UNIT 2 BACTERIA

🦠 BACTERIA: A Complete Overview

Bacteria are single-cell organisms (or living things made of only one cell). They are neither plants nor animals, yet they exist everywhere. To organize this large group, scientists classify them, or group them, mainly based on their fundamental shape.

There are three key shapes. First, bacteria that are shaped like a ball are called spherical bacteria /sferɪkl/, or cocci /ˈkɒksaɪ/. Second, those that resemble a small stick or rod are rod-shaped bacteria, known as bacilli /bəˈsɪlaɪ/. When these rods are slightly curved, they are called vibrio /ˈvɪbriəʊ/. Third, bacteria that look twisted or coiled are the spiral bacteria, or spirilla /spaɪˈrɪlə/. These different forms cause various diseases, such as pneumonia /njuːˈməʊniə/ (a lung infection) and syphilis /ˈsɪfɪlɪs/ (a sexually transmitted disease).

The Bacterial Cell Structure

Every bacterial cell has several distinct parts. The cell’s shape is determined by the strong outer layer called the cell wall, which is made from a complex polymer named peptidoglycan /ˌpeptɪdəʊˈɡlaɪkæn/. Some bacteria also have an extra protective coat called a capsule /ˈkæpsjuːl/. Inside the cell wall is the plasma membrane /ˈplæzmə ˈmembreɪn/. This structure generates energy and transports chemicals. The membrane is described as permeable /ˈpɜːmiəbl/, which means it allows substances to pass through.

The interior of the cell holds the cytoplasm /ˈsaɪtəplæzəm/, a gelatinous substance (a jelly-like fluid). This substance contains the vital components: DNA (which holds all the genetic instructions) and ribosomes /ˈraɪbəˌsəʊm/. Ribosomes are the factories where proteins are synthesized /ˈsɪnθəsaɪzd/ (or created). For the purpose of movement, some bacteria have a whip-like tail called a flagellum /fləˈdʒeləm/ used to propel them. Furthermore, tiny hair-like appendages /əˈpendɪdʒɪz/ known as Pili /ˈpɪlaɪ/ allow the bacteria to stick to surfaces and transfer genetic material.

Ecology and Functions of Bacteria

Bacteria must find energy to survive. Bacteria that live on dead organisms or material produced by living things are called parasites /ˈpærəsaɪt/. The organism a parasite lives on is called the host.

A unique group is the anaerobes /ˈænərəʊb/ (or anaerobic bacteria), which are organisms that can only grow where there is no oxygen. In humans, they are often found in the gastrointestinal tract /ˌɡæstrəʊɪnˈtestɪnəl trækt/ (the digestive system) and can cause serious issues like gangrene /ˈɡæŋɡriːn/ (tissue death).

It is essential to remember that many bacteria are helpful. Non-hazardous bacteria (bacteria that are not dangerous) play a critical role in our survival. For example, in the digestive system, they break down nutrients. They also protect us by competing with pathogenic /ˌpæθəˈdʒenɪk/ bacteria, meaning they fight the disease-causing bacteria for space.

30 MULTIPLE-CHOICE QUESTIONS ON BACTERIA (3 OPTIONS)

I. LEVEL 1: RECALL (Cấp độ Nhớ)

Mục tiêu: Kiểm tra khả năng nhớ lại thông tin trực tiếp từ bài đọc.

1. Bacteria are classified by the reading as organisms that are:

A. Both plants and animals.

B. Neither plants nor animals.

C. Only plants.

2. Which term refers to rod-shaped bacteria?

A. Cocci

B. Spirilla

C. Bacilli

3. The structure that gives the bacterium its shape is the:

A. Plasma membrane.

B. Cell wall.

C. Capsule.

4. What is the gelatinous substance found inside the plasma membrane?

A. Ribosome

B. Cytoplasm

C. Peptidoglycan

5. What is the function of the Flagellum?

A. Sticking to surfaces.

B. Making proteins.

C. Used for movement/propulsion.

6. Bacteria that only grow where there is no oxygen are called:

A. Parasites.

B. Pathogenic.

C. Anaerobes.

7. Where are proteins made, or synthesized, inside the bacterial cell?

A. DNA

B. Ribosomes

C. Cytoplasm

8. The Cell wall is made of a polymer called:

A. RNA.

B. Peptidoglycan.

C. DNA.

9. Which of the following diseases is specifically mentioned as being caused by Spiral bacteria (Spirilla)?

A. Strep throat.

B. Syphilis.

C. Anthrax.

10. What is the term for the organism on which a parasite lives?

A. Hostile

B. Host

C. Carrier

II. LEVEL 2: COMPREHENSION (Cấp độ Hiểu)

Mục tiêu: Kiểm tra khả năng hiểu các khái niệm và mối quan hệ giữa các bộ phận.

