Physics is one of my favourite subjects. It’s a subject about Britpop music, dancing, and it’s also the math of math. Here are the basic GCSE stuff.
Category: Science
C5 Acids and Bases
C5 Acids and Bases
Acids
- Hydrochloric acid (HCl) 盐酸
- Sulfuric acid (H2SO4) 硫酸
- Nitric acid (HNO3)
Bases
- Calcium carbonate (CaCO3) 碳酸钙
- Magnesium oxide (MgO) 氧化镁
Alkalis are bases that are soluble in water. Examples:
- Potassium hydroxide (KOH) 氢氧化钾
- Lithium hydroxide (LiOH) 氢氧化锂
pH scale
Strongest at either extremes.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 |
| Acidic | Neutral | Basic | |||||||||||
Litmus paper turns red if it’s ACID and blue if its base.
Universal indicator is red-yellow for acid, green for neutral, blue-purple for base.
Making salty formulas
- Metal + acid → salt + hydrogen
Example metal: use magnesium. Do not use group 1 metals as too reactive/dangerous.
-
- Sulfuric acid → sulfates (SO42-)
- Nitric acid → nitrates (NO3–)
- Hydrochloric acid → (Cl–)
- Metal oxide + acid → salt + water
Example metal: copper oxide + hydrochloric acid → copper chloride + water
- Metal hydroxide + acid → salt + oxygen + water
Example metal: sodium hydroxide + nitric acid → sodium nitrate + water
- Metal carbonate + acid → salt + carbon dioxide + water
Example metal: calcium carbonate + sulfuric acid → calcium sulfate + water + CO2
Behavior of acids
Strong acids like sulphuric acid will:
Dilute sulphuric acid reacts with reactive metals, carbonates and bases based on the formula above.
Concentrated sulfuric acid act as a dehydrating agent that takes water from everywhere.
Actually making salts through titration
- Pick an acid and an base.
- Put one of them in the burette to do the titration.
- Mix the acid and the alkali/base to do the neutralization reaction.
- Add droplets of universal indicator, which turns green when substance is neutral.
- Or use a pH probe which reads 7 when neutralized.
- Evaporate off the water in evaporating basin.
Acids and pollution
Composition of clean air
- 78% nitrogen
- 21% oxygen
- 1% other (argon, carbon dioxide, water vapour)
Pollution
| Types of pollution | Sources | Problems | Solutions |
| Carbon monoxide (CO) | Incomplete combustion from cars | Toxic because binds with hemoglobin | Catalytic converters in car engine: uses platinum to react CO and Oxygen to become CO2 and water, safe |
| Sulfur dioxide (SO2) | Combustion of fossil fuels (factories) | Acid rain (natural rain is slightly acidic). Corrodes buildings. | React sulphur dioxide with limestone to neutralize it |
| Oxides of nitrogen (NO/NO2) | Car engines | Acid rain, corrodes buildings. breathing difficulties | Catalytic converters in car engine: uses platinum to react NO into nitrogen and oxygen, harmless release back into the air |
The environment needs to be kept neutral.
Soil pH must be kept neutral. It becomes more acidic, acid rain in soil can leach toxins such as Aluminum that become poisonous to animals in the river when washed down. It also leaches minerals that are important for growth by plants.
Neutralisation can be achieved by adding a base such as limestone.
CO2 concentration in air
Carbon dioxide is a product of reaction between acid and a carbonate. Carbon dioxide levels in the atmosphere is increasing due to burning of fossil fuels, deforestation and many more. This is important because carbon dioxide is a greenhouse gas and it causes global warming.
Limestone cycle
- CaCO3 → CaO + CO2 (thermal decomposition)
- CaO (quicklime) (s) + H2O (l) → Ca(OH)2 (s) (slaked lime)
- Ca(OH)2(s) + H2O(l) → Ca(OH)2 (aq) (limewater)
- Ca(OH)2 + CO2 (g) → CaCO3(s) + H2O (l) (white limestone precipitate)
Exam technique: also mention that add the same amount of acid, same concentration……
Limestone can be used to neutralize almost everything!
