LESSON 3MICROORGANISMS

& FOOD

OCR AS Biology – F212 – Module 2

Food & Health

(e) explain that humans depend on plants for food as they are the basis of all food chains. (No details of food chains are required)

Humans are dependent on plants as they are the basis for all food chains

(f) outline how selective breeding is used to produce crop plants with high yields, disease resistance and pest resistance (g) outline how selective breeding is used to produce domestic animals with high productivity

Chose organisms with characteristic you want, breed together individuals with that characteristics, repeat

E.g. Crops with high yield, disease resistance and pest resistance

E.g. domestic animals with high productivity

(h) describe how the use of fertilisers and pesticides with plants and the use of antibiotics with animals can increase food production

Use of fertilisers and pesticides (plants)Fertilisers: provide minerals for growthPesticides: kill pests that feed on crop,

reducing amount of plants damaged/destroyed

Use of antibiotics (animals)Don’t waste energy fighting diseasePromote growth by affecting bacteria in gutIncrease the size of animals when mature

Questions

1) Explain how food production can be increased with the use of pesticides

2) Briefly describe how selective breeding is used to increase food production

3) Give 2 advantages of using selective breeding

Answers1) Explain how food production can be increased with the use of

pesticides• Kills pests• Less plants destroyed• Increased yield

2) Briefly describe how selective breeding is used to increase food production

• Select organisms with useful characteristics to increase food production• Breed together• Select offspring with best characteristics• Breed together• Repeat

3) Give 2 advantages of using selective breeding• Produce high yielding animals/plants• Produce organisms with increased resistance to disease so need to use less

pesticides/antibiotics• Increased tolerance to poor conditions

Learning Objectives Success Criteria

Understand that food spoilage can be harmful to human health.

Understand the methods used to prevent food spoilage.

Understand how microorganisms can be used to make food.

Discuss the advantages and disadvantages of using microorganisms.

Recall the ways in which food spoilage can be seen (E-D)

Describe the ways in which food spoilage can be prevented (C-B).

Explain how microorganisms can be used to make food and the advantages/disadvantages of this (A-A*)

Starter If a nuclear holocaust was imminent, what kind

of food would you stock in your bomb shelter to last you through the next few months?

Canned Food Dry Cereals Pickled Food

Dried/SaltedSnacks

SmokedFood

Food Spoilage How do we know food is spoilt?

For example, meat left out for a while may be covered in harmful bacteria.

The meat may look fine to eat, but consumption could cause major illness.

The signs of food spoilage are not

always immediately visible.

Food Spoilage – Visible Growth Moulds are the most obvious visible form of

microorganism on our food.

Fungi like the ones above feed saprophytically. This means they secrete enzymes onto food and

then absorb the products into their cells.

Mucor fungus on bread.

An orange covered in Penicillium

fungus

Food Spoilage – Toxins Some microorganisms release toxins onto our food. This can cause serious illness, especially in the case of

Clostridium botulinium. This bacteria releases botulin, of which as little as 1µg can

kill a person.

C. botulinium causes the disease, botulism.

Food Spoilage – Infection A very common problem caused by eating spoilt food is

infection. Salmonella bacteria is associated with poultry (both meat &

eggs). The bacteria attack the lining of the stomach and intestine.

Preventing Food Spoilage

Preventing Food Spoilage Use the bottom half of page 158 to find out how fresh food

can be saved from spoilage.

Method How it works...

Salting

Adding sugar

Pickling

Cooling/Freezing

Heat Treatment

Irradiation

Drying

(j) outline how salting, adding sugar, pickling, freezing, heat treatment and irradiation can be used to prevent food spoilage by microorganisms

Bacteria break down food by releasing enzymes and breaking down molecules into their component parts

Drying/Salting – dehydrate microorganisms Adding Sugar – dehydrate microorganisms Pickling – pH kills microorganisms Freezing – slow growth Heat Treatment – denatures enzymes Irradiation – disrupts DNA

Microorganisms In Making Food

Microorganisms in Making Food Microorganisms aren’t all bad – they can be used to make food too.

YoghurtLactobacillus uses lactose in milk to make lactic acid. The milk is partially

digested by the bacteria.

This makes it easy to digest for us.

