B4 BIOENERGETICS Flashcards
what do plants use light for?
for their source of energy ( the reaction that plants use for to trap this light energy is called photosynthesis)
is photosynthesis endothermic reaction or exothermic reaction
endothermic because photosynthesis takes in energy
where does photosynthesis takes place?
leaves of the plant ( leave contains the green chemical chlorophyll which absorbs light energy)
stages of photosynthesis?
the plants takes in carbon dioxide and water into the leaf , light energy is absorbed by chlorophyll, the light energy is then used to convert carbon dioxide and water into the sugar glucose, oxygen is also produced.
word equation for photosynthesis?
carbon dioxide + water ————–>glucose + oxygen
light/chlorophyll
factors affecting photosynthesis?
light intensity , amount of co2 , temperature , amount of chlorophyll
how does light intensity affect photosynthesis?
increase light intensity = increase photosynthesis
(because the plant has more light energy to carry out the photosynthesis reaction so the reaction gets faster)
increase the light intensity = rate of photosynthesis increases = light intensity was limiting (photosynthesis was not as fast as it could have been because there was not enough light)
if we keep increasing light intensity there comes a point where rate of photosynthesis no longer increases
how does the amount of carbon dioxide affect photosynthesis?
increase carbon dioxide = increase photosynthesis (carbon dioxide is the limiting factor , however at some point the rate of photosynthesis no longer increases)
how does the amount of chlorophyll affect photosynthesis?
less chlorophyll = lower rate of photosynthesis (because the leaves can trap less energy)
how does temperature affect photosynthesis?
increase the temperature = rate of photosynthesis increases (because enzymes work faster)
however if we keep increasing temperature the enzyme will denature and the rate of photosynthesis decreases.
uses of glucose?
release energy in respiration (takes place in mitochondria)
produce insoluble storage molecule starch (can be converted back to glucose when it is needed)
produce fat or oil for storage.
produce cellulose, which strengthens the cell wall
Combined with nitrate ions (absorbed from the soil) to produce amino acids for protein synthesis
explain how greenhouses are used to increase the rate of photosynthesis
increase the yields of crop = increase the rate of photosynthesis.
farmers use light and heat to their greenhouse gases they also add extra carbon dioxide.
some gardeners use oil burners which release heat and carbon dioxide
problems
extra cost has to be justified by the increase in yield.
key facts about respiration
- the energy we need
- an exothermic reaction because it releases energy.
-takes place continually in cells
word equation for aerobic respiration
glucose + oxygen —> carbon dioxide + water
key facts about aerobic respiration
releases a great deal of energy (because the glucose molecule has been fully oxidised)
balanced equation for aerobic respiration
C6H12O6 + O2 —–> CO2 + H20
word equation for anaerobic respiration in muscles.
glucose —-> lactic acid
energy
key facts about anaerobic respiration in muscles
does not require oxygen.
releases much less energy (that is because in anaerobic respiration the oxidation of glucose is incomplete)
word equation for anaerobic respiration in plants and yeast cells
glucose —-> ethanol + carbon dioxide
fermentation?
anaerobic respiration in yeast cells
uses of fermentation?
alcoholic drinks e.g beer
(alcohol contains ethanol which is produced by fermentation)
make bread (this creates bubbles in the dough causing the bread to rise)
describe what happens in the body during exercise
during exercise the body needs a great deal of energy for muscle contraction.
- has to react to the increased demand for energy (aerobic respiration) = more oxygen is needed
- breathing rate increases = breathing volume increases ( to provide extra oxygen)
- we breathe more frequently = we take deeper breaths = gets more oxygen into the bloodstream.
- heart rate increases to pump the oxygenated blood around the body.
what does lactic acid cause the muscles
to become fatigued (this causes muscles to stop contracting efficiently)
at this point the body has to remove lactic acid from muscles this causes oxygen debt
oxygen debt?
the amount of extra oxygen needed to react with lactic acid in muscles and remove it from cells
what happens after oxygen debt?
lactic acid is transported out of the muscles by blood.
taken to the liver = converted back to glucose with a series of chemical reactions.
reacting with accumulated lactic acid = removing it from the cells require oxygen
metabolism?
sum of all the chemical reactions in a cell or body.
what is glucose in humans?
glycogen - storage form of glucose
how is protein connected to metabolism?
- don’t need to eat much protein
-excess protein broken down by the chemical urea - urea is excreted by the kidneys
describe how to investigate the effect of light intensity on the rate of photosynthesis
- place cut pondweed in a boiling tube at a fixed distance from a light source.
- count the number of bubbles produced in one minute using stopwatch
3.repeat several times at different distances/light intensities and calculate a mean for each distance. - plot a graph of light intensity (x) against rate of photosynthesis (bubbles per min, y)
problems with this photosynthesis practical?
too fast to count
bubbles aren’t same size.
how do you measure the volume of bubbles produced?
place the pond weed under a funnel
catch the bubbles in a measuring cylinder.
then measure the volume of the oxygen gas produced.
inverse square law?
the relationship between the intensity of light and the distance from its source.
if we double the distance, the light intensity falls falls by four times.
How does the inverse square law apply to photosynthesis?
The inverse square law applies to photosynthesis because the amount of light energy that reaches a plant decreases as the distance from the light source increases.
This means that plants need to be close to a light source in order to perform photosynthesis effectively.
photosynthesis?
the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.
limiting factor?
an environmental factor which can restrict the rate of photosynthesis e.g light intensity
what is aerobic respiration?
an exothermic reaction in which glucose reacts with oxygen to release energy which can be used by cells
what is anaerobic respiration?
an exothermic reaction in which glucose is broken down to release energy in the absence of oxygen
why can anaerobic respiration lead to muscle fatigue?
lactic acid (product of anaerobic respiration) builds up in muscles , preventing efficient contraction
