Week 1 - introducing clinical sciences Flashcards
(132 cards)
1
Q
What is meant by monogenic inheritance? (LO1)
A
Inheritance that is controlled by the expression of one gene or allele.
2
Q
What are alleles? (LO1)
A
Variations of a gene which occur due to a mixed inheritance from mother and father.
3
Q
List the major modes of Mendelian monogenic inheritance. (LO1)
A
- Autosomal dominant
- Autosomal recessive
- X-linked dominant
- X-linked recessive
- Mitochondrial
4
Q
If B represents the dominant brown hair gene and b represents the recessive ginger hair gene, and both mother and father are Bb, what are the possible outcomes for their child? (LO1)
A
BB (brown)
Bb (brown)
Bb (brown)
bb (ginger)
5
Q
Give some examples of autosomal dominant diseases. (LO1)
A
Marfan’s syndrome
Huntington’s disease
Polydactyly
6
Q
Give some examples of autosomal recessive diseases. (LO1)
A
Cystic fibrosis
Sickle cell disease
Tay-Sachs disease
7
Q
Give some examples of X-linked dominant diseases. (LO1)
A
Fragile X syndrome
8
Q
Give some examples of X-linked recessive diseases. (LO1)
A
Haemophilia
Duchenne muscular dystrophy
Fabry disease
9
Q
Give some examples of mitochondrial diseases. (LO1)
A
Leber hereditary optic neuropathy (LHON)
10
Q
What are some key characteristics of autosomal dominant diseases? (LO1)
A
- Occur in every generation.
- Each affected person has at least one affected parent.
- Every generation after your patient will have a 50% charge of inheriting the disease (if they were to have a child with an unaffected person).
- There are no carriers.
11
Q
What are some key characteristics of autosomal recessive diseases? (LO1)
A
- If a patient has the disease, both parents must either be carriers or affected.
- Not necessarily seen in every generation.
12
Q
What are some key characteristics of X-linked dominant diseases? (LO1)
A
- Mostly affects females but can have affected males and females in the same generation.
- There are no carriers.
- Affected father cannot pass it onto his sons but is guaranteed to pass it onto his daughters.
- Heterozygous affected mother has 50% chance of passing it onto her child regardless of gender.
- Homozygous affected mother has 100% chance of passing onto ALL of her children.
13
Q
What are some key characteristics of X-linked recessive diseases? (LO1)
A
- Males more frequently affected.
- Affected males often present in each generations.
- No father to son inheritance.
- If mother is carrier, 50% chance her son is affected, and 50% chance her daughter is a carrier.
- Unaffected father (XY) and affected mother (xx) - 100% chance their son is affected, 50% chance of daughter being carrier.
14
Q
What are some key characteristics of mitochondrial disease? (LO1)
A
- Mutation in the oocyte of the mother.
- Can never be passed on by the father.
- Can be passed on by the mother onto any gender of child.
15
Q
Define polygenic disease. (LO2)
A
A disease thought to be caused by the effects of two or more genes.
16
Q
Describe multifactorial inheritance and give some examples. (LO2)
A
This is when a displayed phenotype is a result of environmental and genetic influences.
Examples:
- Coronary artery disease
- Osteoarthritis
- Schizophrenia
- Hypertension
- Diabetes
- Cancer
- Obesity
17
Q
Describe family clustering. (LO2)
A
When there is a higher frequency of a disease in a family compared to the general population.
18
Q
Why do multifactorial diseases have no clear Mendelian pattern of inheritance? (LO2)
A
This is due to the contribution of environmental factors so it can be difficult to identify the role of genetics in these disorders. It also makes it difficult to determine a person’s risk of inheriting the disorder.
19
Q
Define heritability. (LO2)
A
A measure of susceptibility to a multifactorial disease. This is the proportion of the variance of a trait that is attributed to genetic factors for a given population.
20
Q
How can twin studies help determine the genetic influence on multifactorial diseases? (LO2)
A
Monozygotic twins are almost 100% genetically identical so any variability will be due to environmental influences.
21
Q
Why do we take a family history? (LO3)
A
- It reveals patterns of inheritance which helps with accurate diagnosis.
- Helps manage the whole family unit (e.g. GP).
- Obtains info about ethnic background.
- Could be important in identifying and treating diseases such as cancer and Alzheimer’s.
