B1) Characteristics of living organisms

Movement: an action by an organism or a part of it which changes its position

or place
Respiration: the chemical reactions in cells which break down nutrient
molecules and release energy for metabolism.
Sensitivity: the ability to detect and respond to changes in the internal or
external environment.
Growth: permanent increase in size and dry mass
Reproduction: the processes that make more of the same kind of organism
Excretion: the removal of waste products of metabolism and substance in
excess of requirements.
Nutrition (use these words to mention the role components in the body, e.g.
usage of carbohydrate in sinks): the taking in of materials for energy, growth,
and development.
B2) Cells
Parts of a plant cell: cell wall, cell membrane, cytoplasm, chloroplast,
ribosome, nucleus, large vacuole, mitochondria, vesicle.
Parts of animal cell: same as plant cell but do not have cell wall, chloroplast
( or plastids), and large/ permanent vacuole.
Parts of bacterial cell: cell wall (made from peptidoglycan), cell membrane,
ribosomes, circular loop of DNA, plasmids (small loop of DNA).
Role of cells: GROW and REPAIR body, cells are produced by the DIVISION of

existing cells.
Magnification formula = image size/ actual size
B3) Movement in and out of cells
Diffusion: the net movement of particles from a region of their higher
concentration to a region of their lower concentration (i.e. down a concentration
gradient) as a result of random movement.
Osmosis: Diffusion of water through permeable membrane (on the water
potential concept).
- Substances can move into and out of cells by diffusion/ osmosis
through the cell membrane (water diffuse out of red blood cells if there
is high concentration of salt).
 - Role of diffusion: gain the useful substances required to obtain energy
and grow and get rid of waste products.

Effect of osmosis on cells (by immersing them in solution):

turgid: plant cell with lots of water so it inflates.
turgor pressure: pressure of water and plasma membrane against cell
wall
flaccid: wilting, plant cell shrinks because lack of water.
plasmolysis: plasma membrane pulls away from cell wall due to loss of
water through osmosis.
Active transport: the movement of particles through a cell membrane from a
region from lower concentration to a region of higher concentration (i.e. against
the concentration gradient), using energy from respiration.
Importance of active transport: plant takes in the ions it needs from the soil
around it even when there is lower concentration outside (required for
homeostasis).
B4) Biological molecules

Starch, glycogen & glucose

(monosaccharide &
disaccharide)
Fatty acids & glycerol

Amino acids
(may be
Phosphoru
Iodine: Test for starch (Brown to blue) s)
Benedict’s solution: Test for reducing sugars (Blue to green to yellow to
orange to brick-red). Notice: Needs water bath for heating (precaution)
Biuret: Test for protein (Blue to purple)
Ethanol: Emulsion (liquid lipid) test for fats and oils.
Notice: Need to shake vigorously using screw caps.
B5) Enzymes
Enzymes: protein that are involved in all metabolic reactions, where they
function as a biological catalyst.
Metabolic reaction: the synthesis and breakdown of carbohydrates, lipids, and
proteins
Action of enzyme: All enzymes contain an active site fit with a
*complementary shape (specific shape) of a substrate (this is called lock
and key hypothesis). As the substrate enters the active site to form an
enzyme-substrate complex.
Substrate: a substance that an enzyme (= chemical made by living cells) acts
on to produce a chemical reaction
Factors affect rate of metabolic reaction:
- Temperature (optimum temperature usually at 40 degrees Celsius. As
temperature increases, rate of reaction increases due to more interaction and
higher kinetic energy within materials)
- pH (most: 7 - 7.5, pepsin: 2.0, trypsin: 8.0)

Denature: When a protein/ enzyme’s normal shape gets deformed due to the
broken of hydrogen bonds, so it does not fit to substrate anymore.
- Denature happens when there is extreme pH or elevated temperature.
Link for names of enzymes:

B6) Plant nutrition

Photosynthesis: the process which plants synthesise carbohydrates from raw
materials using energy from light. Light is absorbed by chlorophyll (a green
pigment in chloroplast)
Word equation: carbon dioxide + water  glucose + oxygen
Symbol equation: 6CO2 + 6H2O → C6H12O6 + 6O2
Test for the need of chlorophyll in photosynthesis
1. Place the leaf in the boiling water. This destroys the waxy cuticle
and breaks open the cell membrane
2. Place the leaf in the hot alcohol. This dissolves the chlorophyll from
the leaf
 3. Dip the now colourless brittle leaf into water to soften it.
4. Add iodine solution and look for the blue-black colour.
Test for the need of light:
1. Before starting the experiment, destarched the plant by placing in the
dark for 24 hours
(This ensures that any starch already present in the leaves will be
used up and will not affect the results of the experiment)
2. Following destarching, a leaf of the plant can be partially covered with
aluminium foil and the plant placed in sunlight for a day.
3. The leaf can then be removed and tested for starch using iodine.

