2.2 Answer the following questions

1. What are carbohydrates?

2. Why are they called carbohydrates?

3. What are the functions of carbohydrates in an organism?

4. How are they classified?

5. What is the difference between them?

6. What do simple carbohydrates contain?

7. What do complex carbohydrates contain?

8. What does the liver convert the sugars into?

Unit IV Biology of cell

1. Answer the questions before the passages, then read the text and compare your answers with the given information

1. What is a cell? Who discovered it?

You and all other organisms are made up of cells. Cells are the building blocks of organisms. They form the parts of organisms and carry out all of an organism's processes and functions. They are very complex structures. Because of its small size, however, the cell's structure has not yet been fully understood. Scientists are still carrying out research on cellular systems.

Every adult human body contains about 100 trillion cells. When a million of our body cells are gathered together, they occupy a space no bigger than a pinpoint.Cells were first discovered in Europe in the seventeenth century by Antoni van Leeuwenhoek. They were named by Robert Hooke, an Englishman. The cell theory states that:

1. All organisms are made of cells.A cell is the structural and functional unit of organs, and therefore cells are organisms;

2. Cells are capable of self-reproduction.

There are 200 different types of cells in our bodies. In fact, all of these cells arecomposed of identical components, yet each performs a different task. For example, the muscle cells in your legs enable you to walk and run. Your blood cells transport oxygen to your body cells.

2. What types of cells do you know?

Cells have many shapes and sizes and different structures. Bacteria are single-celled organisms about 1 to 10 micrometers (.00004 to .0004 inch) in size and can be spherical, rod-shaped, or spiral-shaped. They are known as prokaryotes. Prokaryotes are single-cell organisms they are much simpler than the eukaryotic cells. Eukaryotic cells have many different functional compartments, divided by membranes. Prokaryotic cells do not have a nucleus or membrane-boundorganelles such as vacuoles, mitochondria, or lysosomes. Bacteria are prokaryotic cells.

Eukaryotic cell type has a true nucleus. All organisms except bacteria have eukaryotic cells.

3. What does prokaryote consist of?

If a eukaryotic cell is analogous to a big house with many different rooms, a prokaryotic cell is like a one-room, studio apartment. It consists of Plasma Membrane, Cytoplasm and Ribosomes. Plasma Membrane is a double-layer of phospholipids. It is the “bag” that holds all of the intracellular material and regulates the movement of materials into and out of the cell. Prokaryotic cells have no true nucleus. DNA in a prokaryotic cell is not separated from the rest of the cell. It is coiled up in the nucleoid.Most prokaryotes reproduce through binary fission. During binary fission, the single DNA molecule replicates and the original cell is divided into two identical daughter cells.

Typically, eukaryotic cells are more complex and much larger than prokaryotic cells. Prokaryotic cells are about 10 times smaller in diameter than eukaryotic cells. Eukaryotic cells are called so because they have a true nucleus.