Topic 4-Bioenergetics Flashcards Preview

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Flashcards in Topic 4-Bioenergetics Deck (43):

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

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

•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)

1. Source of light placed specific distance from pondweed
2. Pondweed is left to photosynthesise for a set length of time. Oxygen produced will collect in capillary tube
3. 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)

4. Variables should be controller e.g temperature and time to photosynthesise
5. Repeat twice with light at same distance and calculate a mean
6. Repeat whole experiment with light source at different distances from pondweed


The inverse square law links light intensity and distance

Light intensity (is proportional to/fish thing) 1
Distance squared


The inverse square law links light intensity and distance

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

1. To build up larger molecules from smaller ones (eg proteins from amino acids)
2. In animals, to allow the muscles to contract for movement
3. In mammals and birds to keep their body temperature steady in colder surroundings



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