Download EnERGY TRANSFORMATIONS IN NATURE

Photosynthesis & Respiration
INTRODUCTION
• Ecology is the study of the relationships
between organisms and their environment
and an Ecosystem is a community of
organisms in a habitat and how they interact
with each other and the environment that
they live in.
• One of the key parts to ecology is the study
of how energy moves through an ecosystem.
•
•
•
•
Where does this energy come from?
Why is it so important?
How does it flow through an ecosystem?
What factors can effect its movement?
• By developing an understanding of the
answers to these questions, scientists can
get a good sense of what drives an
ecosystem and what is required to make that
ecosystem sustainable
THE NEED FOR ENERGY
• All ecosystems depend on energy
input for them to be able to work
• The energy is important because
organisms use it for:
- movement
- keeping warm
- growth and repair
- metabolic function
- chemical synthesis
• Without this energy, organisms
are unable to
function/move/reproduce and the
biotic components of ecosystem
may die very quickly
THE SOURCE OF ENERGY
• The original source of energy in an
ecosystem comes from the SUN
• Plants, algae and cyanobacteria are
all able to trap the sun’s energy and
use it to create energy rich organic
material in a process called
PHOTOSYNTHESIS
• These organisms are called
AUTOTROPHS or
PRODUCERS as they supply all
of the organic matter and energy on
which the other organisms in an
ecosystem depend
• Photosynthesis evolved as a way to
store the energy in solar radiation as
high-energy electrons in
carbohydrate molecules (solar
energy  chemical energy)
• Plants, algae and cyanobacteria,
known as photoautotrophs, are the
only organisms capable of
performing photosynthesis
• Energy is acquired by living things in
three ways: photosynthesis,
chemosynthesis and consumption
• Photosynthetic and chemosynthetic
organisms are grouped into a
category known as autotrophs:
organisms capable of synthesising
their own food (more specifically,
capable of using inorganic carbon as
a carbon source)
• Autotrophs act as producers and are
critical for ALL ecosystems. Without
these organisms, energy would not
be available to other living
organisms and life itself would not
be possible
Photoautotrophs
•
A Photoautotroph is an organism
that can synthesise its own food by
using light as a source of energy
•
Photoautotrophs, such as plants,
algae, and photosynthetic bacteria,
serve as the energy source for a
majority of the world's ecosystems.
These ecosystems are often
described by grazing food webs
•
Photoautotrophs harness the solar
energy of the sun by converting it
to Chemical energy in the form of
ATP (and NADP). The energy
stored in ATP is used to synthesise
complex organic molecules, such
as glucose
Euglenia
Chemoautotrophs
• VIDEO: David Attenborough on
Geothermal Vents
•
A chemoautotroph is a simple organism, such as
bacteria or protozoans, that derives its energy
from chemical processes rather than
photosynthesis
•
Chemoautotrophs are primarily bacteria that are
found in rare ecosystems where sunlight is not
available, such as in those associated with dark
caves or hydrothermal vents at the bottom of the
ocean . Many chemoautotrophs in hydrothermal
vents use hydrogen sulfide (H 2S), which is
released from the vents, as a source of chemical
energy. This allows chemoautotrophs to
synthesise complex organic molecules, such as
glucose, for their own energy and in turn
supplies energy to the rest of the ecosystem.
Chemoautotrophs make their food using
chemical energy rather than solar energy.
Chemoautotrophs are able to synthesise their
own organic molecules from the fixation of
carbon dioxide.
Chemoautotrophs are able to thrive in very
harsh environments, such as deep sea vents,
due to their lack of dependence on outside
sources of carbon other than carbon dioxide.
•
Hydrothermal vents
Swimming shrimp, a few squat lobsters and hundreds of vent
mussels are seen at a hydrothermal vent at the bottom of the
ocean. As no sunlight penetrates to this depth, the ecosystem is
supported by chemoautotrophic bacteria and organic material
that sinks from the ocean’s surface
•
•
VIDEO: David Attenborough on Geothermal Vents
https://www.youtube.com/watch?v=BXGF3XS-yAI
THE SOURCE OF ENERGY
PHOTOSYNTHESIS
• Photosynthesis is the conversion of light energy
from the sun into chemical energy that can be
utilised by living organisms as an energy
substrate in cellular respiration
• The process occurs in organelles called
CHLOROPLASTS. The grana of the chloroplasts
(looks like a stack of 20 cent coins) contains the
chemical CHLOROPHYLL.
