Category: Chemistry

Knowing the Elements

Knowing the Elements

Choose one element from the periodic table. (You may not select an element that someone else has already selected, and the element must be found in living things!) Use library books or the website on the back of this sheet to find the information asked for below and to write a 1-2 page paper on that element. Your paper must include the following information to receive credit:

v Name of the element?

v Element’s symbol?

v Family the element is found in?

v Period the element is found in?

v Atomic number of the element?

v Atomic Mass of the element?

v Number of protons?

v Number of neutrons?

v Number of electrons?

v Number of electrons in the outermost energy level?

v Is the element a metal, nonmetal, transition element?

v Is the element inert (nonreactive) or reactive?

v What are the other chemical properties of this element (appearance, state of matter, etc.?

v What are some uses by living things for this element?

v Where is this element found inside of living things and in what amount is it present?

 

***Be sure to answer all questions about the element in your paper. Go to other websites if you need to find more information.

Helpful Links:
Http://www.webelements.com/webelements/scholar/index.html
Http://www.chemicalelements.com
Http://www.webelements.com

 

Chemiosmotic Theory

17 October 1978

The Royal Swedish Academy of Sciences decided to award the 1978 Nobel Prize in Chemistry to
Dr Peter Mitchell, Glynn Research Laboratories, Bodmin, Cornwall, UK, for his contribution to the understanding of biological energy transfer through the formulation of the chemiosmotic theory.

Peter Mitchell

Chemiosmotic Theory of Energy Transfer

Introduction

Peter Mitchell was born in Mitcham, in the County of Surrey, England, on September 29, 1920. His parents, Christopher Gibbs Mitchell and Kate Beatrice Dorothy (née) Taplin, were very different from each other temperamentally. His mother was a shy and gentle person of very independent thought and action, with strong artistic perceptiveness. Being a rationalist and an atheist, she taught him that he must accept responsibility for his own destiny, and especially for his failings in life.That early influence may well have led him to adopt the religious atheistic personal philosophy to which he has adhered since the age of about fifteen. His father was a much more conventional person than his mother, and was awarded the O.B.E. for his success as a Civil Servant.

Peter Mitchell was educated at Queens College, Taunton, and at Jesus college, Cambridge. At Queens he benefited particularly from the influence of the Headmaster, C. L. Wiseman, who was an excellent mathematics teacher and an accomplished amateur musician. The result of the scholarship examination that he took to enter Jesus College Cambridge was so dismally bad that he was only admitted to the University at all on the strength of a personal letter written by C. L. Wiseman. He entered Jesus College just after the commencement of war with Germany in 1939. In Part I of the Natural Sciences Tripos he studied physics, chemistry, physiology, mathematics and biochemistry, and obtained a Class III result. In part II, he studied biochemistry, and obtained a II-I result for his Honours Degree.

He accepted a research post in the Department of Biochemistry, Cambridge, in 1942 at the invitation of J. F. Danielli. He was very fortunate to be Danielli’s only Ph.D. student at that time, and greatly enjoyed and benefited from Danielli’s friendly and unauthoritarian style of research supervision. Danielli introduced him to David Keilin, whom he came to love and respect more than any other scientist of his acquaintance.

He received the degree of Ph.D. in early 1951 for work on the mode of action of penicillin, and held the post of Demonstrator at the Department of Biochemistry, Cambridge, from 1950 to 1955. In 1955 he was invited by Professor Michael Swann to set up and direct a biochemical research unit, called the Chemical Biology Unit, in the Department of Zoology, Edinburgh University, where he was appointed to a Senior Lectureship in 1961, to a Readership in 1962, and where he remained until acute gastric ulcers led to his resignation after a period of leave in 1963.