22
Q
How do we take a family history? (LO3)
A
- Start with patient’s closest relatives and go back one generation at a time.
- Include aunts, uncles, grandparents, first cousins, etc.
- Make sure to get info on their names, DOBs, ethnic background, health issues (as well as age diagnosed), age and cause of death, pregnancy outcomes (if relevant).
23
Q
How does the standardised key work when representing relationships? (LO3)
A
Marriage/partnership = single line between individuals.
Divorce/separation = single line between individuals with double slash going through it.
Consanguinous relationship = double line between individuals.
Children/siblings = single line coming from parents’ relationship which splits for the children.
Dizygotic twins = single line coming from parents’ relationship which splits into diagonal lines for twins.
Monozygotic twins = single line coming from parents’ relationship which splits into diagonal lines for twins and a line going across the diagonal ones.
24
Q
How does the standardised key work when representing individuals? (LO3)
A
Male = square.
Female = circle.
Sex unknown = diamond.
Affected male = shaded square.
Affected female = shaded circle.
Affected sex unknown = shaded diamond.
Deceased male = square with diagonal line going through.
Deceased female = circle with diagonal line going through.
Deceased sex unknown = diamond with diagonal line going through.
Pregnancy = relevant gender with P written inside.
Miscarriage male = triangle with male written underneath.
Miscarriage female = triangle with female written underneath.
Miscarriage sex unknown - triangle.
Person providing the pedigree information (male) = square with arrow pointing up to bottom left corner of the square.
Person providing the pedigree information (female) = circle with arrow pointing up to bottom left corner of the circle.
25
How do we recognise an autosomal dominant disease on a pedigree diagram? (LO3)
- Affected individuals in every generation.
- Male to male transmission (confirms that it is autosomal and not X-linked).
- Appears equally in male and female family members.
26
How do we recognise an autosomal recessive disease on a pedigree diagram? (LO3)
- Appears equally in male and female family members.
- Appears across the same sibship (group of offspring with same two parents).
- Skips a generation (but not always).
27
How do we recognise an X-linked dominant disease on a pedigree diagram? (LO3)
- Affected male will pass trait to all daughters.
- Affected male will pass it to none of his sons.
- Mostly females affected.
28
How do we recognise an X-linked recessive disease on a pedigree diagram? (LO3)
- Mostly males affected.
| - Affected father could have unaffected daughter but affected grandson.
29
Describe gram-staining and its mechanism. (LO4)
- Helps distinguish between gram positive and gram negative bacteria using crystal violet stain.
- Gram positive bacteria have a thick layer of peptidoglycan in their cell wall and are easily penetrated by the stain - result: blue.
- Gram negative bacteria have a thin layer of peptidoglycan covered by a lipopolysaccharide layer and are not penetrated by the stain - result: pink (due to counterstain applied afterwards: basic fuchsin stain or Safranin).
30
How do acid-fast Bacilli differ from gram bacteria? (LO4)
Acid-fast Bacilli present the "acid-fastness" characteristic.
This means that mycolic acids in the mycobacterial cell wall create a waxy barrier. This makes the bacteria resistant to decolourisation via acid alcohol.
31
What are the different ways to overcome "acid-fastness"? (LO4)
- Ziehl-Neelsen: heating up bacteria dissolves the mycolic layer enough for carbol fuchsin stain to penetrate the cell.
- Kinyoun: carbol fuchsin stain has a higher phenol concentration than basic Gram stain Fuchsin, hence heating the mycolic layer is not always necessary.
- Fluorochrome: auramine-rhodamine stain binds to the mycolic acid causing bright yellow/orange fluorescence when viewed under a fluorescent microscope.
32
Which areas are normally considered sterile in the body? (LO4)
- Blood and bone marrow.
- Cerebrospinal fluid.
- Serous fluid.
- Tissues.
- Lower respiratory tract.
- Bladder.
33
Which areas are normally considered commensal in the body? (LO4)
- Mouth.
- Nose.
- Upper respiratory tract.
- Skin.
- Gastrointestinal tract.
- Female genital tract.
- Urethra.
34
Describe how we use isolation and culture to detect microorganisms. (LO4)
- Bacteria and fungi grow on agar-based solid media, often showing a characteristic appearance to help identify the species.
