This document provides information about various biology concepts for SPM examination preparation. It contains definitions and explanations of facilitated diffusion, active transport, osmosis, animal and plant cell responses in different solutions, enzyme function, meiosis and digestion. The key points covered are the mechanisms of transport across cell membranes, osmosis and its effects, enzyme characteristics and roles, phases of meiosis, and the stages and processes of digestion in the mouth, stomach and small intestine.

1. BIOLOGY FORM4&5 ikmal hafizah
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COLLECTION OF BIOLOGY
ESSAYS FOR SPM
PREPARED BY :
- MOHD IKMAL BIN ASMUNI
- NUR HAFIZAH BINTI SAZALI
A+ALLAH HELPS THOSE
WHO HELP THEMSELVES
YOU AND ME A+ BIOLOGY

2. BIOLOGY FORM4&5 ikmal hafizah
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Facilitated Diffusion Active Transport Animal and plant cells in an isotonic solution
y For water soluble molecules//molecules
which are not soluble in lipids (ions,
nucleic acid, amino acids and glucose)
y Carrier Protein
y The carrier protein function by
binding to the molecules to pass
through the plasma membrane.
y The molecules move to the carrier
protein which is specific for the
molecules.
y Molecules bind with the carrier
protein at the active site.
y Carrier protein changes its shape and
pass the molecules through the
plasma membrane.
Movement of molecules or ions against
the concentration gradient across the
plasma membranes.
Requires both carrier proteins and
expenditure of energy.
Energy from ATP (adenosine
triphosphate) that is generated during
respiration in the mitochondria.
Has active sites which bind to the ATP
molecules.
The carrier protein changes shape when
the phosphate group from the ATP
molecule binds to it
Then the solute is moved across the
plasma membrane.
y Solution in which the solute concentration
is equal to that of the cytoplasmic fluid.
y Water diffuse in and out of the cells at
equal rate.
y No net movement of water.
y Cells retain its normal shape.
Phagocytosis Simple Diffusion Osmosis: the diffusion of water
y The pseupodia are also used for feeding.
y Amoeba sp. engulfs food by phagocytosis.
y Amoeba sp. is a holozoic organisms which
feed on microscopic organisms such as
bacteria.
y The presence of food causes Amoeba
sp.to advance by extending its pseupodia.
y The pseupodia encloses the food which is
then packaged in food vacoule.
y The food vacoule fuses with lysosome and
the food is digested by hydrolitic enzyme
called lysozyme.
y The resulting nutrients are absorbed into
the cytoplasm.
y Net movement of molecules or ions from
a region of higher concentration to a
region of lower concentration.
y Going down concentration gradient until
an equilibrium is achieved.
y The particles are distibuted equally
throughout the system.
y The concentration gradient provides
energy to move the molecules into and
out of the cells.
y Net movement of freely moving water
from a region of lower solute
concentration to a region of higher solute
concentration through a semi-permeable
membrane.//
y Net movement of water from region
higher water concentration to a region of
lower water concentration.//
y Net movement of water from hypotonic
region to hypertonic region.
**Choose any one

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Hypotonic solution Hypertonic solution Preservation of fish and vegetables
Concentration of solute outside a cell is lower
than concentration ofsolute inside cell.
Animal cells
y Is said to be hypotonic solution.
y Cell placed in hypotonic solution.
y Net movement of water into the cells via
osmosis.
y Cell swells up.
y When extremely hypotonic, cells will
eventually burst
y Cannot withstand the osmotic pressure
because of thin plasma membrane.
y E.g : red blood cells (haemolysis)
Plant cells
y Do not burst
y Rigid cell wall.
y Water diffuse into vacoule of cell via
osmosis.
y Cell swells up and becomes turgid
y Tugor pressure in plant.
y Supporting the plant.
The concentration of solute in the solution is
higher than the concentration of solutes within
the cell.
Animal cells
y Net movement of water from inside to
the outside of the cell.
y Cells shrink//shrivel, internal pressure
decrease.
y Red blood cells immersed in hypertonic
solution , the cell shrink and the plasma
membrane crinkles up.
y Cell undergone crenation.
Plant cells
y Water diffuse out via osmosis.
y Vacoule and cytoplasm shrink and plasma
membrane pulls away from the cell wall.
y This process called plasmolysis.
y Cell becomes flaccid.
Fish
y Fish is covered by salt solution which is
hypertonic to body fluid/cell/tissue.
y More water diffuses out from tissues into
salt solution via osmosis.
y Fish becomes hydrated.
y Prevents bacterial growth in fish tissues.
y Bacteria cells are also
plasmolysed//crenated.
y Prevent decay/last longer.
Vegetables
y Vegetables are immersed in vinegar which
is acidic//has low pH.
y Vinegar diffuses into vegetables tissues.
y Vegetables tissues becomes acidic//has
low pH.
y Prevents bacterial growth in tissues.
y Preventing decay//last longer.

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Differences between facilitated diffusion and active transport
Facilitated diffusion
But
Active transport
D1
E1
Down the concentration gradient
Molecules moves from higher concentration to lower
concentration
Against the concentration gradient
Molecules moves from lower concentration to
higher concentration
D2
E2
Molecules move in both direction across the plasma
membrane
Molecules can move through pore protein or/and carrier
protein
Molecules move in one direction across the plasma
membrane
Molecules move through carrier protein
D3
E3
No ATP/energy used
Molecule can move through pore protein without binding
ATP/energy is used
Energy needed for binding/bind with active site
D4 Molecules need carrier protein and pore protein to help
the movement
Need carrier protein only to help movement
D5 Could achieve equilibrium Will not achieve equilibrium/result in accumulation
D6 Not depended in cellular respiration Depend on cellular respiration/energy
Similarities between facilitated diffusion and
active transport
The Importance of water General characteristics of enzymes
y Both (ways of transportation)need carrier
protein.
y To bind with
molecules/ion/substrate/examples
y Both transport specific molecules only.
y Because the carrier protein have specific
site to certain molecules.
y Both processes occur in living cell.
y Because carrier protein need/can change
shape to allow substances to move across.
y Water is a polar molecule and act as a
solvent.
y Transport medium in the blood,
lymphatic, excretory and digestive
systems and in the vascular tissues of
plant.
y As a medium for biochemiocal reaction.
y Helps in lubricant.
y Regulates/maintaining body temperature.
y Providing support to the cell.
y High surface tension and cohesion.
y Providing miosture (respiratory surfaces
such as alveoli).
y Maintaining osmotic balance and
turgidity.
y Alter or speed up the rates of chemical
reactions
y Remain unchanged at the end of reaction.
y Do not destroyed by reactions they
catalysed.
y Have specific sites called active site to
bind with specific substrates.
y Needed in small quantities.
y Reaction are reversible
y Can be slowed down or stopped by
inhibitors. E.g: lead and mercury
y Require helper molecules, called
cofactors.
y Inorganic cofactor : ferum, copper
y Organic cofactor: water soluble vitamins,
B vitamins .

