Science Consolidated

Health, Disease & Disorder

Health: A state of mental, physical, and social well-being

Disease: A condition that interferes with the normal bodily function of an organism

Disorder: An abnormality in the function of the body or mind

Pathogen

A biological agent that causes disease or illness in a host organism

Micro-organism

A microscopic organism which may exist in its single-celled form or a colony of cells

Infection

The invasion and multiplication of harmful organisms in or on the body’s tissues

Virulence

A pathogen’s ability to cause damage to a host

Endemic, Epidemic, Pandemic & Outbreak

Endemic: A disease outbreak that is consistently present but limited to a particular region

Epidemic: A sudden increase in the occurrence of a disease among the population in a given area

Pandemic: When an epidemic occurs across multiple countries or continents

Outbreak: A sudden, unexpected increase in the prevalence of a particular disease above the base level for that population

Antibodies & Antigens

Antibody: Produced by plasma B cells and released into the blood and lymph in order to neutralize foreign invaders

Antigens: Unique molecules or parts of molecules that can often elicit an immune response

Vaccinations

Vaccination: The artificial introduction of antigens of pathogenic organisms to the body

Vaccine: A preparation containing antigens that stimulates the immune system to produce antibodies and memory cells, providing protection against a particular disease

Zoonotic Disease

An infectious disease that naturally spreads from animals to humans Eg: Avian influenza, which originated from birds, but has mutated to be able to infect humans

Vectors

Organisms that transmit pathogens from an infected host to a susceptible host

Immunity

Immunity: The body’s ability to recognise foreign substances and stimulate cells to destroy or remove them

Immunological Memory: The ability of the adaptive immune system to recognise a pathogen it has encountered before and launch a faster, stronger response

Immunization: Programming the immune system so that the body can respond rapidly to infecting microorganisms

Transmission

The way a pathogen spreads disease from one host to another

Bacteria

• 0.2-10 μm (micrometres)

• DNA - large circular chromosome, smaller circular fragments (plasmids)

• Prokaryotic

• Unicellular

• Peptidoglycan cell wall covered in cilia and flagellum to assist movement

Types of Bacteria

• Spherical - coccus

• Rod shaped - bacillus

• Spiral - spirillum

• Comma shaped - vibrio

Viruses

• 20-300 μm

• Protein coat encloses infectious genetic material (DNA or RNA)

• Neither prokaryotic or eukaryotic

• Non-cellular

Fungi

• Around 50 μm

• DNA within a nucleus

• Eukaryotic

• Can be unicellular (yeasts) or multicellular (moulds)

• Cell wall composed of chitin

Protists (Protozoa)

• 1-300 μm

• DNA

• Eukaryotic

• Can be unicellular, multicellular, or colonial

• Membrane-bound nucleus + organelles, but no cell wall

What are Protist pathogens?

Unicellular eukaryotes that are not classified as plants, animals, or fungi, but may have some plant, animal or fungi features

Infectious disease caused by Bacteria

Tetanus - caused by clostridium tetani - enters the human body through contact with open wounds

Disease caused by a Protist

Malaria - caused by plasmodium parasite - transmitted through mosquito bites, specifically female anopheles mosquitos

Disease caused by a Fungus

Ringworm - skin infection - red circular rashes

Prokaryotic vs Eukaryotic

Prokaryotic cells lack a nucleus and membrane bound organelles whereas eukaryotic cells possess both

DNA viruses vs RNA viruses

• DNA - usually double-stranded & can encode up to hundreds of viral proteins

• RNA (retroviruses) - usually single-stranded & have smaller genomes that encode only a few proteins

• Both can be linear or circular

Infectious vs Contagious vs Non-Infectious Diseases

• Infectious diseases have a causative agent (pathogen)

• Contagious diseases can spread between individuals

• Non-infectious diseases are caused by genetics, environmental influences, or cellular malfunction

• All contagious diseases are infectious, but not all infectious diseases are contagious

Three ways infectious diseases are spread

• Direct or close contact - transmission within 1-2 m such as Ebola and COVID-19

• Indirect contact - transmission outside of 1-2 m such as measles or on a fomite surface