- However, majority of medically relevant bacteria and fungi can be grown in artificial media.
35
Describe why media is important and why we use 'selective' media in culture techniques, (LO4)
- No single media universally supports the growth of all species so it needs to be chosen carefully.
- Selective media is designed to support the growth of one species while suppressing the growth of others.
36
Describe the basic protocol for culture of specimens with normal commensal microbiota. (LO4)
Specimens with normal commensal microbiota must eventually provide a pure microorganism culture. This is ensured by "plating out" specimens on nutrient-varied selective media.
A further subculture is grown in fresh media for testing identity and comparing antibiotic susceptibility.
37
Why is quantification important when carrying out isolation and culture? (LO4)
If the sample has come from someone's urine, it's important to know how much bacteria was in it as this can indicate infection.
e.g. 10^5 bacteria/ml of urine indicates an infection. Numbers lower this are not indicative of infection.
38
What adjustment must be made when culturing microorganisms such as Chlamydia and Rickettsia? (LO4)
Some bacteria such as Chlamydia and Rickettsia and viruses must be grown in host cell tissue cultures as these microorganisms cannot survive on their own.
39
List some disadvantages of carrying out isolation and culture to detect microorganisms. (LO6)
- More labour intensive.
| - Take longer to produce a result hence antibody/antigen detection tests and PCR tests are often used for diagnosis.
40
Describe the function of microscopy and the two types of light microscopy. (LO4)
Light microscopes are used to examine wet or stained preparations.
- Bright field microscopy - light background and dark organisms.
- Dark field microscopy - dark background and light organisms - used for thin culture specimens and showing the movement of a species.
41
What can wet preparations for light microscopy show? (LO4)
- Blood cells.
- Fluid specimens, e.g. urine, faeces, cerebrospinal fluid (CSF).
- Cysts, eggs and parasites in faeces.
- Fungi in skin.
- Protozoa in blood and tissues.
42
Describe the identification of helminths under a microscope. (LO4)
- They are commonly identified by macroscopic worm-like appearances (round-worms, tapeworms and flukes).
- You can also carry out microscopic examination of the species to search for eggs, e.g. in urine or faeces.
43
Describe the identification of protozoa under a microscope. (LO4)
- Morphological traits of protozoa can be seen under the microscope, e.g. different stages of the life cycle.
44
Describe what is meant by direct examination under a microscope. (LO4)
This means putting the specimen you want to examine directly under the microscope without any staining or alterations by lab techniques.
This is quicker and results can usually be obtained on the same day as the specimen was received.
45
Describe fluorescent microscopy briefly. (LO4)
Fluorescent microscopy detects antigens by staining the specimen or tissue with specific fluorescent dye-tagged antibodies so that they're visible under the microscope (immunofluorescence).
46
Describe the identification of fungi under a microscope. (LO4)
- These are macroscopically identifiable from colonies or pure cultures based on visual characteristics, e.g. colour of the colony.
- You can also carry out microscopic examination to identify the morphology of cells in fungi.
47
What can be detected with non-cultural techniques? (LO4)
- Structural components of cells - e.g. cell wall antigens.
- Extracellular products - e.g. toxins.
- Molecular approaches - e.g. specific gene sequences using DNA probes, PCR.
- Microbe susceptibility cannot be determined without cell culture but we could see the presence of resistance genes.
48
Describe what is meant by non-cultural techniques and why would they be used? (LO4)
Used for the detection of specific antibodies to pathogens.
It's important for specimens that cannot be cultivated in the lab, (e.g. Treponema pallidum, some viruses), or are a hazard to lab staff, (e.g. Francisella tularensis which causes tularaemia, Coccidioides immites which is a fungus).
49
Briefly describe the detection of microbial antigens (specific and non-specific techniques). (LO4)
- Can detect antigens by their interactions with specific antibodies.
- OR can detect microbial toxins.
- For non-specific techniques, gas liquid chromatography is used to detect fatty-acid end products of metabolism from anaerobic microorganisms.
50
Briefly explain microbe identification via PCR. (LO4)
- PCR is a specific DNA sequence amplification technique.
- It is useful for pathogens that are challenging to culture.
- Can rapidly (within 1-3 hours) detect a single gene target.
- Is able to identify genes responsible for synthesising toxic products.
