PowerPoint Presentation

Unit 2.1

A Tour of the Cell

CAMPBELL BIOLOGY IN FOCUS

2014 Pearson Education, Inc.

Urry Cain Wasserman Minorsky Jackson Reece

Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge

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Overview: The Fundamental Units of Life

The Cell Theory

All organisms are made of cells

The cell is the simplest collection of matter that can be alive

All cells are related by their descent from earlier cells

Though cells can differ substantially from one another, they share common features

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Figure 4.1

How do your brain cells help you learn about biology?

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Figure 4.1 How do your brain cells help you learn about biology?

Concept 4.1: Biologists use microscopes and the tools of biochemistry to study cells

Most cells are between 1 and 100 m in diameter, too small to be seen by the unaided eye

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Microscopy

Scientists use microscopes to visualize cells too small to see with the naked eye

In a light microscope (LM), visible light is passed through a specimen and then through glass lenses

Lenses refract (bend) the light, so that the image is magnified

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Three important parameters of microscopy

Magnification, the ratio of an objects image size to its real size

Resolution, the measure of the clarity of the image, or the minimum distance between two distinguishable points

Contrast, visible differences in parts of the sample

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Figure 4.2

Most plant and

animal cells

Length of some

nerve and

muscle cells

Viruses

Smallest bacteria

Human height

Chicken egg

Frog egg

Human egg

Nucleus

Most bacteria

Mitochondrion

Super-

resolution

microscopy

Atoms

Small molecules

Ribosomes

Proteins

Lipids

Unaided eye

LM

10 m

EM

1 m

0.1 m

1 cm

1 mm

100 m

10 nm

1 nm

0.1 nm

100 nm

10 m

1 m

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Figure 4.2 The size range of cells and how we view them

LMs can magnify effectively to about 1,000 times the size of the actual specimen

Various techniques enhance contrast and enable cell components to be stained or labeled

Most subcellular structures, including organelles (membrane-enclosed compartments), are too small to be resolved by light microscopy

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Two basic types of electron microscopes (EMs) are used to study subcellular structures

Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look three-dimensional

Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen

TEM is used mainly to study the internal structure of cells

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Figure 4.3a

50 m

Brightfield

(unstained specimen)

Brightfield

(stained specimen)

Differential-interference

contrast (Nomarski)

Phase-contrast

Light Microscopy (LM)

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Figure 4.3a Exploring microscopy (part 1: light microscopy)

Figure 4.3b

50 m

10 m

Fluorescence

Confocal

Light Microscopy (LM)

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Figure 4.3b Exploring microscopy (part 2: light microscopy)

Figure 4.3c

Scanning electron

microscopy (SEM)

Transmission electron

microscopy (TEM)

Longitudinal section

of cilium

Cross section

of cilium

Cilia

2 m

Electron Microscopy (EM)

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Figure 4.3c Exploring microscopy (part 3: electron microscopy)

Concept 4.2: Eukaryotic cells have internal membranes that compartmentalize their functions

The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic

Organisms of the domains Bacteria and Archaea consist of prokaryotic cells

Protists, fungi, animals, and plants all consist of eukaryotic cells

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Comparing Prokaryotic and Eukaryotic Cells

Basic features of all cells

Plasma membrane

Semifluid substance called cytosol

Chromosomes (carry genes)

Ribosomes (make proteins)

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Prokaryotic cells are characterized by having

No nucleus

DNA in an unbound region called the nucleoid

No membrane-bound organelles

Cytoplasm bound by the plasma membrane

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Figure 4.4

(a) A typical rod-shaped

bacterium

0.5 m

(b) A thin section through

the bacterium Bacillus

coagulans (TEM)

Bacterial

chromosome

Fimbriae

Nucleoid

Ribosomes

Cell wall

Plasma membrane

Capsule

Flagella

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Figure 4.4 A prokaryotic cell

Eukaryotic cells are characterized by having

DNA in a nucleus that is bounded by a membranous nuclear envelope

Membrane-bound organelles

Cytoplasm in the region between the plasma membrane and nucleus

Eukaryotic cells are generally much larger than prokaryotic cells

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The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell

The general structure of a biological membrane is a double layer of phospholipids

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Figure 4.5

0.1 m

(a) TEM of a plasma

membrane

Outside of cell

(b) Structure of the plasma membrane

Inside

of cell

Hydrophilic

region

Hydrophilic

region

Hydrophobic

region

Carbohydrate side chains

Phospholipid

Proteins

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Figure 4.5 The plasma membrane

Metabolic requirements set upper limits on the size of cells

The ratio of surface area to volume of a cell is critical

As the surface area increases by a factor of n2, the volume increases by a factor of n3

Small cells have a greater surface area relative to volume

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Figure 4.6

750

Surface area increases while

total volume remains constant

125

150

125

6

1

6

1

6

1.2

5

1

Total surface area

[sum of the surface areas

(height width) of all box

sides number of boxes]

Total volume

[height width length

number of boxes]

Surface-to-volume

ratio

[surface area volume]

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Figure 4.6 Geometric relationships between surface area and volume

A Panoramic View of the Eukaryotic Cell

A eukaryotic cell has internal membranes that divide the cell into compartmentsorganelles

The plasma membrane and organelle membranes participate directly in the cells metabolism

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Figure 4.7a

CYTOSKELETON:

NUCLEUS

ENDOPLASMIC RETICULUM (ER)

Smooth ER

Rough ER

Flagellum

Centrosome

Microfilaments

Intermediate

filaments

Microvilli

Microtubules

Mitochondrion

Peroxisome

Golgi apparatus

Lysosome

Plasma

membrane

Ribosomes

Nucleolus

Nuclear

envelope

Chromatin

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Figure 4.7a Exploring eukaryotic cells (part 1: animal cell cutaway)

Figure 4.7b

CYTO-

SKELETON

NUCLEUS

Smooth endoplasmic

reticulum

Chloroplast

Central vacuole

Microfilaments

Intermediate

filaments

Cell wall

Microtubules

Mitochondrion

Peroxisome

Golgi

apparatus

Plasmodesmata

Plasma membrane

Ribosomes

Nucleolus

Nuclear envelope

Chromatin

Wall of adjacent cell

Rough endoplasmic

reticulum

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Figure 4.7b Exploring eukaryotic cells (part 2: plant cell cutaway)

Figure 4.7c

Nucleolus

Nucleus

Cell

10 m

Human cells from lining of uterus

(colorized TEM)

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Figure 4.7c Exploring eukaryotic cells (part 3: animal cell, TEM)

Figure 4.7d

5 m

Parent

cell

Buds

Yeast cells budding (colorized SEM)

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Figure 4.7d Exploring eukaryotic cells (part 4: fungal cell, SEM)

Figure 4.7e

1 m

A single yeast cell (colorized TEM)

Mitochondrion

Nucleus

Vacuole