1. Cell Structure & Function
Chapter 7
Cell Structure & Function

2. Section 7-1
Life is Cellular

3. What led to the discovery of the cell?
The Microscope
Remember!
Cells make up all living things.

4. The Discovery of the Cell
Early Microscopes:
Scientists didn’t use microscopes until the 1600’s.
Robert Hooke -one of the 1st to look at cells under a microscope.
Gave cells their name.
P. 169, fig. 7-1
He was looking at dead cork cells.

5. Cork Cells (Hooke)

6. Robert Hooke

7. At about the same time as Hooke, Anton van Leeuwenhoek used a tiny microscope to look at pond water.
He discovered the new world of microorganisms.

8. The Cell Theory
In 1838, Matthias Schleiden stated that all plants are made of cells.
In 1839, Theodore Schwann stated that all animals were made of cells.
In 1855, Rudolf Virchow stated that cells could only come from other cells.

9. The Cell Theory: P. 170 All living things are made of cells.
Cells are the basic units of structure & function in living things.
New cells are produced from existing cells.

10. Exploring the Cell
Today, modern biologists use more powerful microscopes & techniques.
Some of the tools they use:
Fluorescent labels & light microscopy
Able to follow molecules moving through a cell.
Confocal light microscopy
Scans cells w/ a laser to make 3D images of cells & their parts.
High-resolution video
Enables us to make movies of cells as they grow, divide, & develop.

12. Another New Method Electron Microscopes (EM):
Can view things 1 million times smaller than that of a light microscope.
2 types of EM’s:
Transmission Electron Microscopes (TEM)
Scanning Electron Microscopes (SEM)

13. TEM: Lets us see cell structures & large protein molecules.
Cells & tx’s must be cut into ultra-thin slices before they are examined.
2D cross sectional image.

14. TEM

15. SEM:
3D images of cells
Objects don’t have to be thinly sliced to view.

16. SEM

17. Remember!
EM’s can only view the nonliving.

18. In the 1990’s, researches perfected a new class of microscope.
The Scanning Probe Microscope
Produces images by tracing the surfaces of samples w/ a fine probe.
Can observe single atoms.
Used to see DNA & protein molecules.

19. Scanning Probe Microscope

20. Prokaryotes & Eukaryotes
Cells come in all shapes & sizes.
But, all cells have 2 characteristics in common:
They have a cell membrane at some point in their lives.
They contain DNA.

21. Cells fall into 2 categories based on if they have a nucleus.
Nucleus –large membrane bound organelle.
Contains cell’s DNA.
Controls many of the cell’s activities.
Organelle –specialized structure that performs important functions w/in the cell.
“Tiny organs”

22. The 2 categories are: Prokaryotes Eukaryotes Pro = before Eu = true
Cells don’t contain a nucleus.
Eukaryotes
Cells do contain a nucleus.
Pro = before
Eu = true
Karyon =kernel

23. Prokaryotes Generally smaller & simpler than eukaryotic cells.
Prokaryotes have DNA, but it’s not contained in a nucleus.
All are unicellular.
Despite their simplicity, prokaryotes:
Grow
Reproduce
Respond to their env.
Some are mobile.
Ex:
Bacteria

25. Eukaryotes Generally larger & more complex than prokaryotes.
Eukaryotes contain membrane bound organelles & a nucleus (DNA).
Eukaryotes can be unicellular or multicellular.
Ex:
Plants
Animals
Fungi
Protists

28. Endoplasmic reticulum
Pro-k vs. Eu-k
Prokaryotes
Eukaryotes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Cell membrane
Contain DNA

29. Endoplasmic reticulum
Plant vs. Animal Cell
Animal Cells
Plant Cells
Cell membrane
Ribosomes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Cell Wall
Chloroplasts
Centrioles

30. Eukaryotic Cell Structure
Section 2
Eukaryotic Cell Structure

31. Comparing the Cell to a Factory
Organelles –literally means “little organs”.
Specialized structures that carry out specific functions in a cell.

32. Cell biologist divide cells into 2 parts:
The nucleus
The cytoplasm
Cytoplasm –portion of the cell outside the nucleus.
Cytoplasm is a gelatinous-like material.

33. Cytoplasm:

34. Nucleus The nucleus is the control center of the cell.
It contains almost all the cell’s DNA & w/ it the coded instructions for making proteins & other important molecules.
Surrounding the nucleus is a double membrane called the nuclear envelope.

35. On the nuclear envelope you will find nuclear pores.
Allow materials to move in & out of the nucleus.
Ex:
Proteins
RNA
Other molecules

36. Chromatin –a granular material visible w/in the nucleus.
It consists of DNA tightly coiled around proteins.
Most of the time chromatin is spread throughout the nucleus.
However, when a cell divides, chromatin condenses to form chromosomes.

