Microbes

Question 1

What can bacteria be useful for ?

Answer 1

Bacteria are useful for the production of yoghurt, treating sewage and in genetic engineering

Question 2

Give three measures that are taken when working under aseptic conditions

Answer 2

The working area is sterilised, hands are washed and face masks and gloves are worn

Question 3

Why would it be dangerous to incubate the growth plates at 37 degrees?

Answer 3

37 degrees is approximate body temperature. You need to avoid growing bacteria that will thrive in your body and therefore make you very sick

Question 4

Why is it necessary to flame the neck of the bottle of agar?

Answer 4

To prevent contamination

Question 5

Which cells ingest and digest pathogens?

Answer 5

Phagocytes

Question 6

Why are fungi dangerous?

Answer 6

They are responsible for the athletes food infection as well as ringworm. They also spoil food

Question 7

What can fungi be used for?

Answer 7

The fungus yeast can be used in the baking and brewing industries, and other fungi can be used in the cheese industry and for producing penicillin

Question 8

Describe the structure of viruses

Answer 8

Their structure is a head capsule containing DNA with a long tail with an end plate attached

Question 9

How can viruses be useful?

Answer 9

Viruses can be used in genetic engineering

Question 10

What term is used to describe a microbe that causes disease ?

Answer 10

Pathogen

Question 11

White blood cells which produce antibody molecules and cause bacterial cells to burst or be clumped together are called … ?

Answer 11

Lymphocytes

Question 12

How do phagocytes prevent infection?

Answer 12

Hey ingest and digest bacteria, dead cells and other foreign particles. They maintain healthy tissues and are essential for immunity

Question 14

Why do you incubate your Petri dish upside down?

Answer 14

The bacteria are respiring; they are producing water vapour which would condense on lid, drop onto the bacteria and wash it off

Question 15

Why is it recommended to work close to a Bunsen when making growth plates?

Answer 15

So that the convection currents carry away any bacteria in the air

Question 16

Why are viruses dangerous?

Answer 16

Viruses cause diseases such as the influenza virus, chicken pox, Mumps and aids (hiv virus)

Question 17

How to lymphocytes prevent infection?

Answer 17

They are released to fight infection. The B cells make antibodies to fight the microorganisms and the T cells kill the microorganisms by killing the infected body cells

Question 18

Describe the structure of bacteria

Answer 18

Cocci are spherical in shape, bacilli are rod shaped and spirochetes are spirals. Some may have a long filament called a flagellum attached which allows them to move

Question 19

When can aseptic technique be used?

Answer 19

During surgery

Question 20

Describe the structure of fungi

Answer 20

They have a spore case and a network of threads forming a structure called a mycelium

Question 21

Groups of bacteria are called …?

Answer 21

Colonies

Question 22

Micro organisms can be grown in Petri dishes containing a growth medium called?

Answer 22

Agar gel

Question 23

What is the name of the process in which pathogens are ingested and digested?

Answer 23

Phagocytosis

Question 24

Non specific defences of the body include: (6)

Answer 24

Skin prevents harmful particles from entering the body, blood clotting stops excess bleeding and bacteria entering wounds, tears help to cleanse the eyes, ear wax protects the inner ear from bacteria & infection, stomach acid kills harmful microorganisms on food and the cilia on the top layer of mucus help to catch harmful particles and prevent them from going deeper into the lungs

Question 25

Describe the experiment carried out by Florey and Cain to show the life saving effects of penicillin

Answer 25

They injected mice with a lethal dose of bacteria and then infected half of the mice with penicillin. The mice injected with penicillin survived and the other mice did not

Question 26

Who developed vaccines ?

Answer 26

Edward Jenner

Question 30

Why is bacteria dangerous?

Answer 30

It causes diseases such as Salmonella and Tuberculosis. They also cause food to go 'off'

Question 31

Why should a loop not be allowed to touch an unsterilised surface?

Answer 31

The loop may become unsterile and therefore affect the results of the experiment

Question 31

Describe two other precautions taken (aside from sterilising the area) when working with microorganisms

Answer 31

- wash hands with soap and water | - treat all microorganisms as potential pathogens (do not grow at 37 degrees)

Question 32

Name the three types of microbe and give an example of each

Answer 32

Bacteria - Salmonella Virus - Influenza Fungi - Ringworm

Question 33

What are the 6 different ways (non specific defences) the body protects itself from infection?

Answer 33

Glands in the skin produce an antiseptic oil Tear glands make an antiseptic fluid which kills bacteria Cells produce mucus which traps dust and germs - cilia move the germs upwards Hydrochloric acid made by the lining of the stomach kills bacteria on food When cut the blood forms a clot which develops a scab to prevent entry of bacteria Ear wax traps foreign particles and germs blown into the ear canal and prevents bacterial growth

Question 34

Explain how the body deals with infection

Answer 34

When a lymphocyte encounters a microbe it will produce antibody molecules – these join onto a specific part of the microbe called the antigen. This can instantly cause the microbe to rupture, or it can group them together. Rupturing of the cells causes them to die, their numbers therefore decrease over time and the infection is reduced