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• Chapter 4 Cell Structure (Sections 4.1 - 4.7)

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4.1 Food for Thought

Helpful intestinal bacteria make vitamins that mammals cant, and they crowd out more dangerous germs

3. Escherichia coliis one of the most common intestinal bacteria of warm-blooded animals only a few of the hundreds of types ( strains ) are harmful 4.

E. coliO157:H7

E. coliO157:H7 makes a potent toxin that can severely damage the lining of the human intestine

5. Causes serious illness in people who eat contaminated foods 6.

4.2 What, Exactly, Is a Cell?

cell

• The smallest unit that has the properties of life

Cells pictured are individual organisms (protists)

7.

Traits Common to All Cells

Although cells differ in size, shape, and function, each starts out with aplasma membrane ,cytoplasm , and a region of DNA (in eukaryotic cells, anucleus )

plasma membrane

• A cells outermost membrane

8. Alipid bilayeris the structural foundation of cell membranes, includingorganellemembranes

9.

Key Terms

organelle

• Structure that carries out a specialized metabolic function inside a cell

cytoplasm

• Semifluid substance enclosed by a cells plasma membrane

nucleus

• Organelle with two membranes that holds a eukaryotic cells DNA

10.

Single Cells

11.

Bacterial Cell

Bacteria are single-celled organisms

12. Archaeans are similar to bacteria in overall structure 13.

Fig. 4.3a, p. 52

plasma membrane

ABacterial cell

cytoplasm

DNA

14.

Plant Cell

15.

Fig. 4.3b, p. 52

BPlant cell

plasma membrane

DNA in nucleus

cytoplasm

16.

Animal Cell

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Fig. 4.3c, p. 52

CAnimal cell

DNA in nucleus

cytoplasm

plasma membrane

18.

Animation: Overview of Cells

19.

Constraints on Cell Size

S urface-to-volume ratiolimits cell size

20. If the cell gets too big, inward flow of nutrients and outward flow of wastes across the membrane will not be fast enough

surface-to-volume ratio

• A relationship in which the volume of an object increases with the cube of the diameter, but surface area increases with the square of the diameter

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Surface-to-Volume Ratio

The physical relationship between increases in volume and surface area constrains cell size and shape

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Animation: Surface-to-Volume Ratio

23.

Cell Theory

The cell is the structural and functional unit of all organisms

cell theory

• Theory that all organisms consist of one or more cells, which are the basic unit of life

24.

History of Cell Discovery

1665: Antoni van Leeuwenhoekfirst observedmany very small animalcules

25. Robert Hooke magnified a piece of thinly sliced cork andnamed the tiny compartments he observed cellae 26. 1820s: Robert Brown was first to identify a cell nucleus 27. Matthias Schleiden, hypothesized that a plant cell is an independentliving unit even when it is part of a plant 28. Schleiden and Theodor Schwann concluded that the tissues of animals as well as plants are composed of cells 29.

Cell Theory

Four generalizations constitute thecell theory :

• 1. Every living organism consists of one or more cells

30. 2. A cell is the smallest unit of life, individually alive even as part of a multicelled organism

31. 3. All living cells come from division of preexisting cells 32. 4. Cells contain hereditary material, which they pass to their offspring during division 33.

Key Concepts

What Is a Cell?

• A cell is the smallest unit of life

34. Each has a plasma membrane that separates its interior from the exterior environment

35. A cells interior contains cytoplasm and DNA 36.

4.3 Spying on Cells

Most cells are far too small to see with the naked eye

37. We use different types of microscopes and techniques to reveal cells and their internal and external details 38.

Types of Microscopes

Light microscopes

39. Phase-contrast microscopes 40. Fluorescence microscope

Electron microscopes

41. Transmission electron Microscopes 42. Scanning electron microscopes 43.

Examples of Microscopes

Compound light microscope

Transmission electron microscope (TEM)

44.

Fig. 4.5a, p. 54

specimen

prism that directs rays to ocular lens

focusing knob

illuminator

condenser lens

stage

path of light rays (bottom to top) to eye

ocular lens

objective lenses

light source (in base)

45.

Fig. 4.5b, p. 54

phosphor screen

incoming electron beam

condenser lens

specimen on grid

objective lens

projective lens

46.

Animation: How a Light Microscope Works

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Different Views, Same Organism

Fig. 4.6, p. 55

ALight micrograph.

BLight micrograph.

CFluorescence micrograph.

DA transmission electron micrograph reveals fantastically detailed images of internal structures.

EA scanning electron micro-graph shows surface details. SEMs may be artificially colored to highlight specific details.

A reflected light microscope captures light reflected from specimens.

A phase-contrast microscope yields high-contrast images of trans- parent specimens. Dark areas have taken up dye.

This image shows fluorescent light emitted by chlorophyll molecules in the cells.

48.

Relative Sizes

49.

Measurements

Units of length:

• 1 centimeter (cm) = 1/100 meter, or 0.4 inch

50. 1 millimeter (mm) = 1/1000 meter, or 0.04 inch

51. 1 micrometer ( m) = 1/1,000,000 meter, or 0.00004 inch 52. 1 nanometer (nm) = 1/1,000,000,000 meter, or 0.00000004 inch 53. 1 meter = 10 2cm = 10 3mm = 10 6 m = 10 9nm 54.

Key Concepts

Microscopes

• Most cells are too small to see with the naked eye

55. We use different types of microscopes to reveal different details of their structure

56.

Animation: How an Electron Microscope Works

57.

4.4 Membrane Structureand Function

A cell membrane functions as a selectively permeable barrier that separates an internal environment from an external one

58. Membranes of most cells can be described as afluid mosaic of lipids (mainly phospholipids) and proteins 59. Lipids are organized as alipid bilayer : a double layer of lipids in which the nonpolar tails of both layers are sandwiched between the polar heads 60.

