Basic Features of
Cell Structure and Function
 Cells are small and are visualized using a microscope
 Cells have a DNA-containing central region surrounded by cytoplasm
 Cells occur in prokaryotic an eukaryotic forms, each with distinctive structures and organization

Cell Theory: Fundamental to
Life
 All organisms are cellular
 Cell: the smallest unit of life
 Cells come only from preexisting cells

Examples of Cells
Fig. 5-2, p. 92

Animation: Overview of cells

Units of Measure
Fig. 5-3, p. 93

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Small molecules
Proteins Viruses
Nucleus
Mitochondria
Atoms Lipids Ribosomes
Smallest bacteria
Most bacteria
Most plant and animal cells
Electron microscope
Light microscope
Fish egg Bird egg
Human height
0.1 nm 1 nm 10 nm 100 nm 1
 m 10
 m 100
 m 1 mm
Unaided human eye
1 cm 0.1 m 1 m 10 m
7

 Link
 Amazing cells
Cell size

Think/Pair/Share
 Why are cells small?

Surface to Volume Ratios
Fig. 5-5, p. 95

Microscopy
 Magnification

Ratio between the size of an image produced by a microscope and its actual size
 Resolution

Ability to observe two adjacent objects as distinct from one another
 Contrast

How different one structure looks from another – enhanced by dyes
11

Microscopy
 2 groups of microscopes based on source of illumination

Light microscope
• Uses light for illumination
• Resolution 0.2 µm

Electron microscope
• Uses an electron beam
• Resolution 2 nm
12

Bright field microscopy
Fig. 5-4a, p. 94

Dark field microscopy
Fig. 5-4b, p. 94

Phase-contrast microscopy
Fig. 5-4c, p. 94

Electron microscope types
 Transmission electron microscopy (TEM)

Beam of electrons transmitted through sample

Thin slices stained with heavy metals

Some electrons are scattered while others pass through to form an image
 Scanning electron microscopy (SEM)

Sample coated with heavy metal

Beam scans surface to make 3D image
16

Transmission electron microscopy (TEM)
Fig. 5-4d, p. 94

Scanning electron microscopy (SEM)
Fig. 5-4h, p. 94

All Cells Contain DNA
 All cells have a central region with DNA

Stores hereditary information (connection to evolution )

Genes are located on DNA

Proteins replicate DNA and copy information to RNA

Cytoplasm
 Cytoplasm

Surrounds the central region
 Cytosol

Aqueous solution of cell
 Organelles

Small organized structures within cytosol

Plasma Membrane
Fig. 5-6, p. 95

Animation: Cell membranes
 Membranes

Plasma Membrane
 Plasma membrane defines cytoplasm
 Lipid bilayer and proteins
 Hydrophobic

Selective passage hydrophilic
 Internal environment of cell different from external

 link
Amazing Cells

Prokaryotes and Eukaryotes
 Prokaryotes

No boundary membrane in central region

Nucleoid

Domains: Archaea and Bacteria
 Eukaryotes

Boundary membrane in central region

True nucleus

Domain: Eukarya

Prokaryotic Cells
 Prokaryotic cells have little or no internal membrane structure

Prokaryotic Cell Structure
Fig. 5-7, p. 97

Animation: Typical prokaryotic cell

Prokaryotic Internal Structure
 Small, little to no membrane structure

Cell wall & capsule
 Plasma membrane allows metabolism

ATP in mitochondria and chloroplasts

Evolution by endosymbiosis

Prokaryotic Information Transfer
 Nucleiod

Chromatin and chromosome

Three domain system (Carl Woese)
 Ribosomes


Only organelle in common with eukaryotes
DNA  messenger RNA  amino acids and proteins

Prokaryotic Mobility and
Ecology
 Many prokaryotes have flagella

Different from eukaryotic flagella
 Prokaryotes relatively simple

Exploit all known habitats

Vastly outnumber eukaryotes

Cycling of biological elements

Table 5-1a, p. 96

Table 5-1b, p. 96

Eukaryotic Cells
 Eukaryotic cells have a membraneenclosed nucleus and cytoplasmic organelles
 Nucleus contains much more DNA than the prokaryotic nucleoid
 Cytoplasm has endomembrane systems dividing cell into functional and structural components

