Topic 9 - Microorganisms

Question 1

Pathogen

Answer 1

A microorganism that causes disease in another living organism. Our body recognises them as foreign due to the presence of their specific shaped antigen

Question 2

Protoctist

Answer 2

Unicellular and multicellular organisms that are not bacteria, viruses, fungi, plants, or animals

Question 3

Bacteria

Answer 3

Unicellular microorganisms which have cell walls but lack membrane-bound organelles and an organised nucleus. Some bacteria can cause disease

Question 4

Virus

Answer 4

An infective agent that consists of a DNA/RNA molecule in a protein coat, which is able to multiply only within the living cells of a host

Question 5

Phagocytes

Answer 5

White blood cells that carry out phagocytosis by engulfing and digesting pathogens.
- Secretes enzymes to break down the pathogen
- The remains get absorbed
- The tri-lobed nucleus allows it to change shape

Question 6

Lymphocytes

Answer 6

White blood cells that release antibodies or antitoxins which help destroy pathogens
- Antibodies released attach to antigens and cause them to clump together (immobalise)
- Chemicals released signal to phagocytes that pathogens are present
- Produce antitoxins to neutralise toxins released by pathogens

Question 7

Antibodies

Answer 7

Y shaped proteins released from lymphocytes which binds to an antigen on a pathogen. They are specifically shaped allowing them to fit their target antigen.

Question 8

Memory cells

Answer 8

Special cells produced by lymphocytes that remember the exact shape of the antibody. Allows lymphocytes to make antibodies faster and in larger quantities upon next infection.

Question 9

Vaccination

Answer 9

The injection of dead or inactive pathogens into the body. An immune response is triggered, so antibodies are produced to attack antigens. Memory cells are also produced in case live pathogens of the same type enter the body.

Question 10

Production of yogurt

Answer 10

• equipment is sterilised to kill off any unwanted microorganisms
• milk is pasteurised (72˚C for 15 secs) and then cooled
• lactobacillus bacteria are added, and the mixture is incubated (40˚C) in a fermenter
• the bacteria ferment the lactose sugar in the milk to form lactic acid
• lactic acid clots the milk, solidifying it into yogurt
• flavours and colours added, yogurt packaged

Question 11

Production of bread

Answer 11

• dough is made by mixing yeast, flour, water and sugar
• dough is left in warm place to rise
• enzymes digest carbohydrates in flour into sugars
• yeast uses the sugar in aerobic respiration, producing CO2
• fermentation (anaerobic respiration) then produces CO2 and ethanol
• dough rises as trapped pockets of CO2 expand
• dough is baked in oven, where yeast ferments until temperature is high enough to kill it
• any alcohol boils away

Question 12

Platelets

Answer 12

fragments of cells that are involved in blood clotting and forming scabs where the skin has been cut or punctured

Question 13

Process of blood clotting

Answer 13

• when the skin is broken platelets arrive to stop the bleeding
• platelets release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin and form an insoluble mesh across the wound, trapping red blood cells and therefore forming a clot, preventing blood loss
• the clot eventually dries and develops into a scab to protect the wound from entry of microorganisms