Human Biology Flashcards
1
Q
Define microorganism
A
A microscopic organism - a living thing that requires a microscope to be viewed.
2
Q
Four main disease-causing microorganisms
A
- Bacteria
- Fungi
- Protists
Viruses are also included, but are not considered living things.
3
Q
Why are viruses not living things?
A
They do not share the common traits of living things (homeostasis, reproduction, metabolism (respiration), growth, response to stimuli).
4
Q
What is a pathogen?
A
- Pathogens are infectious agents that spread between hosts and cause disease
A disease causing microorganism
5
Q
Four main structural features of bacteria.
A
- Cellular
- Prokaryotic
- Unicellular
- No membrane-bound organelles
- No nucleus
6
Q
Characteristics of bacterial DNA
A
- Single circular molecule – bacterial chromosome
- Can contain plasmids - small circular double stranded DNA separate from chromosomal DNA. They can exchanage genetic material between bacteria
7
Q
Coccus shape
A
Spherical
7
Q
Four types of bacteria
A
- Coccus
- Bacillus
- Spirilla
- Vibrio
7
Q
Bacillus shape
A
Rod shaped
7
Q
Vibrio
A
Comma shaped
8
Q
Spirilla shape
A
Curved spiral
9
Q
Define virus
A
A non-cellular microorganism that depends on a host cell to synthesise proteins or replicate.
10
Q
Characteristics of a virus
A
- Non-cellular
- Don’t have cell membranes, cytoplasm, ribosomes, and other cell organelles.
- Unable to make proteins or even replicate on their own.
- Instead, they must depend on a host cell to synthesise their proteins and to replicate.
- Can contain either DNA or RNA
11
Q
How do viruses replicate?
What do viruses do once inside the host cell?
A
Use the cell’s ATP (Adenine triphosphate), ribosomes, enzymes, and other cellular parts to replicate
12
Q
Characteristics of RNA viruses
A
- RNA can be linear or circular
- Usually contain single-stranded RNA
- Sometimes contain double-stranded RNA
- Have smaller genomes that usually encode only a few proteins
13
Q
Characteristics of DNA viruses
A
- DNA can be linear or circular
- Usually double‐stranded DNA
- Rarely single‐stranded DNA
- Can encode up to hundreds of viral proteins
13
Q
Example of an infectious disease caused by bacteria
A
- Strep throat
- Caused by bacteria called group A Streptococcus
14
Q
Lytic cycle
A
- Attachment
- Entry of phage DNA and degradation of host DNA
- Synthesis of viral genomes and proteins
- Assembly
- Release
15
Q
Fungi characteristics
A
- Most are multicellular
- Yeasts: unicellular
- Eukaryotic
- Membrane-bound nucleus with DNA
- Membrane-bound organelles
- Can be microscopic or macroscopic
- Heterotrophs
- Cell walls made of chitin (fibrous substance consisting of polysaccharides)
- Cell membrane has phospholipid bilayer
16
Q
Define:
Protists
A
Unicellular eukaryotes that are not classified as plants, animals, or fungi but have some of their features.
17
Q
Protists characteristics
Size, ~cellular, pro/eukaryotic, nucleus?
A
- Microscopic to macroscopic
- 10 µm (unicellular protists) to several meters or more (multicellular seaweeds).
- Unicellular, multicellular or colonial
- Eukaryotic with nuclear membranes and membrane bound organelles
- Most protists are aquatic organisms
- Nucleus with DNA
18
Q
Protozoa
A
Animal-like protists
19
Q
Infectious disease
A
A disease caused by pathogens.
20
Q
Define:
Non-infectious disease
A
A disease caused by factors such as lifestyle, environment, or genetics. E.g cystic fibrosis, diabetes.
21
# State:
A disease caused by protists
Malaria
22
# State:
A disease caused by a fungus
Candidiasis of the mouth
23
# Define:
Infection
The invasion and multiplication of pathogenic organisms such as bacteria, viruses, protists and fungi that are not normally present within the body.
24
# Define:
Disease
Relates to a malfunctioning of the body or part of the body
Is pathological and can be diagnosed on the basis of recognizably signs and symptoms
25
# Define:
Antigen
Substances that are recognized as foreign by the host’s immune system
26
# Define:
Antibody
- A protein produced by the immune system in response to the presence of an antigen.