Test for the need of CO2:

1. Destarch two plants by placing in the dark for a prolonged period.
2. Place one plant in a bell jar which contains a beaker of sodium
hydroxide (which will absorb carbon dioxide from the surrounding air)
3. Place the other plant in a bell jar which contains a beaker of water (control
experiment), which will not absorb carbon dioxide from the surrounding
air.
4. Place both plants in bright light for several hours.
5. Test both plants for starch using iodine.

Use and storage of carbohydrates made in photosynthesis:

- Starch: energy store
- Cellulose: build cell walls
- Glucose: respiration for energy
- Sucrose: transport in phloem
- Nectar: attract insect for pollination
Nitrate: key part in amino acid contributing protein growth, without nitrogen
plant cannot grow properly. (Sign of deficiency: Yellow vines)
Magnesium: key part in chlorophyll, a necessary part in chloroplast,
contributing to photosynthesis.(Sign of deficiency: Yellow leaves)
Leaf structure:
- Cuticle (wax layer), upper epidermis (transparent layer of cell)
- Palisade layer(tightly packed cell, located at the top, contain lots of
chloroplast)
- Spongy layer(less more cell with air spaces, where transpiration happen)
- Lower epidermis (include guard cell + stomata)
- Guard cell: control gas exchange.
- Stomata: air spaces where diffusion happens.
- Vascular bundle (phloem + xylem, transportation in plants)
- Xylem: dead cells, transporting water and minerals from roots to leaves.
- Phloem: living cells, transporting sucrose and amino acid from leaves to roots
and bud.

Adaptation of leaves: A leaf usually has a large surface area (thin and
broad structure), so that it can absorb a lot of light.
Hydrogencarbonate indicator: can detect increases and decreases in carbon
dioxide concentration. Red: normal air levels, Yellow: increase in CO2, Purple:
decrease in CO2

B8) Transport in plant

xylem - dead cells, transporting water and minerals from roots to leaves.
phloem - living cells, transporting sucrose and amino acid from leaves to roots
and bud.
Root hair cells adaptation: thin cell cover + high surface area (speed up the
uptake of water)
Pathway of water: root hair cells  root cortex cells  xylem  mesophyll
cells  stomata
Transpiration: the loss of water vapour from leaves (from the -spongy-
mesophyll surfaces)
Factors affect transpiration:
- light: higher light, wider stomata for CO2 --> more water diffused
- temperature: higher temperature, higher diffusion, and evaporation rate
- humidity: high humidity lowers the concentration gradient
- air movement: stronger wind, remove water faster.
Reason for wilting: On a hot, dry day, transpiration causes more water to be
lost than is coming in and gets rid of water balance.
source: where nutrients are made mostly which are transported to sink
(summer: leaves, spring/winter/fall: roots)
sink: where nutrients (sucrose and amino acids) are stored (the opposite to
source)
translocation: the process of transporting sucrose and amino acids in phloem
from sources to sink.

B7) Human nutrition

Balanced diet: a diet consisting of the right proportions of every type of
nutrient (carbohydrates, proteins, fats, vitamins, minerals, etc.) in suitably
sized portions.
Factors affect dietary needs: age, pregnancy, breast feeding, activity levels.
Principal dietary sources:
- Carbohydrates: Provide (give) energy
- Fats and oils: Provide energy, insulation (keep us warm), make cell
membrane
- Proteins: For growth and repair by making new cells, enzymes, antibodies
- Vitamins (C and D) & Mineral ions (calcium and iron): To keep our
body working properly - Important nutrients needed in small quantities
+ Ricket: caused by deficiency of calcium and vitamin D
+ Scurvy: caused by deficiency of vitamin C
- Fibre (roughage): Prevent constipation, ensure food move easily through
digestive system
- Water: 60/70% of body is made up of water
Physical digestion: the breakdown of food into smaller species without
chemical change in food molecules. This increases the surface area for
chemical digestion.
 Chemical digestion: the breakdown of large insoluble molecules into smaller
soluble molecules. This produces smaller soluble molecules that can be
absorbed.
Functions of enzymes:
 Amylase: breaks down starch to simple reducing sugar (salivary
glands and pancreas), best in mouth.
 Protease: breaks down protein to amino acids (pancreas), in
stomach with HCl acid (secreted by stomach)
 Lipase: breaks down fats and oils to fatty acids and glycerol (the
pancreas, mouth, and stomach), best in stomach.

