IGCSE Coordinated Science Year 1
Energy Transformations in
Living Organisms
B4.2 & B6.1 Key Notes
Photosynthesis
• Photosynthesis is the fundamental process by
which plants manufacture carbohydrates from
raw materials using energy from light.
C
C
C
C
C
C
Photosynthesis
• Uses the energy from sunlight to perform the
reaction:
6CO2 + 6H2O
light energy
chlorophyll
Carbon Dioxide + Water
light energy
chlorophyll
C6H12O6 + 6O2
Glucose (simple sugars) + Oxygen
Chloroplasts
• Chloroplasts are the location for
photosynthesis
Chloroplasts
• Inside a chloroplast is the pigment
chlorophyll.
• Chlorophyll absorbs certain wavelengths
(colors) of light, trapping the energy from
light.
Light
Reflected
Light
Chloroplast
Absorbed
light
Granum
Transmitted
light
• The light energy is then
converted into chemical
energy and the production
of simple carbohydrates.
• The carbohydrates are
stored as starch.
Why is photosynthesis
important to humans?
Flow of Energy
More than sugar?
• So plants make glucose, but how do they get
protein?
• What element is found in protein but not
glucose?
• Plants make their own
proteins but they must
use nitrogen.
• Nitrogen can be absorbed
from the soil.
• A good fertilizer adds nitrate
to the soil.
Chlorophyll Synthesis?
• If plants want to make
more chlorophyll, they
need more
magnesium.
What is wrong
with this plant?
Plants can have
deficiency diseases
too!
• Natural fertilizers
Nitrogen-containing Fertilizers
• Chemical/Artificial fertilizers
• Contains elements: N-P-K
Fertilizer over-use
• Too much nitrogen can cause water pollution as
it runs off in the water, causing “algae blooms”
• This is eutrophication.
PLANTS –
TRANSPORT REVISION
LAB REVISION
Review!
• Water transport in plants
– Osmosis, transpiration via xylem
– From roots to leaves
• Mineral ion transport in plants
– Diffusion in through the roots, transported dissolved
in water via xylem
– From roots to leaves
• Organic Nutrient transport in plants
– Translocation via phloem
– From source to sink
• Plant Structure
The Pathway of Water Across a Root
Vascular Bundles
• Cross Section of a Root:
Cross Section of a Stem
Section of a Leaf
Dicot Leaf
Dicot Leaf
• What enters and exits through the stoma?
REVIEW
• A group of cells that perform the same
function are called a….
• TISSUE
• What are some tissues in a leaf?
Tissues – ex. palisade mesophyll
Leaf Structure
• What is each structure used for?
(p. 66-67)
• Chloroplasts –
– Photosynthesis (capture light energy to use when
converting CO2 into glucose)
• Stomata and mesophyll cells –
– gas exchange via DIFFUSION
• Vascular bundles (xylem and phloem) –
– transport and support
Experiment to show that light is required for
photosynthesis
Variegated Leaves =
green + white colored
Experiment to show that CO2 is required for
photosynthesis
Experiment to show that oxygen is a product of
photosynthesis
6.1 Respiration
• What do you think our bodies use energy for?
• Our body uses energy for:
– Muscle contraction
– Protein synthesis (creation)
– Cell division
– Growth
– Passing nerve impulses
– Maintaining a constant
body temperature
Energy Transformations
• Where does the body get it’s energy for these
things?
• Where did that energy come from?
RESPIRATION
• Respiration is the chemical reactions that
break down nutrient molecules in living cells
to release energy.
• Aerobic respiration is the release of a
relatively large amount of energy in cells by
the breakdown of food substances in the
presence of oxygen.
Energy
Aerobic Cellular Respiration Equation
6O2
+ C6H12O6 
6CO2
+
6H2O + energy
oxygen + glucose  carbon dioxide + water + energy
Let’s Watch it Work
• Aerobic respiration is done in both plant and
animal cells. Let’s look at the graph of what is
going on in the respiration chamber where there
are some germinating (alive) beans.
• In your notes pages, record:
– the changes you see in the graphs of O2 & CO2
concentrations
– the conclusion you can draw from the data
– What about the lab set-up makes this a fair test?
The Big Idea
• Compare and
contrast
photosynthesis &
respiration.
Problem!!
• What happens when no oxygen is available
for cells to use in respiration? How will our
bodies get energy?
Yeast Anaerobic Respiration Lab
Procedures:
• 1. Stretch out the balloon for a minute.
• 2. Put about 2 spoonful's of yeast + 2 spoonful's of sugar
into the balloons using a funnel.
• 3. Turn the tap water on to WARM. It should not be too hot
or too cold.
• 4. Add as much water as possible to the balloon without it
overflowing.
• 5. Tie off the balloon while pushing out any remaining air.
• 6. Mix the contents of the balloon with your fingers until
you feel no solid chunks left.
• 7. Return to your seat with the balloon, set it on your desk
and wait….
Anaerobic Respiration
• Anaerobic respiration is the release of a
relatively small amount of energy by the
breakdown of food substances in the absence
of oxygen.
Energy
• We also call anaerobic respiration
fermentation.
In your muscles…
• During hard exercise our muscles do this type
of anaerobic respiration:
• glucose  lactic acid + energy
Lactic Acid
• Can anyone describe what lactic acid buildup
feels like in your muscles?
• What is oxygen debt? Read p. 119 & answer
this question in your notes pages.
• How might the type of sport you play affect
what type of respiration your cells perform?
In yeast…
• Yeast & other microorganisms do this type of
anaerobic respiration:
• glucose  alcohol + carbon dioxide + energy
Anaerobic Respiration in Yeast
• The products of anaerobic respiration in yeast are
valuable for brewing alcoholic drinks and bread
making.
• Read p. 52 & 53 to find out more & answer these
questions:
–
–
–
–
How is yeast involved in fermentation?
Why doesn’t bread taste like alcohol?
What makes bread soft and spongy?
What temperature do these (brewing & dough rising)
take place at? Why?
Check out your balloons!
• What has happened to your balloons?
• Write a few sentences in your journal about
how this has happened.