• Chlorophyll is able to absorb the suns energy
and use it to excite molecules to a higher energy
level. This sets off a series of chemical reactions
that ultimately result in the formation of an
organic molecule namely GLUCOSE
• Photosynthesis occurs in 2 stages:
Light dependent phase (in the grana)
Light independent phase (in the stroma)
THE SOURCE OF ENERGY
PHOTOSYNTHESIS
• Photosynthesis can be summarised by the following word and chemical
equations:
Carbon Dioxide + Water
6CO2 (g)

+ 6H2O (l) 
Glucose
+ Oxygen
C6H12O6 (s) + O2 (g)
• The Inputs are CO 2 and H2O. Carbon dioxide comes from the
atmosphere and enters plants through the stomata. Water enters the
plants via the roots in the ground and travels to the leaves via the xylem
• The Outputs are Glucose and Oxygen. The glucose is then used in
Cellular respiration and the Oxygen is released as a waste (although
some can be used in Cellular Respiration)
• The rate of photosynthesis depends the concentrations of Carbon
dioxide and Water as well as factors such as temperature and light
intensity
VIDEO: Crashcourse Photosynthesis
https://www.youtube.com/watch?v=sQK3Yr4Sc_k
• Sunlight excites the chlorophyll
molecule in PHOTOSYSTEM II
• The energy produced helps break
down a water molecule
(PHOTOLYSIS)
• H+ are released into the thylakoid
space
• O2 is a by-product released
• The removed electrons (e -) are
excited to a higher energy state
and then excited again (by
Photosystem I) to an even higher
energy state
• These electrons are then used to
convert the NADP into NADPH (a
carrier molecule)
• Transports H+ across the
thylakoid membrane
• This causes a CHEMIOSMOTIC
gradient for H + to diffuse back
through the membrane which
activates ATP SYNTHASE
• This combines ADP with inorganic
phosphate to produce ATP
• The highly energetic NADPH and
ATP molecules are then fed into
the light-independant reaction
• The second stage of photosynthesis takes place
in the STROMA
• It can occur WITHOUT the presence of sunlight
• It is known as the CALVIN CYCLE
- ATP & NADPH (the products of light
dependant phase are used to convert
CO 2 to
GLUCOSE)
RuBP (Ribulose Biphosphate) is a 5-carbon
sugar that binds C0 2 dissolved in the stroma
 This unstable molecule quickly breaks down
to two molecules of 3-carbon 3phosphoglycerate (3PG)
 The 2 3PG molecules are then converted into
glyceraldehyde 3-phosphate (G3P)
(by adding a high energy phospahte group
from ATP and adding Hydrogen from
NADPH)
 2 molecules of G3P (multi turns of the Calvin
cycle) combine to form 1 molecule of glucose
 G3P is also the starting point for the
synthesis of fats and proteins
LIGHT
-Brighter the light the faster the rate of photosynthesis
-Photosynthesis greater on bright sunny day and out of
the shade
-Up until a point where another factor limits the rate of
photosynthesis
-Plants are adapted to certain conditions so if exposed
to full light they will die eg. Ferns
CO2
-Raw material of photosynthesis
-Changes in its concentration effect the rate of
photosynthesis
-More CO 2, stomata open, greater the rate of
photosynthesis
WATER
-Raw material of photosynthesis
-Lack of water slows photosynthesis
-May cause stomata to close thus reducing CO 2
uptake
-Other processes also affected by the lack of water
TEMPERATURE
-Generally increases as the temperature increases
-Only to a certain temperature as the enzymes
denature at around 40 oC
-Certain plants are adapted to live in certain
temperatures
LIMITING FACTORS
THE FACTOR WHICH IS LEAST AVAILABLE
DETERMINES THE RATE AT WHICH
PHOTOSYNTHESIS OCCURS. THE FACTOR IS THE
LIMITING FACTOR.
1. Waterproof Cuticle
- prevents water escaping or being evaporated
- water is crucial as a raw material for
photosynthesis: transport medium and other
functions
2.
