understanding microbes

Question 1

what is the size of a typical bacterial cell?

Answer 1

just a few microns (thousandths of a mm

Question 2

how can bacteria be classified?

Answer 2

by their shape

Question 3

how do bacteria reproduce?

Answer 3

by splitting in two

Question 4

when can bacteria produce rapidly?

Answer 4

in suitable conditions

Question 5

how can bacteria be grown?

Answer 5

in large fermenters

Question 6

properties of a flagellate bacillus

Answer 6

• flagellum
• cell wall
• bacterial DNA

Question 7

what is yeast?

Answer 7

a fungus

Question 8

properties of a yeast cell?

Answer 8

• nucleus
• cytoplasm
• cell wall
• bud.

Question 9

what are viruses?

Answer 9

• not living cells

* much smaller than bacteria and fungi

Question 10

Describe how yeast reproduces asexually by

budding

Answer 10

the chromosomes are copied and a new nucleus is made. The new cell ‘buds’ off the parent.

Question 11

Describe how the parts of bacterial cells relate to their function

Answer 11

• flagellum for movement
• cell wall to maintain shape, and to stop it from
bursting
• DNA to control the cell’s activities and replication
of the cell.

Question 12

Describe the main shapes of bacteria

Answer 12

• spherical
• rod
• spiral
• curved rods

Question 13

how do bacteria reproduce?

Answer 13

by a type of asexual reproduction called binary fission

Question 14

Describe aseptic techniques for culturing bacteria on

an agar plate

Answer 14

• clean the work surface with bleach before and after using bacteria
• wash your hands before and after handling bacteria and wear gloves
• sterilise all equipment before and after use with disinfectant or in an autoclave
• keep lids on culture dishes where bacteria are growing, and destroy all bacteria at end of experiment

Question 15

Describe the structure of viruses

Answer 15

• a protein coat

* surrounding a strand of genetic materia

Question 16

what can viruses do?

Answer 16

• can only reproduce in other living cells
• only attack specific cells
• may attack plant, bacterial or animal cells

Question 17

Explain how a virus reproduces

Answer 17

• attaching itself to a specific host cell
• injecting its genetic material into the cell
• using the cell to make the components of new
viruses
• causing the host cell to split open to release the
viruses.

Question 18

Describe how yeast growth rate can be increased, its

optimum growth rate being controlled by:

Answer 18

• food availability
• temperature
• pH
• removal of waste products

Question 19

Explain how bacteria:
• can survive on an enormous range of energy
sources
• can exploit a very wide range of habitats

Answer 19

because bacteria can use so many different sources of nutrients and energy, they are able to survive in a very wide variety of habitats.

Question 20

Explain the consequences of very rapid bacterial

reproduction in terms of food spoilage and disease

Answer 20

• diseases spread fast as conditions inside the human body are ideal for bacterial growth
• food can become contaminated by the toxic waste produced by bacteria as they feed, making it very dangerous to eat

Question 21

Describe how yeast growth rate doubles for every 10°C rise in temperature until the optimum isreached

Answer 21

yeast growth doubles for every 10°C rise in temperature. So, increasing the temperature increases the rate of fermentation. But, over 40 degrees C, yeast enzymes are denatured, which causes the rate of fermentation to slow down.