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Unit 1

Life and Levels of Organization of Living Matter

Listening

Life

All of us have an intuitive understanding of what it means to be alive. However, defining life is difficult, partly because living things are so diverse and non-living matter looks like life in some cases. What’s more, living things cannot be described as the sum of their parts. The quality of life emerges as a result of incredibly complex, ordered interactions among these parts. Among the characteristics of living things that, taken together, are not shared by non-living things are the following: living things consist of organic molecules, they acquire and use materials and energy from their environment and convert them into different forms, they grow and reproduce.

Unit 2

Biological Molecules

Protein Structure – a Hairy Subject

A single strand of human hair, thin and not even alive, is nonetheless a highly organized, complex structure. Hair is composed mostly of a single, helical protein called keratin. If we look closely at the structure of hair, we can learn a great deal about biological molecules, chemical bonds, and why human hair behaves as it does.

A single hair consists of a hierarchy of structures. The outermost layer is a set of overlapping shingle-kike scales that protect the hair and keep it from drying out. Inside the hair lie closely packed, cylindrical dead cells, each filled with long strands called microfibrils. Each microfibril is a bundle of protofibrils, and each protofibril contains helical keratin molecules twisted together. As a hair grows, living cells in the hair follicle embedded in the skin whip out new keratin at the rate of 10 turns of the protein helix every second.

Pull the ends of a hair, and you will notice that it is rather strong. Hair gets its strength from three types of chemical bonds. First, the individual molecules of keratin are held in their helical shape by many hydrogen bonds. Before a hair will break, all the hydrogen bonds of all the keratin molecules in one cross-sectional plane of the strand must break to allow the helix to be stretched to its maximal extent. Second, each molecule is cross-linked to neighboring keratin molecules by disulfide bridges between cysteines (particular amino acids). Some of these bridges must break as the hair stretches. Finally, at least one peptide bond in each keratin molecule must break the strand as a whole breaks.

Hair is also fairly stiff. The stiffness arises from hydrogen bonds within the individual helices of keratin molecules together. When hair gets wet, however, the hydrogen bonds between turns of the helices are replaced by hydrogen bonds between the amino acids and the water molecules surrounding them, so the helices collapse. Wet hair is therefore very limp. If wet hair is rolled onto curlers and allowed to dry, the hydrogen bonds re-form in slightly different places, holding the hair in a curve. The slightest moisture, even humid air, allows hydrogen bonds to rearrange into their natural configuration, and normally straight hair straightens out.

Pull gently, and you will discover still another property of hair. It stretches and then springs back into shape when you release the tension. When hair stretches, many of the hydrogen bonds within each keratin helix are broken, allowing the helix to be extended. Most of the covalent disulfide bonds between different levels of the helices, in contrast, are distorted by stretching but do not break. When tension is released, these disulfide bridges contract, returning the hair to its normal length.

Finally, each hair has a characteristic shape: It may be straight, wavy, or curly. The curliness of hair is genetically specified and is determined biochemically by the arrangement of disulfide bridges. Curly hair has disulfide bridges cross-linking the various keratin molecules at different levels, whereas straight hair has bridges mostly at the same level. When straight hair is given a “permanent”, two lotions are applied. The first lotion breaks disulfide bonds between neighboring helices. The hair is then rolled tightly onto curlers, and a second solution, which re-forms the bridges, is applied. The new disulfide bridges connect helices at different levels, holding the strands of hair in a curl. These new bridges are more or less permanent, and genetically straight hair can be transformed into biochemically curly hair. As new hair grows in, it will have the genetically determined arrangement of bridges and will not be curly.

Unit 3

Energy Flow in the Life of a Cell

Introduction

Listen and answer the questions.

