B6

Question 1

State the 4 shapes of bacteria

Answer 1

Curved
Rod-shaped
Spiral
Spherical

Question 2

Draw and label the 6 main parts of a bacterial cell. Explain each

Answer 2

Loop of DNA - controls the cell and its replication of the cell
Cell wall - helps the cell maintain its shape and stops it from bursting
Cell membrane - controls the movement of substance in and out of the cell
Cytoplasm - where most of the chemical reactions in the cell take place
Flagellum - for movement of the cell
Capsule - protects the cell against antibiotics

Question 3

What is the method which bacteria used to reproduce called? What type of reproduction is this?

Answer 3

Binary fission - type of asexual reproduction

Question 4

Why is sterile technique important?

Answer 4

To prevent the bacteria infecting you and causing you to become ill

Question 5

Why can bacteria live in many different environments

Answer 5

They can gain energy from a range of methods

Question 6

State and label the 6 parts of a fungal cell

Answer 6

• Cell wall
• Nucleus
• Cell membrane
• Cell wall
• Cytoplasm
• Vacuole

Question 7

State the 4 things that affect yeast growth

Answer 7

• pH
• Availability of food
• Temperature
• Removal of waste

Question 8

Draw and label the structure of a viral cell

Answer 8

(refer to textbook)

Question 9

Explain how yeast reproduce. State the name of this process. What type of reproduction is this?

Answer 9

• Budding:
  1. The nucleus splits
  2. A bulge forms on the side of the fungal cell, which develops into a new cell
  3. The cells usually remain joined

This is a form of asexual reproduction.

Question 10

State the 4 parts of the body that make up its first line of defence. Explain how each part prevents microbes entering and how microbes can overcome these defences.

Answer 10

(refer to printed-out table)

Question 11

State 4 ways in which microbes can get past the host’s defences

Answer 11

• Contaminated food
• Contaminated water
• Contact
• Airborne transmission

Question 12

State 5 ways in which natural disasters can cause the spread of disease

Answer 12

• Can damage sewage pipes, causing sewage to leak and contaminate water sources
• Can damage water supply systems, cutting off the supply of clean water
• Can cut off electricity so food cannot be refrigerated
• Can destroy homes so people may have to live in crowded places where disease can spread
• Health service may become over-stretched and lacking in supplies

Question 13

Explain the 4 steps of how an infectious disease develops upon entering the body

Answer 13

1. Microbes enter through the mouth, nose or breaks in the skin
2. Microbes begin to use the body to supply the conditions needed for growth and the microbes rapidly reproduce to produce large numbers
3. As the microbes reproduce, they make waste products, some of which are often toxic
4. Large amounts of toxin (toxic waste products) can cause symptoms associated with illness, making the body feel unwell

Question 14

Explain the contributions of Pasteur, Lister and Fleming in treating infectious diseases

Answer 14

• Pasteur - proved that decay was caused by microbes in the air and explained that disease was caused by microbes entering the body. He suggested that illness could be prevented by stopping microbes entering the body (germ theory).
• Lister - developed the idea of antiseptics - solutions that kill microbes. He sprayed his surgical instruments with carbolic acid which killed microbes on his instruments and reduced the number of postoperative infections
• Fleming - discovered that a mould called Penicillin produced a chemical that killed bacteria, developing the first antibiotic

Question 15

State 5 processes in which bacteria are useful

Answer 15

• Making yoghurt
• Making cheese
• Making vinegar
• Making silage (winter fodder - food for cattle)
• Making compost

Question 16

Explain the full process of making yoghurt

Answer 16

(refer to step-by-step in notebook)

Question 17

Explain the full process of brewing

Answer 17

(refer to step-by-step in notebook)

Question 18

State the equation for the fermentation reaction

Answer 18

glucose (sugar) -> ethanol (alcohol) + carbon dioxide

Question 19

Explain how the alcohol content of the liquid gained from fermentation can be increased

Answer 19

By distillation - the liquid is placed in a large contained and heated. The alcohol boils at 80’C while the water doesn’t (alcohol has a lower boiling point than water). The alcohol leaves the column/container as a vapour and when condensed, has a much higher alcohol content than before.