C4 Stoichiometry
C4 Stoichiometry
I can do all the equation things and so can you.
Relative molecular mass, Mr, is the sum of the relative atomic masses of a compound. E.g. H2O would be 2 + 16 = 18.
Mole is the Avogadro’s constant, which defines a specific number of atoms.
The molar gas volume is 24 dm3 at room temperature and pressure. This applies for ANY GAS. Remember to convert the unit.
C3 Rates and Energetics
C3 Rates and Energetics
Energetics
Exothermic is when the reaction releases heat towards its surroundings, potential energy decreases and that more bonds are formed than broken. Most chemical energy is transferred to thermal energy.
Endothermic is when the reaction absorbs heat from its surroundings, potential energy increases and more bonds are broken than formed. Most thermal energy (from surroundings) is transferred to chemical energy.
Rates of reaction
Use of catalysts, increasing temperature and concentration, increasing particle surface area increases rate of reaction.
Use gas syringe and stopwatch to measure reaction within a conical flask, such as HCl with Mg.
In reality
In mills, very fine powder will react with any spark from a machine. Combustion of fine powders can be prevented by having low temperatures and not having them scattered around oxygen, prevention of sparks from machines.
In mines, gases come together to become explosive at high concentrations. There should not be fire within mines or measures should be taken to reduce the concentration of these gases, such as infusing oxygen.
Industrial Processes
In the little real world, people love to eat vegetables. To make vegetables grow quicker, fertiliser is needed. Important ingrediants are nitrogen, phosphorus and potassium 氮磷钾 because:
Nitrogen helps leaves make proteins, absence will cause stunted growth
Phosphorus needed to make proteins and help cell division, absence will grow slower
Potassium controls opening and closing of stomata, also starch and protein. Absense will cause roots develop worse.
Making ammonia by Haber process
Ammonia is NH3, which can become a good fertiliser for nitrogen when reacted with an acid. There is 78% of nitrogen in the air.
Haber process produces ammonia industrially using hydrogen and nitrogen gas.
-
- Obtaining raw materials:
- Hydrogen from natural gas such as fossil fuels
- Nitrogen from fractional distillation of air.
- Conditions for reaction:
- 400-450C temperature
- 200 atm pressure – high pressure allows particles to move faster
- Iron catalyst lowers activation energy
- Reaction formula:
- N2 (g) + 3H2 (g) ←→ 2NH3 (g)
- The reaction is reversible.
- The mixture is cooled so ammonia can be liquified. Remaining N and H are recycled.
Making sulphuric acid with Contact Process
Sulphuric acid can react with ammonia to make ammonium which is a good fertiliser.
- Obtaining raw materials:
- Sulphur from underground deposits
- Air and water
- Conditions for reaction:
- 450°C temperature
- 1-2 atm
- Vanadium oxide catalyst
- Reaction formula/stages:
- Producing sulphur dioxide
- S(l) + O2(g) → SO2 (g)
- Not reversible.
- Making sulphur trioxide
- 2SO2(g) + O2(g) ⇌ 2SO3(g)
- Reversible.
- Making oleum (not included in syllabus)
- Making sulphuric acid
- SO3 (g) + H2O(l) → H2SO4 (aq)
- Irreversible.
- Producing sulphur dioxide
C2 Chemical Bonding
C2 Chemical Bonding
“Welcome, folks, to the Atoms Administration.”
Ions are charged particles that have an excess or deficiency of electrons. Elements form ions by gaining or losing electrons in attempt to achieve a full outer shell. Metals form positively charged ions, cations and non metals negatively charged ions, anions.
Ionic bonding is the type of bonding between a metal and a non-metal including formation of ions and electrostatic attraction between them. They occur in lattice structure, a regular arrangement of alternating positive and negative ions, such as sodium chloride table salt. It is very strong. An ionic reaction is a redox reaction in that one compound gains electron and the other loses electrons.
Molecules and covalent bonds.
