Starter – Which is the odd one
out? Why?
Enzyme
Facilitated
diffusion
Channel Protein
Water
Lunchtime today –
transport and enzymes
tutorial 12.30pm here.
Photosynthesis
SC: Describe products and
reactions of photosynthesis,
limiting factors and structure
of the chloroplast.
Photosynthesis is…………
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Fundamentally important
to virtually all life on
earth
Occurs in green plants,
some bacteria and algae
Transforms radiant
energy (sunlight) into
chemical potential
energy
Organisms called
autotrophs (self feeding)
Requirements for Photosynthesis
CO2 - enters from the air through stomata
 H2O - from the cell sap (originally from
the soil)
 Sunlight - red and blue wavelengths
 Enzymes - to control the reactions

Photosynthesis Equation
The Process of Photosynthesis
Photosynthesis occurs in the chloroplasts
of cells
 There are two phase for photosynthesis:

1. Light
Phase (light dependant) - occurs in the
grana
2. Dark Phase (light independent) - occurs in the
stroma
Chloroplast Structure
Microscope chloroplasts…
Light Phase (Photo part)
Dependent on light
 Occurs in the grana of chloroplasts
 Chlorophyll absorbs light energy - uses it
to split H2O into hydrogen and oxygen
atoms
 Energy in the form of ATP and NADPH is
produced by splitting water

Light Phase (Photo part)
Hydrogen atoms in NADPH are carried to
the stroma to be used in the dark phase
 Some oxygen is released from the
chloroplasts to be used in respiration
 The rest is released into the atmosphere

Calvin Cycle (dark phase)
(The synthesis part)
 Doesn’t need light
 Occurs in the stroma of chloroplasts
 Uses ATP and NADPH from the light
phase in a series of enzyme controlled
reactions.
 CO2 from the air combines with H atoms
from the light phase to produce glucose
molecules

Overview of Photosynthesis
Products of Photosynthesis

Photosynthesis produces complex
carbohydrates:
• glucose - used as fuel for respiration
• starch - which is stored in starch
granules
• cellulose - for forming cell walls
By-Products of Photosynthesis
Oxygen gas is a by-product of
photosynthesis
 Released into the atmosphere
 Used by animals for breathing
 Photosynthesis maintains the atmospheric
CO2 / O2 ratio at a constant level
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To Summarise
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Photosynthesis is the process occurring in green
plants which transforms carbon dioxide and
water into glucose and oxygen using sunlight.
Energy is stored in the forms of glucose, starch
and cellulose
Energy (ATP) produced by splitting H2O in the
light phase…
Is used to fix more energy (glucose) in the dark
phase
Glucose is then used for respiration
To Summarise
Video
Remember
Plant and animal cells carry out respiration
all the time.
 But plants only carry out photosynthesis
during the day.
 They usually carry out more
photosynthesis than respiration

Limiting factors for
photosynthesis
Light levels
 Availability of CO2 and water
 Temperature
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Can you explain why each of these factors
will affect the rate of photoshynthesis?
A few crazy videos about P/S
http://www.youtube.com/watch?v=Q_1mx
ZdF2TY
 http://www.youtube.com/watch?v=g78utcL
QrJ4
 http://www.youtube.com/watch?v=wj8TGh
cCnxs
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