Surface Area: Volume Ratio LabThink about your cell city…(think/pair/share)

What is your nucleus?How many people or beings could be

supported by your nucleus?How well can your cell membrane/cell wall

protect the structures and function of your cell?

What would happen if your cell or institution doubled in size but your nucleus did not?

Importance of SA:V ratio

As a cell grows, the surface area cannot maintain the contents of the cell.

To compensate: elongate and thin or have surface folds to increase SA:V.

Or, it will divide.

Surface Area: Volume RatioSurface area: volume ratio - restriction of

cell size based on its ability to carry out functions.

Surface area = cell membrane (membrane surrounding cell)Regulates what nutriens (food, oxygen) can

enter and how much waste can exitVolume = the endomembrane area

(cytoplasm and organelles)The amount of “stuff” the DNA needs to control

and the cell membrane needs to be able to maintain

Surface to Volume Ratio

0.5 1.0 1.5

0.79

0.06

3.14 7.07

0.52 1.77

Diameter (cm):

Surface area (cm2):

Volume (cm3):

Surface- to-volume ratio: 13:1 6:1 4:1

Surface area: cm2

Volume: cm3

Demands of an oversized cellDNA overload – DNA does not increase as

cell increasesTherefore, DNA cannot support the amount of

work the large cell demandsDecreased efficient of nutrient and waste

transportIn today’s lab, apply this concept!You will see what I mean!

Compound Light MicroscopeTwo or more sets of

glass lenses bend light bounced off of a specimen

Forms an enlarged image through the eyepiece

1000x magnification~200 nm (small

bacteria)

Fig. 4.5a, p. 56

path of light rays (bottom to top) to eye

Ocular lens enlargesprimary image formedby objective lenses

Objective lenses (those closestto specimen) form the primaryimage. Most compound lightmicroscopes have several

stage (holdsmicroscopeslide in position)

Condenser lenses focuslight rays through specimen

illuminator

microscope base housingsource of illumination

Fig. 4.5b, p. 56

Light microscope – Euglena (protist)

Electron MicroscopesSEM

Scanning ElectronMicroscope

Specimen is coated with a thin layer of metal

Beam of electrons scan the cell surfaces

Produces detailed 3D images of cell surfaces

0.1 nm – 100 um

acceleratedelectron flow(top to bottom)

condenser lensto focus beamof electronsonto specimen

objectivelens

intermediatelens

projector lens

viewingscreen (orphotographicfilm)

specimen

Fig. 4.5c, p. 56

Electron MicroscopesTEM

Transmission Electron Microscope

Used to study details of internal cell structures

Magnetic field acts as the “lens”

Accelerated electrons directed through a specimen

0.1 nm – 100 um

frog egg3 mm

Typical plant cell10-100 µm

mitochondrion1-5 µm

chloroplast2-10 µm

human redblood cell7-8 µmdiameter

Trypanosoma(protozoan)25 µm long

Chlamydomonas(green alga)5-6 µm long

Poliovirus30 nm

HIV(AIDS virus)100 nm

T4 bacteriophage225 nm long

tobacco mosaic virus300 nm long

DNA molecule2 nm diameter

UNAIDED HUMAN EYE

ELECRON MICROSCOPES (DOWN TO 0.5 NM)

LIGHT MICROSCOPE (DOWN TO 200 NM)

Escherichia coli (bacterium)1-5 µm long

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

1 millimeter (mm) = 1/1,000 meter

1 micrometer (µm) = 1/1,000,000 meter

1 nanometer (nm) = 1/1,000,000,000 meter

1 meter = 102 cm = 103 mm = 106 µm = 109 nm

1mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm 0.5 nm

Fig. 4.6, p. 57

Light micrograph(phase-contrast process)

Light micrograph(Nomarski process)

Transmission electronmicrograph, thin section

Scanningelectron micrograph

Fig. 4.7, p. 57

Golgi body

vesicle

microfilaments(components of cytoskeleton)

mitochondrion

chloroplast

central vacuole

rough endoplasm reticulum (rough ER)

ribosomes (attached to rough ER)

ribosomes (free in cytoplasm)

smooth endoplasmic reticulum(smooth ER)

DNA + nucleoplasm

nucleolusnuclear envelope

NUCLEUS

plasma membrane

cell wall

Plant Cell

microfilaments

microtubules

components ofcytoskeleton

plasma membrane

mitochondrion

nuclear envelope

nucleolus

DNA + nucleoplasm

NUCLEUS

vesicle

lysosome

rough ER

ribosomes(attached torough ERand free incytoplasm)

smooth ER

vesicle

Golgi body

pair ofcentrioles

Animal Cell

Directions for Cell "City:"In the left hand column are the major organelles of a cell, with their essential function within the cell listed below them.Your job is to choose another organization of your interest:

1) Government2) School3) Sports Team4) Your place of employment5) Family6) A city

List the members or things within your choice that serve the same purpose as the corresponding organelle.

Components of the Cell Presentations:You and a partner will research and prepare a short presentation on your chosen organelle:

You will have time in class to research your organelle and discuss your presentation layout with your partner, as well as computer lab time to put together your powerpoint. Your presentation should include:

a) Structure of the organelleb) Function and location of the organellec) An image of the organelled) You must include information from your text and

one other resource.e) An assessment – how will you know the class

comprehends the characteristics of your organelle?