37. Another structure found in most nuclei is a nucleolus.
The nucleolus assembles ribosomes.
P. 176, fig. 7-7

39. Ribosomes
Ribosomes –small particles of RNA & protein found throughout the cytoplasm.
Ribosomes make proteins by following coded instructions that come from the nucleus.
These instructions are RNA.
Cells that are major protein producers often have numerous ribosomes.

40. Endoplasmic Reticulum (ER)
Endoplasmic Reticulum –an internal membrane system in cells in which lipid components of the cell membrane are assembled & some proteins are modified.

41. There are 2 portions to an ER:
The rough ER
The smooth ER
Involved in the synthesis of proteins.
It is said to be rough b/c it has ribosomes found on its surface.
Newly made proteins enter the rough ER & get modified.

42. The Smooth ER No ribosomes found on the surface.
Contains collections of enzymes that perform special tasks such as:
Synthesis of membrane lipids
Detoxification of drugs
Liver cells tend to have a large amounts of smooth ER.

43. RER
SER

44. Golgi Apparatus (GA)
Proteins made in the ER move to the Golgi Apparatus (GA).
The GA looks like a stack of closely apposed membranes.

45. The GA’s modifies, sorts, & packages proteins & other materials from the ER.
These proteins can be stored in the cell or secreted out of the cell.
Kind of like UPS.
P. 178, fig. 7-9

48. Lysosomes The clean up crew.
Lysosome –small organelles filled w/ digestive enzymes.
Lysosomes are involved in:
Breaking down old organelles.
Digesting foreign matter in the cell.

49. Tay-Sachs -a disease is caused by lysosomes that fail to properly do their job.
Fatal by the age of 4.
More common in eastern European Jews.

50. Vacuoles Vacuoles –an organelle that stores materials such as:
Water
Salts
Proteins
Carbs
Plants have large central vacuoles that can hold, water & wastes.
P. 179, fig. 7-10

51. Mitochondria & Chloroplasts
The power plants of a cell.
Most cells get their energy (E) in 2 ways:
Food (Heterotrophs)
Sun (Autotrophs)

52. Mitochondria: Can be found in almost all eukaryotic cells.
Including plant cells.
Converts chemical E into compounds that are easy for the cell to use.
Ex: ATP (Adenosine Triphosphate)

53. Mitochondria are enclosed by 2 membranes.
An outer membrane
An inner membrane
Highly folded on itself.
Creates more surface area for chemical reactions.

54. Chloroplasts: Found in plants & some other orgs.
They capture sunlight & convert it into chemical E by photosynthesis.
This chemical E is then converted to ATP by mitochondria in the plant.
Also surrounded by 2 membranes.
Contains a green pigment called chlorophyll.

55. Chloroplasts

56. Organelle DNA Chloroplasts & mitochondria contain their own DNA.
No other organelles do.
It is believed that both of these organelles are ancient descendants of prokaryotes.
This is called the endosymbiotic theory.

57. Cytoskeleton
Cytoskeleton –a network of protein filaments that helps the cell maintain its shape.
It is also involved in movement.
The cytoskeleton is made up of:
Microfilaments
Microtubules

59. Microfilaments: Threadlike Made of actin
Forms a tough, flexible framework that supports the cell.
Also responsible for cytoplasmic movement of the cell.

60. Microtubules: Hollow tube-like structures Made of tubulin
Critical to maintaining cell shape.
Also form structures called spindles during cell division.
Tubulin is also used to make centrioles.
Located near the nucleus.
Help organize cell division.

62. Microtubules also help w/ movement.
They make up cilia & flagella.
P. 181, fig. 7-11

64. Section 7-3
Cell Boundaries

65. All cells are surrounded by a thin barrier called the cell membrane.
Many cells also have a strong supporting layer around that membrane called the cell wall.

68. Cell Membrane Cell membranes regulate what enters & leaves a cell.
They also aid in protection & support.
Nearly all cell membranes are a flexible, double layered sheet called a lipid bilayer.
P. 182, fig. 7-12

71. Along w/ lipids, the cell membrane also has proteins & carbohydrates embedded in it.
The lipid bilayer is often called a mosaic, b/c it is made up of many different parts.

72. The proteins form channels & pumps for moving materials across the membrane.
The carbohydrates act like ID cards, allowing individual cells to identify one another.

74. Cell Walls (CW’s) Found in: CW’s lie outside the cell membrane. Plants
Algae (Protists)
Fungi
Many prokaryotes (not all)
CW’s lie outside the cell membrane.

75. Most cell walls allow certain substances to pass through. Such as:
CO2 O2
Its main function is to support & protect the cell.

76. Most CW’s are made of fibers of carbohydrate & protein.
Plant CW’s are made of cellulose.
Cellulose is a tough carbohydrate fiber.
The fiber in your diet.