Chlorophyll (palisade mesophyll)
- palisade mesophyll are packed with green
chloroplasts
- packed on the upper side of the leaf which
receives most sunlight
3. Air Spaces
- large air spaces exist between the spongy mesophyll
- allows air to circulate freely through the interior of the leaf
- CO2 is able to diffuse into these spaces
- Contain water vapour which keeps cell surface moist and
allows CO2
to diffuse through membranes
- O2 also can diffuse into these spaces (out during day/in during
night)
4. Transport Tissues
- network of veins provide strength to the leaf and carry water
and
minerals from roots to leaves
- sugars carried from leaves to other parts of the plant
5. Stomata
- mostly on the lower (shaded) sides of leaves
- cooler and less exposure to sunlight so minimal water
evaporation
- allow CO 2 and O 2 diffusion in and out
C3 Plants
-Plant species that fix carbon exclusively through the Calvin cycle
-The most common pathway for carbon fixation
-On hot days stomata close so C3 plants can conserve water, but CO2 then cannot
diffuse in
C4 Plants
-CO2 is stored in mesophyll cells. It is joined to a 3-carbon molecule to form a 4carbon molecule (hence name C4 plants)
-It then fixed by Rubisco (enzyme that helps bind CO2 to RuBP) in the Calvin cycle
-CO2 gradient remains low in mesophyll cells allowing it to naturally diffuse in, even
when stomata are almost closed
-Means that photosynthesis can occur more readily in hot conditions when the
stomata would otherwise be closed
Eg. Corn, Sugar Cane
VIDEO: Plant Adaptations for Photosynthesis
https://www.youtube.com/watch?v=DGpPHrLF-5M
CAM Plants (Crussulacean Acid Metabolism)
-CO2 gathered at night and forms malate (4 Carbon)
-CAM plants dont transport it away from mesophyll but store it during the night
-Use these for the Calvin Cycle during the day
-Requires 4 more ATP molecules than C3 so tend to grow more slowly
-Lose up to 95% less water than C3 plants as stomata are only open at night
-useful in arid zones
-Can swap to C3 for brief periods when water is available or to keep stomata closed day &
night during drought
• ATP  ADP + Pi
ATP can be broken down into ADP and
inorganic phosphate to release energy to
drive other chemical reactions
Hydrolysis
•Catabolic
Reaction
• ADP + Pi  ATP
ADP and inorganic phosphate can be
joined to create ATP. This stores energy
and allows it to be transported around the
cell
• To make 1 ATP requires 30.7KJ to be stored in
the last bond
• Any reactions that produce less than 30.7KJ can’t
store the energy which is then lost as HEAT
• Any reactions that produce more than 30.7KJ
have the excess released as HEAT
• HELPS KEEP US WARM + WHY ENERGY IS LOST
OUT OF FOOD WEBS
Rephosphorylation
•Anabolic
Reaction
• Heterotrophs are organisms that are
unable to produce their own food, they
function as consumers in the food
chain.
• They rely on the carbohydrates
produced by photosynthetic organisms
for their energy needs
• They obtain energy in the form of
organic carbon by eating autotrophs or
other heterotrophs.
• They break down complex organic
compounds produced by autotrophs
into simpler compounds, releasing
energy by oxidising carbon and
hydrogen atoms into carbon dioxide
and water, respectively.
• Unlike autotrophs, heterotrophs are
unable to synthesise their own food. If
they cannot eat other organisms, they
will die.
• #NOTE: Both autotrophs and
heterotrophs undertake cellular
respiration. It is how they obtain the
substrate (eg. Glucose) that differs
WHY IS PHOTOSYNTHESIS SO IMPORTANT
CELLULAR RESPIRATION
• The products are vitally important to all organisms.
• In particular the carbohydrate (glucose) produced is used as the substrate for the
process of cellular respiration. This is the process all organisms use to make
usable energy in the form of ATP.
• The Oxygen produced in photosynthesis is also a vital ingredient in cellular
respiration
• During the process of cellular respiration not all energy is converted into ATP
and some is lost as heat energy.
• This loss of energy as heat helps maintain the internal temperature of organisms
but it also has a significant effect on how food chains and webs can function as
we will see later
• Overall CELLULAR RESPIRATION can be summarised as:
Glucose
+ Oxygen
C6H12O6 (s) + O2 (g)


Carbon Dioxide + Water
6CO2 (g)
+
6H2O (l)
VIDEO: Photosynthesis
& Cellular Respiration
GLYCOLYSIS
KREB’S CYCLE
• Then Oxygen is used as the FINAL
ELECTRON ACCEPTOR
•
- the H+ ions combine with the
•
oxygen to form water
• 2H+ + ½ O2 + 2e -  H2O
• Oxygen is crucial and the electron
transport chain cant work without it
•
- it helps create a concentration
•
gradient by taking away H+
• 1 NADH (from Glycolysis) = 3 ATP
• 3 NADH (from Krebs) = 9 ATP
• 1 FADH (from Krebs) = 2 ATP
• 1 NADH (from Transition) = 3 ATP
• Total = 17 ATP per Pyruvate therefore
•
34 ATP PER GLUCOSE
• Cellular Respiration generally requires oxygen (for the removal of CO 2 and as the last H +
acceptor during the electron transport chain)
• Aerobic Respiration generates A LOT OF ENERGY (36 ATP)
• Anaerobic Respiration is the partial breakdown of glucose to obtain energy WITHOUT
OXYGEN
• It occurs in the cytoplasm of the cell
• The products of anaerobic respiration (ethanol & lactic acid) are toxic
• The reactions cant carry on indefinitely and do not produce a large amount of energy
VIDEO: BOZEMAN ANAEROBIC
RESPIRATION SUMMARY
• The Ethanol Pathway In
Yeast
Alcoholic fermentation:
SUGAR  ETHANOL + CO2 + ENERGY
• The Lactate Pathway In
Mammals
• Anaerobic respiration in muscle cells that
produces lactic acid
• Lactic Acid causes burning and tiring of muscles
during strenuous exercise
• Lactic Acid is transported to the liver via the
blood
 converted into pyruvate requiring oxygen
 the O2 required is called OXYGEN DEBT
Photosynthesis
Photosynthesis is the process where:
A) heterotrophs obtain food by eating plants.