Blue: alimentary
canal
Red: associated

Stages of digestive system:

1. Ingestion: the taking of substances, e.g. food and drink, into the body.
2. Digestion: the breakdown of food
3. Absorption: the movement of nutrients from the intestines into the blood
4. Assimilation: uptake and use of nutrients by cells
5. Egestion: the removal of undigested food from the body as faeces
Function of hydrochloric acid in gastric juice: killing harmful
microorganisms in food, providing an acidic pH for optimum enzyme activity of
proteases in stomach.
Bile(secreted by liver, stored in gall bladder): an alkaline mixture that
neutralises the acidic mixture of food and gastric juices entering the
duodenum from the stomach, to provide a suitable pH for action in the small
intestine.
Role of bile: emulsifying fats and oils to increase the surface area for chemical
digestion, breaks fats molecules smaller, increases surface area.
Emulsification: digestion of fats.
Peristalsis: the movement of food bolus in alimentary canal

B9) Transport in animals

Circulatory system: a system of blood vessel with a pump and valves to
ensure one-way flow of blood.
Single circulation of a fish: the blood passes through a single
circuit/pathway – where blood is pumped by the heart to the gills for
oxygenation and then the rest of the body.
Double circulation of a mammal: blood passes through the heart twice and
has two separate circuits, one for oxygenated blood and one for
deoxygenated blood.
Advantage of double circulation: higher metabolic rates to be maintained as
there is no mixing of oxygenated and deoxygenated blood.

Arteries: blood is pumped away from the heart. Thicker and elastic wall, smaller
diameter of lumen. (high blood pressure)
Veins: blood returns to the heart. Thinner wall, larger diameter of lumen. (low
blood pressure)
Capillaries: one cell thick wall (short diffusion distance) - allow the
exchange of molecules between the blood and the body's cells
Renal: relating to kidneys
Pulmonary: relating to lungs
*Notice: Activity of the heart may be monitored by ECG (electrocardiogram),
pulse rate & listening sounds of valves closing
Effect of intense workout on pulse rate: More energy and oxygen
required to burn glucose to get more energy, so we breathe more frequently so
more blood pumped to get more oxygen. This requires heart pumps
faster.
Pumping function of heart: the main function of the atrial and ventricular
muscle fibres is to contract and produce force.

Coronary heart diseases:

Heart attack: Vessels fully blocked.
Plaque: Vessels partly blocked
Factors of coronary heart diseases:

