Read the statements and decide whether they are true (T) or false (F). Correct the wrong statements
1. Cells carry out organism’s processes and functions.
2. The cell’s structure is fully described by biologists.
3. Every adult body contains about 100 million cells.
4. Each cell fulfills a different function.
5. Muscle cells are arranged in line.
6. Skin cells transport oxygen to our body cells.
7. Cells are divided into prokaryotic and eukaryotic cells.
8. Prokaryotic cells are more complex than eukaryotic cells.
What do the following numbers refer to in the text?
| 100 200 trillions 1 000 000 trillion |
Order the letters in the words.
1. LECLS are the building blocks of organisms.
2. All cells are composed of TIDENICAL NENPOCOM.
3. Your blood cells transport OGENXY to our body cells.
4. Your skin is a barrier to ROMICSEB.
5. OTICPRORYKA cells do not have a nucleus or membrane-bound organelles.
6. KARYEUOCIT cells have a nucleus.
Match the words to their definitions.
| 1. | cells | a) type of cell that lacks a membrane-bound nucleus and membrane organelles |
| 2. | organism | b) an individual composed of organ systems (if multicellular) |
| 3. | organelles | c) cell components that carry out individual functions, e.g. the cell nucleus. |
| 4. | prokaryote | d) the smallest structural units of living matter capable of functioning independently. |
| 5. | eukaryote | e) a type of cell found in many organisms characterized ny a membrane-bounded nucleus and other membranous organelles |
Retell the text.
Read the text and answer the questions.
The structure of the eukaryotic cell.
Eukaryotic cells are much more complex than prokaryotic cells. They perform chemical activities, much like a factory. Here, we greatly summarize their re and functions. Eukaryotic cells have 3 main parts.
They are: 1) cell membrane; 2) cytoplasm; and, 3) the nucleus,
Some other structures are also found in eukaryotic cells.
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Cell membrane
The cell membrane, or plasma membrane, encloses the cell. It is made up of lipid, protein and a small amount of carbohydrate. The functions of the cell membrane are:
1. Protection of the cytoplasm and its organelles.
2. Exchange of material into or out of the cell.
3. Provides the cell with shape.
4. Links cells to each other and provides communication between cells.
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Cytoplasm
The cytoplasm is the second main part of the cell. The cytoplasm is located between the cell membrane and the nucleus. It is jelly-like (like egg white) in structure. It contains organic and inorganic materials.
Cell organelles are found in the cytoplasm. Cell organelles are the micro- organs of the cell. They have special functions in the cell. We can summarize their function as follows.
1. Ribosomes produce protein.
2. Mitochondria are the power houses of the cell. They produce ATP energy.
3. Golgi bodies are the packaging system of the cell. They produce special materials such as milk.
Vacuoles are the storage centers of the cell. They store water, minerals and waste.
Lysosomes are the stomach of the cell. They enable digestion in the cell.
Peroxisomes are the disposal centers of the cell. They destroy harmful substances.
Endoplasmic reticulum is the transport system of the cell. It produces proteins, lipids and other substances and transports them through the cytoplasm.
Chloroplasts are found in plant cells. They produce food and oxygen by photosynthesis.
Centrosomes are found in animal cells. They aid in cell division.
Nucleus
The nucleus is the control center of the cell (you could say the brain of the cell). In the nucleus, genetic material (chromosomes, made up of DNA and protein) is found. The nucleus also contains the nucleolus, which produces ribosomes.
Other structures of the eukaryotic cell
Cell wall: It is a hard structure which protects the cell. For example, plant cells have a rigid structure because of the cell wall.
Flagellum and cilia: They enable movement of the cell. A flagellum is long, but cilia are short.
Material transport through the cell membrane
The cell membrane has a selectively permeable structure. That means it allows some materials to pass into or out of the cytoplasm. Some materials can pass, but others cannot pass through the cell membrane. Materials exchange is provided for by different methods, including diffusion, osmosis and active transport.
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Diffusion
Diffusion is the movement of molecules from areas of high concentration to areas of low concentration. For example, perfume diffuses throughout г room until its concentration is constant. The cell doe: not use energy for this process, so it can occur in living and non-living cells.
Osmosis
Osmosis is the diffusion of water. Water molecule: move from where they are highly concentrated to where there is a low concentration. Like diffusion energy is not used and osmosis occurs in living and nonliving cells.
Active transport
Active transport is the movement of molecules from areas of low concentration to areas of high concentration. In this process cells use energy. Unlike diffusion and osmosis, it occurs only in living cells.
Exercises
Answer the questions
1. What are 3 main parts of eukaryotic cell?
2. What are the functions of the cell membrane?
3. Where is the cytoplasm located?
4. What are cell organelles?
5. What are cell organelles’ functions?
6. What do we call ‘the brain of the cell’?
7. What protects the cell?
8. What is the difference between flagellum and cilia?
9. How is materials exchange provided for?
2. Find in the text the definitions to the following words:
nucleus vacuoles
golgi bodies osmosis
diffusion amoeba
cell wall active transport
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