Question 20

State 3 advantages and 3 disadvantages of using biofuels

Answer 20

Advantages:
- no overall increase in greenhouse gas levels (as carbon neutral)
- reduces the use of fossil fuels
- no particulates (smoke) produced
Disadvantages:
- some biofuels transfer less energy than other fuel types
- can lead to habitat loss as large areas of plants are grown for biofuels
- habitat loss can lead to extinction of species

Question 21

State 2 reasons why using biofuels may not always keep CO2 levels balanced

Answer 21

• Large forest areas are cleared to grow biofuel crops so there are less plants to absorb carbon dioxide in photosynthesis
• Decaying wood also releases carbon dioxide

Question 22

Explain simply how biogas is produced

Answer 22

By the fermentation of carbohydrates in plant material and sewage by bacteria

Question 23

Explain how biofuel is produced commercially in large amounts

Answer 23

• The plant material or sewage is placed in large anaerobic tanks
• The plant material and sewage continuously flows in and the gas produced in continuously removed
• The solid material in the tank can be removed and used as fertiliser
• The temperature is kept at 32-35’C at which point bacteria grow best, because bacterial enzymes work best

Question 24

State 2 uses of biogas

Answer 24

• Vehicle fuel
• Heating systems
• Generating electricity

Question 25

What is the name of alcohol produced from brewing used as fuel?

Answer 25

Bioethanol

Question 26

State 3 problems with producing biogas

Answer 26

- If methane content drops below 20% the mixture can become explosive - Biogas releases a lower amount of energy compared to other fuel types - Biogas is made using different types of waste material so different types of bacteria are needed to digest the wastes

Question 27

State 5 components of soil

Answer 27

- Fragments of rock - Air spaces - Water - Living organisms - Dead material

Question 28

Describe the relationship between the number/size of air spaces and the ability of the soil to retain water

Answer 28

- If the air spaces are too few and too small, the soil has poor water retention - If air spaces are too large, the soil has poor water retention - If air spaces are many and vary in size then the soil has good water retention

Question 29

Explain the name and structure of the ideal soil

Answer 29

- Loam | - Contains variable particle sizes, providing both good water retention and air spaces for living organisms to respire

Question 30

What is humus?

Answer 30

Dead material which decomposes in the soil to release minerals needed by plants for growth.

Question 31

State 4 ways in which earthworms are beneficial in soil

Answer 31

- form burrows, aerating soil and preventing flooding - release calcium carbonate into gut to digest leaves - this passes out in their waste, helping neutralise acidic soils - mix soil by eating it and passing it out somewhere else - drag dead leaves into soil, which are decomposed by bacteria and fungi, increasing the nutrient content of the soil

Question 32

State 4 advantages of living in water

Answer 32

- Buoyancy - water helps large organisms support their weight - Removal of waste - waste is easily washed away - Steady temperature - organisms don't have to cope with changes in the temperature of the water - Ready water supply - water is drearily available so no risk of dehydration

Question 33

State 2 disadvantages of living in water

Answer 33

- Balancing water - it can be difficult to balance water inside and outside the body - Movement - water is denser than air so it is harder to move through, so organisms use more energy

Question 34

Draw 4 diagrams to explain how amoeba remove excess water

Answer 34

(Refer to diagrams in notebook)

Question 35

State 3 factors which control the number of phytoplankton, how these vary by seasons, and explain the effect these have on their distribution

Answer 35

- Light - increases as days get longer (spring) so phytoplankton population increases - phytoplankton limited to water surface as light doesn't penetrate deep water - Temperature - surface temperature increases in spring so phytoplankton increase but water at the depth is still cold so they are limited to the surface - Minerals - during winter, minerals rise to the surface, so they are in large quantities in spring, when phytoplankton numbers increase (as a result), but phytoplankton are still limited to the water surface due to the temperature and light at the water depths

Question 36

State the 2 types of of plankton is aquatic food webs and their role in the food webs

Answer 36

- Phytoplankton - are producers, make food by photosynthesis | - Zooplankton - are consumers

Question 37

Explain 2 processes through which nitrates get into bodies of water (which results in eutrophication)

Answer 37

- Crops are sprayed with fertilisers. It rains and minerals including nitrates are washed into rivers and lakes. - Untreated sewage which is discharged into water contains large amounts of nitrates

Question 38

Explain the effect of PCBs

Answer 38

They can build up in a food chain and will eventually build up in top carnivores such as killer whales. PCBs suppress the immune system of organisms, leading to a decrease in their population