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Extracellular enzyme ͚Lock and key͛ hypothesis Effects of temperature on enzyme activity
y Extracellular enzyme is produced in a cell,
then packed and secreted from the cell.
It catalyses its reaction outside the cell.
An example is amylase.
y The nucleus contains DNA which carries
the information for synthesis of enzymes.
y Protein that are synthesised at the
ribosomes are transported through the
spaces within the rough ER.
y Proteins that depart from the rough ER
wrapped in vesicles tehat bud off from the
membrane of the rouhg ER.
y These transport vesicle then fuse with the
mebranes of the golgi apparatus and
empty their contents into the
membranous space.
y The proteins are further modified during
their transport in the Golgi apparatus. For
example, carboohydrates are added to
protein to form glycoproteins.
y Secretory vesicles containing these
modified protein bud off from the Golgi
apparatus and travel to the plasma
membrane.
y Enzymes are released.
y The substrate molecule fits into the active
site of the enzyme molecule.
y The substrate is the ͚key͛ that fits into the
enzyme ͚lock͛.
y Various types of bonds such as hydrogen
and ionic bonds hold the substrate
y in the active site forming the enzyme-
substrate complex.
y Once the complex is formed, the enzyme
changes the substrate to its product.
y The product leaves the active site.
y The enzyme is not altered by the reaction
and it can be reused.
y At low temperature, reaction takes place
slowly.
y As temperature increases, movement of
substrate increase.
y Increase their chances of colliding with
each other and with the active site of the
enzymes.
y At optimum temperature, the reaction is
at maximum rate.
y Beyond the optimum temperature, rate of
reaction will not increase.
y Bonds that hold enzyme molecules begin
to break.
y Actives sites destroyed.
y Enzyme denatured.
Prophase Metaphase Anaphase
y Chromosomes in the nucleus condense.
y Chromosomes appear shorter and thicker.
y Consist of sister chromatid joined at the
centromere.
y Spindle fibres begin to form.
y Centrioles migrate at opposite poles.
y At the end, nucleolus disappears and the
nuclear membrane disintegrates.
y Chromosomes align at the metaphase
plate//equatorial plate//middle of the
cell.
y Mitotic spindle are fully formed.
y Two sister chromatids are still attached to
one another at the centromere.
y Ends when the centromere divides.
y Two sister chromatids separate at the
centromere.
y Sister chromatids pulled apart at opposite
poles.
y Chromatids are referred to as daughter
chromosomes.

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Telophase Cytokinesis Uncontrolled mitosis
y Chromosomes reach the opposite poles of
the cell.
y Chromosomes uncoil and revert to their
extended state(chromatin).
y Process of cytoplasmic division.
y Begins before nuclear division is
completed.
y Actin filament formed contractile ring.
y Contracts and constrict pull aring of
plasma membrane inwards.
y Groove of cleavage furrow pinches at the
equator between two nuclei.
y Vesicles join to form a cell plate.
y Cell plate grows until it edges fuse with
the plasma membrane of the cell. Cell
divides.
y Cellulose are produced by the cell to
strengthen the new cell walls.
y Cell divides through mitosis repeatedly
without control.
y Produce cancerous cells.
y Cancer is a genetic disease caused by
uncontrolled mitosis.
y Disruption of cell cycle.
y Cancerous cells divides freely and
uncontrollably not according to the cell
cycle.
y These cells compete with surrounding
normal cells for energy and nutrients.
y Cancer cells formed tumour.
y Tumour invade and destroy neighbouring
cells.
Animal cloning Tissue culture Advantages of cloning
y Somatic cells (from the mammary gland
cells) are removed and grown in a culture.
y Cells stop dividing and enter a non-diving
phase.
y Unfertilised egg is obtained. The nucleus
is sucked out, leaving the cytoplasm and
organelles without any chromosomes.
y Electric pulse stimulates the fusion
between the somatic cells and egg cell
without nucleus.
y Cells divide repeatedly forming an
embryo.
y The embryo is then implanted in a
surrogate mother.
y The cloned sheep of the somatic cell
donor is born.
y Small part of plant is cut. E.g : shoots, bud.
y The part is called explant.
y Enzymes are used to digest the cell walls
of tissue.
y Cells are naked (protoplast).
y Explant/protoplast are steriled then
placed in a glass container which contains
a nutrient solution.
y Culture medium (glucose, amino acids).
y Apparatus must be steriled to make sure
free from microorganisms (bacteria).
y pH and temperature must be at optimum
level.
y Explant divides by mitosis.
y Develops into callus.
y Callus develops into somatic embryo
(planlet).
y Then transferred to soil for growth.
y Biotechnologists to multiply copies of
useful genes or clones.
y Clones can be produced in a shorter time
and in large numbers.
y Cloned plants, however, can produced
flowers and fruits within a shorter period.
y Clones are better quality.
y Delayed ripening.
y Does not need polinating agents.
y Propagation can take place at any time.

