Year 9 Science - Immune System: Main Revision

MAIN INFO

List 6 pathogens

• Parasites

• protozoa

• virus

• fungi

• prion

• prokaryote (bacteria)

List the characteristics of protozoa

• eukaryotic

• unicelluar

• They use vectors for transmission

• free living or parasites

• Feed on organic matter

• Found in a lot of tropical regions

• Contain organelles, unlike bacteria

List the characteristics of fungi

• eukaryotic

• unicellular

• multicellular

• Thrive in warm, moist environments

• Feed on host cells (like animals or humans)

List the characteristics of parasites

• eukaryotic

• unicelluar

• multicelluar

• used a vector for transmition

• used a flagellum to move

• An organism that feeds off (and causes harm to) another organism

• Ectoparasites – live ‘on’ the host. Carry other pathogens. They are vectors for other pathogens.

• Endoparasites – live ‘inside’ the host. Can cause disease directly.

List the characteristics of Bacteria

• unicelluar

• prokaryotic

• may use a flagellum to move

• Come in different shapes (spherical, rod, spiral)

• Reproduces via binary fission

List the characterisitcs of prions

• An infectious protein that converts your normal protein into a prion protein. When an infected cell bursts, the infected proteins are released to infect other cells.

• Responsible for degenerative neurological disorders

Examples:

• Mad Cow Disease

List the characteristics of a Virus

• Acellular (Non-living capsule)

  • Needs a host cell (living organism) to survive

• Injects its genetic material into other cells, forcing them to become infected. The infected cells eventually burst and end up infecting other cells with the new virus

Explain the process a virus undertakes: from infecting one cell to infecting many cells

Attachment: Virus attaches to the host cell.

Entry: Genetic material is injected into the host cell.

Replication: The virus takes over the cell's metabolism,

causing the creation of new proteins and

nucleic acids by the host cell's organelles.

Assembly: Proteins and nucleic acids are assembled into

new viruses.

Release: Virus enzymes cause the cell to burst and

viruses are released from the host cell. These

new viruses can infect other cells.

What is a vector? Give examples

An organism that carries a disease-causing pathogen between hosts. (Eg. mosquito)

What is a parasite?

An organism that feeds off (and causes harm to) another

organism – host. These may also carry pathogenic

microorganisms between hosts.

How do infectious diseases spread?

Infectious diseases spread when pathogens transmit from person to person through direct contact, contaminated objects, airborne droplets, or vector transmission

Explain the first line of defence. What’s its role and is it specific or non-specific?

The first line of defence is a non-specific, chemical and physical barrier that prevents microbes from entering the body.

CHEMICAL:

• stomach acid

• tears

• saliva

PHYSICAL:

• skin

• nasal hair

• eyelashes

• mucus

Explain the seccond line of defence. What’s its role and is it specific or non-specific?

The second line of defence removes pathogens that have entered the body and is non-specific, meaning it attacks any invading microbe. White blood cells called phagocytes engulf and digest the pathogens through a process called phagocytosis. This process can cause inflammation because increased blood flow brings more immune cells to the infected area. Additionally, the body raises its temperature through fever, making conditions less ideal for pathogens to survive and helping to kill them.

Explain the third line of defence. What’s its role and is it specific or non-specific?

The third line of defence is adaptive and specific. The B-cells recognise the antigens on the pathogen and produce antibodies that bind to them. The t-cells then destroy the antigen and infected cells. Afterwards, the immune system creates memory B and T cells that stay in the body, allowing a faster and stronger response if the same pathogen returns and to prevent future infections.

What are the three lines of defence? What’s their role and are they specific or non-specific?

1. Physical and chemical barriers to prevent infection (Innate and Non-Specific): Prevent microbes from entering the body

2. Inhibit and destroy invading pathogens (Innate and Non-Specific): Phagocytes engulf invading microbes, causing inflammation, and the resulting fever helps to kill the pathogens.

3. Adaptive and Specific: B-cells produce antibodies that bind to antigens on pathogens. The T-cells destroy the infected cells, and memory cells are formed to protect against future infections.

What are the cells in the 2nd line of defence? What are their functions?

Phagocytes are white blood cells that protect the body by detecting, engulfing, and digesting harmful pathogens through a process called phagocytosis.

