2004 

YEAST CELLS PRODUCE ETHANOL IN A PROCESS CALLED FERMENTATION. IS THIS PROCESS AFFECTED BY TEMPERATURE ?

Yes. Because the rate of enzyme action is affected by temperature.

DRAW A LABELLED DIAGRAM TO SHOW THE STRUCTURE OF RHIZOPUS. 

DESCRIBE THE STAGES INVOLVED IN THE SEXUAL REPRODUCTION OF A ZYGOSPORE (DIAGRAM)

  1. Occurs between + strain and - strain. When hyphae of opposite strains grow close together, swellings form on both strains and touch each other
  2. Nuclei from both hyphae move into these swellings which are now called progametangia 
  3. cross walls form to produce gametangia
  4. The walls of the gametangia dissolve and a number of fertilisations take place producing a diploid zygote nuclei.
  5. A zygospore  forms around these nuclei. A zygospore is a tough walled capsule.
  6. When conditions are suitable the zygospore germinates.
  7. A hyphae grow out of the zygospore and produces a sporangium at the tip
  8. The sporangium opens releasing many haploid spores which grow into new individuals.

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2005 

EXPLAIN THE TERM SAPROPHYTIC AND PARASITIC FUNGI 

Saprophytic : live off dead organic matter 

Parasitic : live off a living host 

STATE A ROLE FOR EACH OF THESE TYPES

Saprophytic fungi obtain nutrients from dead material. As they digest it, minerals are released and recycled. Responsible for decay. Eg Mushrooms

Parasitic fungi: They are used to control population numbers.

STATE A FUNCTION FOR THE FOLLOWING.

Rhizoids: provide extra surface area for absorption of the digested material and help anchor the rhizopus.

Sporangium: Make spores

Gametangium: involved in sexual reproduction.The walls of the gametangia dissolve and a number of fertilisations take place producing a diploid zygote.

Zygospore: is a tough walled capsule that forms around nuclei. When conditions are suitable the zygospore germinates. (Survival) Also helps involved in dispersal. A hyphae grows out of the zygospore and produces a sporangium tip, The sporangium opens releasing many haploid spores which grow into new individuals.

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2007 

WHAT IS A NUTRIENT MEDIUM

Material allowing growth 

STERILE: all microorganisms are destroyed.

 NAME NUTRIENT MEDIUM USED IN GROWTH ON LEAF YEAST.

Malt agar

DESCRIBE HOW YOU CONDUCTED THIS INVESTIGATION.

  • Collect leaves from ash tree. 
  • Wipe down all lab surfaces, instruments and hands with disinfectant. This prevents unwanted microorganisms from contamination.
  • Use a sterilised cork borer to cut 5 discs from a leaf 
  • Turn malt agar plate upside down to avoid air-borne contamination. Remove lid. 
  • Use sterilised forceps to stick leaf discs (undersides facing down) onto the inside of the agar plate. Use vaseline to stick them.
  • Seal with tape.
  • Place leaf discs with uppermost into an incubator of 25 C  for 24 hours. Then place the plate upside down for 3 days.

RESULTS 

Yeast colonies are seen as circular pink growths on agar.

Control = no growth.

GIVE A ROLE OTHER THAN ANCHORAGE FOR HYPHAE/RHIZOIDS

Digestion of nutrients 

The hyphae release enzymes onto the substrate. Enzyme breaks down starch.This is absorbed back in.

2 EXAMPLES OF HARMFUL FUNGI 

Athletes foot and ringworms

SUGGEST A STIMULUS WHICH TRIGGERS SEXUAL REPRODUCTION

Dehydration