V Remember the following word and word-combinations:

Life-support, biochemical reactions, fascinating, petroleum, cellulose, diet, carbon dioxide, iron, sulfur, hydrogen gas, ammonia, to require, to release, compound, hydrolytic reactions, exergonic, endergonic, amino acid, polysaccharide, cell growth.

VI True or false?

1. We use the term metabolism to refer to the sum of all chemical reactions within a living thing organism.

2. Catabolic reactions are endergonic.

3. Anabolic reactions are exergonic.

4. Bacteria can live on diets of such inorganic substances as carbon dioxide, iron, sulfur, hydrogen gas, and ammonia.

5. All energy released in catabolism is actually available for cellular functions because part of the energy is lost to the environment as heat.

VII Insert the missing words:

1. Reactions are called catabolic, or…

2. Reactions are called anabolic, or…

3. Catabolism occurs when cells break down sugar into…

VIII Give English equivalents to the following words:

Аминокислота, железо, сера, углерод, полисахарид, диоксид.

IX Answer the questions:

1. What does mean metabolism?

2. How metabolism is classified?

3. What is catabolism?

4. What is anabolism?

5. For what biosynthetic reactions do generate the materials?

X Retell the text.

21-23 Practical lesson

Rules of reading: The letter Cc

Word building: suffix of adjective – ive

Text: Enzymes

Assignments to do:

I Remember:

1. Cc is pronounced as follows:

Before e,i,y [s]: city, center, circle

Before constants and other vowels [k]: come, cold, clear

2. - suffix –ive forms the adjectives from the verbs: connective, attentive, active, effective.

II Read the words according to the rules of reading of the letter “Cc”:

Cinema, computer, city, secret, cell, to call, accelerate, specific, cat, circle, cytoplasm.

III Put down the words into 2 columns: the words with the sounds [k], [s]

Cap, face, civil, clean, black, thick, icy, to catalyze, place, cake, cinema, accelerate, lecture, country, advice, car, nice, incident, Nick, across.

IV Form the adjectives from verbs:

To collect, to act, to effect, to respect, to connect, to create, to react.

V Read the international words and guess their meaning. Mind the stress:

Substance, reaction, catalyst, enzyme, protein, specific, active, molecule.

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.