What are the cells in the 3rd line of defence? What are their functions?

B cells produce antibodies that bind to specific antigens on pathogens, marking them for destruction. They also create memory B cells for faster response in future infections.

T cells destroy infected cells and memory T cells are also made to respond quicker next time.

What’s the difference between active and passive immunity? How are they aquired?

ACTIVE IMMUNITY:

• When your body must create antibodies to fight off the antigens

PASSIVE IMMUNITY:

• When you are given the antibodies, whether that be temporarily or long term

How to vaccines work?

Vaccines work by introducing a dead or weakened pathogen into the body. This triggers the immune system to produce antibodies specific to the pathogen’s antigens and creates memory cells. Because the pathogen is weakened or dead, the vaccine usually doesn’t cause serious illness but prepares the body to fight the real infection in the future.

DEFINE: Phacocytes

White blood cells which engulf and destroy invading microbes in the body.

DEFINE: Binary fission

Binary fission is the asexual reproduction of bacteria; it means that one bacterial cell splits into two identical cells - cloning itself.

DEFINE: Infectious disease

A disease caused by a pathogen (like a virus, bacteria, or fungus) that can spread from one person to another.

DEFINE: non-infectious diease

A non-infectious disease is a disease not caused by a pathogen and cannot spread from person to person. (Eg. diabetes, cancer)

What is an endoparasite?

a parasite that lives ‘inside’ the host. Can cause disease directly.

What is an ectoparasite?

a parasite that lives ‘on’ the host. Carry other pathogens. They are vectors for other pathogens.

What is herd immunity?

When most people in a community are vaccinated and immune to a disease, it makes it less likely to spread and protects those who aren’t immune.

Explain the duration of a vaccine’s effectiveness.

Vaccines can last from a few years to a lifetime, depending on what type of vaccine it is. The vaccine for MMR can last up to a lifetime, while the vaccine for influenza requires a booster shot yearly due to the constant mutation of the virus.

How do viruses replicate

Viruses inject their genetic material into a cell, forcing it to make more viruses. After a while, the cell bursts, releasing the new viruses to infect others.

DEFINE: virus

a tiny, non-living particle that infects living cells to reproduce. It contains genetic material (DNA or RNA) and needs a host cell to multiply.

DEFINE: Infection

When a pathogen enters the body, it multiplies and causes harm or disease.

Once infected with a pathogen, how does your body defend itself?

If you are infected with a pathogen, this means it’s gone through the first line of defence and now moves on to the 2nd. The body will produce phagocytes - also know as white blood cells- which engulf and destroys the invading microbe. This then causes inflammation due to the increase of blood flow to the affected area. The body will also experience fever as the pathogen requires certain living conditions such as 36 degree temperature - therefore your body will increase in temperature to kill the pathogen since it cant live in such conditions.

If the antigen passes the 2nd line of defence it then moves on to the third line. The B-cells will recognise the antigen and use plasma to produce specific antibodies to target and bind to the antigen. The t-cells will then destroy the antigen and afterwards both b-cells and t-cells will create memory cells to prevent future infection.

What is the difference bewteen an infectious and non-infectious disease?

An infectious disease is caused by pathogens like bacteria or viruses and can spread between people. A non-infectious disease is not caused by pathogens and cannot be transmitted.

List 3 reasons why scientists consider viruses to be non-living

• needs a host cell

• dont have cell structures

• they don’t carry out any metabolic processes

Whats the difference between phagocytes and antibodies

Phagocytes are apart of the 2nd line of defence, they engulf and destroy the invading microbe. While antibodies are apart of the 3rd line of defence, instead of destroying the antigen, it binds to it in order for the t-cell to destroy it.

How does bacteria reproduce?

Binary fission is how bacteria reproduces, it means that one bacterial cell splits into two identical cells.

What is a pathogen?

A pathogen is any organism that causes disease, including viruses, bacteria, fungi, protozoa, and parasites. They enter the body, multiply, and can make you sick.

DEFINE: Pandemic

a disease occurring throughout an entire country, continent or worldwide.

DEFINE: Epidemic

a disease affecting a large number of people in a particular area in a relatively short period of time.