- Large Y shaped proteins
- Made/secreted by plasma cells
- Bind to antigens to signal an immune response
- Each type of antibody is specific to only one particular antigen
27
Virulence
The ability of a pathogen to produce disease. The virulence of a microorganism is a measure of the severity of the disease it causes.
28
# Define:
Disorder
Disorders are physical or mental conditions that disturb the regular or normal functions of everyday activities and day to day life.
28
# Define:
Endemic
Refers to the constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area. Eg Malaria, chicken pox
29
# Define:
Epidemic
Refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area.
30
# Define:
Outbreak
Carries the same definition of epidemic, but is often used for a more limited geographic area.
31
# Define:
Pandemic
Refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people.
SARS-CoV-2 was declared a pandemic on March 11 2020
32
# State:
Four external non-specific defences
- Skin
- Mucous membranes
- Hair and cilia
- Acids
33
# Describe:
Skin
| Define, what makes it harder for bacteria to colonise, pH, secretions.
- Provides a **physical impervious barrier** to prevent pathogens from entering the body
- **Dead skin cells** are constantly sloughed off to make it harder for invading bacteria to colonise
- Has **low pH between 4.7-5.7**
- Skin needs to be slightly acidic to make it difficult for pathogens to grow
- **Chemical secretions** e.g. sebum (oil) and **antimicrobial peptides** hamper growth of bacteria and fungi
34
# Describe:
Mucous membranes
| Role, purpose of mucus, can be ____
- **Lines cavities** of the respiratory (nose, mouth, lungs), urinary, reproductive and digestive tracts
- **Excrete mucus** that;
- *Protects the underlying cell layers*
- *Traps particles including pathogens*
- *Contains antimicrobial peptides*
- Mucus in respiratory tract can be swallowed and destroyed in the stomach, coughed up, or sneezed out
35
# Describe:
Hairs and cilia
| Where, what, what do they do
- Hairs line the nose cavity and ears
- Cilia
Tiny **hair-like projections**
**Beating motion moves the mucus** with the trapped particles towards throat to be swallowed or coughed up
36
# Describe:
Acids
| Different ones, pH, purposes.
- Stomach juices are **highly acidic**
- *pH = 1-2*
- Kills ingested bacteria and many pathogens in swallowed mucus
- Vagina acidic
- *Reduce growth of micro-organisms*
- **Sweat slightly acidic** and contains **lysozyme** (bacteria killing enzyme)
- Ear wax slightly acidic and contains lysozyme
- *Protects outer ear from some pathogenic bacteria*
37
# Define:
Protective reflexes
A reflex is an involuntary response to a stimulus. The four listed protect the body against infection
38
# State:
Four protective reflexes
- Sneezing
- Coughing
- Vomiting
- Diarrhoea
39
Sneezing stimulus
When the walls of the nasal cavity are irritated.
40
Coughing stimulus
Irritation in lower respiratory tract (bronchi and bronchioles)
41
# Define:
Coughing
| What happens when you cough
Expulsion of air from lungs
42
Coughing/sneezing purpose
The expelled air drives mucus and foreign matter up the trachea towards throat and mouth / out of the nose
43
What is vomiting induced by?
- Psychological stimuli (pain, sight, smell, emotion)
- Excessive stretching of stomach (gasses)
- Bacterial toxins
44
Diarrhoea stimulus
- Results due to irritation of small and large intestines by either;
- Bacteria, Viruses, Protozoa
45
What does the irritation of intestines cause?