B) autotrophs use sunlight to make organic molecules.
C) heterotrophs synthesize glucose from sunlight and CO2.
D) autotrophs depend on detritivores for their food source.
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Photosynthesis
Photosynthesis is the process where:
A) heterotrophs obtain food by eating plants.
B) autotrophs use sunlight to make organic molecules.
C) heterotrophs synthesize glucose from sunlight and CO2.
D) autotrophs depend on detritivores for their food source.
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Photosynthesis
Which structure specifically absorbs light in a plant cell?
A) mitochondrion
B) thylakoid membrane
C) stroma
D) guard cell
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Photosynthesis
Which structure specifically absorbs light in a plant cell?
A) mitochondrion
B) thylakoid membrane
C) stroma
D) guard cell
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Photosynthesis
Light-independent reactions use energy harvested from lightdependent reactions to:
A) produce both NADPH and ATP.
B) drive the assembly of sugar molecules from carbon dioxide.
C) activate light reactions through enzymes.
D) convert chemical energy in one of two photosystems.
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Photosynthesis
Light-independent reactions use energy harvested from lightdependent reactions to:
A) produce both NADPH and ATP.
B) drive the assembly of sugar molecules from carbon dioxide.
C) activate light reactions through enzymes.
D) convert chemical energy in one of two photosystems.
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Cellular Respiration
Which of the following statements about cellular respiration is true?
A) Chemical energy, in the form of glucose and oxygen, is the primary source
of energy.
B) Plants use solar energy to turn glucose into oxygen.
C) All organisms can use sunlight to produce chemical energy, stored as
glucose and oxygen.
D) Cellular respiration occurs only in plants and cannot be performed by
mammals.
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Cellular Respiration
Which of the following statements about cellular respiration is true?
A) Chemical energy, in the form of glucose and oxygen, is the primary source
of energy.
B) Plants use solar energy to turn glucose into oxygen.
C) All organisms can use sunlight to produce chemical energy, stored as
glucose and oxygen.
D) Cellular respiration occurs only in plants and cannot be performed by
mammals.
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Cellular Respiration
What is the main difference between aerobic and anaerobic
respiration?
A) Whether or not oxygen is used as final electron acceptors.
B) The stage where fermentation takes place.
C) The stage at which lactate dehydrogenase in used in the respiration
process.
D) Whether the final electrons are positively or negatively charged.
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Cellular Respiration
What is the main difference between aerobic and anaerobic
respiration?
A) Whether or not oxygen is used as final electron acceptors.
B) The stage where fermentation takes place.
C) The stage at which lactate dehydrogenase in used in the respiration
process.
D) Whether the final electrons are positively or negatively charged.
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Cellular Respiration
Organisms that can make their own food using inorganic molecules
are called__________, while organisms that make their own food
using light energy are called___________.
A) heterotrophs; chemoautotrophs.
B) chemoautotrophs; photoautotrophs.
C) heterotrophs; photoautotrophs
D) photoautotrophs; chemoautotrophs
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Cellular Respiration
Organisms that can make their own food using inorganic molecules
are called__________, while organisms that make their own food
using light energy are called___________.
A) heterotrophs; chemoautotrophs.
B) chemoautotrophs; photoautotrophs.
C) heterotrophs; photoautotrophs
D) photoautotrophs; chemoautotrophs
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Cellular Respiration
What is the net outcome of glycolysis from one molecule of glucose?
A) Two ATP, two NADH, and two pyruvate molecules
B) One ATP, one NADH, and one pyruvate molecule
C) Four ATP
D) One ATP and two NADH molecules
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Cellular Respiration
What is the net outcome of glycolysis from one molecule of glucose?
A) Two ATP, two NADH, and two pyruvate molecules
B) One ATP, one NADH, and one pyruvate molecule
C) Four ATP
D) One ATP and two NADH molecules
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