Science 11th grade
LEARNING OBJECT
LEARNING UNIT
How do the world’s
components change?
Do all the autotrophs carry out the photosynthesis
process in the same way?
S/K
SKILL 1: Differentiate the process of photosynthesis in
Green algae and plants.
SKILL 2: Compare different photosynthetic pigments in
terms of the wavelengths they absorb.
SKILL 3: Illustrate embryophyte’s strategies to minimize
water loss due to evaporation generated by carbon dioxide
absorption.
SKILL 4: Relate RuBisCo enzyme’s efficiency with the
concentration of gases in the Earth’s primitive atmosphere.
SKILL 5: Explain photorespiration.
SKILL 6: Compare adaptation of C3, C4, and CAM plants to
reduce photorespiration.
SKILL 7: Relate the metabolic strategies of C3, C4, and
CAM plants with the conditions of the ecosystems they
inhabit.
SKILL 8: Investigate
photosynthetic efficiency.
Language
the
methods
to
measure
English
Socio cultural context of
the LO
Curricular axis
Colombia
Standard competencies
Explain the importance of photosynthesis as a necessary
energy-conversion process for aerobic organisms
Background Knowledge
Plant tissue, absorption spectrum.
English Review topic
Affixes
Vocabulary box
Atmosphere: The blanket of gas on the surface of a planet
or satellite. Note: The atmosphere of the Earth is roughly
eighty percent nitrogen and twenty percent oxygen, with
Living Environment
traces of other gases.
Cuticle:
Botany. a very thin hyaline film covering the surface of
plants, derived from the outer surfaces of the epidermal cells.
Epidermis: Botany. a thin layer of cells forming the outer
integument of seed plants and ferns.
NAME: _________________________________________________
GRADE: ________________________________________________
Introduction
Life on our planet absolutely depends on photosynthesis, on the one hand,
98% of the oxygene comes from this process; fuel molecules contain carbon,
from which all living beings on the Earth nourish.
Clorophyle, the main pigment in photosynthesis, absorbs violet, blue, and red
wavelengths, and it is green because it reflects that specific type of light.
Animals need of others to obtain energy from food. However, there are others,
such as sea slugs that produce their own energy through photosynthesis. They
eat algae, but do not digest them completely, and whatever remains in their
system continues performing photosynthesis, feeding the slug just the way
plants do.
OBJECTIVES
 To describe the involvement of photosynthetic pigments in the
conversion process from luminous energy to chemical energy in green
algae and plants
 To determine the differences between the three types of photosynthetic
metabolism
 To recognize the importance of photorespiration, generating nutritional
loss to plants, as an antagonistic process to photosynthesis
SKILL 1. Differentiate the process of photosynthesis in Green algae and
plants.
SKILL 2. Compare different photosynthetic pigments in terms of the
wavelengths they absorb.
SKILL 3. Illustrate embryophyte’s strategies to minimize water loss due to
evaporation generated by carbon dioxide absorption.
PHOTOSYNTHESIS
Process by which living beings, such as cyanobacteria, algae, and plants,
produce nutritive substances by using light as their energy source; CO2, water,
and minerals as their input; and chlorophyll as conversion mechanism.
Did you know that…? Besides chlorophyll, there are other pigments in leaves
called carotenoids (red, orange, and yellow pigments) disguised by the
abundance of green pigment? In some ripe-tomato tissues, as well as in the
cells of leaves when they stop synthetizing chlorophyll in Autumn, carotenoids
take over (Curtis & Barnes, 1993, p. 237).
PHOTOSYNTHETIC PIGMENTS
Sales representatives in travel agencies and journalists in TV shows repeatedly
mention Caño Cristales. This river is located in the Llanos Orientales region of
Colombia, and it is commonly known as “the five-color river”, “the melted
rainbow” or “the world’s most beautiful river”. And people call it those names
because the river has algae of several colors on its surface; a phenomenon
caused by the several photosynthetic pigments they contain.
