Welcome to BIO201Welcome to BIO201Welcome to BIO201Welcome to BIO201Dr. Maura ParkerDr. Maura Parker

mhparker@sccd.ctc.edumhparker@sccd.ctc.edu

The Course….• Cell Biology – Cell Anatomy and

Function• Cell Biology – Energy and

Metabolism• Genetics – DNA, Chromosomes

and Inheritance• Genetics – Gene Expression and

Technology

Grading

• 4 exams – 52%• Quizzes – 14%• Lab Reports – 24% (8 labs x 3%

each)• Independent Research – 10%

Student Expectations

• Read before class - quizzes are not announced

• Be prepared with questions – every question is a good question – especially during Review sessions

• Prepare for lab sessions – you have lots to do and 3 hours is not a lot of time!

• DO NOT COPY OTHER STUDENTS’ LAB REPORTS

Expectations for me

• To provide you with the materials to learn

• Be at class prepared• Be at lab sessions prepared• Answer questions• Note: Please send me e-mails and make

appointments if you need to see me

Lecture #1 – Introduction to Cell Biology

• Text – Chapter 6 – pages 94-101• Note: tomorrow is Ch. 6 – pp 102-

111

The Cell is the Fundamental Unit of Life

• all living things are composed of cells

• multicellular and unicellular organisms

• prokaryotes and eukaryotes

The size range of cells

Nucleus

Most bacteria

Measurements1 centimeter (cm) = 102 meter (m) = 0.4 inch1 millimeter (mm) = 10–3 m1 micrometer (µm) = 10–3 mm = 106 m1 nanometer (nm) = 10–3 µm = 10 9 m

10 m

1 m

0.1 m

1 cm

1 mm

100 µm

10 µm

1 µm

100 nm

10 nm

1 nm

0.1 nm

Human height

Length of somenerve and muscle cells

Chicken egg

Frog egg

Most plant andanimal cells

Mitochondrion

Smallest bacteria

Viruses

Ribosomes

Proteins

Lipids

Small molecules

Atoms

Un

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nucleus

Most bacteria

Light Microscopes – Cells can be Seen!

• magnification: image size/object size

• resolution: the minimum distance 2 points can be separated and still distinguished as 2 points

• typically 1000x magnification and 0.2 m resolution

Brightfield (unstained specimen). Passes light directly through specimen. Unless cell is naturally pigmented or artificially stained, image has little contrast. [Parts (a)–(d) show a human cheek epithelial cell.]

(a)

Brightfield (stained specimen). Staining with various dyes enhances contrast, but most staining procedures require that cells be fixed (preserved).

(b)

Phase-contrast. Enhances contrast in unstained cells by amplifying variations in density within specimen; especially useful for examining living, unpigmented cells.

(c)

50 µm

Differential-interference-contrast (Nomarski). Like phase-contrast microscopy, it uses optical modifications to exaggerate differences indensity, making the image appear almost 3D.

Fluorescence. Shows the locations of specific molecules in the cell by tagging the molecules with fluorescent dyes or antibodies. These fluorescent substances absorb ultraviolet radiation and emit visible light, as shown here in a cell from an artery.

Confocal. Uses lasers and special optics for “optical sectioning” of fluorescently-stained specimens. Only a single plane of focus is illuminated; out-of-focus fluorescence above and below the plane is subtracted by a computer. A sharp image results, as seen in stained nervous tissue (top), where nerve cells are green, support cells are red, and regions of overlap are yellow. A standard fluorescence micrograph (bottom) of this relatively thick tissue is blurry.

50 µm

50 µm

(d)

(e)

(f)

Electron Microscopes - What is inside the cell?

Scanning electron micro-scopy (SEM). Micrographs takenwith a scanning electron micro-scope show a 3D image of the surface of a specimen. This SEM shows the surface of a cell from a rabbit trachea (windpipe) covered with motile organelles called cilia. Beating of the cilia helps moveinhaled debris upward toward the throat.

(a)

Transmission electron micro-scopy (TEM). A transmission electron microscope profiles a thin section of a specimen. Here we see a section through a tracheal cell, revealing its ultrastructure. In preparing the TEM, some cilia were cut along their lengths, creating longitudinal sections, while other cilia were cut straight across, creating cross sections.

(b)

Cilia 1 µm

Longitudinalsection ofcilium

Cross sectionof cilium

1 µm

What do the parts inside the cell do?

Tissuecells

Homogenization

Homogenate1000 g(1000 times theforce of gravity)

10 min Differential centrifugationSupernatant pouredinto next tube

20,000 g20 min

Pellet rich innuclei andcellular debris

Pellet rich inmitochondria(and chloro-plasts if cellsare from a plant)

Pellet rich in“microsomes”(pieces of plasma mem-branes andcells’ internalmembranes)

Pellet rich inribosomes

150,000 g3 hr

80,000 g60 min

Cell Fractionation

Prokaryotes vs. Eukaryotes

• bacteria and archaea – prokaryotes• both have plasma membrane,

cytoplasm, chromosomes and ribosomes

• eukaryotes have a membrane-enclosed nucleus

• prokaryotic DNA is in the nucleoid region

Pili: attachment structures onthe surface of some prokaryotes

Nucleoid: region wherethe cell’s DNA is located (notenclosed by a membrane)

Ribosomes: organelles thatsynthesize proteins

Plasma membrane: membraneenclosing the cytoplasm

Cell wall: rigid structure outsidethe plasma membrane

Capsule: jelly-like outer coatingof many prokaryotes

Flagella: locomotionorganelles ofsome bacteria

(a) A typical rod-shaped bacterium

(b) A thin section through the bacterium Bacillus coagulans (TEM)

0.5 µm

A Typical Prokaryotic Cell

Eukaryotic Cells

Intermediate filaments

ENDOPLASMIC RETICULUM (ER)

Rough ER Smooth ER

Centrosome

CYTOSKELETON

Microfilaments

Microtubules

Microvilli

Peroxisome

MitochondrionLysosome

Golgi apparatus

Ribosomes

Plasma membrane

In animal cells but not plant cells:LysosomesCentriolesFlagella (in some plant sperm)

Nuclear envelope

Nucleolus

Chromatin

NUCLEUS

Flagelium

Carbohydrate side chain

Outside of cell

Inside of cell

Hydrophilicregion

Hydrophobicregion

Hydrophilicregion

(b) Structure of the plasma membrane

Phospholipid Proteins

TEM of a plasmamembrane. Theplasma membrane,here in a red bloodcell, appears as apair of dark bandsseparated by alight band.

(a)

0.1 µm

The Plasma Membrane

Tomorrow…..

• Chapter 6 – pp 102-111• Cellular Anatomy – nucleus,

ribosomes, ER, Golgi, lysomsomes, peroxisomes, mitochondria and chloroplasts