B4 - Bioenergetics Flashcards
What is photosynthesis?
The use of energy to change carbon dioxide and water into glucose and oxygen
Where does photosynthesis take place?
Chloroplasts in green plant cells - they contain pigments like chlorophyll that absorb light
What transfers energy to the chloroplasts?
Light
Photosynthesis is endothermic - what does this mean?
This means energy is transferred from the environment in the process
What is the word equation for photosynthesis?
carbon dioxide + water (light)> glucose + oxygen
What is the symbol equation for photosynthesis?
6CO2 + 6H2O (light)> C6H12O6 + 6O2
What are the main ways plants use glucose?
- Respiration
- Making cellulose
- Making amino acids
- Stored as oils or fats
- Stored as as starch
What is cellulose?
For making strong plant wall cells
How are amino acids formed?
Nitrate ions (from the soil) and glucose combine to form amino acids (which then turn into proteins)
How does a plant use fat or oil?
Storing in seeds
How does a plant use starch?
Used for when photosynthesis isn’t happening (winter) and because it is insoluble, it is much better for storing than glucose, so it stop the plant from swelling
What are the limiting factors that affect the rate of photosynthesis?
- Light
- Concentration of CO2
- Temperature
Give examples where the rate of photosynthesis could be affected
- Night
- Winter
- Warmth
What else can be considered a limiting factor?
Chlorophyll which can be affected by disease or environmental stress (lack of nutrients)
How does light intensity affect the rate of photosynthesis?
As the light level is raised, the rate of photosynthesis increases steadily, but only up to a certain point. Beyond that it won’t make any difference because it’ll either be the temperature or CO2 level which is now the limiting factor
How does carbon dioxide affect the rate of photosynthesis?
Similarly to light intensity, as the amount of CO2 increases, the rate of photosynthesis steadily increases as well to a certain point. Beyond that, it won’t make a difference so as long as a plant has plenty of CO2 and light, temperature should be the limiting factor.
How does temperature affect the rate of photosynthesis?
Enzymes work faster with more heat (usually most efficient around 37) but if they get too hot, then they can become denatured (usually happens around 45)
What law links light intensity and distance?
The Inverse Square Law
Inverse Square Law
light intensity ∝ 1 / distance(d)^2
Why does light intensity decrease with distance?
Light intensity decreases in proportion to the square of the distance
What is the most common way to create the ideal environment for plants to grow?
In a greenhouse
What are some different methods to artificially create ideal conditions for farming?
- Greenhouse
- Heater
- Shades
- Ventilation
- Lamps
- Paraffin Heater
- Fertilised
How does greenhouses work?
They help to trap the Sun’s heat, and make sure that the temperature doesn’t become limiting.
What is a common misconception of respiration?
Respiration is breathing
What is respiration?
The exothermic process of transferring energy from glucose and oxygen into carbon dioxide and water
Why do we need respiration?
- To build up larger molecules from smaller ones
- Allow the muscles to contract
- Used to keep body temperature steady
- Produce ATP
What are the 2 different types of respiration?
Aerobic and anaerobic respiration
Aerobic respiration word equation
glucose + oxygen –> carbon dioxide + water
Aerobic respiration symbol equation
C6H12O6 + 6O2 –> 6CO2 + 6H20
Aerobic respiration
- The most efficient way to transfer energy from glucose
- It goes on all the time in plants and animals
- Most of the reactions in aerobic respiration happen in the mitochondria
Anaerobic respiration word equation in muscle cells
glucose –> lactic acid
Anaerobic respiration in muscle cells
- The incomplete breakdown of glucose, making lactic acid
- Anaerobic respiration happens if there is not enough oxygen
- Anaerobic respiration does not transfer nearly as much oxygen as aerobic respiration because the glucose isn’t fully oxidised
- So it is only used when people do vigorous exercise
Anaerobic respiration in plants and yeast word equation
glucose –> ethanol + carbon dioxide
Anaerobic respiration in plants and yeast
- They produce ethanol and carbon dioxide instead of lactic acid
- This is usually called fermentation
- In the food industry, fermentation is used a lot (bread, cider, wine etc.)
Why do you respire more during exercise?
Some muscles contract more frequently than normal so you need more energy. This energy comes from increased respiration.
What happens if you need to respire more?
You need to get more oxygen which affects the breathing rate, breath volume and heart rate. This removes CO2 more quickly at the same time
Anaerobic respiration during exercise
This is not the best way to transfer energy because lactic energy builds up in the muscles which gets painful. Long periods can cause muscles to get tired and then stop contracting efficiently
What is oxygen debt and how is it repaid?
After resorting to anaerobic respiration, you will have an “oxygen debt”. Oxygen debt is the amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from the cells. Oxygen reacts with the lactic acid to form harmless CO2 and water
What usually happens when you are repaying your oxygen debt?
- Your pulse and breathing rate stay
- High levels of lactic acid and CO2
What is another way your body copes with the high level of lactic acid?
Your blood transports the lactic acid to the liver, where the lactic acid is converted back into glucose
What are the effects of exercise in the body?
Your breathing rate and heart rate increase
What is metabolism?
All the chemical reactions in an organism
Give some examples of metabolism
- Conversion of glucose to starch, glycogen and cellulose
- Formation of lipid molecules from a molecule of glycerol and 3 fatty acid molecules
- Reaction of respiration
- Reaction of photosynthesis
- Breakdown of excess proteins in the liver to form urea for excretion in the urine by the kidneys