Photosynthetic pigments are organic substances that absorb light from a color
spectrum, which is later converted to chemical energy to be used by other
living systems. However, not all pigments absorb all colors. For instance,
chlorophyll does not absorb green light and that is why leaves are green
(Overmire, 2003, p.175).
Different wavelength light is absorbed by several types of pigments, causing a
chemical reaction:
PLANT STRATEGIES TO MINIMIZE WATER LOSS DUE TO EVAPORATION
Plants require much more water than an animal weighing the same because
animals retain and circulate water in their bodies. On the other hand, around
90% of the water plants absorb through their roots escapes through leaves in
the form of vapor in a process known as transpiration. This process is the
result of Stomas opening for plants to obtain carbon dioxide and perform
photosynthesis. To transpire, plants take several shapes, sizes, positions,
shades, etc.
DID YOU KNOW THAT…? Transpiration cost is too much? For each carbon
dioxide gram converted in organic matter, a plant loses 500 grams of water,
meaning that a maize crop as large as two soccer fields requires around 5
million liters of water to fully grow (Curtis and Barnes, 1993, p. 666).
Some of the strategies used by plants are:
-
Presence of aciculate (needle shaped), leathery (dry) or spine-shaped
leaves (reducing leaf surface and does not perform photosynthesis).
Inverted stoma cycle (stomas open at night)
Reduction of stomas in leaves.
-
Less number and decreased size of leaves.
Vertical positioning for light-decreased impact.
Internal temperature regulation.
Hairy leaves.
Thick, waxy, water-proof cuticle in their epidermis.
Leaf loss or early ageing (Overmire, 2003, p. 407), (Kimball, 1986, p.
222).
LEARNING ACTIVITY
Electro-magnetic spectrum is defined as the group of radiation wavelengths in
nature. As mentioned above, photosynthetic pigments absorb light from the
visible spectrum. Said absorption (as shown in Figure 1) is represented by a
sine wave: the higher the curve over certain color area, the greater the
absorption by that specific pigment.
Take a look at the following “electro-magnetic spectrum”. Based on it, say if
the following statements are True or False. Mark with an ‘X’.
1. Phycoerithrin is the pigments’ largest light absorption spectrum.
True ( ) False (
)
2. Chlorophyll is the pigment with the highest light absorption levels.
True ( ) False (
)
3. Pigments absorb certain wavelengths (colors) and the ones not absorbed
are the ones reflected. The latter ones are the colors we perceive with
our sight. If Phycocyanin absorbs yellow, orange, and red Wavelengths,
then this pigment’s color must be in between: red.
True ( ) False (
)
METABOLIC STRATEGIES AND ADAPTION MECHANISMS OF PLANTS
REGARDING PHOTOSYNTHESIS
It may seem like grass, trees, and plants, in general, scarcely interact with the
environment, but reality is far from that; they actually build a constantlychanging, full-equipped chemistry lab that produces a vast number of
substances and renovates a large variety of structures. And this has to be so,
in order to create strategies and adaptions mechanisms for plant survival
against environmental adversities.
RUBISCO ENZYME EFFICIENCY AND THE EARTH’S PRIMITIVE
ATMOSPHERE
The RuBisCo enzyme (RuBP) or ribulose, bisphosphate carboxylase/oxygenase,
is the most abundant enzyme in the biosphere and represents around 50% of
soluble protein in vegetables’ leaves (Argenbio, 2007).
The RuBisCo enzyme is a key substance in photosynthesis, as it catalyzes
assimilation and fixation of CO2 in high concentrations, but when CO2
concentration is low, the enzyme involves in photorespiration (oxidation of
sugar resulting in CO2 and H2O).
Therefore, since the earth’s primitive atmosphere had high levels of CO2, and
O2 was present in small quantities, carboxylation rates (RuBisCo - CO2 joint)
were higher than the current ones, suppressing RuBisCo’s oxygenase activity.
