PHOTOSYNTHESIS. Introduction. Cells, Matter, and Energy. ALL cells need energy and matter for growth and reproduction. Some organisms (like plants) obtain their energy directly from the Sun. Other organisms must consume food to obtain energy. Photosynthesis.
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CO2 + H2O C6H12O6 +O2
2. Cellular Respiration = all of the chemical reactions needed to break down (metabolize) carbohydrates and other molecules to transfer chemical energy to ATP.
C6H12O6 + 6O2 6H2O + 6CO2 + ATP
Energy Storage Molecule
simply called LIGHT.
The carbon of a CO2 molecule from the atmosphere is attached to a 5-carbon sugar called RuBP
This forms an unstable 6-carbon compound
The 6-carbon compound breaks down to form two 3-carbon molecules called PGAL(phosphoglyceraldehyde)
Think of PGAL as half a glucose
The 3 PGAL are converted to G3P using energy (ATP) and hydrogens from NADPH from the Light Reaction
For every 3 molecules of CO2 there are 6 molecules of G3P produced
Only 1 is net gain
What happens to the other 5?
Products need to be regenerated to keep the cycle going.
5 of the 6 G3P molecules are regenerated using ATP and producing 3 RuBP molecules which are then ready to receive new CO2 and continue the cycle
The one G3P molecule combined with another G3P molecule is used to make glucose, fructose, sucrose, starch and cellulose for the plant.
It describes how productive a plant is under various conditions
What things would control the rate of photosynthesis?Rate of Photosynthesis
High Intensity Light causes the rate of photosynthesis to increase
The rate will increase until it reaches its saturation point
At the saturation point, the rate of photosynthesis remains constantRate of Photosynthesis
As temperature increases, so does the rate of photosynthesis
Enzymes function at an optimal temperature: If the temperature is too high or too low, enzymes will not function properly
Rate of photosynthesis will slow down or stop.Rate of Photosynthesis
Water is one of the raw materials of photosynthesis
A shortage of water can slow or even stop photosynthesis
Water stress causes stomata to close, preventing CO2 from entering the leafRate of Photosynthesis
An increase in CO2 concentration causes the rate of photosynthesis to increase
More CO2 available means more sugar made in the light independent reactionRate of Photosynthesis
In hot, dry environments plants maximize photosynthesis by limiting water loss.
Leaves of plants contain stomata which are tiny holes in the leaves that release by products and take in raw materials need for photosynthesis
Most plants will close their stomata to prevent water loss but this limits carbon dioxide intake
Some plants will only open the stomata during night
It is a fine balance between receiving the necessary supplies and preventing water loss.
If the CO2 concentration in the cell drops below 50 ppm, the cell begins to undergo PHOTORESPIRATION which results in the fixation of oxygen instead of carbon dioxide.
This is a very wasteful process as it produces a substance that is not useful to the cycle.