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Synthesizing factors affecting
photosynthesis• Identify the factors affecting the rate of photosynthesis,
• Identify the factor that limits the rate of photosynthesis at
different light intensity,
• Explain the effects of temperature and concentration of
carbon dioxide on the rate of photosynthesis,
• Explain the difference in the rate of photosynthesis in
plants throughout the day based on the changes in light
intensity and temperature,
• Identify some ways to meet the need of increasing the
productivity of crops based on factors affecting the rate of
photosynthesis.
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Factors affecting the rate of photosynthesis
• Light intensity
• Concentration of CO2
• Temperature
Limiting factor
• Factor that is in the shortest supply• Determines the rate at which photosynthesis
can take place at any one time
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Light intensity
• Light tend to limit the rate of photosynthesis at low intensities
• As light intensity increases, the rate of photosynthesis
increases.
• A point is reach where the rate if oxygen produced is equal to
the rate at which oxygen is used for respiration. This is called
compensation point.
• At high light intensities, carbon dioxide concentration is the
limiting factor.
• The rate of photosynthesis will increase only when an increase
in the concentration of carbon dioxide. 3
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• When the [CO2] & temperature is at constant,
rate of photosynthesis is directly proportional
to light intensity.
• Graph I shows the initial condition.
• As light intensity increases, the rate _________.
• At point P, the rate of photosynthesis becomes
constant.
• This is due to other factors which is limiting like
CO2.
• After this point, the rate of photosynthesis will
not increase even if light intensity increases.
• Graph II shows the condition when the level of
CO2 is increased.
• The rate of photosynthesis increases greatly as
the CO2 level increases until it becomes limiting
factor again.
Light intensity
Graph II
Graph IP Q
0.13% CO2
at 30oC
0.03% CO2
at 30oC
Light
intensity
R a t e
o f p h o t o s y n t h e
s i s
Effect of light intensity on the rate of
photosynthesis 4
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• C02 is required in dark reaction for the synthesis of glucose
• Concentration of C02 in atm is between 0.03% - 0.04%.
•In places with high densities of plants, competition for C02
arises – will effect the rate of photosynthesis.
• Increase in C02 increases the rate of photosynthesis (if
there is no other limiting factor).
• If light intensity becomes a limiting factor, any increase in
C02 will not increase the rate of photosynthesis.
Concentration of C02
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30oC at high
light intensity
30oC at low
light intensity
Carbon dioxide
concentration
R a t e
o f p h o t o s y n t h e s i s
Effect of carbon dioxide concentration on the
rate of photosynthesis
Concentration of C02
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• Temperature has minimal effect on the rate of the light reactions in
photosynthesis. This is because this phase of photosynthesis
depends on the light energy and not heat.
• Raising the temperature will increase the rate of photosynthesis as
the dark reaction is enzyme catalyzed.
• Rise of 10 oC will double the rate of photosynthesis, until an
optimum rate is reached at a temperature of about 40 oC.
• If temperature increase further above 40 oC, photosynthesis slows
down and eventually stop altogether.
• Heat denatures enzyme and destroy their catalytic function in the
various stages in the Calvin cycle.
Temperature
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Temperature
Temperature, 0 C
R a
t e
o f p h o t o s y n t h e s i s
Effect of temperature on the rate of photosynthesis
60405
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Difference in the rate of photosynthesis
• In tropical countries, there are no seasons and photosynthesis occurs
throughout the year.
• However, the rate of photosynthesis is influenced by the changes in
temperature and light intensity, as can be seen during the day.
• In the morning and evening, the temperature and light intensity is rather
slow, and as such the rate of photosynthesis will be low.
• During mid day, the temperature and light intensity will be at its highest
and will cause photosynthesis to occur at its highest rate for the day.
• Photosynthesis stops at night when there is no light.
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Need of increasing the productivity of
crops• Each of the seasons has it characteristics condition that have an effect on
the productivity of the plants there.
• Summer: Productivity is the highest since the rate of photosynthesis is the
highest in the year.
• Winter: Rate starts to slow down due to low temperature.
• Autumn: Rate of photosynthesis is low because the leaves fall.
• Plants can only grow throughout the year if they planted in green houses,
in which carbon dioxide concentration, temperature, light intensity, water
and mineral can be provided at optimal rates.