It means that back then, RuBisCo enzyme’s activities made photosynthetic
activities easier and vegetal growth rates were higher than photorespiration.
(Mercado, 1999).
Did you know that…?
Although the RuBisCo enzyme is really important, it was considered inefficient
by scientists? Its catalyzing activity is slow (it catalyzes 3 CO2 molecules per
second, while other enzymes catalyze around one thousand molecules per
second) and it catalyzes two competitive reactions: RuBP’s carboxylation and
oxygenation (photosynthesis and photorespiration) (Argenbio, 2007).
PHOTORESPIRATION
Non-mitochondrial respiratory process taking place in the peroxisomes
(organelles where several compounds degrade) of the photosynthetic cells,
where carbohydrates are oxidized to light, oxygen is consumed, and CO2 is
produced (but ATP), unlike conventional respiration processes.
C3, C4, AND CAM PLANTS ADAPTIONS TO REDUCE
PHOTORESPIRATION
Some lawn plants and fine-leaf grass are sometimes drawn by the accelerated
growth of “hairy crabgrass”, that ruins lawn when spreading with its wide
leaves, and therefore it is considered as weed. This is a typical case of hairy
crabgrass (C4 plants) competitiveness over Poa grass (C3 Plants).
Poa Grass: dark green fine, uniform leaves lawn. C3 plants.
Hairy crabgrass. It ruins lawns as it spreads its wide, greenish-yellow leaves. It
is considered weed. C4 plants.
C3, C4, AND CAM PLANTS ADAPTIONS TO REDUCE
PHOTORESPIRATION
C3 PLANTS: rice, potatoes, tomatoes.
Their metabolism is aimed at being efficient, despite photorespiration.
- Higher frequency and stoma opening.
C4 PLANTS: corn, sugar cane, sorghum.
- Their metabolism is aimed at increasing CO2 fixation.
- Lower opening of stomas during less time.
CAM PLANTS: cactus, orchids, aloe vera, pineapple.
- Their metabolism is aimed at avoiding water loss.
- Stomas open at night and close during the day time, avoiding water loss.
C4 AND CAM PLANTS: phosphoenolpyruvate or PEP is used by these plants
during the first stage of photosynthesis, instead of RuBP to fix carbon in the
form of malic acid.
RuBP is “taken” by the pod cells inside leaves, to separate it from O2 and to
avoid complex RuBP+O2 to be formed.
METABOLIC STRATEGIES AND ECOSYSTEM CONDITIONS OF C3, C4,
AND CAM PLANTS
Not all plants perform photosynthesis the same way; some of them have
adapted in such manner that they have also adjusted their photosynthesis
process to their habitats and the weather they live in.
- CO2 is reduced through RuBP, producing
phosphoglycerate, but consuming energy.
- Since these plants live in water and oxygen
rich environments, RuBP joins O2 consuming
part of the carbohydrates produced during
photosynthesis and with a significant water
loss.
- These plants limit photorespiration as they
have an enzyme called PEP carboxylase that
affixes to CO2, but to O2.
- These plants move RuBP away from the
direct contact with O2 through a cell barrier
that limits photorespiration.
-These plants induce a maximum CO2
concentration gradient between the cells and
the medium so that CO2 spreads faster, and
therefore stomas have to be open less and
during less time.
- These plants limit photorespiration as they
have an enzyme called PEP carboxylase that
affixes to CO2, but to O2.
- These plants inhibit photosynthesis during
the day time and take CO2 at night to store
it in the form of malate. Without opening
their stomas and saving water, these plants
transform CO2 in pyruvate to perform
photosynthesis without losing water.
LEARNING ACTIVITY
In three lines, and in a concrete manner, explain photorespiration.
Use the following words: cells, process, respiratory, sugar, photosynthesis,
CO2, oxidize, light, oxygen, and ATP.
Then, socialize with the class.
