IV Read and translate the text about the eukaryotic cell

The eukaryotic cell

Eukaryotes (from the Greek words meaning true nucleus) contain nucleic acids, proteins, lipids, and carbohydrates. The eukaryotic cell is typically larger and structurally more complex than the prokaryotic cell.

The plasma (cytoplasmic) membrane of eukaryotic and prokaryotic cells is very similar in function and basic structure. There are, however, differences in the types of proteins found in the membranes.

The cytoplasm is the substance in which various cellular components are found. A major difference between eukaryotic and prokaryotic cytoplasm is that eukaryotic cytoplasm has a complex internal structure, consisting of exceedingly small rods (microfilaments and intermediate filaments) and cylinders (microtubules). Together, they form the cytoskeleton. The cytoskeleton provides support and shape and assists in transporting substances through the cell.

Attached to the outer surface of rough endoplasmic reticulum are ribosomes, which are also found free in the cytoplasm. As in prokaryotes, ribosomes are the sites of protein synthesis in the cell.

The nucleus is usually spherical or oval, is frequently the largest structure in the cell, and contains almost all of the cell's hereditary information (DNA). Some DNA is also found in mitochondria and in the chloroplasts of photosynthetic organisms.

The first step in the transport pathway is through an organelle called the Golgi complex. It consists of 3 to 20 cisterns. The cisterns are often curved, giving the Golgi complex a cuplike shape.

Lysosomes are formed from Golgi complexes and look like membrane-enclosed spheres. Unlike mitochondria, lysosomes have only a single membrane and lack internal structure.

A vacuole is a space or cavity in the cytoplasm of a cell that is enclosed by a membrane called a tonoplast. In plant cells, vacuoles may occupy 5-90% of the cell volume, depending on the type of cell. Vacuoles are derived from the Golgi complex and have several diverse functions. Some vacuoles serve as temporary storage organelles for substances such as proteins, sugars, organic acids, and inorganic ions. Other vacuoles form during endocytosis to help bring food into the cell.

Spherical or rod-shaped organelles called mitochondria (singular: mitochondrion) appear throughout the cytoplasm of most eukaryotic cells. Mitochondria are often called the "powerhouses of the cell" because of their central role in ATP production. Mitochondria contain 70 ribosomes and some DNA of their own, as well as the machinery necessary to replicate, transcribe, and translate the information encoded by their DNA. In addition, mitochondria can reproduce more or less on their own by growing and dividing in two.

Algae and green plants contain a unique organelle called a chloroplast, a membrane-enclosed structure that contains both the pigment chlorophyll and the enzymes required for the light-gathering phases of photosynthesis.

The centrosome, located near the nucleus, consists of two components: the pericentriolar area and centrioles. This area is the organizing center for the mitotic spindle, which plays a critical role in cell division, and for microtubule formation in nondividing cells.

V Remember the following word and word-combinations:

Nucleic acids, carbohydrates, various cellular components, internal structure, microtubules, hereditary information, the sites of protein synthesis, cavity in the cytoplasm, to occupy, vacuoles are derived from the Golgi complex, temporary storage, organic acids, to replicate, to transcribe, light-gathering, spindle, nondividing cells.

VI Find the sentences with the following word-combinations:

Vacuoles may occupy 5-90% of the cell volume, the sites of protein synthesis in the cell, contain nucleic acids, assists in transporting substances, the types of proteins, the mitotic spindle, spherical or rod-shaped organelles.

VII Insert the missing words:

1. The eukaryotic cell is typically larger and…

2. Some DNA is also found in mitochondria and in…

3. The cytoplasm is the substance…

VIII Translate into English:

1. Эукариоты содержат нуклеиновые кислоты, белки, липиды и углеводы.

2. Ядро содержит наследственную информацию.

3. Лизосомы имеют единственную мембрану.

4. Цитоплазма – это вещество, содержащее в себе различные клеточные компоненты.

5. Главная роль митохондрий – это выделение АТФ.

IX Complete the sentences with a word from the box. Careful! Sometimes no word is necessary.

ago last in for at when on

1. I was born in Africa _____ 1970.

2. My parents moved back to England _____ I was five.

3. We lived in Bristol _____three years.

4. I left college three years _____.

5. I found a flat on my own _____ last year.

6. I usually go home _____ weekend because some friends came to stay.

7. They arrived _____ three o’clock _____ in the afternoon.

8. _____ Saturday evening we went out to a concert.

