What are lysosomes? What are mitochondria?

Lysosomes are membrane-bounded vesicles, containing digestive enzymes. Their normal function is digestion of complex nutrients and broken-down organelles. Mitochondria are the powerhouses of the animal cell, where the products of the metabolism of nutrients are converted into energy in the form of molecule ATP. Plants possess, in addition to mitochondria, similar organelles called chloroplasts. Each chloroplast contains chlorophyll which is used to convert light energy to the ATP. This process is called photosynthesis.

All animal and some plant cells contain a pair of centrioles. Centrioles control the arrangement of microtubes in cytoskeleton.

What is the process called meiosis?

All cells are the products of division of preexisting cells. Simple cell division, or asexual reproduction, normally results in the production of two identical daughter cells. Sexual reproduction is the mingling of the DNA of two different organisms of the same species to produce cells with a new combination of genes. In multicellular organisms sexual reproduction requires the production of male and female germ cells by a process called meiosis.

In higher plants and animals the cells are organized into tissues, or groups of cells with similar structure and functions. Combinations of tissues make up organs with more or less distinct functions. In the animal; the organs are associated in systems that are responsible for certain functions.

Read the text and fill in the gaps with the words in the box.

Cell membrane, cells, microscope, structure, nucleus, cytoplasm.

Cells

1. … are the building blocks of living things, as bricks are of houses. Larger organisms, such as human beings, are made of billions of cells. Each cell is a tiny living unit that is too small to be seen without a 2. …. Cells usually have three main parts. The 3. … (outer "skin") controls what goes in and out of the cell. The 4. … is the area where most of the cell's reactions take place, such as the release of energy by the mitochondria. The 5. … controls all the cell's activities. Different cells do different jobs; this affects their 6. …

Read the text, make up its plan and match English words in A with their English equivalents in B

<== попередня сторінка	\|	наступна сторінка ==>
What do cells consist of?	\|	The Cell

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