AFTER EARTH SPECIAL: PHOTOSYNTHESIS
05 JUNE 2013
Lesson Description
In this lesson, we:
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Review Photosynthesis
Review Cellular respiration
Define carbon footprints
Key Concepts
Photosynthesis
(Solutions for All, Life Sciences, Grade 11, Macmillan, Pg 125)
Light and Dark Phases
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Light phase – this occurs in the grana of the chloroplast. It contains chlorophyll that absorbs
the light energy.
Some of the light energy is used to make ATP (Adenosine triphosphate).
The rest of the energy is used to split water molecules and make energy-rich Hydrogen
atoms. Oxygen is released.
The ATP and the hydrogen are used in the dark phase.
Dark phase – this occurs in the stroma of the chloroplast.
Glucose molecules are produced from the carbon dioxide, ATP and energy-rich hydrogen
atoms.
The light energy absorbed in the light phase is stored in the bonds of the glucose molecule
(Solutions for All, Life Sciences, Grade 11, Macmillan, Pg 121)
Importance of Photosynthesis
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Production of oxygen
Absorption of carbon dioxide
Production of food
Factors Affecting the Rate of Photosynthesis
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Light intensity – the greater the intensity of light, the greater the rate of photosynthesis
(Solutions for All, Life Sciences, Grade 11, Macmillan, Pg 135)
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Concentration of carbon dioxide – an increase in carbon dioxide will increase the rate of
photosynthesis
(Solutions for All, Life Sciences, Grade 11, Macmillan, Pg 135)
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Temperature– enzymes work optimally at 37°C. Lower temperatures mean lower rate of
photosynthesis
(Solutions for All, Life Sciences, Grade 11, Macmillan, Pg 135)
(Solutions for All, Life Sciences, Grade 11, Macmillan, Pg 185)
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There are three stages in aerobic respiration, namely glycolysis, the Krebs cycle and
oxidative phosphorylation.
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Glycolysis: This occurs in the cytoplasm of the cell. Glucose is broken down into pyruvic
acid and energy-rich hydrogens are given off.
The hydrogens move into the mitochondria to be used in oxidative phosphorylation.
Two ATP molecules are produced during glycolysis.
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The Krebs cycle breaks down the pyruvic acid completely into energy-rich hydrogens and
carbon dioxide. The hydrogens will be used in oxidative phosphorylation and the carbon
dioxide will be breathed out.
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Oxidative phosphorylation takes the energy from the energy-rich hydrogens to make ATP.
The energy depleted hydrogens combine with oxygen to make water. This is either breathed
out as water vapour or excreted via the kidneys.
(http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/cell
ular%20respiration/cellular.htm)
(Solutions for All, Life Sciences, Grade 11, Macmillan, Pg 184)
Carbon Footprint
A carbon footprint is defined as:
The total amount of greenhouse gases produced to directly and indirectly support human activities,
usually expressed in equivalent tons of carbon dioxide (CO 2).
In other words: When you drive a car, the engine burns fuel which creates a certain amount of CO2,
depending on its fuel consumption and the driving distance. When you heat your house with oil, gas
or coal, then you also generate CO2. Even if you heat your house with electricity, the generation of the
electrical power may also have emitted a certain amount of CO 2. When you buy food and goods, the
production of the food and goods also emitted some quantities of CO 2.
Your carbon footprint is the sum of all emissions of CO2 (carbon dioxide), which were induced by your
activities in a given time frame. Usually a carbon footprint is calculated for the time period of a year.
Each of the following activities adds 1 kg of CO2 to your personal carbon footprint:
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Travel by public transportation (train or bus) a distance of 10 to 12 km
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Drive with your car a distance of 6 km or 3.75 miles (assuming 7.3 litres petrol per 100 km)
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Fly with a plane a distance of 2.2 km.
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Operate your computer for 32 hours (60 Watt consumption assumed)
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Production of 5 plastic bags
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Production of 2 plastic bottles
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Production of 1/3 of an American cheeseburger (yes, the production of each cheeseburger
emits 3.1 kg of CO2!)
(Adapted from http://timeforchange.org/what-is-a-carbon-footprint-definition)
Links
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http://www.lifeafterearthscience.com/
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http://www.anthropocene.info/en/home
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http://timeforchange.org/what-is-a-carbon-footprint-definition
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http://www.capetown.gov.za/EN/ENVIRONMENTALRESOURCEMANAGEMENT/ENERGYE
FFICIENCY/Pages/CarbonFootprintCalculator.aspx
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http://timeforchange.org/offline-carbon-footprint-calculator