• Vectors

Three ways infectious diseases can be controlled

• Physical preventative methods eg: wearing gloves, masks, hand washing

• Medication - antibiotics/antivirals

• Vaccination

Types of Vaccines

• Live attenuated - microorganisms of reduced virulence, good for long lasting immunity, but bad for individuals with weaker immune systems

  • Eg: Measles, mumps and rubella (MMR) vaccine

• Inactivated - dead microorganisms, safe for people with compromised immune systems but immunity tends to be weaker

  • Eg: Inactivated Polio vaccine (IPV)

• Toxoid - toxins that are produced by bacteria, safer to take but immunity decreases over time

  • Eg: Tetanus vaccine

• Sub-unit - fragment of the microorganism, reduced risk of side-effects, but may require multiple doses

  • Eg: HPV vaccine

Antibiotics

• Bactericidal - kill bacteria by disrupting the cell wall, cell membrane, or essential enzymes

• Bacteriostatic - prevent bacteria from reproducing

• Broad spectrum & narrow spectrum

Antivirals

• A type of medication targeted towards viruses and specifically affects virus-infected cells

• Can prevent virus from entering the cell, exiting the cell, and replicating within the cell

Skin

• First line of defence

• Provides an impervious mechanical barrier to prevent pathogens from entering the body

• Low pH, constant shedding of dead skin cells, chemical secretions → inhibit the growth of pathogens

Mucous Membranes

• First line of defence

• Viscous, slimy secretions that protect internal structures

• Contains lysosomes that destroys bacterial cell walls

Cilia

• First line of defence

• Slender, hairlike structures that protrude from the surface of most mammalian cells

Acids

• 1st line of defence

• Stomach juices are highly acidic to kill ingested bacteria and swallowed pathogens

• Sweat is slightly acidic & contains lysosomes

Phagocytosis

• 2nd line

• The process by which phagocytes change shape and completely enclose a foreign particle, releasing enzymes to destroy it

• Phagocytes include: neutrophils, macrophages, dendretic cells, natural killer cells

Inflammation

• 2nd line

• A chemical response that helps wounds repair and leads to pathogen destruction

• Five cardinal signs of inflammation: pain, heat, redness, swelling, loss of function

Fever

• 2nd line

• Caused by pyrogens released by macrophages

• Occurs when cytokines alter the body’s set temperature

• Slows the replication of bacteria and viruses by shifting the temperature away from their optimal range

Four protective reflexes

• Coughing - irritation occurs in lower respiratory tract and causes expulsion of air from lungs

• Sneezing - occurs when the walls of the nasal cavity are irritated

• Vomiting - can be induced by psychological stimuli, excessive stretching of stomach, or bacterial toxins

• Diarrhoea - Results due to irritation of small/large intestines by bacteria/viruses/protozoa, irritation causes increased contractions of muscles leading to rapid removal of irritant

Blood Components

• Plasma: liquid component, carries nutrients, hormones, waste products, helps to regulate body temp.

• Platelets: Small cell fragments, help with blood clotting

• Red Blood cells (erythrocytes): contains haemoglobin which allows them to transport oxygen from the lungs to the rest of the body & remove carbon dioxide

• White blood cells (leukocytes): part of the immune system, help fight infections by attacking foreign invaders

Macrophages

• Monocytes differentiate into macrophages

• Responsible for detecting, targeting and eliminating foreign substances that are in the body

• Act as Antigen Presenting Cells, meaning they present antigens on the cell surface by protein molecules

Lymphocytes

Adaptive immunity cells which produce antibodies to target specific antigens

Types of Immunity

• Active Immunity - involves the production of antibodies by the body itself and the subsequent development of memory cells

• Passive Immunity - results from the acquisition of antibodies from another source and hence memory cells are not developed

Main parts of the Immune System

• Innate - consists of chemical & cellular defences against pathogens - its purpose is to immediately prevent the spread of pathogens - it is present from birth - first & second line of defense

• Adaptive - response that is specific to the pathogen presented, takes longer to initiate - usually the third line of defense

3 lines of defense

First line of defense - the surface barriers that prevent the entry of pathogens into the body, innate & non-specific

Second line of defense - the non-specific phagocytes and other internal mechanisms that comprise innate immunity

Third line of defense - the specific lymphocytes that produce antibodies as part of the adaptive immune response