Eukaryotic cells
 Mitochondria are the powerhouses of the cell
 Microbodies carry out vital reactions that link metabolic pathways
 The cytoskeleton supports and moves cell structures
 Flagella and cilia are the propellers of eukaryotic cells

Eukaryotic Cell Overview
 Domain Eukarya (true nucleus)

Includes protists, fungi, plants and animals
 Eukaryotic plasma membrane function

Regulate/recognize substances (immune system)

Cell-to-cell binding
 Fungi, plants and many protists have cell walls

 link
Video

Typical Animal Cell
Fig. 5-8a, p. 99

Electron Micrograph of Animal
Cell
Fig. 5-8b, p. 99

Animation: Common eukaryotic organelles

 link
Video

Typical Plant Cell
Fig. 5-9a, p. 100

Electron Micrograph Plant Cell
Fig. 5-9b, p. 100

Which of these organelles are absent in plant cells?
1.
2.
3.
4.
Mitochondria
Centrioles
Peroxisomes
All of the above
25% 25% 25% 25%
1 2 3 4

Eukaryotic Nucleus
 Nuclear envelope separates nucleus and cytoplasm

Two membranes and nuclear pores
 Nucleoplasm within nuclear envelope

Chromatin and chromosomes
 Nucleolus

Genes for ribosomal RNA

If you treat cells with radioactive UTP, where in the cell would you expect the greatest concentration of radioactivity within the first few minutes?
1.
2.
3.
4.
Rough ER
Nuclear matrix
Cytoplasm
Nucleolus
25% 25% 25% 25%
1 2 3 4

Nuclear Envelope
Fig. 5-10, p. 101

Endomembrane System
 Endomembrane system

Connects all membranes

Synthesizes/ modifies membrane proteins

Synthesizes lipids

Detoxification
 Vesicles exchange membrane throughout endomembrane system

ER, Golgi, nuclear envelope, lysosomes, vesicles, plasma membrane

Endoplasmic Reticulum
 Endoplasmic reticulum (ER)

Interconnected network of membrane with cisternae and lumen
 Rough ER

Ribosomes bound to surface

Membrane-associated protein synthesis

Endoplasmic Reticulum
 Smooth ER

No ribosomes

Synthesizes lipids and detoxifies
 Proportion rough/smooth ER reflect cell activities

Endoplasmic Reticulum
Fig. 5-11, p. 102

b. Smooth ER
Cisternae
ER lumen
(mitochondrion) Smooth ER lumen
Fig. 5-11b, p. 102

Golgi Complex
 Golgi complex stack of flattened sacs

Between rough ER and plasma membrane
 Golgi receives and modifies proteins

Molecularly tags vesicles
 Vesicles perform many functions

Exocytosis and endocytosis

Golgi Complex
Fig. 5-12, p. 103

Lysosomes
 Lysosomes

Vesicles from Golgi complex

Hydrolytic enzymes from ER; low pH
 Autophagy removes nonfunctional organelles
 Phagocytosis digests extracellular material

Major function of immune systems

Endocytosis, Exocytosis and Lysosomes
Fig. 5-13-14, p. 104

Vesicle Traffic
Fig. 5-15, p. 105

A membrane protein synthesized in the rough ER may be directed to
1.
2.
3.
4.
Peroxisomes
Lysosomes
Mitochondria
All of the above
25% 25% 25% 25%
1 2 3 4

Brefeldin A is a drug that disrupts transport from the ER to the Golgi apparatus. What other organelles and membranes are affected?
1.
2.
3.
Lysosomes, vacuoles, plasma membrane
Vacuoles, mitochondria, plasma membrane
All organelles and membranes
100%
1

Mitochondria
 Cellular respiration yields ATP
 Mitochondria have two membranes

Outer membrane smooth

Inner membrane folded ( cristae )