PHOTOSYNTHESIS EFFICIENCY
If carefully observed, in a fish tank, small algae release tiny oxygen bubbles
through their leaves, it can easily be concluded said oxygen bubbles are
photosynthesis products. If even much more attention is paid, it will be
noticeable that some algae produce more oxygen bubbles than others.
METHODS TO MEASURE PHOTOSYNTHESIS EFFICIENCY
The methods to measure photosynthesis efficiency include:
Real plant’s gas interchange: from a single leaf to the whole plant, the part
to be tested is put in a chamber (preferably maintaining the same environment
conditions of the plant). The air runs through the chamber and, due to an
infrared
gas
analyzer,
changes
in
the
gases
released
through
respiration/photosynthesis can be known.
Gaining biomass dry weight: Process commenced by determining the
preliminary weight of a seed left to germinate to, later, establish its dry
biomass at its harvesting time. The relation between the time the plant took to
develop and grow until its harvesting time is then determined, using the
biomass weight. Then, the photosynthesis activity values are finally
determined (Gliessman, 2002, p. 51).
LEARNING ACTIVITY
Unscramble the following sentences to give a right meaning regarding the
knowledge of the topic studied.
Group 1. photosynthesis, at, is, which, luminous, plants, energy, the, rate,
efficiency, fix, the, sun’s
Group 2. efficiency, method,
interchange, a, measurement
photosynthesis-,
gas,
real,
plant’s,
is,
SUMMARY
Life on our planet totally depends on photosynthesis. Cyanobacteria, algae,
and plants produce nutritive substances for themselves and for the rest of the
living beings on the planet. Photosynthesis is a very complex process in which
chlorophyll is the main, but not the only, pigment, as there are others such as
carotenoids, phyocyanins, and phycoerythrins. Each of these pigments absorb
water at different wavelengths.
To perform photosynthesis, plants lose lots of water through a process known
as transpiration. To avoid transpiration, plants use several metabolic and
anatomic strategies, such as the metabolism routes of C3, C4, and CAM plants,
in which each one for them adapt to the environment and guarantee their
survival. and guarantee their survival. In plant adapting, the RuBisCo enzyme
plays a central role as it catalyzes CO2 assimilation and fixation during
photosynthesis, although it is also involved in photosynthesis’ antagonistic
process called photorespiration, by which plants lose almost half of their
carbohydrates.
HOMEWORK
In groups of three, students must visit places near their homes. Students must
collect, observe, and analyze the leaves of 10 different plants. Then, they must
identify the possible anatomic strategies they use to avoid losing water.
After that, students stick each one of the leaves collected by grouping them
according to their similarities regarding water efficiency, as seen in Activity 2.
The foregoing must be carried out on a sheet of poster board under the title of
“Plants’ Anatomic Strategies to Avoid Water Loss due to Evaporation”.
Students must present their posters to the class. Presentations (maximum 5
minutes) must explain transpiration and its implications, as well as justify the
strategies found in the collected leaves to avoid transpiration.
EVALUATION
The following diagram shows the relation and exchange of substances and
compounds in plant cells.
Translation: Enzyme 1, chloroplast, chemical energy
1.
Based on the diagram above, and in order to duly show the
interaction between substances and compounds in the corresponding
processes, the spaces marked with ‘I’ and ‘III’ must be replaced by:
a.
b.
c.
d.
Chemical energy – O2.
Solar energy – ATP.
Solar energy – O2.
ATP- O2.
2.
The structure marked as ‘II’ represents:
a.
b.
c.
d.
chlorophyll.
mitochondrion.
peroxisome.
chloroplast.
3.
The diagram above represents two antagonistic process performed
by plants and algae; one is from left to right, and the other from right to
left. these processes respectively are:
a.
b.
c.
d.
photosynthesis and Calvin’s Cycle.
photosynthesis and respiration.
photorespiration and photosynthesis.
photosynthesis and photorespiration.
4.