Humoral Immunity

• Humoral immunity is effective against pathogens that are outside the body cells and involves antibodies produced by B lymphocytes

  • Plasma B cells are responsible for antibody production

  • Memory B cells remain in lymphoid tissue and are responsible for immunity

Cell Mediated Immunity

• Cell-mediated immunity is effective against pathogens within cells and involves the action of T lymphocytes

  • Cytotoxic T cells clone themselves, move to the cite of infection, and release cytokines to destroy it and the pathogen, usually by causing apoptosis (programmed cell death)

  • Suppressor T cells slow down/turn off the immune system to prevent damage to good cells

  • Memory T cells are produced after helper and cytotoxic T cells

• Helper T cells activate both cell mediated & humoral responses

Active vs Passive Immunity

• Active natural - producing antibodies in response to a pathogenic infection

• Active artificial - producing antibodies in response to a vaccine

• Passive natural - receiving antibodies from another organism eg: through breastmilk

• Passive artificial - receiving manufactured antibodies via external delivery

How do antibodies work

• The antibody binds directly to the antigen, neutralizing it

• The antibody acts as a tag on the antigen, making it easier for immune cells to recognize it

• Antibodies can clump multiple antigens together (Agglutination) or pull soluble antigens out of a solution (precipitation)

How can a virus change over time due to mutations

• Viral errors predominantly arises during replication

• Synthesis error - when polymerase adds incorrect nucleotides to the DNA/RNA sequence

• Proofreading - when DNA/RNA mismatches are not corrected by proofreading and/or post-replicative repair

• RNA viruses mutate faster than DNA viruses

How do viruses replicate

Once the virus infiltrates the cell, it multiplies by incorporating its own RNA/DNA into the host’ genetic material and replicating during the cell’s normal DNA replication process

Life Cycle of a Virus

1. Attachment to host cell

2. Entry into host cell

3. Biosynthesis

4. Maturation

5. Release

Attachment to host cell

A portion of the molecule on the viral surface resembles the chemical shape of the body’s molecule and this is how the virus binds to host cell receptors

Entry into the host cell

• Enveloped viruses can enter through envelope fusion, where the viral envelope fuses with the host cell membrane

  • Or through endocytosis, where the host cell membrane encapsulates the viral particle

• Naked viruses can enter through passing their nucleic acid from the viral capsid into the host cell membrane

  • Or also through endocytosis

Biosynthesis

Following entry into the host cell, the viral genome enters the cell’s nucleus where it is replicated, and transcribed into RNA in the ribosomes, if required

Maturation

The capsid is assembled around the viral genome

Release

• Naked viruses are predominantly released by host cell lysis (when the cell membrane ruptures leading to cell death)

• Enveloped viruses are released through budding, where the virus obtains its membrane from the host cell membrane, or through exocytosis, where the virus obtains its envelope and is released via transport vesicles

Atomic Mass

Total number of protons and neutrons

Atomic Number

Total number of protons

Nucleons

Either a proton or neutron within the nucleus of an atom

Strong nuclear force

One of the four fundamental forces in nature, responsible for binding protons and neutrons together inside the nucleus of an atom

Electromagnetic force

A physical interaction that occurs between electrically charged particles, opposite charges attract each other, while identical charges repel each other

Radioactive decay

The spontaneous process by which an unstable atomic nucleus loses energy by emitting ionizing radiation (alpha, beta, gamma) in order to become stable

How does strong nuclear force + electromagnetic force relate to the stability of a nucleus

• The stability of a nucleus depends on the constant competition between the strong nuclear force holding the nucleus together, and the electromagnetic force attempting to split it apart

• The strong nuclear force only effects nucleons that are close to each other and balanced and the electromagnetic force causes the positive protons within the nucleus to naturally repel each other

• Large nuclei eventually become unstable because when a nucleus has too many protons, the electromagnetic force eventually causes it to split apart

Different isotopes have different levels of stability

Because of the balance between protons and neutrons inside the nucleus, and the competing strong nuclear force and electromagnetic force acting on them

Binding Energy

• The energy that needs to be supplied to split a nucleus into its constituent nucleons

• Binding energy is absorbed when an atom or nucleus is broken apart, and released when an atom or nucleus is formed

• Binding energy of products > binding energy of reactant = exothermic (energy released)

• Binding energy of products < binding energy of reactant = endothermic (energy absorbed)

How does Binding Energy relate to the stability of a nucleus and nuclei becoming unstable?

