1
Q
What is the structure of bacteria?
- Size
- Components and functions
A
- Size: not more than 0.01 mm
- May be spherical, rod-shaped, or spiral
- Have cell walls: made of proteins, sugars, and lipids
- Some have a slime capsule inside their cell wall
- Cytoplasm, containing food reserves (glycogen, lipids) and a single chromosome (consisting of a circular DNA strand: plasmid)
- No nucleus: chromosome is just coiled up
- Some have filaments called flagella (for movement)
2
Q
What is Bacteria’s physiology?
- How do they get nutrients?
- How do they respire?
- How do they reproduce?
- How do they carry out heat resistance?
A
- Some have chlorophyll and can photosynthesize
- Most live in, or on their food.
- They produce and release enzymes, and digest the food outside the cell
- Can respire both aerobically and anaerobically
- They reproduce via binary fission (asexual): chromosome replicates, divide into two, and daughter cells become independent bacterium
- Produce heat-resistant spores. When food cools down, spores germinate to produce new colonies.
3
Q
- Benefits / uses of Bacteria?
- Disadvantages?
A
1 - Some feed saprotrophically: decomposition of organic matter
- During decomposition: release essential elements. Eg. proteins broken down do ammonia, ammonia turned into nitrates by nitrifying bacteria
2 - Genetic Engineering (more in genetics)
- Though some are disease-causing. (Parasites: derive food from host while host is still alive. Feed on animal or cell cytoplasm, causing diseases.)
- Some also produce toxins (Eg. the one that causes tetanus)
4
Q
What is the structure of viruses?
- components: what they have and don’t have
A
- There are many different types, and all vary in shape and structure
- Components that all have: Central RNA core, surrounded by a protein coat (called capsid, made of regularly paced protein units called capsomeres)
- Have no nucleus, cytoplasm, organelles, or cell membrane (though some do have membrane outside their protein coat)
5
Q
- How do viruses multiply?
- What does this do to living beings?
- How are they useful?
A
- Sticks itself to a living cell membrane, injects its DNA or RNA into living cell or fully just enters the cell
- Its caspid gets dispersed, the DNA or RNA takes over host cell’s physiology
- Nucleic acid and capsomeres get used to make new virus particles which escape from the cell
- Host cell may get destroyed, giving rise to disease symptoms
- They are used as vectors to deliver recombinant DNA in genetic engineering (more in genetics)
6
Q
What is the structure of fungi?
- the different types
- Components, functions
A
- Instead of cells, made of threads called hyphae (they spread through the material and absorb food from it)
- Hyphae are lined with cytoplasm, containing organelles, food (glycogen and lipids), nuclei
- Some species’ hyphae have cross-walls, dividing them into cell-like compartments. each compartment has one or two nuclei in these species
- In the centre of older hyphae: vacuole
- No chlorophyll or starch grains
- A network of hyphae growing through food: mycelium
- Hyphal wall: may have cellulose, or chitin, or both
- Mushrooms and toadstools are the fruiting bodies
7
Q
Fungal Physiology
- Two types, based on nutrition
- How do they reproduce?
ADD STRUCTURE
A
- Saprotrophs and parasites
- Saprotrophs: feed on dead organic matter. Hyphae secrete enzymes to digest the matter into liquid products, digested products absorbed back (responsible, along w bacteria, for decomposition)
- Parasites: The hyphae penetrate host cell and digest cells and contents
- Can cause plant to die, animals: ringworms, fungal infection
- Reproduce by producing single-celled spores
- Each spore contains: Cytoplasm and nuclei
- When a spore lands on organic matter, germinates to produce mycelium
- Spores are produced asexually, though some do have a sexual process in their lifetime
8
Q
Uses of fungi
- What is penicillum / use?
- What is yeast (features), how does it carry out fermentation?
(come back when doing biotech)
A
- Penicillium: A type of mould, grow on decaying vegetable matter, damp leather, citrus fruits
- an antibiotic effective against fungal skin disease
- Yeast: Generally don’t form true hyphae: instead, spherical unicellular cells
- Thin cell wall with cytoplasm, contain a nucleus, vacuole and food reserves
- Grow on sugars
- Used in fermentation, their enzymes break down sugars into carbondioxide and alcohol. This provides them with energy through anaerobic respiration
9
Q
Role of Microorganisms in decomposition
- What is decomposition?
- How is it carried out?
- What substances are broken down, and what is formed?
- Uses of decomposition?