From 1963 to 1965, he withdrew completely from scientific research, and acted as architect and master of works, directly supervising the restoration of an attractive Regency-fronted Mansion, known as Glynn House, in the beautiful wooded Glynn Valley, near Bodmin, Cornwall – adapting and furnishing a major part of it for use as a research labotatory. In this, he was lucky to receive the enthusiastic support of his fornler research colleague Jennifer Moyle. He and Jennifer Moyle founded a charitable company, known as Glynn Research Ltd., to promote fundamental biological research and finance the work of the Glynn Research Laboratories at Glynn House. The original endowment of about £250,000 was donated about equally by Peter Mitchell and his elder brother Christopher John Mitchell.

In 1965, Peter Mitchell and Jennifer Moyle, with the practical help of one technician, Roy Mitchell (unrelated to Peter Mitchell), and with the administrative help of their company secretary, embarked on the programme of research on chemiosmotic reactions and reaction systems for which the Glynn Research Institute has become known. Since its inception, the Glynn Research Institute has not had sufficient financial resources to employ more than three research workers, including the Research Director, on its permanent staff. He has continued to act as Director of Research at the Glynn Research Institute up to the present time. An acute lack of funds has recently led to the possibility that the Glynn Research Institute may have to close.

Mitchell studied the mitochondrion, the organelle that produces energy for the cell. ATP is made within the mitochondrion by adding a phosphate group to ADP in a process known as oxidative phosphorylation. Mitchell was able to determine how the different enzymes involved in the conversion of ADP to ATP are distributed within the membranes that partition the interior of the mitochondrion. He showed how these enzymes’ arrangement facilitates their use of hydrogen ions as an energy source in the conversion of ADP to ATP.


Chemiosmotic hypothesis: Proposed by Peter Mitchel (1970)
to explain how NADH oxidation is coupled to ATP synthesis.
As electrons are passed down the chain, protons are pumped across the membrane (between the inner membrane and outer membrane of the cristae or thylakoids). This results in a pH and electrical gradient. The protons move back into the matrix through a pore created by ATP synthetase allowing the enzyme to make ATP at the expense of this gradient.

Peter Mitchell’s 1961 paper introducing the chemiosmotic hypothesis started a revolution which has echoed beyond bioenergetics to all biology, and shaped our understanding of the fundamental mechanisms of biological energy conservation, ion and metabolite transport, bacterial motility, organelle structure and biosynthesis, membrane structure and function, homeostasis, the evolution of the eukaryote cell, and indeed every aspect of life in which these processes play a role. The Nobel Prize for Chemistry in 1978, awarded to Peter Mitchell as the sole recipient, recognized his predominant contribution towards establishing the validity of the chemiosmotic hypothesis, and ipso facto, the long struggle to convince an initially hostile establishment.

NOBEL PRIZE IN CHEMISTRY FOR BIOLOGICAL ENERGY TRANSFER

Mitchell’s research has been carried out within an area of biochemistry often referred to in recent years as ‘bioenergetics’, which is the study of those chemical processes responsible for the energy supply of living cells. Life processes, as all events that involve work, require energy, and it is quite natural that such activities as muscle contraction, nerve conduction, active transport, growth, reproduction, as well as the synthesis of all the substances that are necessary for carrying out and regulating these activities, could not take place without an adequate supply of energy.

It is now well established that the cell is the smallest biological entity capable of handling energy. Common to all living cells is the ability, by means of suitable enzymes, to derive energy from their environment, to convert it into a biologically useful form, and to utilize it for driving various energy requiring processes. Cells of green plants as well as certain bacteria and algae can capture energy by means of chlorophyll directly from sunlight – the ultimate source of energy for all life on Earth – and utilize it, through photosynthesis, to convert carbon dioxide and water into organic compounds. Other cells, including those of all animals and many bacteria, are entirely dependent for their existence on organic compounds which they take up as nutrients from their environment. Through a process called cell respiration, these compounds are oxidized by atmospheric oxygen to carbon dioxide and water.