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Synthesis of enzymes
1. The information for the synthesis of enzymes is carriied by the DNA
- The sequences of bases on the DNA are codes to make proteins
2. In the nucleus, the DNA double helix unwinds and exposes its two strands for the synthesis of a messenger RNA (mRNA) strand
- The messenger RNA is synthesised according to the instruction on the DNA
3. The messenger RNA then leaves teh nucleus and moves to a ribosome
4. The messenger RNA attaches itself to the ribosome
- The ribosome acts as a workbench for the messenger RNA
- The messenger RNA contains information which codes for the sequence of amino acids
5. This genetic information is translated into the primary structure of specific protein
6. Each amino acid is bonded to the next and as a result, a chain of amino acids (polypeptide) is formedand is ready for release into the cytoplasm.
Disadvantages of cloning Meiosis I Meiosis II
y Long-term side effects are not yet known.
y May undergo natural mutations. Disrupt
the natural equilibrium of an ecosystem.
y Clones do not show any genetic
variations.
y Has the same level of resistance towards
certain disease.
y Certain transgenic crops contain genes
that are resistant to herbicides.
y These genes may be transferred to weeds
through viruses. These weeds would then
become resistant to herbicides.
y Cloned animals has shorter lifespan.
1. During prophase I, homologous
chromosomes pair up (synapsis) and
crossing over between non sister
chromatids occurs.
2. During Metaphase I, homologous
chromosomes align at the metaphase
plate (equator, middle) of the cell.
3. During Anaphase I, homologous
chromosomes separates and move to
opposite poles. Sister chromatids are still
attached together and move as a unit.
4. At the end of Telophase I, two haploid
daughter cells are formed. Each daughter
cell has only one of each type of
chromosomes, either the paternal or
maternal chromosomes.
1. During Prophase II, synapsis of
homologous chromosomes and crossing
over between non-sister chromatids do
not take place.
2. During Metaphase II, chromosomes
consisting of two sister chromatids align
at the metaphase plate (equator/middle)
of cell.
3. During Anaphase II, sister chromatids
separate, becoming daughter
chromosomes that move to opposite
poles.
4. At the end of Telophase II, four haploid
daughter cells are formed. Each daughter
cell has the same number of
chromosomes as the haploid cell
produced in Meiosis I, but each has only
one of the sister chromatids.

8. BIOLOGY FORM45 ikmal hafizah
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Digestion in mouth Digestion in stomach Digestion in small intestine
y Secretion of saliva by three pairs of
salivary glands
y Saliva contains the enzyme salivary
amylase
y Begins the hydrolysis of starch to maltose.
Starch + water maltose
y An additional digestive process occurs
further along the alimentary canal to
convert maltose to glucose.
y pH is maintained at 6.5-7.5
y Epithelial lining of the stomach contains
gastric glands.
y These glands secrete gastric juice.
Consists of mucus, HCL and enzyme
pepsin and renin.
y HCL make the pH around 2.0.
y High acidity destroy bacteria.
y Acidity stop the activity of salivary
amylase enzyme.
Protein + water polypeptides
y Renin coagulate milk by converting the
soluble milk protein, caseinogen into
soluble caesin.
y Stomach contents become a semi-fluid
called chyme.
y Chyme gradually enter the duodenum.
y Duodenum received chyme from stomach
and secretion from the gall bladder and
pancreas.
y Starch, protein and lipids are digested.
y Bile which produced by the liver and
stored in the gall bladder enter the
duodenum via the bile duct.
y Bile helps neutralise the acidic chyme and
optimise the pH for enzyme action in
duodenum.
y Bile salts imulsify lipids, breaking them
down into tiny droplets.
y Providing high TSA for digestion.
y Pancreas secrete pancreatic juice into
duodenum via pancreatic duct.
y Pancreatic juice contains pancreatic
amylase, trypsin and lipase.
y Pancreatic amylase complete the
digestion of starch to maltose.
y Trypsin digests polypeptides into
peptides.
y Lipase complete the digestion of lipid into
fatty acid and glycerol.
y Glands in the ileum (small intestine)
secrete intestinal juice which contain
digestive enzyme needed to complete the
digestion of peptides and disaccharides.
y Peptides digested by erepsin into amino
acids.
y Maltose digested by maltase into glucose.
y Disaccharides digested by its own enzyme
into monosaccharides and glucose.
Salivary amylase
pepsin

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Digestion of cellulose by ruminant Digestion of cellulose by rodent Digestion
y Partially chewed food is passed to the
rumen (largest compartment of the
stomach).
y Cellulose is broken down by cellulase
produced by bacteria.
y Part of the breakdown products are
absobed by bacteria, the rest bythe host.
y Food enters the reticulum.
y Cellulose undergoes further hydrolysis.
y The content of the reticulum, called the
cud, is then regurgitated bit by bit into the
mouth to be thoroughly chewed.
y Helps soften and break down cellulose,
making it more accessible to further
microbial action.
y The cud is reswallowed and moved to the
omasum.
y Here, the large particles of food are
broken down into smaller pieces by
peristalsis.
y Water is removed from the cud.
y Food particles moved into obamasum, the
true stomach of the ruminant. (e.g : cow).
y Gastric juice complete the digestion of
protein and other food substances.
y The food then passes through the small
intestine to be digested and absorbed in
the normal way.
y Caecum and appendix are enlarged to
store the cellulose-digesting bacteria.
y The breakdown products pass through the
alimentary canal twice.
y The faeces in the first batch are usually
produced at night.
y Faeces are then eaten again. To absorb
the products of bacterial breakdown.
y The second batch of the faeces are harder
and drier.
y Allows rodent (give example) to recover
the nutrients initially lost with the faeces.
y Protein
- In stomach, pepsin breakdown
protein into polypeptides.
- HCL being secreted to provide acidic
medium for the digestion to occur.
- In duodenum, trypsin breakdown
polypeptides into peptides.
- In small intestine, arepsin break dwon
peptides into amino acids.
y Fats
- Bile salts breaking up fats into small
fat droplets in the duodenum.
- In duodenum/small intestine, lipase
breaks lipids into fatty acids and
glycerol.
y Carbohydrates
- In mouth, salivary amylase hydrolyse
starch into maltose.
- In duodenum, pancreatic amylase
hydrolyse starch into maltose.
- In small intestine, maltase hydrolyse
maltose into glucose.

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Absorption of digested food Assimilation of digested food Formation faeces
y Absorption of digested food occur in the
ileum.
y Glucose/amino acids initially diffuse into
blood capillaries.
y The remaining of the glucose/amino acids
actively transport into blood capillaries.
y All blood capillaries converge into hepatic
portal vein, which lead to the liver (and
transport to all parts o fthe body).
y Glycerol and fatty acids diffuse to the
epithelial cell which lining the ileum) and
combine to form fat droplets.
y Fatty acids and glycerol then enter the
lacteal (lymphatic system).
y Return back to the blood stream at left
subclavian vein.
Explain the assimilation of glucose and amino acid
in body cells.
y Glucose is oxidised to produce energy,
carbon dioxide and water by cellular
respiration.
y Amino acid is used to synthesis
protoplasm (the component of cell). By
this way new cells will be synthesised
causing growth.
y Amino acid also can be used to synthesis
enzyme, hormone or antibody.
y Faeces which contain dead cells that are
shed from intestinal linings, toxic
substances and bile pigments enter the
colon by action of peristalsis.
y In colon, more water is absorbed. The
undigested food residues harden to
become faeces.
y Faeces contain undigestible residues that
remain after the process of digestion and
absorption of nutrients that take place in
the small intestine.

