B6 - Bacteria, Fungi and Viruses Flashcards
Describe the structure of a bacterial cell.
- cell membrane, controlling the movement of molecules into and out of the cell
• cytoplasm, a jelly-like substance where most of the cell’s reactions occur
• cell wall, having the same function as in a plant cell of maintaining the shape of the cell and preventing it from bursting, but made of a different chemical instead of cellulose
• loop of DNA, controlling the cell and its replication. Bacterial cells do not have a nucleus. - capsule, a slimy protective capsule around the outside of the cell wall in some bacteria. It is this capsule that protects bacteria against antibiotics
• flagellum, whip-like flagella for movement in some bacteria.
How do scientists find out about the structure of a bacteria?
Bacterial cells can only just be seen using a light microscope. To see ne detail, biologists use high powered microscopes called electron microscopes. These microscopes magnify thousands of times more than a light microscope.
What are the four different types of bacteria? Give an example of what each causes.
- Cocci bacteria which cause acne spots ( spherical)
- Bacillus bacteria ( bacilli )which can cause food poisoning ( rod - shaped )
- Vibrio bacteria which cause the disease cholera ( curved )
- Spiral bacteria ( spirilli ) which cause stomach ulcers ( spiral)
How do bacteria reproduce?
Binary fission : reproduce very fast. Most of the time they reproduce by dividing into two, and they can do this as quickly as once every two hours.
What is a consequence of the fast reproduction of bacteria?
Harmful bacteria, such as those that spoil food, can reproduce fast. So food such as milk left out in a warm room will go off very quickly. If you then eat this food, the bacteria may reproduce very quickly in your body. The rate of reproduction may be too fast for your immune system to handle, making you ill.
Where can bacteria live ? Where do they get their energy from?
Bacteria have such a wide range of adaptations that they are found living in almost all environments on Earth.
Bacteria survive by obtaining energy from a wide range of sources – some from the Sun by photosynthesis, but others from dead bodies, and from chemical reactions in their cells.
Describe the process and precautions of growing bacteria in a lab.
They are grown on a jelly called agar in a plate-like dish called a Petri dish. The plates are incubated to keep them warm, and the bacteria grow very fast.
They need to take care not to contaminate the plates with other bacteria, and not to allow the bacteria to infect yourself. To do this you need to keep instruments and surfaces free of microbes, or sterile. Working in this way is called aseptic or sterile technique.
How can scientists see yeasts?
Yeasts are single celled, but larger than a bacterial cell. They can be clearly seen under a light microscope, but the internal detail can be seen better using an electron microscope.
Describe the structure of a fungal cell.
Fungal cells have many parts in common with other cells. The fungal cell has a membrane, cytoplasm, and nucleus which function as they do in plant cells. The cell wall is similar to a plant or bacterial cell. It has the same function, but is made of a different chemical called chitin.
How do yeasts reproduce ?
The cells reproduce mainly asexually by a process called budding. The nucleus divides first, then a bulge forms on the side of the parent cell, which will develop into a new cell. Often the cells remain joined.
What is the optimum growth rate of budding controlled by?
•availability of food • temperature
pH • amount of waste products.
Describe the growth rate of yeast
For every 10 oC rise in temperature, the growth rate of yeast doubles. This is only true up to an optimum temperature, above which the yeast’s enzymes begin to be damaged.
Describe the structure of a virus. Is it alive?
Viruses are made of a protein coat inside which is the genetic material. Viruses do not have a cell structure, and they do not carry out many of the processes of living things. For these reasons, some biologists don’t consider viruses to be living things.
Where do viruses live?
They cannot live independently – they can only live inside the cells of another organism, called the host. Each virus can only invade specific host cells; for example, animal viruses cannot invade plant cells. Once inside a host’s cell, the virus takes over the cell.
How do viruses reproduce?
- the virus attaches to a specific host cell
- the genetic material of the virus is injected into the host cell
- the viral genes cause the host cell to make new viruses
- the host cell splits open, releasing the new virus