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• Methane burners are used to help increase the
concentration of carbon dioxide and the temp.
• Artificial lighting is also used in green houses to
provide necessary light intensity to increases
the productivity of plants.
Need of increasing the productivity of crops
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Technology Used In FoodProduction
• The efforts by various agencies to
diversify food production
• Methods used to improve the quality and
quantity of food production
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The efforts by various agencies to diversify
food production
•
Ulam – Malay traditional food which is accepted by otherraces
– Rich in ions, vitamins, fibre & used in preparing herbal
medicine and drinks
– Ex: pegaga, shoots of papaya, kacang botol, petai
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• Protein sources – Encouragement by government to consume meat products
– Main source of protein – chicken, fish & meat
– Ex: rabbit meat : soft texture, rich in protein, low cholesterol & suitable for
young kids
– Ex: freshwater fish like tilapia, jelawat & haruan are low in cholesterol
– Ex: ostrich meat : nutritious, rich in protein & low in fat
The efforts by various agencies to diversify
food production
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• Consuming mushroom –
– Ex: button mushroom, abalone mushroom & shittake
mushroom
– Have high nutrient content
– Increases the body’s immune system
The efforts by various agencies to diversify
food production
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Methods used to improve the quality
and quantity of food production
• Methods:
– Direct seeding
– Hydrophonics
– Aerophonics – Breeding of plants and animals
– Tissue culture
–
Genetic engineering – Proper soil management
– Biological control
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Evaluating the technological
development in food processing
• Explain the necessity for food processing,
• Describe the development of food processing technology
• Relate food processing methods with factors causing food
spoilage,
• Assess the methods of food processing to justify the choice of
consuming certain processed food.
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Necessity for food processing
• Food processing:
– Process of preparing food to make it more attractive, more
palatable and to last longer
– To preserve food from factors that cause food spoilage:
microorganism
• Necessity for food processing:
– To preserve food from spoilage
– To avoid food wastage
– To prevent food poisoning
– To increase commercial value
– To diversify the use of food substances 18
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Causes of food spoilage
•
Microorganism: – Decomposing bacteria & fungi
– Acts on carbohydrate and protein – producing
CO2, water, NH3
– These spoils the food and makes it toxic
• Oxidation of food
– The condition in which oxygen acts on food.
– Usually fruits change color. Ex: apple turns brown
– Oily food becomes rancid and smells
– Rancid food is harmful to body19
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Increasing commercial value of food
• Commercially processed food contains
additives
• Additives preserves the freshness of food,
improve the taste, appearance and texture of
processed food
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Diversifying the uses of food
substances
• Food industry increases the variety of food
produced from one food source
• Ex: milk
– Used to make cheese, yoghurt, ice cream, butter
and chocolates
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Relate food processing methods with
factors causing food spoilage
• Methods of food preservation:
– Cooking
– Pickling food
– Fermentation
– Drying
– Pasteurization
– Canning
– Refrigeration
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Cooking• Heating at high temperature
•
Kills bacteria• Denature enzymes that causes food spoilage
Pickling food• Food immersed in acidic solution – vinegar
– pH reduced, microorganism is prevented from
growing
• Food immersed in salt and sugar
– Microorganism lose water through osmosis – dies.
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Fermentation
• Addition of yeast to food
• Fermentation produces ethanol at highconcentration – prevents juices to become spoiled
• Tapai – a fermented traditional drink is produced by
the fermentation of tapioca
Drying
• Drying under hot sun removes water from food• Prevents microorganism from growing
• Ultraviolet ray from sun kills bacteria
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Pasteurization
• Usually the preservation of milk
• To destroy bacteria that can cause disease like
tuberculosis and typhoid
• Retains natural flavour of milk
• Milk is heated to 630C for 30 minutes or 720C for 15
seconds and then cooled at temperature below 100
C
• Pasteurised milk can be refrigerated for few days.
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Canning• Uses heat sterilization to kill microorganism
•Food is packed in cans, steamed in high temperature& drive pressure out
• Cans are then sealed and cooled
• Vacuum created within the cans prevents growth of
microorganisms.
Refrigeration
• Food stored at temperature 00C can remain fresh for
a long period of time
• Low temperature prevent the growth of
microorganisms or the germination of spores 26