77. Diffusion Through Cell Boundaries
The movement of molecules from one side of the cell membrane to the other.

78. Measuring Concentration
Recall what a solution is.
What’s a solute?
What’s a solvent?
Concentration –the mass of solute in a given volume of solution, or mass/volume.
Lets figure concentration of a solution.
If you dissolved 12g of salt in 3L of water, the concentration would be: 12g/3L = 4 g/L

79. Diffusion
Diffusion –process of molecules moving from an area of high concentration to an area of low concentration.
Equilibrium –when the concentration of a solute is the same throughout a solution.
Diffusion will go on until EQ is reached.

80. What does diffusion have to do w/ a cell membrane?
P. 184, fig. 7-14
Diffusion requires no E output by the cell.
It’s free!

82. Osmosis Biological membranes are selectively permeable.
Some substances can pass & some can’t.
Water passes very easily.
However, many solutes can’t.
Osmosis –the diffusion of water through a selectively permeable membrane.

83. How Osmosis Works
H2O moves from an area of high H2O concentration to an area of low H2O concentration.
Water moves across the membrane until EQ is reached.

84. Osmosis
Section 7-3

86. 3 types of Osmotic Solutions: P. 186, fig. 7-16
Isotonic
Concentrations are equal on both sides of the membrane.
Normal looking cells
Hypertonic
Solution outside the cell has a higher solute concentration than the inside of the cell.
Water leaves the cell.
Cells shrink
Hypotonic
Solution has a lower solute concentration than the cell.
Water enters the cell.
Cells swell

90. Plant Cells

91. Plant Cells

92. Turgid
Flaccid

93. Red Blood Cells

94. Osmotic Pressure Osmosis exerts a pressure known as osmotic pressure.
Osmotic pressure -the pressure exerted by the flow of water through a semi permeable membrane.
This can cause serious problems for a cell.
Cells can swell to the point of bursting.

95. Fortunately, animal cells are in a isotonic solution & don’t come into contact w/ pure H2O.
If they did they would burst.
Also, plant cells & bacterial cells have cell walls that prevent the cell from bursting.

97. Facilitated Diffusion
Facilitated diffusion –movement of specific molecules across CM’s via protein channels.
P. 187, fig. 7-17
There are hundreds of protein channels that allow only certain substances to cross different membranes.

98. This process does not require E. It acts just as diffusion.
It goes from high to low concentrations.

99. Facilitated Diffusion

100. Active Transport
When cells move materials against the concentration gradient, they are using Active Transport.
This process requires E.
Active transport is carried out by transport proteins or pumps found in the membrane.

101. Transport of larger molecules can be done through 2 active transport processes:
Endocytosis
P. 188, fig. 7-18
Exocytosis
For each of these processes, the shape of the membrane changes.

102. Endo & Exo

103. Molecular Transport
Endocytosis –process of taking material into the cell by infolding or pocketing of the CM.
This process forms a vacuole in the cell.
This process works for:
taking in food
larger molecules
other cells
2 examples of endocytosis are:
Phagocytosis
Pinocytosis

104. Phagocytosis – extensions of cytoplasm surround a particle & package it w/in food vesicles.
Amoebas use this method
Fig. 7-18

105. Pinocytosis –the process of taking in liquids from the surrounding env.

106. Many cells also release large amounts of material from the cell.
This process is called exocytosis.
Ex:
The removal of water by a contractile vacuole is an example of this kind of active transport.

107. http://highered. mcgraw-hill

108. The Diversity of Cellular Life
Section 7-4
The Diversity of Cellular Life

109. Unicellular Organisms
Unicellular orgs. –made of one cell.
Unicellular orgs. can:
grow
respond to the env.
reproduce
transform E

110. Unicellular orgs. dominate life on Earth.
Examples on P. 190, fig. 7-20

111. Multicellular Organisms
Orgs. made up of many cells.
Multicellular orgs. have cells that are specialized.
Cell Specialization –process in which cells develop in different ways to perform different tasks.
P. 191, fig. 7-21

112. Specialized Animal Cells
Examples of specialized cells in animals:
Red blood cells
Transport O2 throughout the body.
Pancreatic cells
Produce enzymes that aid in digestion.
Contain cells specialized for making proteins.
These cells have numerous ribosomes.
Muscle cells
Able to contract & relax, causing movement of our bones.

113. Specialized Plant Cells
Guard cells of the stomata:
Monitor a plants internal conditions, & makes changes accordingly.

115. Levels of Organization
The levels of organization in a multicellular org. are as follows:
Individual Cells
Tissues
Organs
Organ systems
Organism
P. 192, fig. 7-22

116. Examples neurons (nerve cells) nervous tissue brain
central nervous system
human

117. Tissue –a group of similar cells that perform a specific function.
Ex:
The collection of cells in the pancreas that make proteins.
Most animals have 4 types of tx:
Muscle
Epithelial
Nervous
connective

119. Organs –many groups of tx’s working together.
Each muscle is an organ.
However, it also contains nervous tx, & connective tx.

120. Altogether, organ systems make up the organism.
Organ system –a group of organs working together to perform a specific function.
Digestive system
Reproductive system
Nervous system
Altogether, organ systems make up the organism.

121. Body Systems