9. _____ we got home we listened to some music.

10. We got up late _____ Sunday morning.

11. _____the afternoon we went for a walk.

12. I bought a car a few weeks _____.

13. I had an accident _____ last night.

14. It happened _____ seven o’clock _____ the evening.

15. I took my car to the garage _____ this morning.

16. It will be ready _____ two weeks.

16-17 Practical lesson

Rules of reading: Theletter Gg

Word formation: suffix of adjectives – ic, -al

Text:Evolution of eukaryotes

Assignments to do:

I Remember:

a) Gg is pronounced as follows:

Before e,i,y [dʒ] : page, gene, biotechnology

Before constants and other vowels [g]: game, glad, bag

b) Suffixes –ic, -al form adjectives from the nouns:

person – personal

history – historical

base - basic

II Read the words paying attention to the pronunciation:

Gate, gem, gas, age, gym, page, egg, gene, game, gag, green, geography.

III Give the transcription to the following words:

Bag, page, big, give, guess, gloves, go, great, general.

IV Read and translate the following words:

Central, experimental, academic, electric, prokaryotic, practical, monumental, historical, bacterial, social.

V Read and translate the text about evolution of eukaryotes

The Evolution of Eukaryotes

Biologists generally believe that life arose on Earth in the form of very simple organisms, similar to prokaryotic cells, about 3.5 to 4 billion years ago. About 2.5 billion years ago, the first eukaryotic cells evolved from prokaryotic cells. Recall that prokaryotes and eukaryotes differ mainly in that eukaryotes contain highly specialized organelles. The theory explaining the origin of eukaryotes from prokaryotes, pioneered by Lynn Margulis, is the endosymbiotic theory. According to this theory, larger bacterial cells lost their cell walls and engulfed smaller bacterial cells. This relationship, in which one organism lives within another, is called endosymbiosis.

According to the endosymbiotic theory, the ancestral eukaryote developed a rudimentary nucleus when the plasma membrane folded around the chromosome. This cell, called a nucleoplasm, may have ingested aerobic bacteria. Some ingested bacteria lived inside the host nucleoplasm. This arrangement evolved into a symbiotic relationship in which the host nucleoplasm supplied nutrients and the endosymbiotic bacterium produced energy that could be used by the nucleoplasm. Similarly, chloroplasts may be descendants of photosynthetic prokaryotes ingested by this early nucleoplasm. Eukaryotic flagella and cilia are believed to have originated from symbiotic associations between the plasma membrane of early eukaryotes and motile spiral bacteria called spirochetes.

Studies comparing prokaryotic and eukaryotic cells provide evidence for the endosymbiotic theory. For example, both mitochondria and chloroplasts resemble bacteria in size and shape. Further, these organelles contain circular DNA, which is typical of prokaryotes, and the organelles can reproduce independently of their host cell. Moreover, mitochondrial and chloroplast ribosomes resemble those of prokaryotes, and their mechanism of protein synthesis is more similar to that found in bacteria .

VI Remember the following word and word-combinations:

To arise, simple organisms, the first eukaryotic cells evolved from prokaryotic cells, to differ, to pioneer, relationship, ancestral, rudimentary nucleus, to ingest, nutrient, descendant, cilia, to originate, host cell.

VII Find in the text pairs of synonyms and remember trhem:

Hereditary, alike, form, generate, compare, elementary.

VIII Paraphrase the sentences using synonyms:

1. Biologists generally believe that life arose on Earth in the form of very simple organisms, similar to prokaryotic cells, about 3.5 to 4 billion years ago.

2. According to the endosymbiotic theory, the ancestral eukaryote developed a rudimentary nucleus when the plasma membrane folded around the chromosome.

3. For example, both mitochondria and chloroplasts resemble bacteria in size and shape.

4. Further, these organelles contain circular DNA, which is typical of prokaryotes, and the organelles can reproduce independently of their host cell.

5. Moreover, mitochondrial and chloroplast ribosomes resemble those of prokaryotes, and their mechanism of protein synthesis is more similar to that found in bacteria .