Topic 4-Bioenergetics Flashcards
Where does photosynthesis take place
In the chloroplasts in green plant cells. They contain pigments like chlorophyll which absorb light
How is energy transferred to the chloroplasts from the environment
By light
Is photosynthesis endothermic or exothermic
Endothermic
This means that energy is transferred from the environment in the process
Word equation for photosynthesis
Carbon dioxide + water —-> (light) glucose + oxygen
Symbol equation for photosynthesis
6CO2 + 6H2O ——> (light) C6H12O6 + 6O2
Plants use glucose in 5 main ways
•For respiration
This transfers energy from glucose which enables the plants to convert the rest of the glucose into various other useful substances
Plants use glucose in 5 main ways
•Making cellulose
Glucose is converted into cellulose for making strong plant cell walls
Plants use glucose in 5 main ways
•Making amino acids
Glucose is combined with nitrate ions (absorbed from the soil) to make amino acids, which are then made into proteins
Plants use glucose in 5 main ways
•Stored as oils or fats
Glucose is turned into lipids (fats and oils) for storing in seeds
Plants use glucose in 5 main ways
•Stored as starch
Glucose is turned into starch and stored in roots, stems and leaves, ready for use when photosynthesis isnt happening, like in winter. Starch is insoluble which makes it much better for storing than glucose-a cell with lots of glucose in would draw in loads of water and swell up
The limiting factors that affect rate of photosynthesis are
- light
- temperature
- amount of carbon dioxide
- amount of chlorophyll
Effects of light on rate of photosynthesis
Light provides the energy needed for photosynthesis.
As the light level is raised, the rate of photosynthesis increases steadily but ot up to a certain point (the optimum).
Beyond that, light wont make any difference because it will be either co2 or temperature that is the limiting factor
Effects of carbon dioxide levels on rate of photosynthesis
CO2 is one of the raw materials needed for photosynthesis.
The amount of CO2 will only increase the rate of photosynthesis up to a certain point (the optimum). After this CO2 is no longer a limiting factor
Effects of temperature on rate of photosynthesis
Temperature affects the rate of photosynthesis because it affects the enzymes involved
Usually if temp is the limiting factor its because it is too low (enzymes work slower at low temps). But if the plant gets too hot the enzymes will be damaged. This happens at about 45 degrees
Required practical:
Oxygen production shows the rate of photosynthesis
(The pondweed one)
- Source of light placed specific distance from pondweed
- Pondweed is left to photosynthesise for a set length of time. Oxygen produced will collect in capillary tube
- At the end, use syringe to draw gas bubbles up tube along a ruler and measure length of bubble. This is proportional to volume of O2 produced
Required practical:
Oxygen production slows the rate of photosynthesis
(The pondweed one)
PART 2
- Variables should be controller e.g temperature and time to photosynthesise
- Repeat twice with light at same distance and calculate a mean
- Repeat whole experiment with light source at different distances from pondweed
The inverse square law links light intensity and distance
EQUATION
Light intensity (is proportional to/fish thing) 1
——
Distance squared
The inverse square law links light intensity and distance
Explanation
As the distance increases the light intensity decreases. Light intensity is in proportion to the square of the distance (inverse square law). If you halve the distance the light intensity will be 4 times bigger
Use 1/d(squared) to measure light intensity
The most common way to artificially create the ideal environment for plants to grow
In a greenhouse
How greenhouses use heat
Greenhouses help trap the suns heat, and make sure temperature doesn’t become limiting. In winter a farmer may use a heater as well to keep temperature at ideal level. In summer it could get too hot so they may use shades and ventilation to cool it down
How greenhouses use light
Light is always needed for photosynthesis so commercial farmers often supply artificial light after the sun goes down to give their plants more time to photosynthesise
How carbon dioxide is used in greenhouses
Farmers can also increase the level of carbon dioxide in the greenhouse. A fairly common way is to use a paraffin heater to heat the greenhouse. As thr paraffin burns it produces carbon dioxide as a by product.
How enclosure is used in greenhouses
Keeping plants enclosed in a greenhouse also makes it easier to keep them free from pests or diseases. The farmer can also add fertilisers to the soil to provide all the minerals needed for healthy growth
Results of using a greenhouse
If the farmer can keep the conditions just right the plants will grow faster and a decent crop can be harvested more often which can then be sold to make profit.
Respiration (definition)
Respiration is the process of transferring energy from glucose which goes in every cell
Is respiration endothermic or exothermic
Exothermic, it transfers energy to the environment
How can energy transferred by respiration be used
- To build up larger molecules from smaller ones (eg proteins from amino acids)
- In animals, to allow the muscles to contract for movement
- In mammals and birds to keep their body temperature steady in colder surroundings
Metabolism
Metabolism is all the chemical reactions in an organism
The sum of all the reactions in the body is metabolism (example)
In some of the reactions, larger molecules are made from smaller ones EG: Glucose is combined with nitrate ions to make amino acids then proteins
In other reactions, larger molecules are broken down into smaller ones EG: Excess protein is broken down in a reaction to produce urea
Aerobic respiration
Respiration using oxygen
Where does aerobic respiration occur
Most of the reactions in aerobic respiration happen inside the mitochondira
Word equation for aerobic respiration
Glucose + oxygen —-> carbon dioxide + water
Symbol equation for aerobic respiration
C6H12O6 + 6O2 ——> 6CO2 + 6H2O
Anerobic respiration
Respiration without oxygen
Word equation for anaerobic respiration
Glucose—-> lactic acid
Anaerobic respiration is plants and yeast cells
Anaerobic respiration in yeast cells is called fermentation. Fermentation by yeast can be used to make bread and alcoholic drinks.
Anaerobic respiration in plant and yeast cells
Word equation
Glucose—> ethanol + carbon dioxide
Effects of excercise
Muscles need energy from respiration to contract, when excercising muscles contract more so more energy is needed. Breathing rate and volume increase to get more oxygen into blood and heart rate increases to get oxygenated blood round the body faster, this removes CO2 more quickly as well
Effects of vigourous excercise
When doing vigourous excercise the body can’t supply oxygen to the muscles quick enough so they respire anaerobically. This causes lactic acid to build up in the muscles which is painful. Long periods of excercise may also cause muscle fatigue which causes the muscles to stop contracting efficiently
Oxygen debt
After anaerobic respiration when you stop excercising you’ll have an oxygen debt.
An 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
Physical effects of oxygen debt
You have to keep breathing hard after you stop excercising to get more oxygen into the blood which is transported to muscle cells. The pulse and breathing rate stay high whilst there are high levels of lactic acid and CO2
Alternative way of the body coping with a high level of lactic acid
The blood that enters your muscles transports the lactic acid to the liver, in the liver the lactic acid is converted back to glucose
To investigate the effects of excercise on the body
Take your pulse after: •sitting down for 5 minutes •after 5 minutes of gentle walking •after 5 minutes of slow jogging •after 5 minutes of running