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Photosynthesis mechanism Photosynthesis mechanism Uses of enzyme (Chapter 4)
y The formation of starch in plants is by the
process ofphotosynthesis which occurs in
chloroplasts.
y The two stages in photosynthesis are the
light and dark reactions.
y Light reaction:
y P3:Takes place in grana.
y P4: Chlorophyll captures light energy
which excites the electrons of chlorophyll
molecules to higher energy levels.
y P5: In the excited state, the electrons can
leave the chlorophyll molecules.
y P6: Light energy is also used to split water
molecules into hydrogen ion (H+) and
hydroxyl ions (OH-) (Photolysis of water).
y P7: The hydrogen ions then combine with
the electrons released by chlorophyll to
form hydrogen atoms.
y P8: The energy from the excited electrons
is used to form energy-rich molecules of
adenosine triphosphate /ATP.
y P9: Hydroxyl ion loses an electron to form
a hydroxyl group. This electron is then
received by chlorophyll.
y P10: The hydroxyl groups then combineto
form water and gaseous oxygen.
y Dark Reaction:
y P11: Take place in stroma.
y P12: Do not require light energy.
y P13: The hydrogen atoms are used to fix
carbon dioxide in a series of reactions
catalysed by photosynthetic enzymes
y P14: and caused the reductionof carbon
dioxide into glucose.
y P15: The glucose monomers then undergo
condensation to form starch which is
temporarily stored as starch grains in the
chloroplasts.
y Enzymes are used as biological
detergents.
· Protease degrades coagulated proteins
into soluble short-chain peptides.
· Lipase degrades fat or oil stains into
soluble fatty acid and glycerol.
· Amylase degrades starch into soluble
shorter-chain polysaccharides and sugars.
y Enzymes are used in the baking industry.
· Protease is used in the breakdown of
proteins in flour for the production of
biscuits.
· Amylase is used in the breakdown of
some starch to glucose in flour for making
white bread, buns and rolls.
y Enzymes are used in the medical field.
· Trypsin is used to remove blood clots
and to clean wounds.
· Various other enzymes are used in
biosensors.
y Enzymes are used in industries because:
·They are effective.
·They are cheap and easy to use.
·They can be re-used, thus only small
amounts are needed.
· They don't require high temperature to
work, thus this reduces fuel costs.

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Aerobic respiration Anaerobic respiration in human muscle Anaerobic respiration in yeast
y Continuous supply of oxygen.
y Glucose molecules are oxidised by
oxygen.
y Complete breakdown of glucose in the
presence of oxygen.
y A large amount of energy released.
y Carbon dioxide and water are produced as
waste products.
y Most of the nergy released is used to
synthesise adenosine triphosphate (ATP)
from adenosine diphosphate (ADP) and
inorganic phosphate.
y ATP acts as instant energy source.
y ATP consists of phosphate bonds which
can be easily broken down to release
energy.
ATP ADP + phosphate + energy
y During a vigorous exercise (running), the
breathing rate is increased.
y This is to supply more oxygen to the
muscles for rapid muscular contraction.
y However, the supply of oxygen to muscles
is still insufficient.
y and the muscles have to carry out
anaerobic respiration to release energy.
y The glucose is converted into lactic acid,
with only a limited amount of energy
being produced.
y An oxygen debt builds up in the body,
when no oxygen use in energy production.
y High level of lactic acid in the muscles
cause them to ache.
y After running, the athlete breathes more
rapidly and deeply than normal for
twenty minutes.
y There is recovery period after 10 minutes
until it reaches 20 minutes when oxygen is
paid back during aerobic respiration.
y About 1/6 lactic acid is oxidized to carbon
dioxide, water and energy.
y Yeast normally respires aerobically.
y Under anaerobic condition, yeast carry
out anaerobic respiration.
y Produces ethanol.
y Process known as fermentation.
y Catalysed by the enzyme zymase.
- Ethanol produced can be used in
making wine and beer.
- In bread making, the carbon dioxide
released during fermentation of yeast
causes the dough to rise.
Similarities between the sturucture of digestive and digestion processof ruminants and rodents
S1 y Both alimentary canal contains bacteria/protozoa
P1 y To secrete extracellular enzyme//to digest
P2 y To digest cellulose into glucose
S2 y Both have large surface area
P1 y To increase rate of diffusion //hydrolysed food
Energy released

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Differences between the sturucture of digestive and digestion processof ruminants and rodents
Aspects Ruminant (has)
But
Rodent (has)
Number of stomach chamber D1
E1
4 stomach chamber
Have to digest cellulose
1 stomach chamber
Do not have to digest cellulose
Size of caecum D2
E2
Small//short caecum
Do not digest cellulose
Big//long size caecum
A place to digest cellulose
Bacteria D3
E3
In reticulum
For secrete cellulase enzyme
In caecum
For secrete cellulase enzyme
Number of times yhe food passes
through the stomach chamber
D4
E4
Twice
To complete the digestion//
Once
To absorb digested food
Regurgitated D5 Twice in mouth cavity Once in mouth cavity
Breathing mechanism in man Breathing mechanism in man (continuation) Transport of O2 and CO2 in human body
y Diaphragm is a muscular sheet in the
body cavity separating the thorax from
the abdomen.
y At the start of inhalation, the muscles of
the diaphragm contract , making it less
arched.
y This helps to increase the volume of the
thoracic cavity and reduce the pressure
of the thoracic cavity. Air rushes into the
lungs.
y When the muscles of the diaphragm
relax , it returns to its arched condition ,
reducing the volume of the thoracic
cavity and increasing the pressure of the
thoracic cavity. Air is forced out of the
lungs.
y The muscles between the ribs areknown
as intercostals muscles.
y During inhalation the external
intercostals muscle contracts and raise
the lower ribs.
y This helps to increase the volume of the
thoracic cavity and reduce the pressure of the
thoracic cavity. Air rushes into the lungs.
y During exhalation the external intercostals
muscles contract , the ribs return to their
original position , reduce the pressure of the
thoracic cavity. Air is forced out of the lungs.
y The alveoli are thin-walled air sacs with the
lungs.
y These sacs are surrounded by a network of
capillaries.
y During inhalation the alveoli are filled with
air and gaseous exchange occurs between the
alveoli and the capillaries.
y Oxygen from the alveoli diffuses into the
capillaries while carbon dioxide diffuses from
the capillaries into the alveoli.
y Gaseous exchange across the alveolus
occurs by diffusion.
y Diffusion of gas depends on differences
in partial pressure between two regions.
y The partial pressure/ concentration of
oxygen in the air of the alveoli is higher
compared to the partial pressure/
concentration of oxygen in the blood
capillaries.
y Therefore, oxygen diffuse across the
surface of the alveolus and blood
capillaries into blood.
y The transport of oxygen is carried out by
the blood circulatory system.
y Oxygen combines with respiratory
pigment called haemoglobin in the red
blood cells.
y To form oxyhaemoglobin.
y When the blood passed the tissue with
low partial pressure of oxygen,

