Revision notes for Biology

I wrote these notes for my Biology common test revision, but it doesn't cover everything. Hope you'll find them useful.

*there may be typos coz I didn't proofread. sorry. And some pages are incomplete, especially the ones on respiration coz I didn't bother to draw arrows using the computer to show substances involved.

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  • Created by: saraht
  • Created on: 25-09-11 15:07
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Mineral requirement of plants
Element Form in soil Main function Deficiency symptom
Nitrogen (N) NO3- and NH4+ Synthesis of protein and Poor growth
chlorophyll Yellow leaves (appear in
older leaves first)
Phosphorus PO43- Synthesis of nucleic acids Poor growth, particularly
(P) and some proteins roots
Required in some Necrosis: purple patches
enzymatic reactions form on leaves
Potassium (K) K+ Promotes photosynthesis Poor growth
and transport in plants Curled up leaves with
Required in some dark-coloured edges
enzymatic reactions
Magnesium Mg2+ Synthesis of chlorophyll Poor growth
(Mg) as Mg is part of the Yellow leaves
Transport in plants
Xylem vessels Phloem sieve tubes Companion Cells
Shape/Form Continuous Hollow Cylindrical cells Narrow cells
Tubes forming long tubes
Functions Transport water & Transport organic Support activities
dissolved minerals solutes of sieve tubes
Direction of Upwards Upwards/downwards
transport (root leaves) (site of production
storage/need; site of
storage need)
Living/dead cells Dead Living Living
Cytoplasm Absent Present (in strands) Present
Nucleus Absent Absent Present
Lignified cell wall Present Absent Absent
End wall between Disappeared Perforated, forming
cells sieve plates
*Phloem = translocation (from source to sink). Explained by Mass Flow Hypothesis.
Water on mesophyll cells surfaces evaporate in to the intercellular space vapours
are lost through diffusing out of the stomata
Loss of water vapour from intercellular space is replaced by evaporation of water
from mesophyll cells around the space water potential in these mesophyll cells
With a lower water potential, the mesophyll cells draw water from neighbouring
cells by osmosis. A water potential gradient is created between neighbouring cells
which continue to draw water from their neighbouring cells

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Eventually, water is drawn from the xylem vessels by osmosis, which creates a force,
the transpiration pull, which draws water up the xylem vessel from the roots.
*Xylem has the lowest water potential, followed by cortex.…read more

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Bubble potometer = measure the rate of WATER UPTAKE by leafy shoot.
Assumption: the rate of water uptake = rate of transpiration (i.e. most water
absorbed is used to compensate for water loss. However, some water is actually
retained in plant for support and some are used as reagents for chemical reactions)
Rate of movement of bubble is measured. Tap of reservoir remains CLOSED.…read more

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Structures and functions of various parts of a flower
Flower Part Structure Function
Calyx Consists of sepals Protects flower bud
Corolla Consists of petals Protects inner parts of flower
Maybe brightly coloured to attract insects
May have nectaries that secrete nectar for insects
to feed on
May have insect guides to attract insects
Stamen Consists of filament Anther produce pollen grains that carry male
and anther gametes
Carpel Consists of stigma, Stigma receives pollen grains
style and ovary Ovary produces ovules that contain ova
Insect-pollinated…read more

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Asexual reproduction VS Sexual reproduction in plants
Vegetative propagation Production of flowers and seeds
(asexual reproduction) (sexual reproduction)
Advantages Disadvantages
Desirable characteristics can be Unfavourable characteristics may be
retained (genetically identical) created during meiosis & fertilization
No external agents External agents required for
pollination, seed and fruit dispersal
Offspring obtain food directly from Food stored in seeds is limited; seeds
parents may fail to germinate (unfavourable)
Occurs at a relatively fast rate (can Occurs at a relatively slow rate (have
grow vegetative parts during growth)…read more

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Amniotic fluid
Protects foetus against mechanical shock
Provides a stable environment
Prevent desiccation
Allows foetus to move
*umbilical vein oxygenated blood; umbilical arteries deoxygenated blood
Growth = irreversible increase in SIZE and MASS
Cell division: through mitotic cell division, the number of cells
Cell enlargement: assimilation of food substances + synthesis of new materials
size of cells
Development = irreversible change in FORM and COMPLEXITY
Results from cell differentiation
Differentiation: the process of forming specialised cells to carry out different
Similar types of specialised…read more

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Growth curve
height / dry mass / size
*shape of the curve
depends on parameter
*typical sigmoid growth
: Lag phase slow growth
: Log/acceleration phase rapid growth
: Exponential phase maximum growth rate
: Deceleration phase growth rate decreases
: Stationary phase remains unchanged
Maintaining energy flow in ecosystem, provide the basic food source, maintain a
constant O2 ­ CO2 balance
Structure of a leaf Adaption to photosynthesis
Leaf Broad and flat Provides a large surface area for absorbing sunlight…read more

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Structure of a chloroplast Adaption to photosynthesis
Stroma Jelly like fluid Contains enzymes that catalyses photosynthetic
Thylakoid Membranous sacs with Provides a large surface area to pack chlorophyll
space inside
Large in numbers;
arranged in stacks (grana)
Grana are interconnected Allows efficient transport of photosynthetic products
with the chloroplast
1 Photochemical reactions (thylakoids chlorophyll)
Photophosphorylation (e- transport chain): ATP for next stage
Photolysis of water (NADPH) produce O2
2 Carbon fixation: Calvin cycle (stroma)
CO2 fixation RuBP + CO2 2GP (use 4ATP)
2GP 2TP…read more

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Aerobic respiration
C6H12O6 + 6 O2 6 CO2 + 6 H2O
1 Glycolysis (cytoplasm)
glucose 2 TP 2 pyruvate (**net gain of 2 ATP)
2 Krebs cycle (matrix)
Oxidative decarboxylation
2 pyruvate 2 acetyl-CoA (2-C)
2 acetyl-CoA + 2 oxaloacetic acid 2 TCA
2 TCA 2 oxaloacetic acid
3 Oxidative phosphorylation + e- transport system (cristae)
Stage ATP (direct) H­donor ATP (from H) Total ATP
Glycolysis 2 2 NADH 8
Oxidative decarboxylation 0 2 NADH 6
Krebs cycle 2 24
Total…read more

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Photosynthesis VS Respiration
Respiration Photosynthesis
Site of All living cells (cytoplasm and Chloroplast-containing cells
occurrence mitochondria)
Type of Catabolism; breaks down organic Anabolism; builds up organic food
metabolism food by oxidation to release by reduction to store energy
Energy change Chemical energy in food is Light energy from the sun is
converted to ATP and heat converted to chemical energy in
Cyclic reactions Krebs cycle: Calvin cycle:
CO2 is removed from substrate CO2 is fixed into the cycle by RuBP
Forms NADH and…read more


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