Components of blood: red blood cells, white blood cells, platelets, and plasma.
Red blood cells: transporting oxygen, role of haemoglobin.
White blood cells: phagocytosis (engulfing pathogens with phagocytes),
antibody production (lymphocyte)
Platelets: clotting red blood cells together to block wounds. (prevent blood
loss and entry of pathogens)
Plasma: the transport of blood cells, ions, nutrients, urea, hormone, and carbon
dioxide.
B10/ Disease and immunity
Pathogen: disease-causing organism
Transmissible disease: a disease in which the pathogen can be passed from
one host another.
Features of virus: protein coat & genetic material (& probably envelope)
Pathogen can be transmitted by direct contact - through blood and other
body fluids or indirect contact - contaminated surfaces, food, animals and air.
Body defences against pathogens: skin, hairs in the nose, mucus – goblet
cells/ ciliated epithelial cells, stomach acid and white blood cells.
Factors controlling the spread of disease: a clean water supply, hygienic
food preparation, good personal hygiene, waste disposal, sewage treatment.
(these above reduce the spread of pathogens and germs)
Active immunity: defence against a pathogen by the body’s production of
antibody. Gained after an infection by a pathogen or by vaccination.
Antibodies: proteins that bind antigens with complementary/specific shapes
leading to direct destruction of a specific type of pathogens or making of
pathogens for destruction by phagocytes.
Vaccination is available for some pathogens to help control the spread of
disease. It teaches the body to produce antibodies for a specific pathogen.
Process of vaccination: weakened pathogens or their antigens are put into
the body  the antigens stimulate an immune response by lymphocytes
which produce antibodies  memory cells are produced that give long-term
immunity.
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B11/ Gas exchange in humans
Parts of breathing system: mouth, larynx, trachea, bronchus, bronchiole,
alveoli (plural of alveolus), intercostal muscle, ribs, diaphragm, thorax (chest)
inspired air: 21% oxygen, 0.04% carbon dioxide.
exhaled air: 16% oxygen, 4% carbon dioxide, higher water vapour.
adaptation of alveoli: moist surface (easy to diffuse), great amount - high
surface area - curvy shape (increase rate of diffusion), one cell thick wall (easy to
diffuse short distance), constant blood supply - covered by capillaries(maintain
diffusion gradient - difference concentration in and out of the alveoli), good
ventilation system (maintain constant supply of air)
Inspiration (breathe in)
-Diaphragm moves down (relax)
-Intercostal muscles contract
Exhalation (breathe out)
-Diaphragm moves up (contract)
-Intercostal muscles relax
Experiment on carbon dioxide use limewater.
Effect of physical activity on the rate and depth of breathing: More energy and oxygen
required to burn glucose to get more energy, so we breathe more frequently and deeply.
(same as effect on heart rate)

B12) Respiration
Uses of energy in living organisms: muscle contraction, protein synthesis,
cell division, growth, the passage nerve impulses, and the maintenance of a
constant body temperature.
Aerobic respiration
Carbon dioxide + water  glucose + oxygen
Anaerobic respiration
Glucose  alcohol + carbon dioxide (+ little energy)
Glucose  Lactic acid (+ energy) or ethanol + CO2 - through lactic
fermentation. (anaerobic produce less energy than aerobic respiration)
Lactic acid builds up in muscle create an oxygen debt  continuation of fast heart rate to
transport lactic acid in the blood from the muscles to the liver  continuation of deeper and
faster breathing to supply oxygen for aerobic respiration of lactic acid  aerobic respiration
of lactic acid in the liver.
Lactic acid is taken to the liver by the blood, and either: oxidised to carbon dioxide and
water, or. converted to glucose, then glycogen - glycogen levels in the liver and
muscles can then be restored.

B13) Coordination and response:

  NOTICE: HORMONAL/ ENDOCRINE SYSTEM ARE THE SAME
Sense organs: eyes for sight, ears for sound, nose for smell, tongue and nose
for taste, and skin for touch (temperature), chemical: taste, smell, touch.
The temperature regulation of homeostasis:
- Vasodilation, vasoconstriction to capillaries
(reduces heat loss, less area)
- Shivering, sweating
- Hairs erect, lie down.
Negative feedback: a mechanism control
system responds when conditions change
from the ideal or set point and returns
conditions to this set point.
Ovary: Oestrogen
Testis: Testosterone

B14) Drugs
Drug: any substance taken into the body that modifies or affects chemical
reactions in the body.
The way antibiotics work: affect the working of bacterial cells, either by
disrupting their structure or function or by preventing them from
reproducing.
However, some bacteria are resistant to antibiotics which reduces the
effectiveness of antibiotics. This may arise from natural selection.
Some antibiotics kill bacteria but do not affect viruses.
In order to reduce the rate of development of antibiotic-resistant strains:
 doctors should not prescribe antibiotics inappropriately, such as for
the treatment of non-serious infections.
 patients should always complete the full course of antibiotics to
ensure all bacteria are killed and none survive to mutate and form
resistant strains.
 the agricultural use of antibiotics should be restricted.

B15) Reproduction
Asexual reproduction: a process resulting in the production of genetically
identical offspring from one parent.
 Advantages: the population can increase rapidly when the conditions
are favourable. only one parent is needed. it is more time and energy
efficient as you do not need a mate.
  Disadvantages: it does not lead to genetic variation in a population.
the species may only be suited to one habitat. disease may affect all
the individuals in a population.
Sexual reproduction: a process involving the fusion of the nuclei of two
gametes to form a zygote and the production of offspring that are
genetically different from each other.
Species: a group of organisms that can reproduce to produce fertile
offspring.
(Advantages and disadvantages of sexual production is opposite to those of
asexual.)
Sexual production in plants:
Pollination: the transfer of pollen grains from an anther to a stigma.
Requirement of plants for germinations of seeds: water, oxygen, and a
suitable temperature.
Sexual reproduction in humans:
Fertilisation: the fusion of the nuclei from a male gamete (sperm) and a
female gamete (egg cell).