Non-metallic elements form covalent bonds with each other, in which electron is shared between atoms.
| Ionic | Covalent | |
| Melting point | high | low |
| Volatility | higher | lower |
| Solubility | Generally soluble to form solutions that conducts electricity | Insoluble in water and solutions in other solvents will not conduct electricity |
| Electrical conductivity | Conducts when molten / liquid, when there is a sea of delocalized electrons | never |
| Structure | Solid: positive negative ions attracts together to form regular 3D ionic lattice. Strong, regular structure is produced, crystalline solid that has a high melting point.
Liquid: contains free-moving ions that conducts electricity. |
Solid: Atoms bond into molecules held together by weak forces of attraction, hence low melting point. Liquid: has free moving molecules and hence does not conduct electricity. |
Giant structures
Giant covalent structures are massive networks of covalently bonded molecules that has a regular repeating pattern in which many lattice structures occur. Examples are diamonds and graphite, which are allotropes of carbon. Diamonds have 4 carbon bonds while graphite has 3.
Diamond is very hard and a hexagonal structure is created around each carbon atom. They have very strong covalent bonds.
Graphite occurs in layers and in each layer, each atom is bonded to 3 bonds and forms a hexagonal shape. There is a 1 free electron from each carbon atom. The bonds between the layers are not strong covalent bonds but weak intermolecular forces due to free electrons. Hence, graphite is used in pencils and lubricants since layers can slide off each other and it rubs off each other. Layers of graphite come onto the paper.
Silicon dioxide also makes hexagons, each silicon is bonded to 4 oxygen atoms covalently. Each oxygen atom is bonded to 2 silicon atoms. It is a giant covalent structure and it has strong bonds. It is a lattice structure that continues in 3D with regular patterns.
Structure of a substance determines its physical properties.
| Diamond | Graphite | |
| Hardness | The hardest known substance | Soft and slippery |
| Melting point | >3500C | |
| Appearance | Transparent, shiny and sparkly | Opaque, dull, black/silver |
| Conductivity | Does not conduct electricity | Conductor |
| Uses | Jewellery, cutting, drill heads | Lead in pencils, lubricant |
Metallic bonding
Metals conduct electricity because there is a lattice of positive metal ions in a sea of delocalized electrons in a tightly packed regular structure, in which electricity can flow freely. Ions are held together by attraction to bonding electrons.
Malleability is due to non-directional metallic bonds since bonding electrons are free to move, making them easy to bend.
C1 Particles and the Periodic Table
C1 Particles and the Periodic Table
Atom is the smallest unit of an element, all matter is composed of atoms, has a nucleus with protons and neutrons and electrons on its shells.
Molecule is the smallest physical unit of a chemical compound.
Physical changes do not change the chemical composition of a substance, e.g. change of state, change of shape. No bonds are broken but intermolecular forces between molecules are broken.
Chemical changes makes a new substance in that bonding happens. Atoms of the elements are rearranged.
Elements are composed of one single type of atoms with the same number of protons.
Compounds are two or more atoms bonded together.
Mixtures are congregation of two or more substances that do not bond together. The product of the random distribution of one substance through another without any chemical reaction, as distinct from a compound.
Atomic structure
An atom has a nucleus, containing protons and neutrons, and shells on which electrons form.
| Relative Charge | Relative mass | |
| Protons | +1 | 1 |
| Neutrons | 0 | 1 |
| Electrons | -1 | negligible |
Proton number/atomic number is the number of protons in an atom.
Nucleon number is the # of protons and neutrons in an atom.
Periodic table is arranged in ascending shells and valence electrons, etc. Noble gases do not react because they have no valency electrons, a full outer shell.
Isotopes are atoms of the same element with the same proton number but different # of neutrons.
Relative atomic mass Ar is a comparison of a mass of an element to an atom of carbon-12, and the relative atomic mass always equals the nucleon number on the periodic table.
Destruction oxidation
Metal oxides are basic and most non-metal oxides are acidic. If non-metal oxides are not acidic, they are neutral (such as pure water). Some oxides of metals can behave as acidic even though they are basic. They are called amphoteric oxides.