• A higher binding energy per nucleon means a nucleus is more tightly bound and more stable

• A low binding energy per nucleon indicates instability and a tendency to undergo radioactive decay

Mass Defect

• The mass lost when separate nucleons bind to form a nucleus

• mass of nucleons - mass of nucleus

• The total mass of a stable nucleus is always less than the masses of the constituent nucleons, this difference in mass is known as the mass defect

• This lost mass is converted directly into released energy through E=mc²

Mass Defect & Binding Energy

• Binding Energy = mass defect x speed of light² (E=mc²)

• Energy = Mass x Speed of Light (3 × 10⁸)²

• To split a nucleus into nucleons, the binding energy must be supplied to their nucleus, to replace the mass defect

Alpha Radiation (α)

• 2 protons + 2 neutrons (a helium nucleus)

• Mass: 4 u (atomic mass units)

• Charge: +2

• Speed: 5-10% the speed of light

• Ionizing ability: Strongly ionizing, double positive charge & large mass allows them to strongly attract + strip electrons away from neutral atoms they pass

• Penetrating power: Weakly penetrating, travels 1-5cm in air, can be stopped by paper or the outer layer of human skin

Beta Radiation (β)

• High energy, high speed electron

• Mass: 1/1860 the mass of a proton

• Charge: -1

• Speed: aprox. 30-90% the speed of light

• Ionizing ability: Moderately to weakly ionizing, stronger than gamma rays but weaker than alpha particles

• Penetrating power: Moderately penetrating, travels a few metres in air, can be stopped by 5mm of aluminium

Gamma Radiation (γ)

• High frequency electromagnetic waves

• Mass: 0

• Charge: 0

• Speed: The speed of light

• Ionizing ability: Weakly ionizing, they do not frequently interact with matter due to their lack of mass and electric charge

• Penetrating power: Highly penetrating, travels for an infinite range through air, can be stopped by 10cm of lead or several metres of concrete

Alpha Decay

• Where an unstable atomic nucleus changes into a new element by shooting out an alpha particle

• Atomic mass reduces by 4 and atomic number reduces by 2 in daughter nucleus

Beta Decay

• When an atom’s nucleus decays and releases a beta particle, a neutron turns into a proton which stays in the nucleus, and a high energy electron is emitted

• Atomic mass remains the same, but atomic number increases by 1 in daughter nucleus

Gamma Decay

Where an unstable atomic nucleus drops from a high-energy excited state to a lower energy state by releasing gamma rays

Half Life

• The time it takes for half of the nuclei in a radioactive sample to decay (t½)

• The more unstable an isotope is, the faster it decays, resulting in a shorter half-life

Nuclear Fusion

• A nuclear reaction in which 2 or more light atomic nuclei combine to form one or more different, heavier atomic nuclei and subatomic particles

• The difference in mass between reactants & products manifests as the release of energy

• This results from the difference in nuclear binding energy

Nuclear Fission

• A nuclear reaction the occurs when an atomic nucleus splits into 2 or more pieces, which can happen spontaneously but is often triggered by the absorption of a neutron

• The total mass of fission products is slightly less than original reactants, with the loss of mass converting into energy

Why does nuclear fusion release more energy than nuclear fission?

Fusion reactions have a larger mass defect than fission reactions, therefore, more mass is converted into more energy to be released

Main components of nuclear power stations

• Reactor vessels - encase and prevent radiation from escaping

• Control rods - absorb neutrons to control nuclear reactions

• Fuel rods - contain pellets of enriched uranium & generate heat through controlled nuclear fission

• Steam generator - a heat exchanger that uses heat from the reactor core to power a turbine and generate energy

• Moderator - slows down fast neutrons produced during fission so they can effectively cause nuclear fission

How do nuclear power stations work to generate electricity?

