Bioenergetics Flashcards
what do plants use for their energy source
light
what reaction do plants use to trap the light energy
photosynthesis
is photosyntheisis exo / endo thermic
endothermic as it takes in energy from surroundings
where does photosynthesis take place
leaves
what do leaves contain, what does this do
chlorophyll absorb light energy
what happens in first stage of photosyntheisis
plant takes carbon dioxide + water into the leaf
second stage of photosynthesis
light energy absorbed by chlorophyll
what is the light energy (taken in during photosynthesis) used for
used to convert the carbon dioxide and water into glucose
word equation for photosynthesis
carbon dioxide + water
( light energy ) =
glucose + oxygen
chemical equation for photosynthesis
CO2 + H2O = C6H12O6 + O2
photosynthesis is an ……….
reaction in which …… is transferred from the ……… to the
……… by …..
Photosynthesis is an endothermic
reaction in which energy is transferred from the environment to the
chloroplasts by light.
what happens as light intensity increases
why
rate of photosynthesis increases
plant has more light energy to carry out photosynthesis reaction, so reaction gets faster
how can you tell if light intensity was a limiting factor
if we increase light intensity
and
rate of photosynthesis also increases
that tells us light intensity was limiting
what does it mean if a factor is limiting
rate of photosynthesis wasn’t as fast as possible because something wasn’t high enough
(light intensity
temp
co2 conc..
chlorophyl)
what happens if we keep increasing light intensity
we reach a point where rate of photosynthesis no longer increases
what happens to the graph for rate of photosynthesis / light intensity when light intensity is no longer a limiting factor
the graph levels of, a straight line
what happens to the graph for rate of photosynthesis / light intensity when light intensity is no longer a limiting factor
the graph levels of, a straight line
when the graph for rate of photosynthesis / light intensity levels off, what 2 things does this mean
light intensity is no longer the limiting factor
something else is now in short supply eg CO2
when something eg co2 is the limiting factor, what does this look like on the graph
horizontal line going upwards from 0
when something eg co2 is the limiting factor, what does this look like on the graph
horizontal line going upwards from 0
when something eg co2 is the limiting factor, what does this look like on the graph
horizontal line going upwards from 0
what does the graph for CO2 / rate of photosynthesis look like
same as graph for light intensity
horizontal up to a certain point - limiting factor
graph levels off, straight line- no longer limiting factor, something else is in short supply
why does lack of chlorophyll lead to lower rate of photosynthesis
because leaves trap less light energy than normal
what does an increase in temperature do to the rate of photosynthesis
how
3 points
as we increase temperature,
the enzymes in photosynthesis work faster
so rate increases
what happens if we keep increasing the temp
the enzymes denature
rate of photosynthesis falls
describe graph for temperature and rate of photosynthesis
steady increase, horizontal line till a point.
begins to curve down wards.
falls more rapidly
5 uses of glucose from photosynthesis
breathe storage fat to strengthen the protien
- used for respiration
- converted into insoluble starch for storage
- used to produce fat or oil for storage
- used to produce cellulose, which strengthens the cell wall
- used to produce amino acids for protein synthesis.
what is glucose used for in respiration
to release energy in respiration
where does respiration take place
in mitrochondria
when does photosynthesis produce glucose
in the day, when there’s light
when do plant cells respire
all the time, even at night
what do plants do with starch
convert it back into glucose when needed (eg night)
what do plants use fats and oils as
as a storage from of energy
what does cellulose do
strengthens the cell wall
what is cellulose made from
from glucose- produced by photosynthesis
what are amino acids used by the plant for
amino acids used to synthesise protiens
what do plants do to make amino acids from glucose
absorb nitrate ions from the soil
what is the aim of the RP for photosynthesis
Investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed
RP
what is the effect of light intensity measured by
measured by counting the number of O2 bubbles formed per minute.
RP
what 8 equipment is needed for photosynthesis RP
● a boiling tube
● freshly cut 10 cm piece of pondweed
● a light source
● a ruler
● a test tube rack
● a stopwatch
● 0.2% solution sodium hydrogen carbonate
● a glass rod
describe 4 brief steps for RP photosynthesis
. place cut pondweed in boiling tube (containing sodium hydrogen carbonate solution) at a fixed distance from a light source
. count no. of bubbles produced in 1 minute using stopwatch
. repeat several times, different distances/ light intensities and calculate a mean for each distance
. plot a graph for light intensity (x) against rate of photosynthesis (bubbles per minute,y)
step 1 in depth
Place a test tube rack containing a boiling tube 10 cm away from the light source, measured using the ruler.
step 2 in depth
Fill boiling tube with a fixed volume of sodium hydrogen carbonate solution.
step 3 in depth
Place the cut pondweed into the boiling tube with the cut end at the top. Gently push the pondweed down with the glass rod.
step 4 in depth
Leave the boiling tube for 5 minutes.
step 5 in depth
Start the stopwatch + count number of bubbles produced in one minute.
step 6 in depth
For each light intensity/distance, repeat the count twice more and take a mean.
step 7 in depth
record in table
step 8 in depth
repeat steps 1-7 for more distances
step 9 in depth
plot graph for rate of photosynthesis( bubbles ) and light intensity
why is it best to use an led light source for RP photosynthesis
dont release much heat- would change the temp of the experiment
what would we do if we had to use a normal light bulb instead of a led light
place beaker of water between light and tube so it absorbs light
what does sodium hydro carbonate solution release
carbon dioxide (needed for photosynthesis)
where do the bubbles come from
the cut end of the pondweed
why can you see bubbles
because oxygen is produced from photosynthesis
2 problems with experiment
bubbles too fast to count properly
bubbles not the same size
what solves the problems in the experiment
we can measure volume of oxygen produced instead of counting bubbles
place pondweed under funnel
catch bubbles in measuring cylinder filled with water
use measuring cylinder to measure volume of oxygen produced
why can we use the no. of bubbles to calculate rate of photosynthesis
oxygen bubbles are a product of photosynthesis.
no. of bubbles produced in a given time is proportional to rate of photosynthesis
describe the relationship between light intensity and rate of photosynthesis from inverse square law
if you double distance
number of bubbles per minute falls by a factor of 4
Potential Hazards
There is a potential allergy risk from the pondweed.
