Bioenergetics Flashcards
What is photosynthesis?
Uses energy to change carbon dioxide and water into glucose and oxygen.
Where does photosynthesis take place?
In the chloroplasts, they contain pigments like chlorophyll that absorbs light.
Is photosynthesis endothermic or exothermic?
Photosynthesis is endothermic, this means that it does not release energy, it takes in energy.
What is the word equation for photosythesis?
carbon dioxide + water = glucose + oxygen
What is the symbol equation for photosynthesis?
6CO2 + 6H2O → C6H12O6 + 6O2
What do plants use glucose for?
- For respiration
- Making cellulose
- Making amino acids - glucose is combined with nitrate ions (absorbed from the soil) to make amino acids, which are then made into proteins.
- Stored as oils or fats - glucose is turned into lipids for storing in seeds
- Stored as starch - stored in roots, stems and leaves, ready for use when photosynthesis isn’t happening, like in the winter. Starch is insoluble which makes it better for storing than glucose.
What are the limiting factors for the rate of photosynthesis?
- Light intensity
- Concentration of CO2
- Temperatures
- Amount of chlorophyll in the plant
How can you tell what the limiting factors are, from a graph with the rate of photosynthesis on the y axis and the light intensity on the x axis?
The limiting factor will always be the ones that have not been mentioned. For example the light intensity has been mentioned but the CO2 and the temperature haven’t been mentioned. So the limiting factor is either the temperature or the CO2.
What are the points about temperature for photosynthesis?
The temperature needs to be just right. If the temperature is too low then the enzymes needed for photosynthesis would work more slowly. But if the temperatures get too hot, the enzymes will become damaged and denatured. This happens at around 45 degrees C.
Describe the process of the required practical for the rate of photosynthesis?
1) Pour sodium hydrogen carbonate into a boiling tube to the brim.
2) Put the pond weed into the boiling tube.
3) Now cut the stem of the pond weed while under water so that there’s a place to count the number of oxygen bubbles from.
4) Use a light bulb that doesn’t produce much heat so that there aren’t two variables that are changing.
5) Move the boiling tube closer to the light source, making sure that there is a 10 cm distance between the light source and the boiling tube. Leave the pond weed there for a few minutes so that it can adjust to the levels of light.
6) Now count the number of bubbles that appear from the cut section of the stem in 1 minute. Make sure to be only counting from the cut surface to keep it a fair test.
7 ) Now move the boiling tube so that it is 20 cm away from the light source. Leave the test tube for a few minutes to allow the pond weed to adjust to the light.
8) Repeat the experiment at 30 then 40 then 50 cm.
What is the inverse square law that links the light intensity and distance.
light intensity ∝1/distance(d)²
∝ means proportional
What is an artificial method for creating ideal conditions for plants?
- Using a greenhouse
- Greenhouses trap the sun’s heat
- Artificial lights may be used
What is respiration?
- Respiration is not breathing in and out. It is the transferring of energy from the breakdown of glucose and it goes on in every cell in the body continuously.
Where does respiration take place?
In plants and in humans, everything needs to respire.
Is respiration exothermic or endothermic?
Exothermic - it transfers energy to the environment
What is respiration used for?
- To build up large molecules from smaller ones
- In animals it is used to allow the muscles to contract
- In mammals energy is used to keep them warm
What is metabolism?
- The total of all the reactions that happen in a body is called metabolism.
What are examples of metabolism?
• conversion of glucose to starch, glycogen and cellulose
• the formation of lipid molecules from a molecule of glycerol and three
molecules of fatty acids
• the use of glucose and nitrate ions to form amino acids which in turn
are used to synthesise proteins
• respiration
• breakdown of excess proteins to form urea for excretion.
What is aerobic respiration?
- It’s respiration using oxygen, it’s the most efficient method of transferring energy.
- Happens in plants and animals
- Happens in mitochondria
What is the word and symbol equation for respiration?
glucose + oxygen = carbon dioxide + water
C6H1206 + 6O2 = 6CO2 + 6H20
What is the word equation for anaerobic respiration in muscles?
glucose = Lactic acid
What is anaerobic respiration?
- It is the incomplete breakdown of glucose into lactic acid
- When you do vigorous exercise your muscles undergo anaerobic respiration
- Not as good of an energy transfer as aerobic
What is anaerobic respiration in plants and yeast cells?
- Produce ethanol and carbon dioxide
- Called fermentation
- Used to make bread (carbon dioxide makes bread rise) and alcoholic drinks
What is the word equation for anaerobic respiration in plants?
glucose = ethanol + carbon dioxide