During both photosynthesis and respiration, energy is conserved in a compound called adenosine triphosphate, abbreviated as ATP. When ATP is split into adenosine diphosphate (ADP) and inorganic phosphate (Pi), a relatively large amount of energy is liberated, which can be utilized, in the presence of specific enzymes, to drive various energy-requiring processes. Thus, ATP may be regarded as the universal ‘energy currency’ of living cells. The processes by which ATP is formed from ADP and Pi during photosynthesis and respiration are usually called ‘photophosphorylation’ and ‘oxidative phosphorylation’, respectively. The two processes have several features in common, both in their enzyme composition – both involve an interaction between oxidizing (electron-transferring) and phosphorylating enzymes – and in their association with cellular membranes. In higher cells, photophosphorylation and oxidative phosphorylation occur in specific membrane-enclosed organelles, chloroplasts and mitochondria, respectively; in bacteria, both these processes are associated with the cell membrane.

The above concepts had been broadly outlined by about the beginning of the 1960s, but the exact mechanisms by which electron transfer is coupled to ATP synthesis in oxidative phosphorylation and in photophosphorylation remained unknown. Many hypotheses were formulated, especially with regard to the mechanism of oxidative phosphorylation; most of these postulated a direct chemical interaction between oxidizing and phosphorylating enzymes. Despite intensive research in many laboratories, however, no experimental evidence could be obtained for any of these hypotheses. At this stage, in 1961, Mitchell proposed an alternative mechanism for the coupling of electron transfer to ATP synthesis, based on an indirect interaction between oxidizing and phosphorylating enzymes. He suggested that the flow of electrons through the enzymes of the respiratory or photosynthetic electron-transfer chains drives positively charged hydrogen ions, or protons, across the membranes of mitochondria, chloroplasts and bacterial cells. As a result, an electrochemical proton gradient is created across the membrane. The gradient consists of two components: a difference in hydrogen ion concentration, or pH, and a difference in electric potential; the two together form what Mitchell calls the ‘protonmotive force’. The synthesis of ATP is driven by a reverse flow of protons down the gradient. Mitchell’s proposal has been called the ‘chemiosmotic theory’.

This theory was first received with scepticism; but, over the past 15 years, work in both Mitchell’s and many other laboratories have shown that the basic postulates of his theory are correct. Even though important details of the underlying molecular mechanisms are still unclear, the chemiosmotic theory is now generally accepted as a fundamental principle in bioenergetics. This theory provides a rational basis for future work on the detailed mechanisms of oxidative phosphorylation and photophosphorylation. In addition, this concept of biological power transmission by protonmotive force (or ‘proticity’, as Mitchell has recently began to call it in an analogy with electricity) has already been shown to be applicable to other energy-requiring cellular processes. These include the uptake of nutrients by bacterial cells, cellular and intracellular transport of ions and metabolites, biological heat production, bacterial motion, etc. In addition, the chloroplasts of plants, which harvest the light-energy of the sun, and the mitochondria of animal cells, which are the main converters of energy from respiration, are remarkably like miniaturized solar- and fuel-cell systems. Mitchell’s discoveries are therefore both interesting and potentially valuable, not only for the understanding of biological energy-transfer systems but also in relation to the technology of energy conversion.

http://nobelprize.org/nobel_prizes/chemistry/laureates/1978/press.html

 

 

Chemistry Notes BI

Chemistry Notes

I. Matter Is Composed of Elements

A. Matter

1. Matter refers to anything that takes up space and has mass.

2. All matter (living and nonliving) is composed of basic elements.

a. Elements cannot be broken down to substances with different chemical or physical properties.

b. Six elements (C, H, N, O, P, S) are commonly found in living things.

B. Elements Contain Atoms

1. Chemical and physical properties of atoms (e.g., weight) depend on the subatomic particles.

a. Different atoms contain specific numbers of protons, neutrons, and electrons.

b. Protons and neutrons are in nucleus of atoms; electrons move around nucleus.

c. Protons are positively charged particles; neutrons have no charge; both have about 1 atomic mass unit of weight.

d. Electrons are negatively charged particles; weight about 1/1800 atomic mass unit.

