Unit 4 - Photosynthesis + uses of photosynthesis + rate of photosynthesis Flashcards
What do plants use as their sources of energy
Plants use light for their source of energy
Define photosynthesis
Photosynthesis is the process by which plants make food using carbon dioxide, water and light
The ______ that plant use to trap this ______ energy is called _______
The reaction that plants use to trap this light energy is called photosynthesis
photosynthesis is an _____
reaction in which _______ is transferred from the ________to the
_________by _______.
photosynthesis is an endothermic
reaction in which energy is transferred from the environment to the
chloroplasts by light.
What type of reaction is photosythesis. Why?
Photosynthesis is an example of an endothermic reaction. This is because photosynthesis takes in energy
This means that energy is transferred from the environment in the process
Where does photosynthesis take place
Photosynthesis takes place in the leaves of a plant in the chloroplasts.
What do leaves contain
Leaves contain the green chemical chlorophyll. Chlorophyll can absorb the light energy
Describe the process of photosynthesis
In the first stage of photosynthesis, the plant takes in carbon dioxide and water
Light energy is then absorbed by chlorophyll
This light energy is then used to convert the carbon dioxide from the air and water from the soil into the sugar glucose.
In this reaction oxygen is also produced
Describe the path taken by a carbon atom as it moves from being part of the carbon dioxide in the air to being part of a starch molecule in a plant
Carbon atom moves from air into air spaces in leaf,
into plant cells,
into chloroplasts,
joins with water to make glucose,
and is converted to starch for storage
Explain why photosynthesis is an endothermic reaction
Photosynthesis needs a bigger input of energy from environment
to break bonds holding carbon dioxide and water together
that is released when new bonds form in glucose and oxygen.
Where in the plant does most photosynthesis happen (which tissue)
The palisade mesophyll is the tissue where most photosynthesis happens
State the word equation for photosynthesis
carbon dioxide + water → glucose + oxygen
add the word ‘light’ over the arrow
State the symbol equation for photosynthesis
CO2 +H2O → C6H12O6 +O2
add the word ‘light’ over the arrow
State the factors that affect photosynthesis
Carbon dioxide concentration
Temperature
Light intensity
Amount of chlorophyll in a plant
State the uses of glucose produced by photosynthesis for plants
How plants use glucose
The glucose produced in photosynthesis may be:
- used for respiration
- converted into insoluble starch for storage
- used to produce fats or oils (lipids) for storage
- used to produce cellulose, which strengthens the cell wall
- used to produce amino acids for protein synthesis.
Explain why the glucose produced in photosynthesis can be used for respiration
The glucose produced in photosynthesis can be broken down to release energy in respiration which is used for cellular processes such as active transport
Explain the use of insoluble starch after it has been produced by glucose
The glucose produced in photosynthesis can be converted into the carbohydrate, starch and stored in the roots, leaves and cells.
These stores are used when photosynthesis isn’t happening e.g. at night or winter
The starch can be converted back to glucose by the plant when it is needed.
Why is it important that the starch used for storage is insoluble
Starch is insoluble which makes it much better for storing than glucose.
This is because a cell with lots of glucose in would draw in loads of water (by osmosis) and swell up.
Explain how the glucose produced in photosynthesis can used to produce fats or oils (lipids) for storage
The glucose produced in photosynthesis can be converted to fats or oils.
Fats and oils are used by the plant as a storage form of energy.
These are stored mainly in seeds and are used as a compact energy store
Explain why the glucose produced in photosynthesis can be used to produce cellulose
The glucose produced by photosynthesis is converted into cellulose which strengthens the cell wall
Explain why the glucose produced in photosynthesis can be used to produce amino acids
The glucose produced in photosynthesis is combined with nitrate ions (which plants absorb from the soil) to produce amino acids for protein synthesis.
When does photosynthesis only produce glucose
Photosynthesis only produces glucose during the day, when there is light
When do plant cells respire
Plant cells respire all the time including at night
What factors affect the rate of photosynthesis
Temperature
Light intensity
Carbon dioxide concentration
Amount of chlorophyll in the leaves
Describe and explain the trend in a light intensity/rate of photosynthesis graph
As light intensity increases, so does rate of photosynthesis, up to a certain point.