Lamp may get hot.
Be careful to keep water away from electrical power outlets and wiring
what is the equation for inverse square law
light intensity =
1/distance squared
between pondweed and light source
describe graph for light intensity on rate of reaction.
describe what it means
initially rate increases as light intensity increases
light intensity is limiting
rate stops increasing at a certain point
something else must be limiting
how can we tell what has become the new limiting factor in a graph of light intensity and rate of photosynthesis
if we increase something else
eg carbon dioxide
and do the same experiment again
and the rate of photosynthesis increases to a higher number this time,
(graph goes higher before leveling off)
then we know that Co2 was the limiting factor
what 3 things can be changed in an experiment to affect rate of photosynthesis
light intensity
temp
co2 concentration
(very hard to change chlorophyll
how can you tell if a factor is no longer the limiting factor
is you increase it but rate of photosynthesis stays the same
what happens if we increase the temp too much
enzynes in leaf will start to denature
rate of photosynthesis will fall
why do farmers want to increase rate of photosynthesis
it will increase the yeild of crops they produce
what do farmers do to increase rate of photosynthesis
light and heat greenhouses
add extra CO2
what is an issue with using a greenhouse
expensive so
extra price needs to be justified by increase in yield
what do farmers use to save costs in greenhouses
how does this save cost
oil burners,
release heat & CO2 at the same time
explain what farmers use greenhouses for
enhancing conditions through limiting factors to gain maximum rate of photosynthesis while still maintaining profit
define cellular respiration
exothermic reaction which releases energy + continuously occurring in living cells
3 things we need energy for
movememt
keep warm
chemical reactions
how are protiens made
chemically joining amino acids
what are the two types of respiration
aerobic
anaerobic
word equation for aerobic respiration
glucose + oxygen = carbon dioxide + water
what is released in respiration
energy
why does anaerobic respiration release a lot of energy
the glucose has been fully oxidised
2 cells where anaerobic respiration can be used
muscle cells
plant/ yeast cells
what do muscle cells need energy for
for contraction
Anaerobic respiration in muscles is represented by the equation:
glucose —– > lactic acid
what happens in anaerobic respiration in muscle cells
glucose is converted to lactic acid
why does anaerobic respiration release less energy than aerobic
because the oxidation of glucose is incomplete
Anaerobic respiration in plant and yeast cells is represented by the
equation:
glucose —-> ethanol + carbon dioxide
what does anaerobic respiration mean
respiration without oxygen
what happens during anaerobic respiration in plant and muscle cells
glucose is converted into ethanol and co2
what is fermentation
anaerobic respiration in yeast cells
2 things fermentation of yeast cells is used for
to make bread
alcoholic drinks
what is the alcohol produced from fermentation
ethanol
why is fermentation of yeast useful to make bread
the co2 produced from anaerobic respiration in yeast cell (fermentation)
creates bubbles in the dough
causing bread to rise
during exercise, what does the body need energy for
for muscle contraction
during exercise, what does the body react to
the increased demand for energy
what increases during exercise
heart rate
breathing rate
breath volume
why does aerobic respiration increase during exercise
the body cells require more oxygen
why does breathing rate and volume increase,
to get more oxygen into the blood stream
why does heart rate increase
to pump oxygenated blood round the body
when does anaerobic respiration take place in muscles
when not enough oxygen can be supplied to the muscles - exercising hards
what does the incomplete oxidation of glucose leads to
build up of lactic acid + oxygen debt
what happens during long periods of vigorous activity
. During long periods of vigorous
activity muscles become fatigued and stop contracting efficiently.
how is the condition oxygen debt created
the body has to remove the lactic acid from the muscles
how is lactic acid transported out of muscles
by the blood
where does the blood transport the lactic acid
to the liver
what happens to the lactic acid when it reaches the liver
converted back to glucose
describe process of lactic acid being formed to it being converted back into glucose
when not enough oxygen can be supplied to muscle cells, anaerobic respiration takes place in the muscles.
lactic acid is produced
Blood flowing through the muscles transports the lactic acid
to the liver where it is converted back into glucose.
what is the oxygen debt
amount of extra oxygen the body needs after exercise to react with the
accumulated lactic acid and remove it from the cells.
why is the oxygen debt formed
because reacting with the accumulated lactic acid and removing it from cells requires oxygen
what is one way the body overcomes oxygen debt
breathe rapidly after exercise
what do enzymes use the energy released by respiration for
to synthesise new molecules in the cell
define metabolism
sum of all the chemical reaction in a cell or body
2 things glucose is converted to in plants
cellulose and starch and amino acids
what does cellulose in a plant do
strengthens plant cell wall
what is starch
a storage form of glucose
what is glucose reacted with in plants to make amino acids
nitrate ions
what are amino acids used for
to synthesise proteins
what 2 things is glucose converted into in humans + animals
glycogen
lipid
what is glycogen
a storage form of glucose
how are lipids made
1 molecule of glycerol
3 molecules of fatty acids
reacted together
where are lipids found
in cell membrane
what happens to excess protiens
broken down into chemical urea
what happens to the urea
excreted by kidneys