2. Isotopes have different weights.

a. Isotopes are atoms with the same number of protons but differ in number of neutrons; e.g., a carbon atom has six protons but may have more or less than usual six neutrons.

b. Isotopes have many uses:

1) Determine diet of ancient peoples by determining proportions of isotopes in mummified or fossilized human tissues

2) Tracers of biochemical pathways

3) Determine age of fossils using radioactive isotopes

4) Source of radiation used in medical diagnostic and treatment procedures

C. Atoms Have Chemical Properties

1. Protons are positively charged; electrons are negatively charged; Oppositely charged protons and electrons are attracted to each other.

2. Atom’s proton number determines atom’s number of electrons and its chemical properties.

3. Arrangement of atom’s electrons is determined by total number of electrons and electron shell they occupy.

a. Energy is the ability to do work.

b. Electrons with least amount of potential energy are located in K shell closest to nucleus; electrons having more potential energy are located in shells farther from nucleus.

c. Atomic Configurations

1) Bohr model helps determine number of electrons in outer shell.

2) Inner shell contains up to two electrons; additional shells contain eight electrons.

3) Elements are arranged in rows in periodic table according to number of electrons in outer shell.

d. How atoms react with one another is dependent upon number of electrons in outer shell.

1) Atoms with filled outer shells do not react with other atoms.

2) In atom with one shell, outer shell is filled when it contains two electrons.

3) For atoms with more than one shell, the octet rule applies; outer shell is stable when it contains eight electrons.

4) Atoms with unfilled outer shells react with other atoms so each has stable outer shell.

5) Atoms can give up, accept, or share electrons in order to have a stable outer shell.

e. Electrons Occupy Orbitals

1) Orbital is a volume of space where rapidly moving electrons are predicted to be found.

2) An orbital has a characteristic energy state and a characteristic shape.

3) At first energy level (K shell), there is only one spherically shaped orbital, where at most two electrons are found about the nucleus.

4) At second energy level (L shell), there is one spherically shaped orbital and three dumbbell shaped orbitals; the second energy level contains at most eight electrons.

5) Higher energy levels may contain more orbitals; however, outer shells have a maximum of four orbitals and eight electrons.

II. Atoms Form Compounds and Molecules

A. Molecules

1. Molecules are atoms held together by chemical bonds.

2. Molecules form when two or more atoms of same element react with one another (e.g., O2).

3. Two or more different elements react or bond together to form a compound (e.g., H2O).

4. Electrons possess energy; bonds that exist between atoms in molecules contain energy.

B. Opposite Charges in Ionic Bonding

1. Ionic bonds form when electrons are transferred from one atom to another.

2. Losing or gaining electrons, atoms participating in ionic reactions fill outer shells, and are more stable.

3. Example: sodium with one less electron has positive charge; chlorine has extra electron that has negative charge. Such charged particles are called ions.

4. Attraction of oppositely charged ions holds the two atoms together in an ionic bond.

C. Sharing in Covalent Bonding

1. Covalent bond results when two atoms share electrons so each atom has octet of electrons in outer shell.

2. Hydrogen can give up electron to become hydrogen ion (H+) or share with another atom to complete its outer shell of two electrons.

3. Structural formulas represent shared atom as a line between two atoms; e.g., single covalent bond (H H), double covalent bond (O O), and triple covalent bond (N N).

D. Oxidation Is the Opposite of Reduction

1. Oxidation merely means the loss of electrons (or loss of hydrogen atoms).

2. Reduction merely means the gain of electrons (or gain of hydrogen atoms).

3. In ionic reaction Na + Cl Na+Cl-, sodium has been oxidized, chlorine has been reduced.

E. Some Covalent Bonds Are Polar

1. In nonpolar covalent bonds, sharing of electrons is equal.

2. With polar covalent bonds, the sharing of electrons is unequal.

a. In water molecule (H2O), sharing of electrons by oxygen and hydrogen is not equal; the oxygen atom with more protons dominates the H2O association.

b. Attraction of an atom for electrons in a covalent bond is called electronegativity; oxygen atom is more electronegative than hydrogen atom.

c. Oxygen in water molecule, more attracted to electron pair, assumes small negative charge.