1. What is caused within a system by any use of energy (according to the second law of thermodynamics)?

2. How does energy flow in chemical reactions?

3. Give an example of an exergonic reaction.

4. How is cellular energy carried between coupled reactions?

The flow of energy among atoms and molecules obeys the laws of thermodynamics. The first law of thermodynamics states that, assuming there is no influx of energy, the total amount of energy remains constant, although it may change in form. The second law of thermodynamics states that any use of energy causes a decrease in the quantity of concentrated, useful energy and an increase in the randomness and disorder of matter. Entropy is a measure of disorder within a system.

Chemical reactions fall into two categories. In exergonic (Greek for “energy out”) reactions, the product molecules have less energy than do the reactant molecules, so the reaction releases energy. In endergonic (Greek for “energy in”) reactions, the products have more energy than do the reactants, so the reactions can occur spontaneously, but all reactions, including exergonic ones, require an initial input of energy (the activation energy) to overcome electrical repulsions between reactant molecules. Exergonic and endergonic reactions may be coupled such that the energy liberated by an exergonic reaction drives the endergonic reaction. Organisms couple exergonic reactions such as light-energy capture or sugar metabolism with endergonic reactions such as synthesis of organic molecules.

Energy released by chemical reactions within a cell is captured and transported about the cell by energy-carrier molecules such as ATP and electron carriers. These molecules are the major means by which cells couple exergonic and endergonic reactions that occur at different places in the cell.

Unit 4

Principles of Evolution

Introduction

Listen to a brief biography of a very famous scientist. A student first to say the scientist’s name will win the contest.

1. The son of a country parson who greatly loved flowers, in his youth he set himself the task of establishing new system for describing and ordering animals, plants and minerals.

2. He studied at the university in Lund, Uppsala and in Harderwijk, Holland, where he obtained his M.D.

3. In Holland worked as superintendent of George Clifford's botanical garden near Harlem; published Systema Naturae, presenting his new system of taxonomy.

4. Having returned to his motherland, he was appointed a physician to the admiralty, helped to found the Academy of Science, became a professor of medicine at the University of Uppsala;

5. Renovated the university's botanical garden, where he lived for the rest of his life; was elevated to the nobility.

6. Brought an urgently needed simplicity to the classification of plants; worked out a sexual system, grouping plants in classes, according to the number and order of stamens, and then into orders, mostly according to the number of pistils; although he realized that this was an artificial structure, he did not fully work out a more "natural" system;

7. Was the first to work with species as a clearly defined concept;

8. Introduced binomial nomenclature based on genus and species; concluded that for every natural plant order, only one species had been created originally.

9. Published his most influential work Philosophia botanica (an expansion of Fundamental botanica)in 1751.

10. In Species plantarum he described about 8000 plant species; his definitive 10^th edition of Systema naturae appeared in 1758-59.

11. In Oeconomica naturae he developed concepts of the balance and competition in nature among the insects, animals and plants.

12. Was less influential in the classification of the animal and mineral kingdoms but did group man with the apes, and was the to recognize whales as mammals; his insect orders are still recognized.

Based on the Concise Dictionary of Scientific Biography 2000 New York

Answer: Linneus (or von Linne), Carl.

Unit 5

The History of Life on Earth

Introduction

Listen to the account of the history of ideas concerning the generation of life on Earth and discuss in pairs whether the following sentences are true or false.

How and when did life first appear on Earth? Just a few centuries ago, this question would have been considered trivial. Although no one knew how life first arose, people thought that new living things appeared all the time, through spontaneous generation from both nonliving matter and other, unrelated forms of life. In 1609, a French botanist wrote, “There is a tree… frequently observed in Scotland. From the tree leaves are falling: upon one side they strike the water and slowly turn into fishes, upon the other they strike the land and turn into birds.” Medieval writings abound with similar observations and delightful recipes for creating life – even human beings. Microorganisms were thought to arise spontaneously from broth, maggots from meat, and mice from mixtures of sweaty shirts and wheat.

