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SQA (c) Making Food
Photosynthesis
• G_____ plants make their own food which they store as s_____.
• Green leaves contain c________.• Chlorophyll converts l______ energy to
c_______ energy• Equation of photosynthesis• CO2 + H20 + light glucose + oxygen
energyR___ m___ P_
reentarch
hlorophyll
ighthemical
aw aterials roducts
Equation of aerobic respiration
Glucose + oxygen CO2 + + energy H20
Photosynthesis
Photosynthesis CANNOT work without:• Carbon dioxide• Water• Chlorophyll• Sunlight
If any of the above are in short supply they are said to be Limiting Factors”.
Starch Test• Boil leaf in w_____ to
k____ the cells• Boil in a________ to
remove c___________• Rinse in h__ water• Add i________ s______
to test for s________• Rinse leaf in c_____
water
aterill
hlorophylllcohol
ot
odine olutiontarch
old
Starch Test Results
Leaf from light
Leaf from dark
Variegated leaf
Leaf with CO2
Leaf without CO2
black
black
brown
brown
brown
black
yellow
green
Fate of CO2 in Photosynthesis (C)
• During photosynthesis CO2 gas is taken in by plants and made into glucose
• Glucose provides energy for cellular processes e.g. cell growth, cell division
• Glucose can also be converted • to the storage carbohydrate called starch• Or to the structural carbohydrate called
cellulose ( makes up the plant cell wall)
Fate of CO2 in Photosynthesis (C)
glucoseStructural Carbohydrate(e.g. cellulosein cell walls)
Used immediatelyfor energy
Stored as starch and converted back when glucose is needed for energyby plant.
CO2
Photosynthesis2
1
3
4
5 6
7
8
glucose
cellulose
starch
B CO2
D A C
cellulose
starch glucose
Used for energy / respiration
Made into cellulose /plant cell walls
Stops light reaching leaf
Elodea Bubbler• When g_____ plants
photosynthesise they produce o__.
• In a______ plants, this oxygen is given off as b_____ which are easily seen.
• The n______ of bubbles produced every m______, i.e. the rate, gives us an idea of how f____ the plant is p____________.
reen
ubbles
quatic
reen
umberinute
asthotosynthesing
Limiting Factors (C)
• Photosynthesis depends on c______ d_______, w_____, l_____ i_______ and t__________.
• If they are in s_____ supply, they cut down or L_____ the rate of photosynthesis.
• Light, water, carbon dioxide and temperature can act as “L Factors”.
arbonioxide ater ight ntensityemperature
hortIMIT
imiting
Limiting Factors – light (C)At point X on the graph l______ intensity is limiting the rate of photosynthesis.
At point X - as light intensity increases. the r____ of photosynthesis i________
At point Y on the graph light intensity is n__ l_____ l________ as photosynthesis slows down even though light intensity is still i___________.
X
Y
ight
atencreases
o onger imiting
ncreasing
Limiting Factors – CO2 (C)
A
B
At A CO2 concentration is the limiting factor as the rate of photosynthesis is increasing as the concentration of CO2 is increasing
At B CO2 concentration is not the limiting factor as photosynthesis is slowing down even though the concentration of CO2 is still increasing
At B there must be another limiting factor e.g. light intensity or temperature
Limiting Factors –temperature (C)
X
Z
YAt X the rate of photosynthesis is increasing as the enzymes of photosynthesis are working faster
At Y the rate of photosynthesis is at its highest because the enzymes of photosynthesis are at their optimum temperature
At Z photosynthesis slows down because enzymes are being d enatured
Limiting Factors (C)• At X the
limiting factor is light intensity
• At Y temperature is limiting
• At Z CO2 concentration is limiting
Y
Z
Light intensity temperature
CO2 concentration
Mass of sugar produced (g)
Light intensity
Rate of photosynthesis increases
Rate of photosynthesis increases
Plant transport – what you should know
• The transport system of a plant does t___ jobs.
• One is to t________ materials needed for photosynthesis.
• W____ from r_____ to l______• The other is to transport n________
produced by photosynthesis. S_____ from l____ to roots and fruits and
all parts of the plant
wo
ransport
ater oots eaves
utrients
ugar eaves
Plant transport – what you should know
• Tubes, in the stem, called x_____ carry the w_____ and m_______ from the r_____ to the l______
• Tubes called the phloem carry the s______ made in p__________ from the leaves to all other parts of a plant
• Up to y______ leaves and f______• Down to r______ and t_______
ylem
ater inerals oots eaves
ugar hotosynthesis
oung ruits
oots ubers
Xylem structure• D____ cells – no
cell c_______• Contains l______• Carries w_____
and m______ up to leaves
• S________ plant
ead
ontents ignin
ater inerals
upports
Phloem structure• Made of l_____ cells• T___ cell types• S_____ cells and
c___________ cells• Has sieve p______• Carries n_______
from leaves to r____, f______ and y_______ leaves
1
2
3
Sieve plate
Sieve cell
Companion cell
iving
wo
ieve
ompanion
lates
utrients
oots ruits
oung
Leaf• Leaves are f____, t_____ and b_____• Leaves don’t o_______ so they don’t block
s_______ needed for photosynthesis• Leaves have s_______ on their e_______• Plants take in CO2 from the a___ through
stomata which can o____ and c_____• W_____ v______ is l____ through the
stomata
lat hin road
verlap
unlight
tomata pidermis
ir
pen lose
ater apour ost
Cross section of leaf (c)
chloroplasts
0.5
stomata Gas exchange/ gases in / out
More on lower surface
ylem
Water would evaporate into the air
D phloem
B CO2 and water
cuticle upper epidermis
Palisade mesophyll
Spongy mesophyll
stoma Guard cells
Moist air space
Leaf vein xylem
Xylem/ leaf vein B
F
C
1 3
2 4 5
Transport minerals support
Sieve plate Companion cell
Transports food / nutrients /sugar
epidermis
Guard cells