| + water
- Irritation causes **increased contractions of muscles** leading to rapid removal or irritant
- Faeces is watery as material does not remain in large intestine long enough for water absorption
46
# State:
Three internal non-specific defences (second line of defence)
- Phagocytosis
- Inflammation
- Fever
47
# Define:
Phagocytosis
Process wherein a cell binds to the item it wants to engulf on the cell surface and draws the item inward while engulfing around it
Phagocytes are attracted by an inflammatory response of damaged cells
Engulf microorganisms that penetrate our external defences
48
Types of phagocytes
- Phagocytic Leukocytes (white blood cells)
- Neutrophils
- Macrophages (develop from monocytes)
49
Inflammation
| Definition, purpose, symptoms
- Response to any tissue damage
- Purpose:
- Reduce spread of pathogens by destroying them
- Prevent entry of additional pathogens
- Remove damaged tissue and cell debris
- Begin repair of the damaged tissue
- Symptoms:
- Redness, swelling, heat, pain
50
Steps of the inflammatory response
1. Injury to tissue – mast cells release histamine and heparin (and other substances) into tissue fluid
2. Histamine causes capillaries to become more permeable
3. When capillaries are more permeable then more blood can flow to the area – this results in heat to the area (warm blood) which can help kill pathogens, it also means fluid flows into the area to dilute any toxins and results in swelling
4. Heparin is released to prevent clotting in the immediate area of injury
5. Complement system proteins attract phagocytic cells
6. Phagocytes die and build up in the area (this is what pus is) The chemicals released by the mast cells attract phagocytes
- *Engulf microorganisms that penetrate our external defences*
7. The abnormal conditions in the tissue stimulate pain receptors
51
Fever
- Body temperature raises to inhibit growth and increase rate of reaction of enzymes
- Temperature controlled by hypothalamus (normal: set point temperature 37)
- When you have a fever, the hypothalamus sets point temperature above 37
- You feel cold → shiver → vasoconstrict → body temperature increases
- Crisis point - fever breaks → set point returns to 37
- Feel hot → sweat, vasodilate → body temperature returns to normal
52
Bacteria characteristics
* Prokaryotic
* No membrane-bount DNA/organelles
* Cytoplasm + ribosomes = protein synthesis
* Plasma membrane made out of peptidoglycan
* Unicellular
53
COVID structure
- Large (60-140nm diameter)
- Large spike-like projections (9-12 nm long) on the surface appear like a crown Enveloped virus
- Contains single-stranded RNA (26-32kb = big for viruses) encoding structural and non-structural proteins
54
COVID replication cycle
1. SARS-CoV-2 attaches to the host cell
2. Viral-host membrane fusion and release of viral DNA
- The membrane of the virus and the host fuse and viral DNA is released.
3. Translation and cleavage of polyproteins
- The host cell’s ribosomes are used to translate proteins necessary to form the replication complex and RNA polymerases for transcription and translation of the viral RNA to take place
4. Transcription of full length strand by replication complex
- Replication n**Replication** of full-length RNA strand 5’-3’ (sense strand) into 3’-5’ RNA strand (anti-sense strand)
5. Transcription and replication of viral genome
- **Second replication** step of a new 5’-3’ strand for new virus assembly
- Also **Transcription** of different mRNAs ready for translating proteins to construct new virus
6. Translation of structural and accessory proteins
7. Trafficking of newly synthesised viral proteins from (rough) endoplasmic reticulum (ER) to the Golgi
- **Translation** of mRNAs of proteins in the host’s rough endoplasmic reticulum
8. Assembly of mature virion in a budding vesicle
- The processed proteins and RNA strand (step 5) form a new mature virion
9. Mature virion release via exocytosis
55
Ways infectious diseases are spread
* Direct or close contact (transmission within 1-2m)
* Indirect contact (transmission outside of 1-2m)
* Vectors (organisms that transmit pathogens from an infected host to a susceptible host. e.g. mosquitos/insects)
56
# State:
Major blood components
Plasma, white blood cells (leucocytes), platelets (thrombocytes), red blood cells (erythrocytes)
57
Plasma
| Role
Transports nutrients, hormones, proteins, vitamins and minerals around our body
58
Types of white blood cells
Macrophages, lymphocytes (B and T cells).
59
Specific defence (third line of defence)
Blood and lymphatic system
60
# Define:
Humoral response (antibody mediated)
Antibodies produced by B cells cause the destruction of extracellular microorganisms and prevent the spread of intracellular infections.
| B cells
61
# Define:
Cell mediated response
Cell-mediated immunity provides resistance to the intracellular phase of bacterial and viral infections. Occurs when T-cells are stimulated, resulting in the production of killer T-cells and helper T-cells as well as memory cells.