This indicates that light intensity is limiting factor.
However, after a certain point, an increase in light intensity has no effect on rate of photosynthesis …
… (the rate of photosynthesis no longer increases as light intensity increases) …
This indicates that light intensity is no longer limiting factor and something else probably is, such as: temperature or CO2 concentration
How do you know if a particular variable was a limiting factor
If we increase the light intensity, and the rate of photosynthesis increases, it shows that light intensity was the limiting factor (photosynthesis was not as fast as it could have been because there was not enough light)
How do you know if a particular variable is no longer a limiting factor
If we keep on increasing light intensity there comes a point where the rate of photosynthesis no longer increases. This shows to us that at this point, light intensity is no longer the limiting factor.
Something else is now in short supply - co2 concentration
Describe and explain the trend in a carbon dioxide concentration/rate of photosynthesis graph
As carbon dioxide increases, so does rate of photosynthesis, up to a certain point.
This indicates that light intensity is limiting factor.
However, after a certain point, an increase in carbon dioxide concentation has no effect on rate of photosynthesis …
… (the rate of photosynthesis no longer increases as carbon dioxide concentration increases) …
This indicates that carbon dioxide is no longer limiting factor and something else probably is, such as: temperature or light intensity
Describe and explain the trend in a temperature/rate of photosynthesis graph
As we increase the temperature, the enzymes involved in photosynthesis work faster so the rate increases
This indicates that temperature is limiting factor
If we keep increasing the temperature, the enzymes in the leaf will denature and the rate of photosynthesis fall.
Enzyme graph
What is the effect of a low temperature on the rate of photosynthesis
If the temperature is the limiting factor its because its too low - the enzymes needed for photosynthesis work more slowly at low temperatures
Explain how greenhouses are used to increase the rate of photosynthesis
Increasing the rate of photosynthesis, increases the yield of crops farmers produce.
To do this, farmers light and heat their greenhouses. They also add extra carbon dioxide.
Light is needed for photosynthesis
Artificial light can be provided to keep the plants photosynthesising efficiently (even at night)
CO2 can be added to the greenhouse (e.g. using paraffin heaters to heat the greenhouse and generate CO2 as a by-product. This is cost effective)
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Due to the cost of doing this, (the extra cost has to be justified by the increase in yield)
Keeping plants in a greenhouse makes it easier to keep pests and diseases at bay. Fertilizers can be added to the soil to provide minerals for healthy growth
Explain the effect of amount of chlorophyll in the leaves regarding the rate of photosynthesis
The amount of chlorophyll in a plant can be affected by a disease.
E.g. a leaf with patches of chlorophyll/tobacco mosaic virus
These leaves trap less light energy than normal leaves, therefore they will have a lower rate of photosynthesis
All living cells _________
All living cells respire
How can plants also produce proteins
To produce proteins, plants also use nitrate ions that are absorbed from the soil
The energy we need is supplied by a process called
Cellular respiration
What type of reaction is respiration and why?
Exothermic reaction because it releases energy
When does respiration take place.
Respiration takes place continually in all living cells
Why do organisms need energy
Organisms need energy for
chemical reactions to build larger molecules • movement
• keeping warm.
Types of respiration
Aerobic
Anaerobic
What is respiration (aerobic)
Aerobic respiration is an exothermic reaction in which glucose is broken down using oxygen, to produce carbon dioxide and water and release energy for the cells
What is anaerobic respiration
Anaerobic respiration is an exothermic reaction in which glucose is broken down in the absence of oxygen to produce lactic acid in animals and ethanol and carbon dioxide in plants and yeast
Word equation for aerobic respiration
glucose + oxygen — carbon dioxide + water
What happens during aerobic resporation
In aerobic respiration, the glucose is reacted with oxygen gas
This produces carbon dioxide and water and releases energy
When do cells start respiring anaerobically
When there is a shortage of oxygen, muscle cells start respiring anaerobically
Explain why aerobic respiration releases a great deal of energy
That is because the glucose molecule has been fully oxidised
Explain why anaerobic respiration releases a lot less energy than aerobic respiration
As the oxidation of glucose is incomplete in anaerobic respiration much less energy is transferred than in aerobic respiration
What is glucose needed for
Needed for growth
Metabolic reactions
Anaerobic respiration in muscles is represented by the equation:
glucose ———- lactic acid
Glucose is converted to lactic acid. Anaerobic respiration does not require any oxygen.
