Brown's Biology AQA GCSE Additional Science-BIOLOGY 2
for GCSE Additional Science or GCSE Biology
REVISION NOTES GUIDE SUMMARY: What do you need to know
for the examinations? What do you need to able to do in the exams? In AQA GCSE Science
A examinations HT means for higher tier students only.
Sorry, but I don't have much time to answer questions, but if you see any
apparent errors or wish to comment, please
email me. All my notes, learning
objectives, comments for exam revision are based on the official AQA GCSE Science A Key Stage 4
AQA GCSE Science BIOLOGY 2 Unit
all green plants and algae use light
energy to make their own food.
Know that all green plants and algae obtain the raw materials
they need to make this food from the air and the soil.
Know that the conditions in which plants
are grown can be changed to promote growth.
You should be able to use your
skills, knowledge and understanding to be able to:
AQA GCSE Science BIOLOGY Unit B2.3.1 Photosynthesis
a) Know that photosynthesis is summarised
by the equation:
carbon dioxide + water == light
energy/chlorophyll ==> glucose + oxygen
is the process by which plants make food, for themselves, and for most
animal life, including us too!
The chlorophyll is in structures
The carbon dioxide diffuses in
through the stomata of the guard cells - effectively pores that can open and
close ie CO2 in, and oxygen O2 out in the day and O2
in at night.
b) Know that during photosynthesis:
light energy is absorbed by a green substance called chlorophyll, which is
found in chloroplasts in some plant cells and algae,
this energy is used by
converting carbon dioxide (from the air) and water (from the soil) into
oxygen is released as a by-product.
c) Know that the rate of photosynthesis
may be limited by:
(i) shortage of light (usually
sunlight) slows photosynthesis - since the greater the light
intensity, the greater the rate of photosynthesis
(ii) low temperature, slows down
the rate of photosynthesis - a general rule for all chemical reactions
(iii) shortage of
carbon dioxide will also slow down the rate of photosynthesis,
So these are three factors
affect the rate of photosynthesis - see the three graphs below.
d) Know that light, temperature and the
availability of carbon dioxide interact and in practice any one of them may
be the factor that limits photosynthesis.
e) Know that the glucose produced in
photosynthesis may be converted into insoluble starch for storage in leaves,
roots and stems.
The insoluble nature of starch
makes it a very useful concentrated chemical store of energy - if it was
soluble, it would dissolve and diffuse all over the place.
Know that plant
cells use some of the glucose produced during photosynthesis for
respiration - release of energy to power the cell functions.
Plants need energy from sugars
to power their own life supporting systems just as we do.
The energy released enables the
plant to convert glucose plus other elements/ions like nitrogen/nitrate into
other essential useful chemical substances - some are listed below.
f) Know that some glucose in plants
and algae is used:
to produce fat or oil for storage
- sources of energy via aerobic respiration, seeds contain food stores based
on oils and fats (think of cooking oil from olives or sunflower seeds),
cellulose, which makes up and strengthens the cell walls eg of the xylem and
to produce proteins after amino
acids are first synthesised from glucose and nitrate ions.
g) Know that to produce proteins, plants
also use nitrate ions that are absorbed from the soil.
GCSE Science-Biology courses
AQA GCSE Science A BIOLOGY *
EDEXCEL GCSE Science BIOLOGY
OCR GCSE 21st Century
Science A - BIOLOGY * OCR GCSE Gateway
Science A BIOLOGY
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