Some elements are metalloids, intermediate between metal and non metal.
| Metals | Non-metals |
| Metallic sheen, glossy | Dull and light |
| High density | Low density |
| Good electrical and heat conductor | Poor conducter |
| Strong | Weak |
| Malleable | Brittle |
Group # = # of valence electrons. 1-3 Metals, 4-8 non-metals.
G1 Alkali metals
Lithium, sodium and potassium are a collection of relatively soft metals that are solid at room temperature and reacts violently with water to form strong alkali solutions
Reactivity increases down the group because elements with more shells are less stable. Melting points and hardness of G1 metals decreases down the group.
They FFMM, Fizz Float Melt Move on water’s surface.
G7 Halogens
Halogen reactivity is highest at top of the group. Chlorine will displace every halogen below it. Chlorine is yellow-green, bromine is red, iodine is brown-black.
G8 Noble gases
They are unreactive and they are useful to provide an inert atmosphere, where reaction is not desired. I.e. Argon in lamps, and helium for filling balloons.
Transition metals
They are a collection of metals having high densities and melting points that form colorful compounds and often act as catalysts.
Chemistry
Chemistry is a subject about Taoism, political spectra and intuition. Here are the units taught en mi escuela.
C1 Particles and the Periodic Table
B8 Inheritance
B8 Inheritance
Types of variation
Variation is the small differences that exist between members of the same species.
Continuous variation is influenced by both genes and environment, resulting in a range of phenotypes between extremes that are usually bell curved. E.g. height, weight.
Discontinuous variation is caused by genes alone and results in a limited number of distinct phenotypes with no intermediates. E.g. blood type, eye color
Generating genetics
DNA is a carrier of genetic information that is capable of self replicating.
Genes is a length of DNA that is the unit of heredity, codes for a specific protein. Can be copied and passed on to the next generation.
Chromosome is a thread of DNA that is made up of a string of genes.
Inheritance is the transmission of genetic information through generations.
Chromosome > genes > DNA.
Haploid means having a single set of unpaired chromosomes.
Diploid means containing 2 complete sets of chromosomes, one from each parent.
Gamete is a mature haploid male or female germ cell which is able to unite with another of the opposite sex in sexual reproduction to form a zygote.
Zygote is a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.
Cell division
Mitosis makes body cells with 46 chromosomes.
The nuclear division giving rise to genetically identical cells in which chromosome # is maintained by exact duplication. Look at notebook for details.
Meiosis makes sex cells with 23 chromosomes. It is reduction division where chromosome # is halved from diploid to haploid, and it happens during gamete production. Consult notebook for pretty pictures.
They are important becauses mitosis is for growth and repair while meiosis is for reproduction.
Inheritance
Phenotype is the ‘phenomenon’ – outcome of a certain genetic trait.
Genotype is the specific genes the organism has. (e.g. female XX male XY)
Alleles are 2+ alternative forms of a gene that codes for the same proteins.
Homozygous refers to an individual that has 2 identical alleles of a gene.
Heterozygous refers to having 2 different alleles of a gene.
Dominant refers to a gene is expressed in offspring even when inherited from only one parent.
Recessive refers to a gene that is expressed only when inherited from both parents.
I can draw punnett squares and so can you.
Sex is determined by X and Y sex chromosomes. A female has 2 x chromosomes and eggs only carry an X chromosome. Male has 1 X and 1 Y, and sperm carries either X or Y chromosome. The whole Chromosome is used in the cross rather than the alleles of a gene.
Mutation
Mutation is a change in gene/chromosome caused by chemical/random/radiation.
E.g. sickle cell anemia that causes the red blood cell to take another shape, caused by mutation in gene that codes for hemoglobin.
Artificial selection
People choose the characteristics they want to appear in the next generation. You can do this to everything that breeds except people, because that is very unethical.
E.g. Cattles may be bread for quantity/quality of milk/meat
Sheeps for quant/qual of wool
Plants for taste/pest tolerance/drought tolerance.
Selective breeding
Is when you select two parents with ideal traits and breed them together to pass on those traits. E.g. I take the sweetest strawberries and the biggest strawberries and breed them together so I get both genetic characteristics, I am a perfect strawberry yay.