11. The Plasma membrane is described as being “permeable.” This suggests that:

A. It blocks all substances from entering the cell.

B. Substances can pass through it.

C. It is rigid and maintains the cell’s shape.

12. Based on the reading, what is the primary difference between Cocci and Bacilli?

A. The environment they live in (with or without oxygen).

B. Their shape (spherical versus rod-shaped).

C. Their method of feeding (parasite or not).

13. If a bacterium is classified as a “Parasite,” you can conclude that it:

A. Generates its own energy from chemicals like sulfur.

B. Gets its energy from plants or animals, often dead or living.

C. Cannot move without a flagellum.

14. The Pili and the Flagellum differ mainly in their function because:

A. The Pili are for movement, while the Flagellum is for attaching.

B. The Pili are for sticking/transferring material, while the Flagellum is for propulsion (movement).

C. Both are used to generate energy.

15. What conclusion can be drawn about Gram positive bacteria?

A. They have curved, rod-shaped forms.

B. Their Cell wall is thicker than other types of bacteria.

C. They do not possess a capsule.

16. Why are the bacteria in the digestive system considered helpful?

A. Because they generate the oxygen we breathe.

B. Because they break down complex food items (nutrients) into usable forms.

C. Because they cure all diseases caused by pathogenic bacteria.

17. If a bacterium is described as “pathogenic,” the reader should understand that it:

A. Is strictly rod-shaped.

B. Is disease-causing.

C. Is non-hazardous.

18. Why is the Cytoplasm important according to the text?

A. Because it acts as the outer protective layer.

B. Because it is the fluid where the cell’s genetic material and ribosomes are located.

C. Because it is the site where movement begins.

19. Why is the transfer of genetic material via Pili potentially harmful to humans?

A. It prevents the synthesis of proteins.

B. It can contribute to the spread of illness.

C. It causes the bacterium to lose its ability to move.

20. The reading states that individual bacteria cannot be seen without a microscope, but colonies can be seen with the naked eye. This demonstrates that:

A. All bacteria are harmless.

B. A large group of bacteria is visible, while a single cell is not.

C. Only pathogenic bacteria can form colonies.

III. LEVEL 3: APPLICATION (Cấp độ Vận dụng)

Mục tiêu: Kiểm tra khả năng sử dụng thông tin từ bài đọc để giải quyết tình huống hoặc đưa ra suy luận mới.

21. A scientist discovers a new bacterium that moves very quickly in liquid environments. Which structure would you expect this bacterium to definitely possess?

A. Capsule.

B. Flagellum.

C. Pili (without a flagellum).

22. If a patient has an infection caused by a bacterium found exclusively in deep, wounded tissue with no air exposure, the doctor would likely suspect the infection is caused by:

A. Anaerobes.

B. Spherical bacteria.

C. Bacteria that feed on ion and sulfur.

23. An antibiotic is designed to stop the creation of proteins in the bacterial cell. Which internal component is the target of this drug?

A. DNA.

B. Ribosomes.

C. Plasma membrane.

24. If a drug is specifically designed to prevent bacteria from sticking to a surface in the body, which structure is the most logical target for the drug’s action?

A. Flagellum.

B. Pili.

C. Cell wall.

25. A new species of bacteria is discovered. Its cell wall is found to be very thin. Based on the reading’s classification of cell walls, this bacterium would NOT be classified as:

A. Rod-shaped.

B. Gram positive bacteria.

C. Pathogenic.

26. The text suggests that Non-hazardous bacteria help prevent disease. They achieve this by:

A. Immediately destroying the pathogenic bacteria with enzymes.

B. Occupying the space (territory) that the disease-causing bacteria wants to attack.

C. Transferring genetic material to the pathogenic bacteria to neutralize them.

27. If a bacterium is found to absorb its energy by breaking down dead skin cells, it would best be defined as a(n):

A. Anaerobe.

B. Parasite.

C. Vibrio.

28. Why is it logical to conclude that the Plasma membrane must be located inside the Cell wall?

A. Because the Plasma membrane is made of peptidoglycan.

B. Because the Cell wall gives the bacteria shape and the membrane is described as found within it.

C. Because both structures are permeable.

29. A laboratory test shows a bacteria species rapidly changing its shape. What structural component is likely weakened or damaged?

A. DNA.

B. Cell wall.

C. Flagellum.

30. The text suggests that the oxygen we breathe was probably created by the activity of bacteria. This supports the general idea that:

A. All bacteria are pathogenic.

B. Bacteria are fundamentally important to the overall life support system of the planet.

C. Bacteria are primarily parasites.