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Transport of O2 and CO2 in human body
(continuation)
Explain how energy flows through the food chain
and how it is lost to the environment.
Colonisation and succession in mangrove
swamps
y Oxyhaemoglobin dissociates to release
oxygen.
y Carbon dioxide released by repairing
cells can be transported by dissolve
carbon dioxide in the blood plasma.
y Bind to the haemoglobin.
y As carbaminohaemoglobin.
y In form of bicarbonate ions.
y Carbon dioxide is expelled with water
vapour from the lung.
y Energy flows through the food chain in one
direction .
y In the food chain, the plant is the producer,
the rat is the primary consumer, the snake is
the secondary consumer and theeagle is the
tertiary consumer.
y In the food chain, the plant is the producer,
the earthworm is the primary consumer, the
bird is the secondary consumer and the
snake/ eagle is the tertiary consumer. Each
level of food chain is called a trophic level.
y Energy is transferred from one trophic level
to another trophic level.
y When energy is transferred from one trophic
level to another level as much as 90% of the
chemical energy in the food consumed by
primary consumer is used for its metabolic
activities and lost as heat.
y Only 10% of the energy in an organism is
passed on to the organism at the next trophic
level.
y The pioneer species of a mangrove
swamp are the Sonneratia sp. and
Avicennia sp.
y The presence of this species gradually
changes the physical environment of
the habitat.The extensive root systems
of these plants trap and collect
sediments, including organic matter
from decaying plant parts.
y As time passes, the soil becomes more
compact and firm. This condition
favours the growth of Rhizophora sp.
Gradually the Rhizophora sp. replaces
the pioneer species.
y The prop root system of theRhizophora
sp. traps silt and mud, creating a firmer
soil structure over time.
y The ground becomes higher. As a result,
the soil is drier because it is less
submerged by sea water.
y The condition now becomes more
suitable for the Bruguiera sp., which
replaces the Rhizophora sp.
y The buttress root system of the
Bruguiera sp. forms loops which extend
from the soil to trap more silt and mud.
y As more sediments are deposited, the
shore extends further to the sea. The
old shore is now further away from the
sea and is like terresterial ground.
y Over time, terrestrial plants
like nipah palm and Pandanus sp. begin
to replace the Bruguiera sp.

15. BIOLOGY FORM45 ikmal hafizah
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Green house effects Explain briefly why humans carry out the activity
as shown in diagram above
Explain the impacts of the activity shown above
on the environment
y Green house effect.
y Ultra violet(uv) from solar radiation is
absorbed by the earth and some of them
is reflected back to the atmosphere in the
form of heat/infra red.
y Heat or infrared radiation cannot be
reflected back to the atmosphere.
y Because it is trapped by green house
gases such as CO2, nitrogen dioxide and
methane.
y Heat/infrared warmed the surface of
earth.
y Earth temperature increases.
y The human population grows rapidly. The
demands for food and housingareas have
increased.
y Vast areas of forest are cleared for
agricultural and commercial purposes.
y Urbanization and industrialization have
caused more forests to be cleared for
road construction and housing areas.
y Deforestation is also caused by the
demands for timber and fuel wood.
y Deforestation causes soil erosion ,
landslides, flash floods and global
warming.
y Causes the soil to become loose and less
stable.
y Without the protection of green plants,
the soil is exposed to the forces of wind
and rain.
y The top layer of soil is washed away
gradually by the rainwater.
y This is known as soil erosion.
y Soil erosion causes the depletion of
minerals from the soil, therefore the soil
becomes infertile and unsuitable for
agriculture.
y Landslides may happen on steep hillsides
during heavy rain.
y It is because rainwater flows quickly and
causes the top layer of the soil to
crumble.
y Rivers and drains are silted and the flow
of water is blocked.
y Therefore, water flows inland and this
causes flash floods in the lower areas
during rainy seasons.

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Human blood vessels Circulatory system in fish and human Blood clotting
Arteries
carries blood away from heart
transport blood quickly, at high pressure
muscle of tissue enables the artery to
constrict and dilate
walls of arteries are strong and elastic,
have small lumen
Capillaries
thin walled blood vessels
allow rapid gaseous exchange via diffusion
nutrients, wastes and hormones are also
exchanged across here
one cell thick
Veins
blood returns from capillaries to heart
through veins
blood flows in low pressure
have large lumens and valves (prevent
back flow)
Similarities
both have closed circulation
both have a heart
Differences
Fish Human
Has single circulation Has double circulation
Heart divides into 2
chambers
Heart is divided into 4
chambers
Septum is absent Septum is present
Deoxygenated blood
flows from heart to
gills
Deoxygenated blood
flows from heart to
lungs
Oxygenated blood
flows from gills to
body cells
Oxygenated blood
flows from lungs to
heart
- clumped platelets, damaged cells, clotting
factors form activators (thromboplastins)
- activators together with calcium ions and
vitamin K, converts prothrombin to
thrombin
- thrombin catalyses the conversion of
soluble protein fibrinogen into insoluble
fibrin.
- fibrin is a fibrous protein which combines
to form a mesh of long threads over the
wounds, trapping red blood cells and
sealing the wound.
- blood clot hardens when exposed to air
forming scab
Difference between blood and lymph Type of immunity Phagocytosis
- lymph has a large numbers of lymphocyte
compare to blood
- lymphocyte is produced by lymph nodes
in lymph system
- lymph has lower content of oxygen
compare to blood
active immunity, body produces its own
antibodies in response to stimulation by
an antigen
passive immunity, body receive an
antibodies from outside source
- the phagocyte is attracted by chemicals
produced by bacterium
- Phagocytes extend its pseudopodium
(legs) towards bacterium to engulf it.
- ingestion of bacterium forms phagosome
- phagosome combines with lysosome
- lysosome releases lysozyme into
phagosome
- bacterium inside the phagosome will be
destroyed by lysozyme
- phagocyte releases the digested products
from cell
Lymph ʹ formed - brought back into the blood
circulatory system.
Respiratory gases Active immunity ʹ Passive immunity

