Bioenergetics revision
Photosynthesis and respiratioin
Photosynthesis
Water + Carbon Dioxide
From roots/soil
6 H2O +
From air
through stoma
6 CO2
Chlorophyll
• Green pigment
• Found in chloroplasts
• Absorbs light energy
Sunlight
chlorophyll
Glucose + Oxygen
Stored as
starch
Released into air
C6H12O6 +
Don’t forget that plants also
carry out Respiration to make
energy.
6 O2
Plant Tissues
Know the features
of each layer and
how they help
photosynthesis
Factors Affecting Photosynthesis
As factor rises, so does the rate of photosynthesis
Temperature
- Above 45oC, enzymes denature
Carbon dioxide
Light intensity
Nutrients
Water
Space to grow
All of these, at a particular time, may be the limiting factor.
Temperature
Light Intensity
• Without enough light,
a plant cannot
photosynthesise very
quickly, even if there
is plenty of water and
carbon dioxide.
Increasing the light
intensity will boost
the speed of
photosynthesis.
Can you explain what
is happening here?
CO2
• Sometimes
photosynthesis is
limited by the
concentration of
carbon dioxide in
the air. Even if
there is plenty of
light, a plant cannot
photosynthesise if
there is insufficient
carbon dioxide.
Something other than CO2
concentration is acting as a
limiting factor
Temperature
• If it gets too cold, the
rate of photosynthesis
will decrease. Plants
cannot photosynthesise
if it gets too hot. Why?
Greenhouses and Poly-tunnels
•Controls the environment
•Light
•Temperature
•Nutrient levels
•Water levels
•Predators
•Weeds
Reduces the chance of
Limiting factors
Hydroponics
Growing in plants in nutrient rich water, not soil.
Respiration
• Site of respiration- mitochondria
Needed for energy to:
•Build new molecules and cells
•Movement- needed to make muscle
•Takes place in all cells (apart from RBCs). cells contract
•Carried out by the mitochondria.
•Keep birds and mammals (warm
blooded) at a constant temperature
Aerobic Respiration
Glucose + Oxygen
C6H12O6 + 6 O2
Carbon dioxide + Water
6 CO2
Anaerobic Respiration
•Takes place where no oxygen is present.
•Muscle cells
Glucose
Lactic Acid
•Yeast Cells
Glucose
Ethanol (alcohol)
+ 6 H2O
Anaerobic Respiration
produces less energy than
Aerobic Respiration!
The Effects of Exercise
Heart rate 
Breathing rate 
 more Oxygen and Glucose
supplied to muscles
 Increase in Respiration rate
 More Energy for muscle
contraction.
Glycogen
Stored glucose found
in muscles
Oxygen Debt
Amount of oxygen needed to
breakdown Lactic acid, formed during
anaerobic respiration.
Lactic acid + Oxygen
Carbon dioxide + water
B2 REVISION – CHAPTER 2 – ORGANISMS IN THE ENVIRONMENT
What is the equation for
photosynthesis
Explain how plants use glucose for
the following:
Respiration
How doe the follow factors affect organisms in their
environment?
Temperature:
Where in the plant does it occur?
Light:
How are leaves adapted to
perform photosynthesis?
Transport
Water:
Storage
Explain how light, CO2 and temperature are limiting factors of
photosynthesis
CO2 and O2:
How do we measure the distribution of organisms?
How do we know this data is accurate?
KEY WORDS:
Photosynthesis
Glucose
Limiting factors
Quadrat
Sample size
Range
Mean
Median
Mode
Transect
Reproducible
Valid
Variables
ASSESSMENT: