Chap 6 lecture Part 1 with Audio

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 6Chapter 6

A Tour of the Cell


Overview: The Importance of Cells

• All organisms are made of cells

• The cell is the simplest collection of matter that can live

• Cell structure is correlated to cellular function

• All cells are related by their descent from earlier cells


How do the different parts of a cell function separately and together?


Concept 6.1: To study cells, biologists use microscopes and the tools of biochemistry

• Though usually too small to be seen by the unaided eye, cells can be complex

• Two important parameters of microscopy

– Magnification- ratio of object image to real size

– Resolution- clarity of the image

• Light microscopes pass light through specimen and then through glass lenses

– Resolution of 200 nanometers, i.e. small bacteria

– Magnification 1000 times the actual size

LE 6-2

Measurements1 centimeter (cm) = 10–2 meter (m) = 0.4 inch1 millimeter (mm) = 10–3 m1 micrometer (µm) = 10–3 mm = 10–6 m1 nanometer (nm) = 10–3 µm = 10–9 m

10 m

1 mHuman height

Length of somenerve andmuscle cells

Chicken egg

0.1 m

1 cm

Frog egg1 mm

100 µm

Most plant andanimal cells

10 µmNucleus

1 µm

Most bacteria

Mitochondrion

Smallest bacteria

Viruses100 nm

10 nmRibosomes

Proteins

Lipids

1 nmSmall molecules

Atoms0.1 nmU

na

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d e

ye

Lig

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mic

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Ele

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Light Microscope

Brightfield(unstained)

Brightfield(stained)

Phase-contrast

50 µm

Confocal

Differential-Interference-Contrast(Nomarski)

Fluorescence

50 µm

50 µm

LE 6-41 µm

1 µm

Cilia

Longitudinalsection ofcilium

Cross sectionof cilium

Used to study subcellular structures

Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3D

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

TEMs are used mainly to study the internal ultrastructure of cells

Electron Microscopes


Isolating Organelles by Cell Fractionation

• Cell fractionation takes cells apart and separates the major organelles from one another

• Ultracentrifuges fractionate cells into their component parts


Isolating Organelles by Cell Fractionation

Homogenization

HomogenateTissuecells

Differential centrifugation

Pellet rich innuclei andcellular debris

Pellet rich in mitochondria (and chloroplasts if cellsare from a plant)

Pellet rich in “microsomes”(pieces of plasma membranesand cells’ internal membranes)

Pellet rich in ribosomes

150,000 g3 hr

80,000 g60 min

20,000 g20 min

1000 g(1000 times the force of gravity)10 min

Supernatant pouredinto next tube

Cell fractionation enables scientists to determine the functions of organelles


Concept Check

• How do the stains used for light microscopy compare with those used for electron microscopy?

• Which type of microscope would you use to study…

• Changes in the shape of a white blood cell?

• Surface texture of hair?

• Detailed structure of an organelle?

Prokaryotic vs. Eukaryotic Cells

Nucleus- no yes

Membrane

Bound organelles no yes

Plasma membrane yes yes

Cytosol yes yes

Chromosomes yes yes

Ribosomes yes yes

Domain Bacteria, Archea protist ,fungi, plant

animal

The two types of cells

LE 6-6

A typicalrod-shapedbacterium

A thin section through thebacterium Bacilluscoagulans (TEM)

0.5 µm

Pili

Nucleoid

Ribosomes

Plasmamembrane

Cell wall

Capsule

Flagella

Bacterialchromosome

LE 6-7

Total surface area(height x width xnumber of sides xnumber of boxes)

6

125 125

150 750

1

11

5

1.2 66

Total volume(height x width x lengthX number of boxes)

Surface-to-volumeratio(surface area volume)

Surface area increases whileTotal volume remains constant

Larger organisms do not have larger cells- simple more cells

Hydrophilicregion

Hydrophobicregion

Carbohydrate side chain

Structure of the plasma membrane

Hydrophilicregion

Phospholipid Proteins

Outside of cell

Inside of cell 0.1 µm

TEM of a plasma membrane

Function - selective barrier that allows sufficient passage of oxygen, nutrients, and waste

Structure - double layer of phospholipids

The boundary of every cell – Plasma membrane

Flagellum

Centrosome

CYTOSKELETON

Microfilaments

Intermediate filaments

Microtubules

Peroxisome

Microvilli

ENDOPLASMIC RETICULUM (ER

Rough ER Smooth ER

MitochondrionLysosome

Golgi apparatus

Ribosomes:

Plasma membrane

Nuclear envelope

NUCLEUS

In animal cells but not plant cells:

Lysosomes

Centrioles

Flagella (in some plant sperm)

Nucleolus

Chromatin

A Panoramic View of the Eukaryotic CellA Panoramic View of the Eukaryotic Cell

LE 6-9b

Roughendoplasmicreticulum

In plant cells but not animal cells:

Chloroplasts

Central vacuole and tonoplast

Cell wall

Plasmodesmata

Smoothendoplasmicreticulum

Ribosomes(small brown dots)

Central vacuole

Microfilaments

IntermediatefilamentsMicrotubules

CYTOSKELETON

Chloroplast

Plasmodesmata

Wall of adjacent cell

Cell wall

Nuclearenvelope

Nucleolus

Chromatin

NUCLEUS

Centrosome

Golgiapparatus

Mitochondrion

Peroxisome

Plasmamembrane

A Panoramic View of the Eukaryotic CellA Panoramic View of the Eukaryotic CellA Panoramic View of the Eukaryotic CellA Panoramic View of the Eukaryotic Cell


• A eukaryotic cell has internal membranes that partition the cell into organelles

– Nucleus – contains most of the DNA

– Ribosomes – use info from DNA to make proteins

– Endomembrane system – variety of tasks, protein synthesis, transport, lipid metabolism, detoxification

– Lysosyme – digest macromolecules

– Vacuoles

– Mitochondria – cellular respiration

– Chloroplasts - photosynthesis

Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions

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Chap 6 lecture Part 1 with Audio