17. BIOLOGY FORM45 ikmal hafizah
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- when blood flows from arteries into
capillaries, there is higher hydrostatic
pressure at artial end of capillaries
- high pressure causes some plasma to pass
through capillary walls into intercellular
spaces
- interstitial fluid fills the spaces between
cells and constantly bathes the cells
- 90% of interstitial fluid diffuses back into
blood capillary
- 10% of interstitial fluid goes into the lymph
capillaries and known as lymph
- lymph capillaries unite forming larger
lymphatic vessels
- from lymphatic vessels, lymph eventually
passes into thoracic duct
- hence lymph drains back into blood
Transportation in respiratory gas.
oxygen enters alveoli during inhalation
gaseous exchange occurred at alveoli
(oxygen diffused into blood capillaries
while carbon dioxide diffused out)
the diffusion of these gases caused by
different of partial pressure of both
gaseous
partial pressure of oxygen in alveoli is
higher than partial pressure of oxygen in
blood capillaries
oxygen diffused in cytoplasm of red blood
cell
oxygen combines with haemoglobin
forming oxyhaemoglobin
oxyhaemoglobin then sent to all parts of
body
heart pumped the oxygenated blood to all
body cells
oxygen diffused from blood capillaries to
cell because partial pressure of oxygen in
blood capillaries is higher than in cell
carbon dioxide diffuse from cell to blood
capillaries because partial pressure of
carbon dioxide in cell is higher than in
blood capillaries
deoxygenated blood going back to heart
by vena cava and to lungs by pulmonary
artery
Active immunity
- obtained by vaccination (artificially
acquired)
- vaccine contains dead/weakened
bacteria/pathogen/virus
- white blood cells stimulated to produce
antibodies against pathogen
- also obtained when an individual has
recovered from certain diseases(naturally
acquired)
- a ready made supply of antibody will give
immunity towards the disease
Passive immunity
- obtained by injecting
antibodies/antiserum (artificially
acquired)
- no antigen is put into body, so body does
not produce its own antibodies
- obtained by a baby when antibodies from
mother͛s blood plasma diffuse into foetus
through placenta (naturally acquired)

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Movement of water froom root to leaves Movement of water from root to leaves Effect of no lignin formation on the function of
tissue xylem
Movement of water from root to leaves aided by
root pressure, capillary action and transpirational
pull.
Root pressure
y cell sap of root hair(usually) hypertonic to
surrounding soil solution
y water diffuses into root by osmosis
y cell cap becomes more dilute compared
to neighbouring cell
y water moves to these adjacent cells which
become more diluted themselves, so
osmosis continues across the cortex
y (at the same time) ions from soil are
actively secreted into xylem vessels and
causes osmotic pressure to increase
y Water flows continuously into xylem and
create a pressure(root pressure)
y Root pressure gives an initial upward
force to water and mineral ions in xylem
Capillary action
y water moves up through xylem in stems
by capillarity
y capillary action is due to combined force
of cohesion(water molecules have
attraction for each other) and
adhesion(water molecules are attracted
to the side of vessels)
y water molecule form a continuous water
column in xylem vessel (due to cohesion
and adhesion)
y the cohesion of water prevent the water
column in xylem breaking apart
y the adhesion of water prevents gravity
from pulling the water down the column
Transpirational pull
y the lost of water from mesophyll cells
during transpiration is replaces by water
which flows in from xylem vessels in
leaves
y this creates a tension/suction force in
water column because water has cohesive
properties called transpiration pull
y the transpiration pull draws water from
xylem in the leaves/stem/roots
y the continuous flow of water through
plant is known as transpiration stream
y lignin is important to make tissue xylem
strong
without lignin, tissue xylem will collapse
therefore, it cannot form a continuous
hollow tube
to allow water to flow upwards
continuously
y lignin makes the tissue become
impermeable
materials cannot pass in xylem cells
causes the tissue to become hollow
allows continuous flow of water
(choose one of the * and the explanations below)

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light intensity and stomata and cells effect the
rate of water loss
Adaptation of the muscle which enables it to
contracts
Movement takes place involves muscles,
tendons, bones, ligaments and joints
y F1- from 0500 to 0170(time/hours), rate
of water loss increases
y E1- light intensity increases
y E2- stimulates photosynthesis in guard
cells
y E3- this makes energy available for
potassium to move into guard cells by
active transport
y E4- guard cells become
hypertonic(compared to cell sap) of
epidermal cells
y E5- water molecules from epidermal cells
diffuse into guard cells by osmosis
y E6- causing guard cells to bend outwards
y E7- stoma opens (allows water to escape)
y F2- from 0170 to 0300(time/hours) rate of
water loss decreases
y E8- lisght intensity decreases/rate of
photosynthesis decreases
y E9- guard cells become flaccid and bend
inwards
y E10- stoma closes, prevents water from
escaping
y Notes: (F1 + any 5Es) + (F2 + 3Es)
the skeletal muscle consist of bundles of
muscle fibres and a large supply of nerves
and blood vessels
a muscle fibre is made up of bundles of
smaller units called myofibrils
each myofibril is made up of 2 types of
protein filaments: the actin and the
myosin which interact and cause muscle
contractions
the muscle͛s nerve endings control its
contractions
Muscle
quadriceps femoris contract while biceps
femoris muscles relax (leg straightened)
biceps femoris contract while quadriceps
femoris relax (leg bent)
calf muscles contract to lift up the heels
feet push downwards and backwards
repeated contraction and relaxation of
muscle result in running movement
Ligaments
it connects 2 bones together
give support and strength to joints for
movement
strong and elastic
Joints
a hinge joint allow the movement of leg to
swing back and forth
Tendon
connect muscles to bones
strong and non elastic
force is transferred to bones through
tendons
Bones
femur/ thigh bone is long, heavy and
strong
provide support to body weight