The processes described in the diagram above, performed by
algae and plants, are carried out through specialized enzymes. If those
processes were performed by a C3 plant, such as rice or tomato,
enzyme 1 would be:
a.
b.
c.
d.
PEP.
phosphoenolpyruvate.
carotenoid.
RuBisCo.
Choose True or False with an ‘X’ as it corresponds.
5.
Strategies used by plants to avoid transpiration include hairy
leaves with a thick and impermeable cuticle.
False (
) True (
)
6.
C3 plants limit photorespiration using the PEP carboxylase enzyme
that affixes to CO2, but not to O2, as a metabolic strategy.
False (
) True (
)
7.
Photosynthesis efficiency may be considered as the rate by which
plants fix energy.
False (
) True (
)
Match concepts on the left to definitions on the right.
8.
CAM PLANTS
A. Rice and potato plants
have metabolisms
aimed at being efficient
despite photorespiration
through a higher
stoma opening and frequency
9.
C3 PLANTS
B. Corn and sugar cane plants
have a metabolism
aimed at increasing
CO2 fixation
By smaller and less time
opening stomas.
10.
C4 PLANTS
C. Cactus and pineapple
have a metabolism
aimed at avoiding
water loss by opening
stomas at night and
closing them during the day time
Bibliography
Argenbio
(2007).
Biología
celular.
Retrieved
http://www.argenbio.org/index.php?action=biotecnologia&opt=4
Avers, J. (1991).
Iberoamericana.
Biología
celular
(2ª
Ed.).
México.
Grupo
from
editorial
Curtis & Barnes (1993). Biología (5 ed.). Madrid. Médica Panamericana.
Gliessman (2002). Agroecología. Costa Rica. Litucat-turrialba.
Kimball, J. (1986). Biología (4a ed.). Wilmington. Addison-Wesley.
Mercado (1999). Fotosíntesis y Cambios en la Composición de la Atmósfera.
Retrieved
from
http://www.ciencia.cl/CienciaAlDia/volumen2/numero2/articulos/articulo6.html
Overmire, T. (2003). Biología (1 ed.). México, D.F. Limusa.
Salguero, S. ¿Cómo optimizar el uso del agua? Rutas fotosintéticas: C3, C4 y
CAM.
Retrieved
from
http://www3.uah.es/pedrovillar/Docencia/Ecologia%20Grado%20Biologia/Arch
ivos/Seminarios/C3,%20C4,%20CAM/Salguero,%20Sanchez%20et%20al.pdf
GLOSSARY
Biomass: quantity of matter obtained through photosynthesis by a group of
organisms.
Catalyze: process carried out by an enzyme that decreases activation energy
in a chemical reaction, but without getting involved.
Pod cell: type of plant cell found in leaves involved in the photosynthesis
process.
Stomas: small openings in the epidermis of leaves, by which plants’ gas
exchange is performed.
Concentration Gradient: difference in the concentration of solutes present in
two mediums.
Wavelength: net distance travelled by a wave in a specific tie interval.
Mesophile: layer of internal cells, surrounded by two epidermis layers in a
plant leaf.
Nanometer: one of the smallest length measures equal to one billionth of a
meter.
Peroxisome: cell organelle containing substances that intervene in the
formation and destruction of peroxides.
Pigment: color compound that absorbs light in a wavelength spectrum
Respiration: process to degrade and release energy upon molecules with high
energetic contents.
Vocabulary Box
Atmosphere: The blanket of gas on the surface of a planet or satellite. Note:
The atmosphere of the Earth is roughly eighty percent nitrogen and twenty
percent oxygen, with traces of other gases.
Cuticle:
Botany. a very thin hyaline film covering the surface of plants, derived
from the outer surfaces of the epidermal cells.
Epidermis:
Botany. a thin layer of cells forming the outer integument of seed
plants and ferns.
Retrieved from: http://www.dictionary.com
English Review Topic: Affixes