In 1668 the Italian physician Francesco Redi disproved the maggots-from-meat hypothesis simply by keeping flies (whose eggs hatch into maggots) away from uncontaminated meat. Then in the mid-1800s, Louis Pasteur in France and John Tyndall in England disproved the broth-to-microorganism idea. Although their work effectively demolished the notion of spontaneous generation, it did not address the question of how life on Earth originated in the first place.

For almost half a century, the subject lay dormant. Eventually, biologists returned to the question of the origin of life and began to seek answers. In the 1920s and 1930s, Alexander Oparin in Russia and John B. S. Haldane in England noted that the oxygen-rich atmosphere that we know would not have permitted the spontaneous formation of the complex organic molecules necessary for life. Oxygen reacts rapidly with other molecules, disrupting chemical bonds and thus tending to keep molecules simple. Oparin and Haldane speculated that the atmosphere of the young Earth was very low in oxygen and rich in hydrogen in the form of hydrogen gas (H2), methane (CH4), and ammonia (NH3). Given these and other conditions Oparin and Haldane proposed that life could have arisen from nonliving matter through ordinary chemical reactions. This process is called chemical evolution, or prebiotic evolution: that is, evolution before life existed.

1. Several centuries ago no one thought it difficult to answer the question of how living things had arisen. T

2. Earlier people thought that life had appeared spontaneously from nonliving things and other forms of life. T

3. In Medieval texts the authors suggested ways of creating nonliving things from living things. F: “Medieval writings abound with similar observations and delightful recipes for creating life – even human beings”

4. People thought that microorganisms had arisen from broth and wheat. F: “Microorganisms were thought to arise spontaneously from broth, maggots from meat, and mice from mixtures of sweaty shirts and wheat.”

5. Francesco Redi proved that maggots did not arise from rotting meat. T

6. Louis Pasteur’s ideas did not answer the question of how life on Earth had originated. T

7. Alexander Oparin thought that complex organic molecules could be formed spontaneously only if oxygen was around. F: “Alexander Oparin in Russia and John B. S. Haldane in England noted that the oxygen-rich atmosphere that we know would not have permitted the spontaneous formation of the complex organic molecules necessary for life.”

8. Oxygen keeps molecules simple. T

9. Oparin and Haldane argued that the primordial atmosphere consisted of hydrogen gas, methane and free oxygen. F: “Oparin and Haldane speculated that the atmosphere of the young Earth was very low in oxygen and rich in hydrogen in the form of hydrogen gas (H2), methane (CH4), and ammonia (NH3).”

10. Prebiotic evolution means evolution of nonliving matter to become living matter. T

Unit 6

Biotechnology

Introduction

Listen to the abstract and compare the answers with your ideas:

- What is a definition of biotechnology?

- What are goals of genetic engineering?

In its broadest sense, biotechnology is defined as any industrial or commercial use or alteration of organisms, cells, or biological molecules to achieve specific practical goals. By this definition, biotechnology is nothing new – it is as old as the use of yeast to make bread rise or to ferment grape juice into wine, a process that originated 10,000 years ago. It is as old as selective breeding of plants and animals in agriculture. Squash fragments preserved in a dry cave in Mexico were recently dated as 8000-10,000 years old. Their seeds are larger and their rinds thicker and more colorful than those of wild varieties, providing evidence or selective breeding – a very early form of genetic manipulation by humans. Prehistoric art and animal remains suggest that dogs, sheep, goats, and camels were domesticated 10,000 – 12,000 years ago.

Modern biotechnology commonly utilizes genetic engineering, the modification of genetic material to achieve specific goals. Genetically engineered cells may have genes deleted, added, or replaced. The major goals of genetic engineering are threefold:

1.to understand more about the processes of inheritance and gene expression;

2.to provide better understanding and treatment of various diseases, particularly genetic disorders, and

3.to generate economic benefits, including improved plants and animals for agriculture and efficient production of valuable biological molecules.

Unit 7

The Double Helix

Introduction

Listen to the text “Red Bread Mold Provided Insight into the Role of Genes”. Say whether the following statements are true or false.