Natural selection
The process whereby organisms better adapted to their environment tend to survive and produce more offspring, and this is how evolution happens over successive generations. Variation in different members of the same species cause some to be better adapted, and overpopulation ensures that some survive. Better genes get passed on.
Evolution is change in the heritable characteristics of biological populations over successive generations.
Antibiotic resistance
Similarly, the overuse of antibiotics may cause bacteria that are resistant to everything because they have survived over the usage and evolved. They are called superbugs.
B7 Plant and Human Reproduction
B7 Plant and Human Re-production
Asexual reproduction
Asexual reproduction is the process resulting in the production of genetically identical offspring from one parent. Examples: bacteria, sea stars, yeast, strawberry
| Advantages | Disadvantages |
|
|
Sexual reproduction is the process involving the fusion of haploid nuclei to form a diploid zygote and the production of genetically dissimilar offspring.
| Advantages | Disadvantages |
|
|
Flowers for Algenon
| Structure | Function |
| Sepals | Protect the unopened flower |
| Petals | Brightly colored to attract insects |
| Anthers | Making and storage of pollen, male gametes |
| Stigmas | Catches pollen grains for temporary storage |
| Ovaries | Contains ovules, female gametes |
Pollination is the transfer of pollen grains from the male part of the plant (anther of stamen) to the female part of the plant (stigma.)
Some agents of pollination are wind, water, animals (like bees/insects and humans.)
Structural adaptations of insect-pollinated and wind-pollinated flowers
| Insect pollinated | Wind pollinated |
| Large, bright, conspicuous petals | Small or none at all |
| Strongly scented | No scent |
| Nectaries at base of petals for insects | No nectaries |
| Anthers within flower for insects to brush past when reaching for nectar | Anthers outside |
| Stigma within flower for insects to brush past when reaching for nectar | Stigmas large and outside petals |
| Sticky, spiky pollen grains | Smooth, light pollen grains |
| Many pollen produced | Even more pollen produced |
Seed germination
| Factor affecting germination | Why |
| Oxygen | Needed for respiration and chemical changes for mobilization of food reserves. |
| Water | Absorbed through micropyle, needed to activate enzymes which convert insoluble food stores into soluble nutrition needed for growth and energy. |
| Temperature | For enzymes to work at their optimum temperature |
| (Light) | Not a requirement but some seeds need some exposure to light before germination |
Structure of seeds and function
Radicle, Plumule and cotyledons is the embryo of the seed.
| Structure | Function |
| Radicle | Grows as root |
| Plumule | Grows as shoot |
| Cotyledons | Food storage |
| Testa | Hard outer protective layer |
Seed dispersal
Seed and fruit dispersal by wind and animals provides a means of colonising new areas, prevention of local competition.
Dispersal by wind: dandelions seeds are blown away by wind.
Dispersal by animals: Fruits such as apples, berries are eaten by animals, their seeds are inedible and therefore excreted/uneaten and carried by the animal to new areas; alternatively hooked fruits like rambutan can stick to the animal’s fur and be carried away.
Sexual reproduction in humans
| Structure | Function |
| Penis | Introducing the sperm cells into the vagina during intercourse |
| Sperm ducts | Conveys sperm to the urethra |
| Urethra | Leads the sperms to the outside through the penis |
| Scrotum | Sac that holds testes and suspended outside body to have cooler conditions for sperm production |
| Prostate gland | Produces a fluid to nourish the sperm cells and help them swim vigorously, this fluid together with sperm is called semen |
| Testes | Produces sperm from their coiled tubes and makes the sex hormone |
| Structure | Function |
| Uterus | For the implantation and development of the embryo |
| Vagina | Receive sperm cells during intercourse and birth canal |
| Oviduct | Lead mature ova to the uterus, region where fertilisation takes place |
| Ovary | Produces eggs at puberty and also female sex hormones |
| Cervix | Connects uterus to vagina |
Male and female gametes
Ovum/egg has cytoplasm, and a layer of jelly between membrane, and nucleus containing chromosomes.