20. BIOLOGY FORM45 ikmal hafizah
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Adaptation of plant which enable it to float Skeletal system of earthworm and fish adapted
for its movement
Adaptive features which helps in birds and fish
locomotion
have fine aerenchyma wall tissues (plants
become more lighter)
have air spaces/air sacs (becomes more
easy to float)
have big and swell stem/petiole (increase
the air to help plant floating)
have fine and many roots (trap gas
bubbles)
Movements in earthworm
earthworm has hydrostatic skeleton
moves by changing hydrostatic pressure
of fluid in its segment
each segment of the body has its own set
of muscles
o an outer layer of circular muscles
running around the body causes the
worm to become long and thin when
they contract
o an inner layer of longitudinal muscles
causes the worm to get short and
thick when they contract
as the circular muscles contract, the
longitudinal muscles will relax
simultaneously in antagonistic action
causes the hydrostatic pressure to be
transferred from anterior part to posterior
part causing the worm to move forward
Movements in fish
fish has an endoskeleton
it provides place for attachment of
muscles
when the left myotome contracts, right
myotome will relax in antagonistic action
causes the vertebral column to curve
toward the left
the fish also has fins with different
functions for locomotion
Bird
aerofoil wing ʹ to generate the upward lift
a pair of antagonistic muscle (pectorolis
major and minor) pulled down and up the
wings
single organ (one testes/kidney)//small
skull ʹ to reduce weight
streamlined body shapeʹ reduce air
resistance
waterproof feather ʹ avoid increase in
body weight during raining
Fish
streamed lined body ʹ reduce water
resistance
myotome muscle are W/V ʹ shaped which
act antagonistically
air sac ʹ maintain buoyancy in water
fins
o dorsal and ventral fin ʹ
prevent/helps in yawing and
rolling
o tail fin ʹ provides thrust and
controls direction
o pelvin and pectoral fin ʹ act as
brakes/to slow down

21. BIOLOGY FORM45 ikmal hafizah
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Support is achieved in submerged and floating
plants
Osteoporosis and osteoarthritis happen -
prevented
Important to have healthy musculoskeletal
system - ways maintaining a healthy
musculoskeletal
Submerged plants
posses air sacs within the leaves and the
stem to help the plant to stay upright in
water
water buoyancy provides support
have very few woody tissue/vascular
tissue
thin/narrow/flexible leaves ʹ provide little
resistance to water flow
Floating plants
stem have plenty of air sacs
aerenchyma tissues helps to stay afloat in
water
do not have woody tissues
natural water buoyancy to help them float
have broad leaves that are firm but
flexible to resist being torned by wave
action
Osteoporosis
a disease in which bone mass is reduced
and the boned become porous and lighter
occurse most often in old people, partially
women who have gone menopause
bodies of postmenopausal women do not
produce sex hormone, oestrogen
causes more bone minerals to be lost than
deposited
as a results, bones become soft and brittle
can be prevented by
o doing weight-bearing exercise,
strengthen the muscles and bones
o taking diet rich in calcium,
phosphorus and vitamin D
o takin in vitamin C, increase bone
mass
o refraining from smoking
Osteoarthritis
Osteoarthritis is part of ageing process
due to wear and tear of cartilage between
bones at certain joints
Patient has painful, swollen stiff knees
which restrict daily activities (walking,
climbing)
If treatment fails to relieve the pain, a
surgeon can replace the damaged joints
with artificial ones made of plastic or
metal
The musculoskeleton system where bones,
muscles, ligaments and tendons work together
like a machine to bring about movement
musculoskeleton helps to support our
body
if any part of system injured, we will
experience discomfort, pain and loss of
mobility
it also affect othe organs and physiological
processes in body (respiration/digestion)

22. BIOLOGY FORM45 ikmal hafizah
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Important to have healthy musculoskeletal
system - ways maintaining a healthy
musculoskeletal
Osteoarthritis and arthritis gout occur - effect of
the diseases
Support system in woody plants differs from that
of non-woody plants
Ways to maintain
having balanced diet. Take diet rich in
proteins, vitamins A, C n D together with
minerals (calcium,phosphate n iron) for
building strong bones. Drinking
fluoridated water will also harden the
bones
adopt a good posture while standing,
sitting, walking and while performing
certain tasks to ensure that our body is
always supported. This is important
because bad posture will put undue
pressure on our muscles and spine and
this will in turn affect the functions of our
internal organs (lungs, heart and stomach)
wear proper attire for daily activities.
Wear loose and comfortable clothes. Tight
clothes restrict our movement. Woman
wearing high heels tilt the body forwards.
To counteract this, the woman bendsher
knees and throws her trunk forwards,
causing the spine to curve even more
taking precautions during vigorous
activities
practice correct and safe techniques when
exercisingto prevent serious injuries to
the musculosketonn system
Muscular dystrophy
muscle destroying disorder
weakness/weaking of muscles
mostly in male
affect the heart muscle ʹ heart attack
results in poor balance/wobbling/poor
movement
Osteoporosis
condition characterized by lost of normal
density of bone
resulting in fragile bone
bone fracture
no symptom before any bone fracture
consequences ʹ fracture of
vertebrae//reduction of in height over
time//stooped posture
Non-woody plants (herbaceous plants)
(support in herbaceous plants is) provided
by the turgidity of
parenchyma/collenchyma cells
(when there is enough warm in the
ground) the cells take in water by osmosis
and become turgid
The turgor pressure of fluids in the
vacuoles pushes the cell contents/plasma
membrane against the cell wall
Creating support for its tem/roots/leaves
The thin thickening die cell walls with
cellulose/collenchyma cells gives support
to herbaceous plants

23. BIOLOGY FORM45 ikmal hafizah
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Support system in woody plants differs from that
of non-woody plants
Synapse ʹ The event as a nerve impulse is
transmitted across a synapse
Knee jerk
Woody plants
woody plants have specialized
tissues/sclerenchyma tissues/xylem
vessels.tracheids to give them support
these tissues have cellulose walls which
have deposits of lignin for added strength
sclerenchyma cells have very thick walls
(do not allow water to pass through)
(these cells are dead cells) their function is
to provide support
Xylem vessels have thick walls of lignin
which are deposited during the plant͛s
secondary growth
The lignified xylem vessels form the
woody tissues of the stem
This makes the plant stronger and also
provides support for the plant
Tracheids are also dead cells with thick
walls and very small diameters
They are found with xylem vessels and
together they support the plants
Synapse is a narrow gap between an axon
terminal and a dendrite of another
adjacent neuron. A chemical is used by
neuron to transmit an impulse across a
synapse. The chemical is called
neurotransmitter
The transmission of information across a
synapse involves the conversion of
electrical signal into chemical signal in the
form of neurotransmitter
Neurotransmitter is produced in vesicles
in a swollen part of the axon terminal
called synaptic knob
Synaptic knob contains abundant
mitochondrion to generate energy for the
transmission
When an impulse arrived at the synaptic
knob, the vesicles release the
neurotransmitters into the synapse
The neurotransmitters molecules diffuse
across the synapse to the dendrite of
another neurons
The dendrite of another neurons is
stimulated to trigger a new impulse which
travel down a long neuron
the knee jerk action involves two types of
neurons named afferent and efferent
neurons
when a hammer hits a tendon that
connect to quadriceps muscle in the thigh
to a bone in the lower leg
as the hammer strike, the force stretches
the quadriceps muscle and stimulates the
stretch receptors in the muscles,
triggering nerve impulse
afferent neurons transmit the information
to the quadriceps muscle and the muscle
contracts swing the leg forward
if the patient is able to swing the leg
forward, it indicates that the patient͛s
nerve system is still functioning
if there is no response, it shows that the
patient͛s nervous system fails to function
properly