Key Terms

lipid bilayer

• Structural foundation of cell membranes; double layer of lipids arranged tail-to-tail

fluid mosaic

• Model of a cell membrane as a two-dimensional fluid of mixed composition

61.

A Lipid Bilayer

62.

Basic Cell

At its most basic, a cell is a lipid bilayer bubble filled with fluid

63.

Membrane Proteins

Proteins associated with a membrane carry out most membrane functions

64. All membranes havetransport proteins 65. Plasma membranes also havereceptor proteins ,adhesion proteins ,enzymes, andrecognition proteins 66.

Key Terms

transport protein

• Protein that passively or actively assists specific ions or molecules across a membrane

adhesion protein

• Membrane protein that helps cells stick together in tissues

receptor protein

• Binds to a particular substance outside of the cell

recognition protein

• Tags a cell as belonging to self (ones own body)

67.

Membrane Proteins

68.

Recognition and Receptor Proteins

69.

Transport Proteins

70.

Fig. 4.8b-e, p. 57

Lipid Bilayer

Cytoplasm

Extracellular Fluid

EThis transport protein, an ATP synthase, makes ATP when hydrogen ions flow through its interior.

BRecognition proteins such as this MHC molecule tag a cell as belonging to ones own body.

CReceptor proteins such as this B cell receptor bind substances outside the cell. B cell receptors help the body eliminate toxins and infectious agents such as bacteria.

DTransport proteins bind to molecules on one side of the membrane, and release them on the other side. This one transports glucose.

71.

Animation: Cell Membranes

72.

Variations on the Model

Archaeans do not build phospholipids with fatty acids instead, the tails of archaean phospholipids form covalent bonds with one another

73. Archaean membranes are far more rigid than those of bacteria or eukaryotes 74.

Key Concepts

Cell Membranes

• All cell membranes consist mainly of a lipid bilayer and different types of proteins

75. The proteins carry out various tasks, including control over which substances cross the membrane

76.

Animation: Lipid Bilayer Organization

77.

Animation: Fluid Mosaic Model

78.

4.5 Bacteria and Archaeans

Single-celled bacteria and archaeans are the smallest and most diverse forms of life:

• The cytoplasm containsribosomesandplasmids

79. A single, circular chromosome is located in anucleoid

80. Many have acell wall ,flagella orpili 81.

Key Terms

ribosome

• Organelle of protein synthesis

plasmid

• Small circle of DNA in some bacteria and archaeans

nucleoid

• Region of cytoplasm where the DNA is concentrated inside a bacterium or archaean

82.

Key Terms

flagellum

• Long, slender cellular structure used for motility

pilus

• A protein filament that projects from the surface of some bacterial cells sex pilus

cell wall

• Semi-rigid but permeable structure that surrounds the plasma membrane of some cells

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Bacteria

84.

Archaeans

85.

Body Plan of Bacteriaand Archaeans

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Fig. 4.11, p. 58

flagellum

cytoplasm,with ribosomes

DNA in nucleoid

pilus

plasma membrane

cell wall

capsule

87.

Animation: Typical Prokaryotic Cell

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Cell Walls

The cell wall of most archaeans consists of proteins

89. The wall of most bacteria consists of a polymer of peptides and polysaccharides 90. Sticky polysaccharides form a slime layer, or capsule, around the wall of many types of bacteria 91.

Biofilms

Biofilmsare shared living arrangements among bacteria and other microbial organisms

biofilm

• Community of different types of microorganisms living within a shared mass of slime

92. May include bacteria, algae, fungi, protists, and archaeans

93.

A Biofilm

A biofilm organizes itself into neighborhoods, each with a distinct microenvironment that stems from its location within the biofilm and species that inhabit it

94.

Key Concepts

Bacteria and Archaea

• Archaeans and bacteria have few internal membrane-enclosed compartments

95. In general, they are the smallest and structurally the simplest cells, but they are also the most numerous

96.

4.6 Introducing Eukaryotic Cells

All protists, fungi, plants, and animals are eukaryotes

Eukaryotic cells start out life with membrane-enclosed organelles, including a nucleus

97. Most eukaryotic cells contain an endomembrane system (ER, vesicles, and Golgi bodies), mitochondria, and a cytoskeleton 98.

Components of Eukaryotic Cells

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Animal and Plant Cells

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Fig. 4.13, p. 60

nucleus

cell wall

central vacuole

vacuole

plasma membrane

chloroplast

mitochondrion

101.

4.7 The Nucleus

The nucleus contains the cells genetic material (DNA)

102. In the nucleus, ribosome subunits are assembled in dense regions callednucleoli

The nucleus has a double-membranednuclear envelopesurroundingnucleoplasm

103.

Key Terms

nucleolus

• In a cell nucleus, a dense, irregularly shaped region where ribosomal subunits are assembled

nuclear envelope

• A double membrane that constitutes the outer boundary of the nucleus

nucleoplasm

• Viscous fluid enclosed by the nuclear envelope

104.

The Nuclear Envelope

The nuclear membrane controls passage of certain molecules between the nucleus and the cytoplasm

105. Receptors and transporters stud both sides of the nuclear envelope; other proteins form nuclear pores 106. The outer bilayer of the double membrane is continuous with the membrane of the ER 107.

The Nucleus

Fig. 4.14, p. 61

nucleoplasm

nuclear envelope

nuclear pore

nucleolus

ER

cytoplasm

DNA

108.

Nuclear Pores

Fig. 4.15, p. 61

nuclear pore

cytoplasm

nuclear envelope (two lipid bilayers)

109.

Animation: Nuclear Envelope