CheeseMilk is allowed to curdle. The solid,

curdled milk is acted upon by Lactobacillus and additional flavours can be achieved by contamination

with Penicillium.(e.g. Blue cheese)

Microorganisms in Making Food

Bread

Bread is made to rise by yeast.Yeast respires anaerobically,

releasing carbon dioxide bubbles.These cause bread to rise.

AlcoholCereal grains contain the sugar

maltose, which yeast respire upon.Alcohol is produced as a product of anaerobic respiration by the yeast.Cereals are replaced with grapes

when making wine.

QuornTM

A very well-known protein produced by a fungus is Mycoprotein. This is the protein present in the meat-substitute food product known

as Quorn.

Quorn is a very healthy option as it contains no animal fat or cholesterol, which as you now know can be harmful to health.

The mycoprotein in Quorn is made by

the fungus:Fusarium venenatum

Question

1) Describe an example of the use of microorganisms in food production

2) What is meant by the term ‘food spoilage’

3) Describe how adding sugar to food can prevent spoilage

4) What is the name of the food preservation that involves exposing food to gamma or x rays?

Answers1) Describe an example of the use of

microorganisms in food production• Bread making (yeast makes carbon dioxide)• Wine making (yeast turns sugar into alcohol)• Cheese making (bacteria curdles milk)• Yoghurt (bacteria turn sugar into lactic acid)

2) What is meant by the term ‘food spoilage’• Deterioration of the food’s characteristic

3) Describe how adding sugar to food can prevent spoilage

• Inhibits growth of microorganisms• By interfering with their water absorption

4) What is the name of the food preservation that involves exposing food to gamma or x rays?

• Irradiation

What are the advantages & disadvantages of using microorganisms to make food?

Think, Pair, Share

(i) describe the advantages and disadvantages of using microorganisms to make food for human consumption

AdvantagesFaster production of proteinIncreased/decreased on demandNo animal welfare issuesSource of protein for vegetarians

DisadvantagesNot want to eat food grown on wasteProtein needs to be isolatedCould grow pathogenic organisms by

accidentNot taste or texture of traditional protein

Learning Objectives Success Criteria

Understand that food spoilage can be harmful to human health.

Understand the methods used to prevent food spoilage.

Understand how microorganisms can be used to make food.

Discuss the advantages and disadvantages of using microorganisms.

Recall the ways in which food spoilage can be seen (E-D)

Describe the ways in which food spoilage can be prevented (C-B).

Explain how microorganisms can be used to make food and the advantages/disadvantages of this (A-A*)

Past Paper QuestionsPlenary

[3]

bacteria / (bacterial) cells, divide / increase in number / multiply / reproduce / proliferate / replicate ;

(secrete) enzymes / named enzyme ; food, digested / broken down ; protein / named protein / polypeptides → peptides / amino

acids OR fat / triglycerides → fatty acids OR starch / amylose / glycogen → glucose / sugar ;

production / release / excretion / secretion, of, toxins / named toxin / waste products ;

(causes) change in, appearance / smell / texture / taste ;

[3]

bacteria, reproduce / AW, more rapidly / faster ; (so) more bacteria present ; more, toxins / waste, produced / released / AW more enzymes, secreted / AW ; enzyme, action faster / works better / more effective,

at higher temperatures ; (substrate and enzymes have) more kinetic energy ; more, enzyme-substrate complexes / ESC /

(successful) collisions between substrate and active site ;

[4]

salting ; lack of water due to, osmosis / low water potential (outside cell) ;

sugar ; lack of water due to, osmosis / low water potential (outside cell) ;

(air / freeze) drying ; idea that enzymes cannot mobilise / intracellular transport impaired / reactions have

no medium in which to occur / (microbes) cannot move ;

pickling / (use of) vinegar ; (low pH) denatures / changes tertiary structure of / changes 3D shape of, enzymes /

proteins substrate no longer fits active site / active site shape changes / prevents ESC ;

heat treatment / cooking ; denatures / changes tertiary structure of / changes 3D shape of, enzymes / proteins substrate no longer fits active site / active site shape changes / prevents ESC ;

irradiation / UV / gamma rays / X-rays / ionising radiation ; destroys / damages / changes / mutates, DNA / genes / genetic material ;