| T cells
62
Humoral response (steps)
* The lymphoid tissue contains thousands of different B-cells
* Each type of B-cell is specific to an antigen
* When one type of B-cell is activated by an antigen (Primary response)
* Activated B-cells enlarge and divide into a clone
* Most of the clone become plasma cells secreting antibodies
* The remaining clone B-cells remain as memory cells
* Antibody-antigen complex inactivates the antigen in various ways
* Antigens are also presented to helper T cells, which further help to activate the B cells (via the release of cytokines)
63
Primary response vs secondary
Primary: First exposure of antigen to immune reaction
Body responds slowly taking several days to build up large amounts of antibodies
Secondary: Second or subsequent exposure to antigen
Body responds much faster
Memory B-cells are activated producing plasma cells and therefore antibodies at a faster rate to attack the antigen
64
Cell mediated response (steps)
* Antigen presenting cell travels to the nearest lymph node to present antigen to T-cells
* T-cell specific to the antigen becomes sensitised
* Sensitised T-cells enlarge and divide into a clone
* Some cells in the clone become memory cells
* Initiate faster response on subsequent exposure to antigen
* Other cell of the clone differentiate into three different types of T-cells – killer T-cells, helper T-cells and suppressor T-cells
65
Macrophages
- Involved in specific and non-specific defence
- Phagocytic
66
Lymphocytes
- Involved in specific and non-specific defence
- Predominantly produced in bone marrow, but also in lymphoid tissues
- Two main types:
- B-cells
- T-cells
67
Platelets (thrombocytes)
Facilitate blood clotting and tissue healing
68
Red blood cells (erythrocytes)
Transport oxygen around the body
69
B-cells
* Originate in the bone marrow
* B lymphocytes mature in the bone marrow
70
T-cells
- Originate in the bone marrow
- T lymphocytes migrate to the thymus where they mature
71
Where do b and t cells go (once mature)?
Both mature B-cells and T-cells enter the bloodstream, from which they migrate to the peripheral lymphoid organs.
72
Lymph nodes
Lymph nodes are a site where pathogens can be destroyed
73
Physical preventative measures
- Washing hands
- Wearing gloves
- Wearing masks
74
Antibiotics
— Drugs that fight infections caused by bacteria (e.g. penicillin)
75
Bactericidal antibiotics
kill bacteria by disrupting; cell wall, cell membrane or action of essential enzymes
76
Bacteriostatic antibiotics
prevent bacteria from reproducing usually by disrupting protein synthesis
77
Broad spectrum antibiotics
Affect a wide range of different types of bacteria
78
Narrow spectrum antibiotics
Affect only specific types of bacteria
79
Antiviral
| And why are they harder to make
— Antivirals treat infections caused by viruses
- Work by inhibiting replication of the virus
- A bacteria is a cell which we can target, but a virus infects your cells so they’re harder to get.
80
Immunisation
programming the immune system so that the body can respond rapidly to infecting micro-organisms, i.e. developing an immunity. This can occur naturally or artificially.
81
Vaccination
the artificial introduction of antigens of pathogenic organisms to the body
Vaccine: the antigen preparation used in artificial immunisation
82
Immunity
Resistance to infection by invading micro-organisms
83
Passive immunity
When a person is given antibodies produced by someone else. Antibodies are not produced by the person receiving the antibodies.
Can be natural → mother to baby across placenta
Can be artificial → injection of antibodies into blood stream
This provides instant immunity but is short lived as the antibodies break down and are excreted
84
Active immunity
When the body manufactures antibodies in response to an antigen
Your body has produced the antibodies yourself.
Immunity lasts longer because memory cells are produced
85
Natural immunity
- No human intervention required
- Occurs naturally within the body
- Can be passive or active
86
Artificial immunity
- Giving an antibody via injection
- Giving an antigen to someone to stimulate an immune response
- Can be passive or active
87
Role of lymphocytes (white blood cells) in humoral (antibody) mediated immunity.
Lymphocytes in humoral immunity produce antibodies that target and neutralize pathogens in the body fluids.
88
Role of lymphocytes (white blood cells) in cell-mediated immunity.
In cell-mediated immunity, lymphocytes directly destroy infected or abnormal cells, promoting the elimination of intracellular pathogens.
89
Humoral vs cell mediated
Humoral response involves antibodies that neutralize pathogens in body fluids, cell-mediated response uses cells to directly destroy infected cells.
90
Types of vaccines
- Live attenuated vaccines
- Inactivated vaccines
- Toxoid vaccines
- Sub-unit vaccines.
- mRNA/ Viral Vector
91
Live attenuated vaccines
Micro-organisms of reduced virulence
92
Inactivated vaccines
Contain dead micro-organisms
93
Toxoid vaccines
Injection of toxins that are produced by bacteria
94
Sub-unit vaccines.
Fragment of the micro-organisms is used
95
mRNA/ Viral Vector
Genetic message sent to the cell, cell produces the antigen fragment