24. BIOLOGY FORM45 ikmal hafizah
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When the hand touches a hot object Roles of cerebellum and medulla oblongata -
reflex action when finger being stung by a bee
Glomerular filtrate formed
the heat on the object stimulates the
nerve endings (receptors) in skin
impulses are triggered
impulses travel along the sensory/afferent
neuron to spinal cord
in spinal cord, the impulses are
transmitted first across a synapse to the
interneurone and then across another
synapse to the motor/efferent neurone
At synapse
when an impulse reach a presynaptic
membrane, it triggers the synaptic
vesicles to release neutrotransmitter into
the synaptic cleft
the neurotransmitter diffuse across the
synaptic cleft
and bind to receptors which are attached
to the postsynaptic membrane
the binding of the neurotransmitter to the
receptors leads to the generation of a
new impulse
impulses leave the spinal cord along the
motor/efferent neurone to the effector
the effector is the biceps muscle which
then contracts. This brings about a sudden
withdrawal of the hand
Cerebellum
coordination of movement
controls of balance/posture
Medulla oblongata
controls/increase breathing
controls/increase heart rate
controls blood pressure/sweating
Reflex action
receptors in the skin of the finger detects
pain
nerve impulse is generated in pain
receptor
electrical impulses are sent via the
afferent(sensory) neurone to spinal cord
impulses are transferred to the
interneurone in the spinal cord
interneurone sents impulses to the
efferent neurone
efferent neurone sents impulses to
biceps/muscle
biceps/muscle contract (triceps relax)
causing the arm to bend
when blood enters the glomerulus,
ultrafiltration takes place
because blood from the aorta reaches the
nephron/glomerulus at high pressure
and due to the different artiole and
efferent arteriole
the high pressure forces fluid through the
filtration membrane into capsular space
forming glomerular filtrate

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Structure and the role of nephron- formation of
urine
Formation of urine Consequences of kidney failure
Structure and the role of nephron
nephron is the functional unit of a kidney
a nephron consist of 3 major parts
(glomerulus, and its associated vessels)
the Bowman͛s capsule
a long narrow tube called the renal
tubule, which made up of proximal
convoluted tubule, loop of Henle and
distal convoluted tubule
the distal convoluted tubules of several
nephrons join to a common collecting
duct
the loop oh Henle is a long hairpin-shaped
region of the nephron that descends into
the medulla and then returns to the
cortex
ultrafiltration, reabsoprtion and secretion
blood is under relatively high pressure
when it reaches the nephron
high blood pressure in glomerulus, forces
fluid to filter through the filtration
membrane into the lumen of Bowman͛s
capsule
forming glomerular filtrate
contains water, glucose, amino acids,
mineral salts and other small molecules
the glomerular filtrate will flow into
proximal convoluted tubule
selective reabsoption occurs
by active and passive transport
forming relatively high solute
concentration in the peritubular
capillaries
thus large volume of water is reabsorbed
into the blood by osmosis
increase the concentration of urea in the
convoluted tubule
glomerular filtrate then flow into loop of
henle and distal convoluted tubule
more water and minerals being
reabsorbed back into the blood
take place in the distal convoluted tubule
urea/toxins/ammonia/ect being secreted
by passive diffusion and active transport
from blood capillary into distal convoluted
tubule
filtrate reaches the collecting duct (now
called urine). flows down the ureter, the
bladder and urethra and is finally excreted
if both kidneys stop functioning, the blood
osmotic pressure and blood volume
cannot be maintained
the built up of toxic wastes in the body
can result in life-threatening conditions
they have to undergo haemodialysis
another treatment for impaired kidney
functions is the transplant of a healthy
kidney from a donor to the patient
Avoid drug and alcohol ʹ why ʹ affects -
coordination systems
Geotropism is brought about in a plant root and
shoot - advantages
Tips of shoot contribute to growth in oat
seedlings

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Drugs
some drugs are stimulants/cocaine
increases the activities of the central
nervous system
excessive use leads to temporary
euphoria followed by depression
causes the user to see/hear/perceive
things that do not exist
some drugs like narcotic/heroin/morphine
block pain signals
induce feelings of euphoria/slows down
nerve impulses
Alcohol
strong depressant
affects coordination and judgement
inhibits releases of ADH from posterior
pituitary
less water will be absorbed into blood
stream/ more urine produced
alcohol/drugs are addictive
develop dependence on
alcohol/drugs/develop severe withdrawal
effects
long term usage can damage organs
brain damage/stomach ulcers
Shoot
the auxin that is produced at the tip of
shoot
auxin moves downwards/accumulate on
the underside of the shoot tip due to the
pull of gravity
the high concentration of auxin
accelerates the growth
stimulating greater cell elongation on the
underside relative to the cells on the
upper side
this differential elongation causes the
shoot to bend away from gravity/grow
upwards
Root
the auxin that is produced at the tip of
root
auxin moves downwards/accumulates on
the underside of the root tip due to the
pull of gravity
the hight concentration of auxin inhibits
the growth
slowing down cell elongation on the
underside relative to the cells on the
upper side
this differential elongation causes the
shoot to bend towards gravity
*without tip of a shoot, an oat seedling
cannot grow
this proves elongation of plumule is
dependent on the presence of the tip of
the shoot
*if the tip of the coleoptile is first
removed and placed on an agar block
which is transferred onto the cut stump of
another oat seedling the plumule still
grows straight upwards
this means that the tip of the shoot
carried chemical messengers which has
diffused into the agar block
the chemical messenger then diffuses into
the plumule and causes the plumule to
elongate
*if the agar block is placed asymmetrically
(a little to one scale of the center), the
shoots bend away from the scale with the
agar block as though it is growing towards
the light
This is because a higher concentration of
the growth promoting chemical
messenger accumulates below the agar
block
This means that the agar block contains a
chemical messenger produced in the
shoot
The chemical stimulates growth as it
diffuses down into the shoot
The chemical messenger is auxin