• A nuclear reactor is a device in which nuclear reactions are generated

• The chain reaction is controlled to release large amounts of steady heat

• This heat is used to create steam, which powers a turbine and generates electricity

Controlled vs Uncontrolled nuclear reactions

• Uncontrolled reactions occur when neutrons escape too quickly resulting in the rapid release of nuclear energy, causing an explosion

• Controlled reactions occur when the neutrons produced from nuclear fission are slowed and absorbed to maintain a steady chain reaction

Advantages of using nuclear energy

• Longer operational lifetime than traditional coal power plants

• Reliable and fuel efficient

Disadvantages of using nuclear energy

• Lengthy development times, mean they are unable to satisfy immediate electricity demands

• Dangerous radioactive waste is produced, which must be safely dealt with and disposed of securely underground

What is Energy?

The capacity to do work or cause change

What is Energy Consumption?

Energy consumption refers to all the energy used to perform an action, manufacture something, or simply inhabit a building

Direct vs Indirect energy use

• Direct energy use refers to the energy that is immediately consumed in the moment

  • Eg: Turning on a light

• Indirect energy use refers to the energy that is consumed in the creation or transport of goods and services - the user does not directly use the energy, but causes the energy use elsewhere

  • Eg: Energy used to manufacture a lightbulb

What are Fossil Fuels?

• Non-renewable resources made from the remains of plants and animals that died millions of years ago and have been subjected to immense heat and pressure causing them to turn into a carbon-rich fuel

• Three types: coal, oil, natural gas

What happens to the concentration of CO₂ in the atmosphere when we burn fossil fuels?

Burning fossil fuels releases large amounts of CO₂ into the atmosphere at a faster rate than it can be removed - this causes the overall CO₂ concentration to increase

Describe the Greenhouse Effect

1. Earth’s surface absorbs visible light from the sun & increases in temperature

2. Earth’s surface emits infrared radiation, most of which passes through the atmosphere

3. Some infrared radiation is absorbed by molecules of greenhouse gas

4. These molecules of greenhouse gas increase in vibrational energy

5. Increased vibrations causes more collisions with other molecules of gas

6. Kinetic energy of gases in the atmosphere increases causing the temperature of the atmosphere to increase

Effects of the Greenhouse Effect

Global:

• Greenhouse effect aintains relatively warm average global temperature, whereas enhanced greenhouse effect causes average surface temperature to increase, causing extreme weather

• Greenhouse effect keeps water moving through the water cycle, but enhanced greenhouse effect causes sea levels to rise & flood coastal regions due to melting ice sheets

Local:

• Greenhouse effect creates stable biomes with predictable weather, but enhanced greenhouse effect causes water scarcity and wildfire risks as the temperature continues to increase

Common Greenhouse Gases

• Carbon Dioxide - CO₂

• Methane - CH₄

• Nitrous Oxide - N₂O

• Chlorofluorocarbons (CFCs)

• Hydrofluorocarbons (HFCs)

What is Organic Chemistry?

The study of compounds based on carbon atoms and their structures, properties, and reactions

Process of Fractional Distillation

1. Crude oil is heated until most of it evaporates and turns into a gas, where it is pumped into the fractionating column

2. Column is hot at bottom, cool at top, vaporized oil rises

3. When a substance reaches a height in the column where the temperature is equal to its boiling point, it condenses to form a liquid

4. Crude oil is then separated into different fractions at different heights, each fraction contains hydrocarbons with similar boiling points

5. Heavy fractions with longer molecular chains condense near the bottom, lighter fractions with shorter molecular chains condense near the top

Boiling Point

The temperature at which a substance changes from a liquid into a gas (or gas to liquid)

Viscosity

How difficult it is for a liquid to flow

Volatility

How easy it is for a substance to change into a gas

Flammability

How easy it is for a molecule to catch fire and burn in the air

Longer chain hydrocarbons

• High boiling point

• High viscosity

• Low volatility

• Low flammability

Shorter chain hydrocarbons

• Low boiling point

• Low viscosity

• High volatility

• High flammability

Fractions within a fractionating column (must be in order)

1. Refinery gas

2. Petrol

3. Naptha

4. Kerosene

5. Diesel

6. Fuel oil

7. Lubricating oil

8. Residue/Bitumen

Alkanes

• Homologous series of hydrocarbons that contain only carbon-carbon single bonds

• Are saturated

• General formula: C_nH_2n+2