B4 - Bioenergetics Flashcards
Photosynthesis
carbon dioxide + water = glucose + oxygen
6CO2 + 6H2O = C6H12O6 + 6O2
Uses of Glucose in Plants
It’s stored as starch, fats or oils and is used for respiration, production of cellulose and production of amino acids for protein synthesis.
The Rate of Photosynthesis and Limiting Factors
Limiting factors are things which stop the photosynthesis reaction from occurring at a faster rate. Temperature, light intensity and carbon dioxide level are all limiting factors:
- increasing the temperature will increase the rate of reaction, but only up to 45°C as above this temperature, the enzymes for this reaction become denatured
- increasing light intensity increases rate of reaction as there’s more energy to carry out reactions
- increasing CO2 concentration will also increase the rate of reaction because there are more reactant available
Investigating the Effect of Light Intensity on the Rate of Photosynethsis
1) measure 20cm³ of sodium hydrogen carbonate solution and pour into boiling tube
2) place a 10cm piece of pondweed and gently attach a paper clip to one end
3) clamp the boiling tube and place a metre rule next to the clamp stand
4) place the lamp 10cm away from the pond weed
5) wait 2 minutes then start a stopwatch and count the number of bubbles produced in a minute
6) repeat this, moving the lamp an extra 10cm away each time until you’ve done 5 different distances
7) repeat the experiment to improve validity
Greenhouse Economics
To grow plants in the most suitable conditions, a greenhouse can be used. A greenhouse traps the sun’s radiation as heat, so temperature is not a limiting factor for the rate of photosynthesis. Artificial lighting can also be installed to provide constant energy and prevent light intensity being a limiting factor. Also, a paraffin heater can be used - not only to maintain suitable temperature, but as the by-product of combustion of paraffin is CO2. Whilst regulating conditions can be expensive, the harvest of crops is much healthier and faster.
Inverse Square Law and Light Intensity
The intensity of light is inversely proportional to the square distance from the source, or in other words, if an object is moved twice as far away from the light source, the light intensity received is reduced to one quarter
Light intensity = k x 1/d²
Respiration
An exothermic chemical reaction occurring inside the mitochondria of all living cells to release energy for living functions and processes, e.g. warmth, building molecules for growth and repair and movement.
Aerobic Respiration
With oxygen:
glucose + oxygen = carbon dioxide + water + energy
C6H12O6 + 6O2 = 6CO2 + 6H2O + energy
Anaerobic Respiration
Without oxygen/glucose is not completely oxidised:
glucose = lactic acid + energy
C6H12O6 = 2C3H6O3 + energy
(less energy released than in aerobic respiration)
Fermentation
Anaerobic respiration in plants and yeast; used in bread-making and beer-brewing.
glucose = ethanol + carbon dioxide + energy
C6H12O6 = C2H5OH + CO2 + energy
Effect of Exercise
The body (specifically the muscles) demand more energy, so the amount of respiration reactions occurring increases. The heart pumps faster and breathing rate and breath volume increase to supply more oxygen to the muscles for respiration.
If the muscles don’t receive enough oxygen, the anaerobic respiration begins occurring. This produces lactic acid which builds up in muscles and results in oxygen debt
Metabolism
The combination of all the reactions in a cell or in the body, including respiration.
Energy released during respiration is used during metabolic processes to synthesise new molecules:
- glucose converted into starch, glycogen and cellulose
- glycerol and fatty acids are joined to form a lipid molecule
- amino acids are joined to form proteins
Oxygen Debt
During vigorous exercise, when the body carries out anaerobic respiration, lactic acid is produced. This is transported to the liver via the bloodstream. The liver then coverts the lactic acid back into glucose, however, oxygen is needed to carry out this reaction - the amount of oxygen required by the body to convert the build-up of lactic acid back into glucose and remove it from the respiring cells is called oxygen debt