Male gametes: Size – small, motility - capable of locomotion, structure – head

region, flagellum , and other adaptive features, number – produced every day in
huge numbers.
Female gametes: Size – bigger, motility – uncapable of locomotion, structure –
spherical, number – 1 per menstrual cycle
Adaptive features of male and female gametes: Unit 2
Uterus lining is controlled by oestrogen (secreted by ovary). Thick lining
prepares for the development of foetus.
Role of testosterone and oestrogen during
puberty:
- Testosterone: growth of penis and testes,
growth of
facial and body hair, muscles develop, voice
breaks, testes start to produce sperm.
- Oestrogen: breast development, body hair
grows, hips get wider, menstrual cycle begins.
Sexually transmitted infections (STI): an infection that is transmitted
through sexual contact.
Human immunodeficiency virus (HIV) is a pathogen that causes STI, and it
may lead to AIDS.
Transmission methods of HIV: via the exchange of body fluids from people
living with HIV, including blood, breast milk, semen, and vaginal
secretions.
Restriction methods: sexual encounter, reduce sexual activity, reduce the
period of infectiousness individuals, vaccination.

B16) Inheritance
Chromosome: structure that are made of DNA, which contains genetic
information in the form of genes.
Genes: length of DNA that codes for a protein.
Allele: alternative form of a gene.
XX: Female, XY: Male.
Haploid: have only one set of chromosomes, included in gametes(23
chromosomes in human)
Diploid: have two sets of chromosomes, included in zygote.(46 chromosomes
in human)
Mitosis: a nuclear division giving rise to genetically identical cells.
- Replication of chromosomes occurs before mitosis. During mitosis, the
copies of chromosomes separate, maintaining chromosome number in
each daughter cell.
Meiosis: reduction division in which the chromosome number is halved from
diploid to haploid resulting in genetically different cells.
- Meiosis is involved in the production of gametes.
Monohybrid inheritance
Inheritance: the transmission of genetic information from generation to
generation
Genotype: the genetic make-up of an organism and in terms of allele present
Phenotype: observable features of an organism
Homozygous: having two identical alleles of a particular gene
- Two identical homozygous individuals breed together will be pure
breeding.
Heterozygous: having two different alleles of a particular gene
Dominant allele: the allele that is expressed if it presents in the genotype.
Recessive alle: the allele that is only expressed when there is no dominant
allele of the gene present in the genotype.
Ratio: 1:1 (1 recessively homozygous and 1 dominantly heterozygous),
3:1(2 dominantly heterozygous), ratio = 1 (1 dominantly homozygous
and 1 recessively heterozygous)

B17) Variation and selection

Variation: differences between individuals of the same species.
Continuous variation: variation that results in a range of phenotypes between
two extremes, no distinction categories, no limit on the value, tends to
be quantitative, can be influenced by living condition. EXP: Weight, length,
…
Discontinuous variation: variation that results in a limited number of
phenotypes with no intermediates, distinct categories, tends to be
qualitative, and cannot be influenced by living condition. EXP: ABO blood
group, eye colour,…
Mutation: a genetic change. It is the way that new alleles are formed.
Natural selection:
1. Genetic variation within a population
2. Production of many off spring
3. Struggle for survival, including competition for resources
4. A greater chance of reproduction by individuals that are better
adapted to the environment than others
5. These individuals pass on their alleles to the next generations.
(The development of strains of antibiotic-resistant bacteria is an example
of natural selection)
Selective breeding:
1. Selection by humans of individuals with desirable features
2. Crossing these individuals from a mixed population to produce the
next generation
3. Selection of offspring showing the desirable feature
4. This is repeated through many generations
B18) Organisms and their environment

Energy flows from primary to tertiary consumers with LOSSES.

 Losses of energy are due to:
 Indigestible matter
 Energy used in movement
 Excretion

B19) Human influences on ecosystem