Mitochondrial matrix
 Mitochondria have own genome

Endosymbiosis

Mitochondria
Fig. 5-16, p. 106

Microbodies
 Microbodies

Single membrane organelles

Not part of endomembrane system
 Microbody enzymes link biochemical pathways
 Examples

Peroxisomes, glyoxysomes or glycosomes

Microbodies
Fig. 5-17, p. 107

Cytoskeleton
 Cytoskeleton

Maintains shape and organization

Interconnected protein fibers and tubes
 Most prominent in animal cells

Plants and fungi also use cell walls and central vacuole

Cytoskeleton
 Network of three different types of protein filaments
 Microtubules


Long, hollow cylindrical structures
Dynamic instability
 Intermediate filaments

Intermediate in size

Form twisted, ropelike structure
 Actin filaments


Also known as microfilaments
Long, thin fibers
65

Cytoskeleton Examples
Fig. 5-18, p. 107

Cytoskeleton Components
 Main elements of animal cytoskeletons

Microtubules are supportive

Intermediate fibers thinner, interconnected with microtubules

Microfilaments thinnest

68

Cytoskeleton Components
 Each element assembled from proteins

Microtubules from tubulin

Intermediate fibers from intermediate filaments

Microfilaments from actins

Major Components of Cytoskeleton
Fig. 5-19, p. 108

Microtubules
 Many microtubules originate from centrosome

Originate from centrioles

Anchor major organelles

Microtubules provide tracks for mobile organelles

Microtubules
 Organelle movement by motor proteins

Vesicle attached to motor protein “walks” along microtubule

Requires ATP
 Cytoskeleton allows large cellular movement

Amoeboid motion, cytoplasmic streaming, cell division

Kinesin
Fig. 5-20a,b, p. 108

Flagellar and Ciliary Beating Patterns
Fig. 5-22, p. 110

1.
Taxol, a drug approved for treatment of breast cancer, prevents depolymerization of microtubules. What cellular function that affects cancer cells more than normal cells might taxol interfere with
?
Maintaining cell
33% shape
33% 33%
2.
3.
Cilia or flagella
Chromosome movements in cell division
1 2 3

Specialized Structures of Plant
Cells
 Chloroplasts are biochemical factories powered by sunlight
 Central vacuoles have diverse roles in storage, structural support, and cell growth
 Cell walls support and protect plant cells

Chloroplasts
 Chloroplasts have multiple membranes for photosynthesis

Outer smooth, inner folded; stroma inside both

Thylakoids and grana inside stroma

Endosymbiosis
 Plastids are plant organelles that include chloroplasts , amlyoplasts and chromoplasts

Chloroplast Structure
Fig. 5-24, p. 111

Central Vacuoles
 Central vacuoles


Large vesicles in plants
90% of many plant cell’s volume

Turgor pressure from water

Other functions
 Tonoplast

Membrane surrounding central vacuole

Cell Walls
 Cell walls

Extracellular structures

Provide structure and contain pressure

Cellulose fibers for tensile strength, other organic molecules for compression resistance
 Two types of cells walls

Primary

Secondary

Cell Wall Structure
Fig. 5-25, p. 112

The Animal Cell Surface
 Cell adhesion molecules organize animal cells into tissues and organs
 Cell junctions reinforce cell adhesions and provide avenues of communication
 The extracellular matrix organizes the cell exterior

Cell Adhesion and Junctions
 Cell adhesion molecules bind cells together nonpermanently

Glycoproteins bind to specific molecules on other cells
 Cell junctions seal spaces between cells permanently

Direct cellular communication

Functions of Cellular Junction
 Anchoring junctions “weld” cells together

Desmosomes and adherens
 Tight junctions prevent small ion movement

Seal spaces and fuse membranes
 Gap junctions allow passage without membrane control

Same tissue

Animal Cell Connections
Fig. 5-26, p. 114

Extracellular Matrix
 Collagen proteins

Tensile strength and elasticity
 Proteoglycans

Interlinkage

Changes consistency (jellylike to hard and elastic)
 Fibronectins

Connect cells via integrins

Extracellular Matrix
Fig. 5-27, p. 115

Video: Fluid mosaic model