Oxygen is not needed for this reaction
Anaerobic respiration in plant and yeast cells is represented by the equation:
glucose ———- ethanol + Co2
Glucose is converted to ethanol and co2, no oxygen is needed for this reaction
what is fermentation
Anaerobic respiration in yeast cells
What is anaerobic respiration in yeast cells called and what is it used for
Anaerobic respiration in yeast cells is called fermentation and has economic importance in the manufacture of bread and alcoholic drinks.
This reaction is used to make alcoholic drinks. The alcohol in these drinks is ethanol which is produced by fermentation
For bread : the co2 produced by fermentation is useful. This creates bubbles in the dough causing the bread to rise
Describe the body’s response to exercise
Describe what happens in the body during exercise
During exercise the human body reacts to the increased demand for energy.
During exercise the body needs a lot of energy for muscle contraction
Because the body needs more energy, aerobic respiration increases
This means that the body cells require more oxygen
To provide this extra oxygen, both the breathing date and breath volume increase.
(We breathe more frequently and take deeper breaths)
This gets more oxygen into the blood stream
The heart rate increases to pump this oxygenated blood around the body.
_________
The heart rate, breathing rate and breath volume increase during exercise to supply the muscles with more oxygenated blood.
Describe what happens if insufficient oxygen is supplied to the muscles, whilst the body is exercising hard
If insufficient oxygen is being supplied in the muscles, anaerobic respiration takes place in muscles.
During anaerobic respiration, , the oxidation of glucose in incomplete. This causes a build up of lactic acid and creates an oxygen debt
During long periods of vigorous activity muscles become fatigued and stop contracting efficiently.
When can anaerobic respiration start taking place in the muscles
if insufficient oxygen is supplied to the muscles, whilst the body is exercising
Explain the role of the liver and how lactic acid is removed (produced by anaerobic respiration)
The lactic acid is transported out of the muscles by the blood.
The lactic acid is then taken to the liver and converted back to glucose in a series of chemical reactions
Reacting with the accumulated lactic acid and removing it from the cells requires oxygen
The oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells
What is an oxygen debt
The oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells
Explain why people continue breathing rapidly for some time after finishing exercise
During exercise, the muscles can start respiring anaerobically if insufficient oxygen is being supplied to the muscles
When the exercise is over, the lactic acid has to be broken down to produce carbon dioxide and water. This requires oxygen
The amount of oxygen needed to break down the lactic acid to carbon dioxide and water is known as the oxygen debt
Therefore people continue breathing rapidly for some time after finishing exercise (their heart rate and breathing rate remain high), to supply the oxygen needed to pay off the oxygen debt
(get more oxygen into the blood, which is transported to the muscles cells)
The bigger the oxygen debt …
The effect of a big oxygen debt
The bigger the oxygen debt, then the larger amount of lactic acid in your body, as a result, more oxygen is needed to break down the lactic acid to carbon dioxide and water.
Therefore you will continue to breathe rapidly for a longer amount of time
Effects of lactic acid
During long periods of vigorous activity , the lactic acid causes the muscles become fatigued.
This causes the muscles to stop contracting efficiently
Proteins are made by ______
Chemically joining amino acids
Why do muscles need a lot of energy
Muscles need a lot of energy for contraction
What happens in muscle cells when there is a shortage of oxygen
Muscle cells respire anaerobically
Anaerobic respiration does not require any ______
Oxygen
Which type of respiration releases the least amount of energy
Anaerobic respiration releases much less energy than aerobic respiration
Explain why a lot of energy is not used when you are sitting down
Because you are not moving.
Why does the body need a lot of energy when we are exercising
For muscle contraction
what are the waste products in aerobic respiration
what do the body cells need from respiration
Waste products - Co2 and water
The body cells respire to release energy needed for movement, keeping warm and for chemical reactions to build larger molecules
