VI Read and translate the text about enzymes

Enzymes and Chemical Reactions

Substances that can speed up a chemical reaction without being permanently altered themselves are called catalysts. In living cells, enzymes serve as biological catalysts. As catalysts, enzymes are specific. Each acts on a specific substance, called the enzyme's substrate (or substrates, when there are two or more reactants), and each catalyzes only one reaction. For example, sucrose (table sugar) is the substrate of the enzyme sucrose, which catalyzes the hydrolysis of sucrose to glucose and fructose.

As catalysts, enzymes typically accelerate chemical reactions. The three-dimensional enzyme molecule has an active site, a region that interacts with a specific chemical substance.

The enzyme orients the substrate into a position that increases the probability of a reaction. The enzyme-substrate complex formed by the temporary binding of enzyme and reactants enables the collisions to be more effective and lowers the activation energy of the reaction. The enzyme therefore speeds up the reaction by increasing the number of molecules that attain sufficient activation energy to react.

An enzyme's ability to accelerate a reaction without the need for an increase in temperature is crucial to living systems because a significant temperature increase would destroy cellular proteins. The crucial function of enzymes, therefore, is to speed up biochemical reactions at a temperature that is compatible with the normal functioning of the cell.

VII Remember the following word and word-combinations:

Speed up, catalyst, sucrose, hydrolysis, to accelerate, three-dimensional, to increase, to interact, to attain, temporary binding of enzyme, significant temperature, crucial, compatible.

VIII Fill in the gaps with the proper words:

1. Enzymes typically … chemical reactions.

2. In living cells, … serve as biological catalysts.

3. Substances that can speed up a chemical reaction without being permanently altered themselves are called…

4. The … enzyme molecule has an active site, a region that interacts with a specific chemical substance.

5. The crucial function of enzymes is … biochemical reactions at a temperature that is compatible with the normal functioning of the cell.

IX Translate into English:

Вещества, ускоряющие химические реакции, биологические катализаторы, катализирует только одну реакцию, ферменты ускоряют химическую реакцию, увеличение числа молекул, разрушить клеточные белки.

X Answer the questions:

1. What does mean catalyst?

2. What is crucial function of enzymes?

3. How is formed the enzyme-substrate complex?

4. How does catalyze hydrolysis of sucrose?

5. How are called the enzymes in living organisms?

24-26 Practical lesson

Rules of reading: The3^rdtype of reading

Word formation: suffix of noun – ing

Text:Photosynthesis

Assignments to do:

I Remember:

a) The combination of a vowel +r is pronounced as follows:

A	O	E I Y U
[a:]	[o:]	[Ә:]
large	fork	Term, firm, fur

b) Suffix – ing forms the nouns from the verbs: to begin - beginning

II Read the words paying attention to the pronunciation:

Burn, fur, firm, sir, far, fork, car, corn, thirst, Earth, organism, article.

III Give the transcription to the following words:

First, or, term, her, sister, word, sugar, art, large, sir, verb.

IV Form the nouns from the verb:

To learn, to begin, to release, to follow, to read.

V Read the international words and guess their meaning:

Photosynthesis, energy, carbon dioxide (CO₂), atmosphere, synthesis, fixation, to summarize, granule, adenosine diphosphate, adenosine triphosphate, assembly.

VI Read and translate the text about photosynthesys

Photosynthesis

Photosynthesis is the conversion of light energy from the sun into chemical energy. The chemical energy is then used to convert CO ₂ from the atmosphere to more reduced carbon compounds, primarily sugars. The word photosynthesis summarizes the process: photo means light, and synthesis refers to the assembly of organic compounds. This synthesis of sugars by using carbon atoms from CO ₂ gas is also called carbon fixation. Continuation of life as we know it on Earth depends on the recycling of carbon in this way. Cyanobacteria, algae, and green plants all contribute to this vital recycling with photosynthesis.

Photosynthesis can be summarized with the following equations:

1. Plants, algae, and cyanobacteria use water as a hydrogen donor, releasing O₂

6 CO₂ + 12 H₂ 0 + Light energy---- C₆H₁₂ 0₆ + 6 H₂0 + 6 O₂

2. Purple sulfur and green sulfur bacteria use H₂S as a hydrogen donor, producing sulfur granules.

6 CO₂ + 12 H₂S + Light energy---- C₆ H₁₂0₆+ 6 H₂ 0 + 12S

In the course of photosynthesis, electrons are taken from hydrogen atoms, an energy-poor molecule, and incorporated into sugar, an energy-rich molecule. The energy boost is supplied by light energy, although indirectly.

Photosynthesis takes place in two stages. In the first stage, called the (light) reactions. Light energy is used to convert ADP and to ATP. In the second stage, the light-independent (dark) reactions, these electrons are used along with energy from ATP to reduce CO₂ to sugar.

VII Remember the following word and word-combinations:

Conversion, light energy, the assembly of organic compounds, to contribute, vital recycling, equation, purple sulfur bacteria, green sulfur bacteria, in the course of photosynthesis, energy-poor molecule, energy-rich molecule.

VIII Find the pairs of synonyms:

Conversion, primarily, assembly, sugars, firstly, carbohydrates, stage, donor, synthesis, step, giver, alteration.

IX Find the pairs of antonyms:

Light, poor, directly, reach, indirectly, donor, dark, keeping.

X Translate into English:

Превращение световой энергии солнца в химическую энергию, атом водорода, серные гранулы, бедная энергией молекула, богатая энергией молекула.

XI Answer the questions:

1. What does mean photosynthesis?

2. How is called synthesis of sugars by using carbon atoms from CO₂ gas?

3. What organisms do realize photosynthesis?

4. How many stages do have photosynthesis?

5. How are differentiated light and dark reactions?