Sperm cell has tail, midpiece, mitochondria in midpiece, nucleus in head. Energy for swimming is produced in mitochondria.
| Ovum/egg | Sperm | |
| Size | Large; visible to the human eye | Very small |
| Numbers/amount | One produced every month | Many millions produced |
| Mobility | Pushed around the oviduct | Has a tail to move |
Menstruation
Occurs every 29 days and controlled by oestroen and progesterone produced in the ovary.
- Period arrives and lasts for 5 days. Lining of the uterous breaks down and blood/cells past out of the vagina.
- Day 6 – a new ovum starts to develop in the ovary. Ovum develops a sac of fluid around it to be called a follicle. Follicle releases oestrogen to repair the lining of the uterus.
- Ovum is released – ovulation at day 14. Remaining follicle releases a different hormone that maintains the lining of the uterus should fertilisation occur. The lining is thickened to increase chances of implantation.
- Next 7 days is the receptive stage and fertilisation will cause embryo to be implaced in the lining. If not fertilized, ovum dies and passes out of the vagina.
- Low level of prosgesterone leads to the uterus lining being shed and cycle starts again.
Fertilisation in humans
It’s the fusing together of sperm and ovum nuclei.
Sperms will swim through the uterus and up to the oviducts to fetilize.
After fertilisation takes place in the oviduct, the fertilized ovum/zygote begins to divide, forming a ball of cells that starts to move down the oviduct into uterus, becoming an embryo. Implantation occurs when embryo sinks into soft lining of uterus.
Function of a bunch of things related to pregnancy
| Structure | Function |
| Amniotic sac | Produces the amnionic fluid and encloses the fluid (rupturing just before birth) |
| Amniotic fluid | Prevents fetus from drying out, prevents temperature fluctuations and unequal pressures acting on the fetus, acts as a shock absorber to prevent physical damage |
| Placenta | Supplies the fetus with oxygen and nutrients, to be dissolved in blood |
| Umbilical cord | it supplies oxygen, it delivers nutrients, and it helps to withdraw blood rich in carbon dioxide and depleted in nutrients (excretory products) |
Breastfeeding
| Advantages | Disadvantages |
|
|
Bottle-feeding formula milk
| Advantages | Disadvantages |
|
|
HIV/AIDS
HIV is transmitted in blood and semen, etc.
| Methods of transmission | Prevention |
| Unprotected sex with infected person | Usage of condoms; abstinence |
| Drug use while sharing a needle with infected person | Don’t take drugs they bad for you / use sterilized needles |
| Transfusions of unscreened blood | Screen the bloody blood |
| Infected mother to child | Feed a baby with bottle milk |
| Use of unsterilized surgery instruments | Sterilize them |
How does it affect immune system?
- HIV virus lowers the amount of lymphocytes called CD4 cells.
- Once a person’s CD4 cell count is low, opportunistic diseases start making a person sick, and these symptoms are called AIDS. common ones are herpes and fungal infections.
- Weakens the immune system and makes it defunct without medicine.
B5 Human Transport and Exchange
The circulatory system
The circulatory system is a system of tubes with a pump and valves to ensure one-way flow of blood.
Organisms could have single or double circulatory systems.
Double circulation is a low pressure circulation to the lungs, which is meant to pick up oxygen, and a high pressure circulation to the body tissues, which is meant to deliver oxygen. We have double circulation because we are big animals.
Effect of physical activity on pulse rate
More physical activity means higher pulse rate because the body needs more oxygen for movement and the heart works to deliver more oxygen to the body organs.
Blood in the heart
(septum is the middle separation muscle)
- Deoxygenated blood enter the right atrium via superior and inferior vena cava.
- Blood is pumped into the right ventricle.
- Blood is pumped out of the heart towards the lungs through the pulmonary artery.
- Oxygenated blood enters the left atrium through the pulmonary vein.
- Blood is pumped into the left ventricle.
- Blood is pumped towards the body through the aorta.
Blood vessels
Coronary heart disease
Little blood vessels feeding oxygen to the heart (coronary arteries) is clogged.
May lead to heart attacks.