A
- Breakdown of dead organisms as well as waste material e.g faeces and urine
- Carried out by bacteria and fungi
- They feed saprotrophically, secreting digestive enzymes outside their bodies breaking down the organic matter into smaller soluble molecules
- Carbohydrates are respired releasing carbon dioxide
- Proteins are excreted as waste products like ammonia
- Uses: 1 - Hummus formation: dead mater into peat
2 - Fermentation: making alcohol, bread etc. (more in biotech)
3 - Putrefication: decomposition of proteins under anaerobic conditions
4 - Sewage: decomposed by bacteria and fungi
10
Q
Bread production
A
- Micro-organism used: yeast
- the only required fermentation product: carbondioxide
1 - Flour, water salt, oil, yeast are mixed to make dough
2 - Water activates amylase present in flour, it digests starch present to sugar
3 - Yeast ferments the sugar to alcohol and carbondioxide
4 - Protein called gluten makes dough sticky and thick, holds the gas bubles
5 - left to sit at 27’C, CO2 makes it rise
6 - baked at 200’C. Bubbles expand more, yeast killed, small quantity of alcohol produced evaporates, dough turns into bread.
11
Q
Alcohol production
A
- cane molasses is used. it should have 50% fermentable sugar (i.e. simple sugars)
1 - molasses is diluted, sugar concentration brought down to 15% (because enzyme action on sugar needs free water molecules)
2 - Small quantity of urea (ammonium sulfate) added (for nitrogen)
3 - yeast culture added (steel tanks)
4 - resultant fermentation mesh distilled - conditions: 25 - 30’C temperature, 5 pH
12
Q
Yogurt Production
A
- Made by fermentation of milk by bacteria
1 - Fat and protein content is adjusted and the milk is homogenized (mechanical process which breaks up fat droplets)
2 - Pasteurization (heated to 70’C, cooled quickly to 7’C)
3 - Starter culture added: A mixture of Streptococcus thermophilus and Lactobacillus Bulgarius - They act on the milk sugar: Lactose, convert it to lactic acid.
- Lactic acid coagulates the milk protein: Casein, to produce thick consistency
- Fermentation temperature: 46’C
- at the end: cooled to 5’C
- pH: lactic acid makes it 4.4
13
Q
Cheese production
A
1 - Fat and protein content is adjusted and the milk is homogenized (mechanical process which breaks up fat droplets)
2 - Pasteurization
3 - Culture added: usually Streptococcus or Lactobacillus
- Fermentation temperature: around 40’C
4 - A mixture of enzymes, rennet, is added
- Rennet contains enzyme chymosin: coagulates the casein (milk protein) and forms curds
5 - Liquid part (whey) is drained from curds
6 - Curds are partially dried and compressed
- bacterial enzymes act on the proteins and fats in the curds, partly digesting them to amino acids and fatty acids
14
Q
Fermenters
- features, conditions
A
- Fermenters: giant tanks, up to 100,000 litres in capacity
- Sometimes called bioreactors
Used to produce food and drinks , and to grow microorganisms - Filled with a nutrient solution
- Conditions (temperature, pH, nutrients, oxygen concentration, waste product concentration, sterile conditions) are carefully controlled
- 26’C, 4-5 pH
Key features:
1 - cool water jacket for optimum temp
2 - Air supply
3 - paddles to stir liquid
4 - outlet pipe to harvest product
5 - outlet for waste gases
15
Q
How do antibiotics attack bacteria?
A
- Bacteriostatic antibiotics: Disrupt production of cell wall, or cause them to burst open, to prevent bacteria from reproducing, or interfere with protein synthesis and arrest bacterial growth
- Bacteriocidal: kill the bacteria
16
Q
Production of penicillin
- process
A
- The carbohydrate source is sugar, mainly lactose
- produced by the mould Penicillium chrysogenum
- nutrient solution w sugars, minerals, amino acids added
- A starter culture with spores and filaments of Penicillium added
- The mould begins to make penicillin when it starts to use up all the growth medium
- this happens about 40 hours in to incubation period and continues for many days
- Penicillin is secreted out of the cells
- Fermenter now contains a dense mass of cells, unused nutrients, waste products and penicillin solution
- contents are filtered
- penicillin is extracted from the solution using a series of organic solvents
- re-dissolved into a solution of sodium hydrocarbonate and is allowed to crystallise
- can be stored at room temperature, and modified to produce a range of antibiotics
17
Q
- Objective of single-cell protein?
- what micro-organisms are used?
- What is one that has been commercially used, how is it produced, advantages and disadvantages?
A
- To produce micro-organisms in bulk to use as human food or animal feed.
- Unicellular algae, fungi and bacteria.
- commercially used: mycoprotein made from a fungus: Quorn.
- The fungus is grown in a medium containing glucose and mineral salts, at 30’C, in a fermenter.
- the process is called continuous culture.
- Medium is circulated around, and fungus is filtered off and dried at a steady rate.
- This is cheaper than doing it in batches, because avoids repeated sterilization.
Disadvantages:
1 - More expensive than conventional crops
2 - colorless and tasteless.
3 - contain toxic amounts of nucleic acids which have to be removed, because of the high nucleus to cytoplasm ratio
Advantages:
1 - Rich in protein
2 - low in fat
3- good level of dietary fibre
4 - vegan alternative
so healthier than most meat options.
O level Biology
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