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

hlorophyllight

hemical

aw aterials roducts

Equation of aerobic respiration

Glucose + oxygen CO2 + + energy H20

PhotosynthesisPhotosynthesis 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

otodine olution

tarchold

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

78

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