Causes: Too much saturated fats, smoking, stress.
Preventative measures: Eat less saturated fats, don’t smoke, exercise, meditate
Blood vessels
Artery
- Thick muscular walls to resist high pressure
- Elastic muscular walls to produce pressure and assist blood flow
- Small lumen
Vein
- Thinner muscular wall
- Larger lumen
- Valves to prevent blood backflow
Capillaries
- One cell thick to allow diffusion
Composition of Blood
- Red blood cells: transports oxygen and carbon dioxide
- Small size: fits into capillaries
- Biconcave shape: maximizes surface area for oxygen absorption
- No nucleus: fits more hemoglobin
- Contains hemoglobin: it binds with oxygen
- White blood cells (phagocytes; lymphocytes): defends the body against diseases
- Phagocytes phagocytosis.
- Lymphocytes make antibodies.
- Plasma: dissolves blood cells, ions, soluble nutrients, hormones and CO2 to allow transport
- Platelets: stops bleeding by clumping near a wound
Immune system
White blood cells guard the body against invasions.
Phagocytes: Engulfs pathogens (all foreign cells) and digests them. This is called phagocytosis.
Lymphocytes: Makes and releases antibodies towards the antigens on the pathogens, binding them together, paralyzing them for phagocytes to digest them.
Tissue rejection with immune system
If a person needs organ transplant, immune system will recognize the new organ as foreign and starts attacking it. It may trigger a response and antibodies may be produced. When this happens, it’s called tissue rejection. You can prevent this by using a relative’s organ or suppressing your immune system (but not your emotions. Let’em out sister)
Gas exchange
Alveolus has large surface area and a thin wall to allow maximum diffusion across.
It is moist so cells would not dry and gases can dissolve.
There is a high concentration gradient due to blood movement.
Mucus is made by goblet cells to trap bacteria, while cilia hair sweeps the mucus away.
Inspired air has more oxygen and less carbon dioxide. Expired air has more carbon dioxide and water and less oxygen. To confirm, bubble expired air through limewater for white precipitate.
Don’t smoke
| Components of tobacco | Effects |
| Tar | Increases risk of cancer, causing bronchitis and damages cilia, coating and lining air passages |
| Nicotine | Addictive and increases heart rate and blood pressure |
| Carbon monoxide | Combines with hemoglobin to prevent oxygen cells being transported; could die |
| Smoke particles | Irritates air passages and results in chronic bronchitis, coughing, etc. |
Effects of physical activity on rate and depth of breathing
Higher physical activity leads to quicker and deeper breathing due to the need for oxygen for muscles to release energy.
Respiration
Respiration is the chemical reactions that break down nutrient molecules in living cells to release energy.
How is energy used in humans?
- Muscle contraction
- Protein synthesis
- Cell division
- Growth
- Passage of nerve impulses
- Maintenance of constant body temperature.
Aerobic respiration: Is the release of a relatively large amount of energy through breaking down food substances in cells in presence of oxygen. Occurs when excess oxygen is present.
Equation: C6H12O6 + 6O2 → 6CO2 + 6H2O
Anaerobic respiration: Is the release of a relatively small amount of energy through breaking down food substances in cells in absence of oxygen. Occurs when there is a lack of oxygen. Breaks down glucose into lactic acid (a toxin), causes muscle cramp and creates oxygen deficit that will need to be later recovered through aerobic respiration. Extra oxygen breathed in after anaerobic respiration is used to break lactic acid down to water and carbon dioxide.
Equation: C6H12O6 → 2C3H6O3
Anaerobic respiration in yeast
In brewing:
- Yeast is dissolved in warm sugar solution.
- Yeast respires anaerobically to release ethanol and carbon dioxide, making the drink alcoholic and fizzy. This process is called fermentation.
In making bread:
- Yeast is mixed with sugar and water.
- Flour is added to make dough and left to warm.
- The dough rises as yeast releases carbon dioxide which creates air bubbles in bread.
- High temperature when baking kills the yeast and evaporates alcohol.
In yeast equation: glucose → alcohol + carbon dioxide
IGCSE REVISION 