air that we breathe.
Flagella (singular: flagellum) are much longer than cilia. Flagella occur in many prokaryotes and single-celled eukaryotes, and many algae and plants have cells with one or more flagella. In animals, however, only one type of cell has a flagellum. But this one type of cell has a critical role in every single animal species. By forming the tail of a sperm cell, a flagellum makes possible the rapid movement of the most mobile of animal cells. Some spermicidal birth control methods prevent conception by disabling the flagellum and immobilizing the sperm cells. 36

37. Cytoskeleton is present ___, while mitochondria is present __
A. Only in animals; only in plants B. Only in plants; only in animals C. In both animals and plants; in both animals and plants D. Only in animals ; in both animals and plants
Ans: C