Chapter 3Intro,3.1,3.2

Spider Webs and Carbon

Orb-Weaving Spider Web

• Contains carbon

Polymer Science U. of A.

Orb Spider Web

Spiders secrete their silk from glands located on their lower side

• Silk being secreted from glands in the spigots

• (SEM x3,740)

Spinnerets

Web Design

Straight Strands

• Radial

• Dry

• Inelastic proteins

Radial Strands• “Spiraling strand”-captures

insects

• Wet

• Sticky

• Highly elastic (stretch up to 4X’s)

The web is started with a horizontal thread stretched between two supports. The spider lets out a thread that is carried to another support by a breeze or air current. The spider then pulls in the excess to stretch the thread taut.

Dragline being silked from spinnerets

• The spider then moves to the center of the sagging, loose thread, and drops, letting out another thread and forming a ‘Y’.

• When the spider reaches the anchor point, it walks down the support to affix the new thread to another support point. The spider will spin threads between anchor points to give the web a frame.

• The spider makes the non-sticky scaffolding, from the outer edge to the center, attaching sticky threads that form the trap.

• The spider cuts away the non-sticky scaffolding as it progresses toward the center. The whole process of

• building a web takes about a half hour.

Web Design

largest spigot produces the spider's safety line, called the

dragline.•The smaller spigots produce lots of short sticky threads that make a strong attachment point for other silk lines.

Coils..then straightens

• Normal – Stretched 5X - Stretched 20X

Spider web glue droplets

• SEM

• on a strand of spider silk

Why is there so little sag?

• Coiling and uncoiling of silk fibers

• When the prey is no longer pressing against the strand…the fluid’s surface tension “beads” and rewinds the fiber

The spider uses its rear legs to pull and stretch the coagulated silk from

the spinnerets

What is Web Silk Made Of?

• the primary constituents of spider silk turn out to be the two simplest amino acids,

glycine and alanine

• "Dragline spider silk is actually stronger than Kevlar synthetic fiber- and Kevlar is several times stronger than steel"

Spider Silk

• Dragline silk • at least 5X’s stronger than steel,

• 2X’s more elastic than nylon waterproof and stretchable.

Why don't spiders stick to their webs?

• Why don't spiders stick to their webs?

• Silk line with middle claw and bristles.

Only a tiny area of its body in contact with the silk lines (the tips of its legs) + has a secretory lubrication on the claws

Spider Silk Research

• January 2002 spliced DNA from spiders into cells taken from hamsters and cows

• These cells produced spider silk proteins

Make Artificial Silk for:

• Artificial tendons and ligaments

• Surgical sutures

• Bulletproof vests

• Space Station Coatings

• Fishing line

USES

-wear-resistant shoes and clothes

-stronger ropes, nets, seatbelts, and parachutes

-rust-free panels and bumpers for automobiles

-improved sutures and bandages, artificial tendons and ligaments, and supports for weakened blood vessels.

-soldiers and police long for bulletproof vests

Organic Compounds

•Contain carbon and synthesized by cells

Carbon

6 p6 n6 e-

Carbon can bond to 4 e-

• Total of 6 electrons

• 4e- in outer shell

Can bond to 4 H

Hydrocarbons

•Contain hydrogen and carbon

METHANE

• One carbon

Carbon Skeleton

• Carbon Chain

• Here with 6 carbons (hexane)

Unbranched

Can be branched

• Like here with isooctane

• (8 carbons)

Rings

• Cyclohexane

AspirinNote the ring

Aspirin

• These are the same

• Single bond (ethane)

• Double bond (ethene)

• Triple bond (ethyne)

Single, Double, Triple Bonds

Isomers• Same molecular

formula but different structure (orientation)

• All C5H12

Functional Groups

•Groups of atoms that usually participate in chemical reactions

Functional Groups

• hydroxyl

• Carbonyl• (double bond to C)

or

Functional Groups

• Carboxyl –COOH or

• Amino -NH2

Which functional group?

•Amino

•carbonyl

Which functional group?

• carbonyl

Which functional group?

• carbonyl

Which functional group?

•carboxyl