the chemical context of life chapter 2. a chemical connection to biology ex. ants maintain duroia...
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A Chemical Connection to Biology
Ex. Ants maintain Duroia hirsuta “devil’s gardens,” in Peru by injecting formic acid into other plants
Ants Myrmelachista schumanniThis plant is the only species in this tropical rain forest!
HCO2H.
Methanoic acid
Formic acid stinging ants
Some beekeepers use formic acid as a fumigant to kill a mite which attacks the bees.
Most ant species probably use it as a disinfectant
decalcifier; reducer in dyeing for wool; dehairing and plumping hides; tanning; electroplating; coagulating rubber latex; silage and grain preservation; solvents of perfume; lacquers;
Scientific method• Two saplings of a common Amazonian tree, Cedrela odorata, or Spanish
cedar, were planted inside each Devil’s garden near the base of a D. hirsuta tree actively patrolled by worker ants. A sticky insect barrier was applied to one cedar sapling to exclude ants, while the other sapling was left untreated.
• The results were immediate. Worker ants promptly attacked the untreated saplings by injecting formic acid into the leaves, which began to die within 24 hours. "Most of the leaves on these saplings were lost within five days, and the proportion lost was significantly higher than on ant-excluded saplings,". Cedars treated with the insect barrier fared lived.
• Independent variable = • Control group =• Controlled variables =• Dependent variable =
Matter, elements, and compounds
• matter - anything that takes up space and has mass
• Matter is made up of elements
• element - substance that cannot be broken down to other substances
Na Cl NaCl
Sodium and water
compound -consists of 2 or more elements in fixed ratio-characteristics different from those of its elements
Essential Elements of LifeAbout 25 of the 92 elements are essential to life
(humans)
• CHON =96% of living matter
• Also…….
• Trace elements required by an organism in minute quantities
(b) Iodine deficiency
Trace amounts of iodine required for thyroid function
Copper deficiency prevents full opening of leaves
An element’s propertiesdepend on structure of its atoms
• atom =smallest unit of matter that still retains properties of element
• subatomic particles• Neutrons (no electrical charge)• Protons (+ charge)
– # protons defines the element
• Electrons (- charge)
Isotopes
• Isotopes – Atoms of an element that differ in # of neutrons
• Radioactive isotopes – Isotope decays particles and energydecay– Half life = lifetime for ½ of the isotopes to decay
FYI
number of protons and neutrons
number of protons
12Cis stable , 6 neutrons 14C is radioactive, 8 neutrons98.89% of carbon
FYI• Atomic numbers (# protons) 1 through 40 are considered stable isotopes• Elements 41 through 82 are stable. The half lives of elements 41 through 82 are so long
that their radioactive decay has yet to be detected by experiment (100 million times longer than the age of the universe)
• 83 through 94 radioactive decay can be detected. – uranium has one or more isotopes with half lives long enough to survive as remnants of the explosive big
bang
• 94 and higher only observed experimentally – extremely short half life• Tritium (3H) low energy beta particle. 12.35 years. Used to tag DNA. No shield necessary.
Wear gloves.• Carbon-14 decays into nitrogen-14 by emission of a beta particle. Half life 5730 years. No
shield, wear gloves, can penetrate skin. • Phosphorus-32 a beta particle. Half life 14.2 days. Use plexiglass. • Iodine-125 gamma rays. 60 day half life. biological assays, nuclear medicine imaging and
in radiation therapy. Thyroid cancer treatment. Use lead shield.• Polonium has 26 isotopes, all radioactive. 250 billion times more toxic than hydrocyanic
acid. It is readily soluble in weak acid. It was the first element discovered by Marie Curie, in 1898, and named after her native Poland. Her daughter Irene was contaminated with polonium in a laboratory accident and died of leukemia at the age of 59.
FYI• 2006, Litvinenko fell ill. Earlier he had met two former KGB officers in London. Had to
do with information on death of journalist killed at her Moscow apartment 2006. • For several days , Litvinenko experienced severe diarrhea and vomiting. Litvinenko's
condition worsened as doctors searched for what caused the illness. Litvinenko began to become physically weak, and spent periods unconscious
• Shortly after death, it was found Litvinenko had significant amounts of (210Po) in his body. The poison was in Litvinenko's tea cup.
• Polonium was identified after Litvinenko's death, on 23 November. Doctors could not detect polonium earlier because it only emits alpha particles that do not penetrate human skin, thus being invisible to hospital radiation detectors . An alpha-emitting substance can cause significant damage only if ingested or inhaled, acting on living cells like a short-range weapon.
• The symptoms seen in Litvinenko appeared consistent with an administered activity of approximately (50 mCi which corresponds to about 10 micrograms of 210Po. 200 times the lethal dose
A PET scan (positron emission tomography) detects locations of intense chemical activity. Inject patient with radioactive glucose. A scanner measures collisions of the radioactive glucose with active cells to locate tumor
Radiolabeled glucose atom used in PET scans
Example: Use of isotopes in research
Hypothesis:Cells reproduce faster at higher temperatures
Hela cells
3H-thymidine,building block of DNA
Cells
Isolated DNA is radioactive
Add tritiated thymidine to cells. Cells incorporate isotope into new DNA
1 cells at 10oC215oC320oC425oC530oC635oC740oC845oC950oC
1 2 3
7 8
9
• Structural formula represents atom bonding
H–OH
• Molecular formula abbreviation
H2O
Chemical Formulas
4. Van der Waals Interactions
• Between molecules of the same substance • Similar to hydrogen bonds but weaker• BBC gecko • Van der waals gecko and synthetic glue
Molecular Shape and Function
• molecules have specificity/function based on shape
• similar shapes can have similar biological effects
(a) Structures of endorphin and morphine
(b) Binding to endorphin receptors
Naturalendorphin
Endorphinreceptors
Morphine
Brain cell
Morphine
Natural endorphin
Key Carbo
nHydrogen
NitrogenSulfurOxygen
Chemical reactions
Chemical reactions make and break chemical bonds– reactants - starting molecules– products - final molecules