3. Hydrogen Bonding

a. Hydrogen bond is weak attractive force between slightly positive hydrogen atom of one molecule and slightly negative atom in another or the same molecule.

1) Many hydrogen bonds taken together are relatively strong.

2) Hydrogen bonds between complex molecules of cells help maintain structure and function.

III. Water Is Essential to Life

A. Life Evolved in Water

1. All living things are 70-90%.

2. Because water is a polar molecule, water molecules are hydrogen bonded to each other.

3. With hydrogen bonding, water is liquid between 0° C and 100° C which is critical for life.

B. Water Has Unique Properties

1. The temperature of liquid water rises and falls more slowly than that of most other liquids.

a. Calorie is amount of heat energy required to raise temperature of one gram of water 1° C.

b. Because water holds heat, its temperature falls more slowly than other liquids; this protects organisms from rapid temperature changes and helps them maintain normal temperatures.

2. Water has a high heat of vaporization.

a. Hydrogen bonds between water molecules require a large amount of heat to break.

b. This property moderates earth’s surface temperature; permits living systems to exist here.

c. When animals sweat, evaporation of the sweat takes away body heat, thus cooling the animal.

3. Water is universal solvent, facilitates chemical reactions both outside of and within living systems.

a. Water is a universal solvent because it dissolves a great number of solutes.

b. Ionized or polar molecules attracted to water are hydrophilic.

c. Nonionized and nonpolar molecules that cannot attract water are hydrophobic.

4. Water molecules are cohesive and adhesive.

a. Cohesion allows water to flow freely without molecules separating, due to hydrogen bonding.

b. Adhesion is ability to adhere to polar surfaces; water molecules have positive, negative poles.

c. Water rises up tree from roots to leaves through small tubes.

1) Adhesion of water to walls of vessels prevents water column from breaking apart.

2) Cohesion allows evaporation from leaves to pull water column from roots.

5. Water has a high surface tension measured by how difficult it is to break the surface of a liquid.

a. As with cohesion, hydrogen bonding causes water to have high surface tension.

b. Permits a rock to be skipped across pond surface; supports insect walking on water surface.

6. Unlike most substances, frozen water is less dense than liquid water.

a. Below 4° C, hydrogen bonding becomes more rigid but open, causing expansion.

b. Because ice is less dense, it floats; therefore, bodies of water freeze from the top down.

c. If ice was heavier than water, ice would sink and ponds would freeze solid.

C. Water and Acids and Bases

1. Covalently bonded water molecules ionize; the atoms dissociate into ions.

2. When water ionizes or dissociates, it releases a small (107 moles/liter) but equal number of H+ and OHB ions; thus, its pH is neutral.

3. Water dissociates into hydrogen and hydroxide ions: H O H H+ + OH-.

4. Acid molecules dissociate in water, releasing hydrogen ions (H+) ions: HCl Cl H+ + Cl-.

5. Bases are molecules that take up hydrogen ions or release hydroxide ions. NaOH Cl Na+ + OH-.

6. The pH scale indicates acidity and basicity (alkalinity) of a solution.

a. Measure of free hydrogen ions as a negative logarithm of the H+ concentration (-log [H+]).

b. pH values range from 0 (100 moles/liter; most acidic) to 14 (1014 moles/liter; most basic).

1) One mole of water has 107 moles/liter of hydrogen ions; therefore, has neutral pH of 7.

2) Acid is a substance with pH less than 7; base is a substance with pH greater than 7.

3) As logarithmic scale, each lower unit has 10× amount of hydrogen ions as next higher pH unit; as move up pH scale, each unit has 10× basicity of previous unit.

7. Buffers keep pH steady and within normal limits in living organisms.

a. Buffers stabilize pH of a solution by taking up excess hydrogen or hydroxide ions.

b. Carbonic acid helps keep blood pH within normal limits: H2CO3 H+ + HCO3-.

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