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Introduction: Photosynthesis and respiration are two processes which help make ATP, which helps drive biological reactions.
Photosynthesis is the process whereby a plant uses light energy and carbon dioxide to make glucose and water and ATP.
Respiration is the process whereby mitochondria help break down organic substances such as glucose in order to make ATP and release energy.
It is important to remember that plants photosynthesise but also respire!
Limiting factors for photosynthesis:
-Light: Plants absorb specific wavelengths of light. They reflect green light and so appear green (absorb red and blue)
-Temperature: Temperature affects kinetic energy of particles, stomata opening as well as enzyme action. If temperature is too high, enzyme active sites denature and lose complementarity to substrate (less ES-complexes formed). If temperature is too high, stomata close (water retention, less CO2 enters)
-Carbon dioxide: CO2 makes up a very small percentage of gas in the air. Increasing this concentration will increase the rate of photosynthesis, up to a point where stomata close (4%).
-Chlorophyll: The amount of chlorophyll present will determine how much light energy is converted into food (sucrose) in the plant.
6CO2 + 6H2O C6H12O6 + 6O2 (+ATP also made)
Measuring oxygen production to view rate of photosynthesis:
-Seal pondweed using a bung in a test tube with water. Attach a capillary tube also with water to the top of the bung.
-Place a lamp at a given distance from the test tube and switch it on.
-As oxygen is produced by photosynthesis, bubbles move along the capillary tube.
-The volume of oxygen produced is calculated using the distance travelled by the bubble.
-Independent variables (temperature/light intensity/distance of lamp) can be changed to see how the rate of photosynthesis changes.
Changing independent variables:
Temperature: Using a water bath and using ice to make lower temperatures
Light intensity: Using a more powerful lamp or bulb. Using different filters on the light.
Distance from light source: Using a ruler/tape measure gradually move the lamp in small increments (5cm)
Light intensity is inversely proportional to 1/distance²
Sugars produced by photosynthesis such as glucose (which combines with fructose to form sucrose) are useful in many processes. Glucose can be used for respiration, as well as in cellulose cell walls (made of a isomer of glucose). Glucose can also be useful as forms of energy storage in seeds.
C6H12O6 + 6O2 6CO2 + 6H2O (+ATP also made)
Aerobic respiration requires oxygen. During exercise, there is an increased demand for oxygen, which must be catered for by changes in bodily processes. This increased demand for oxygen is processed by regions of the brain and responses include:
Heart rate increases
Breathing rate increases
Breath volume increases
During anaerobic respiration, the build up of lactic acid is bad for cells, so must be removed. This is done using oxygen, which is what oxygen debt is.
Aerobic Respiration is the process whereby glucose is broken down using oxygen to release chemical energy in the form of ATP. This releases carbon dioxide and water.
VS
Anaerobic Respiration is the process whereby glucose is broken down in the absence of oxygen to release chemical energy in the form of ATP.
In plants, glucose is oxidised to ethanol, whereas in animals, glucose is oxidised to lactic acid, responsible for muscle cramps and fatigue
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