The cell

A cell is the fundamental organizational unit of life. One of the most important generalizations of modern biology is the cell theory. There are two components of the cell theory. It states: (1) that all living things are composed of cells and (2) that all cells arise from other cells. Living things are chemical organizations of cells and capable of reproducing themselves.

There are many types of cells, and just as many classifications to go with them. There are plant cells, animal cells, eucaryotic cells, procaryotic cells, and many others. Also within each of these divisions, there are smaller subdivisions pertaining to the specific properties or functions of the cells. Cells exhibit considerable variation in properties based on different arrangements of components. Cells also vary in size, although most of them fall in the range of 5 to 20 mm

In total there are about 50 billion cells in your body! Each cell is so small it cannot be seen with the naked eye. However, with the help of a microscope we are able to study cells and discover how they work.

Nearly all cells have a nucleus, which is the control center of the cell. Ribosomes in cells do as the nucleus tells them. They act like factories, making proteins and other chemicals for our body. To work properly a cell needs energy and this energy comes from the food we eat. Power stations in the cell, called mitochondria, change the energy stored in food into a form of energy that can be used by the cell.

We start life as one cell, which divides into two. These cells also divide, and as more cells grow they form different shapes and sizes. Each of these different types of cell has its own job to do. Similar types of cell will join together to make tissues, which form organs like our brain and lungs.

How long a cell lives depends upon the type of cell it is. Skin cells die quickly and are constantly replaced by new cells. Nerve cells should last a human lifetime and cannot be replaced even if they are damaged.

The control center of the cell is called the nucleus. Inside the nucleus of each cell lie tiny threads called chromosomes. Inside the chromosomes are smaller structures called genes. It is in the genes that the instruction manual lies. The instructions are in the form of a chemical called DNA. DNA is shaped like a twisted ladder, known as a double helix.

Ribosomes make proteins, as instructed by the nucleus. The golgi apparatus packs up the proteins made by ribosomes, ready to be stored or transported. Lysosomes help break down substances in the cell. The cell membrane allows food in the form of sugars to enter, and allows waste chemicals made in the cell pass out. Cilia are like tiny hairs that beat, pushing mucus or fluid over the cell surface. Inside a cilia there are 20 little tubes, arranged in pairs, to make it strong.

Notes to the text:

To fall in the range – входить в диапозон.

Classifications to go with them – классификации, которые соответствуют им.

II. COMPREHENSION CHECK.

Say whether the following statements are true or false:

2 Think of 8 questions to the text.

III. LANGUAGE FOCUS.

1. Say it in another way (give synonyms):

All living things consist of cells.

Cells are also different in size.

Each cell is so small that it can be seen only with the help of a microscope.

Almost all cells have a nucleus.

A cell needs energy to work in a proper way.

Mitochondria change the energy kept in food into a form of energy that can be used by the cell.

The cells form various shapes and sizes.

Inside the nucleus of each cell lie very small threads called chromosomes.

Ribosomes make proteins as the nucleus tells them.

The cell membrane permits waste chemicals made in the cell pass out.

k) Cilia look like minute hairs.

l).Little tubes are set (settled) out in pairs.

a) Put the parts of the sentences in the right order:

2 Themselves, of, living, are, things, reproducing, capable.

3 Properties, in, considerable, exhibit, cells, variation.

4 The, a, is, center, nucleus, control, cell, the, of.

5 Eat, the, from, food, comes, we, energy, the.

6 Constantly, new, by, cells, are, skin, replaced, cells.

7 Of, nucleus, cell, threads, inside, each, lie, the, tiny.

8 Break, lysosomes, substances, down, help, cell, the, in.

9 Many, are, inside, little, a, there, tubes, cilia.

b) Translate from Russian into English:

А). расположенные попарно, расщеплять вещество, мельчайшие волоски, в общем, почти все клетки, контролирующий центр клетки, клеточная мембрана, химические отходы.

Б).

а). Все живые организмы состоят из клеток.

б). Жизнь начинается из одной клетки.

в). Продолжительность жизни клетки зависит от типа клетки.

г). Каждая клетка очень мала, поэтому ее нельзя увидеть невооруженным глазом.

д). У каждой клетки своя функция.

е). Чтобы хорошо работать, клетке нужна энергия, которая поступает с пищей.

ж). Митохондрии изменяют накопленную в пище энергию в такую энергию, которой может воспользоваться клетка.

з). Клетки различаются по свойствам и размерам.

и). Нервные клетки не восстанавливаются.

к). Одинаковые клетки соединяются и образуют ткани.

IV. FOLLOW-UP ACTIVITIES.

1) Discuss will your partner:

The cell theory.

The nucleus as the control centre of the cell.

Ribosomes, genes and DNA.

Дата добавления: 2015-09-03