51
What is RT-PCR? (LO4)
Real-time PCR (RT-PCR) uses fluorescently labelled sequence-specific probes (TaqMan) to visualise the amount of gene amplification in real time.
52
Give an example of serological tests. (LO4)
Enzyme-linked immunosorbent assay (ELISA).
53
When would a serological test be done? (LO4)
- It's used to look for antibodies within a patient. produced after fighting an infecting pathogen.
- IgM and IgG can both be detected in serum.
- High sensitivity assays use chemiluminescent or time-resolved fluorescent labels.
54
When would we typically see IgM antibodies in the serum (serological testing)? What does its presence indicate? (LO4)
- IgM antibodies are detected earlier in the infection (7-10 days after onset of symptoms).
- IgM is usually indicative of active infection.
55
When would we typically see IgG antibodies in the serum (serological testing)? What does its presence indicate? (LO4)
- IgG antibodies are detected 2-4 weeks after the infection as this is when resultant IgG production completes.
- IgG antibodies only show that the patient has come into contact with infection at some point in the past.
56
Describe serological tests in clinical medicine. (LO4)
- Classic diagnostic medicine: rise (4x) in antibody titre between 'paired sera'. Collected in acute phase of infection (5-7 days after onset of symptoms) and in convalescence (e.g. 3-4 weeks).
- Delayed result = used in retrospective diagnosis.
- Limited use for clinical management.
57
Describe the key characteristics of bacteria. (LO5)
- Prokaryotes.
- Single-celled.
- Cell wall.
- Lots of ribosomes (smaller than those possessed by eukaryotes).
- Can carry out transcription and translation at the same time.
- Size: 0.1-10μm in diameter but exceptions exist.
- DNA in the form of nucleoid and plasmids.
- Divide by binary fission.
- Can exchange genetic material.
- Absence of membrane-bound organelles.
58
What is a nucleoid? (LO5)
Single circular chromosome.
59
What is a plasmid? (LO5)
Extracellular circular DNA molecules.
60
By which characteristic are bacteria classified? What are the types? (LO5)
They are classified by shape.
1. Coccus (spherical).
2. Bacillus (rod-shaped).
3. Spirochates (spiral).
Other shapes do occur but these three are the most common.
61
What are the 3 different classifications of Coccus bacteria? (LO5)
1. Streptococci - occur in long chains.
2. Diplococci - occur in pairs.
3. Staphylococci - occur in clusters like grapes.
62
Describe the key features of spirochaetes. (LO5)
- Long, thin, spiral-shaped bacteria with an outer membrane.
- Between the cell wall and the outer membrane are 'internal flagella' which are filaments running the length of the bacterium.
- Spirochaetes are motile through a spinning action and the filaments flex the bacterium to achieve this.
- E.g. Vibrios - shaped like a comma.
63
What colour would Bacillus bacteria stain during a gram stain? (LO5)
Blue/purple - most Bacillus are gram positive bacteria hence the colour.
64
What common disease do cocci cause? (LO5)
- Strep throat.
- Spread through droplets.
- Management by antibiotics - amoxicillin or penicillin.
- Caused by gram positive bacteria.
- Can be caused by Streptococcal A.
65
What diseases apart from Strep throat can be caused by Streptococcus A? (LO5)
Strep A can get into the blood, deep muscle or fat tissue. It's invasive and it can cause:
- bacteraemia (blood infection).
- endocarditis (heart lining infection).
- meningitis (brain and spinal cord inflammation).
- peritonitis (peritoneal/intestinal inflammation).
- urinary tract infection.
- streptococcal toxic shock syndrome (infection causing low blood pressure and injury to organs such as the kidneys, liver and lungs).
66
What diseases are caused by Streptococcus B?
Strep B causes infections in newborn babies such as:
- lung infection.
- blood poisoning.
- meningitis.
67
What disease is caused by Bacillus bacteria? (LO5)
- Diphtheria
- Spread through droplets.
- Vaccine is available - Tdap - protects against tetanus, diphtheria and pertussis which are all potentially life-threatening.
- Caused by gram positive bacteria.
- Caused by Corynebacterium diphtheriae.
68
How does Corynebacterium diphtheriae make diphtheria potentially life threatening? (LO5)
- It makes a toxin that causes respiratory distress.
- Grey pseudomembrane can cover the throat (tonsils, pharynx, larynx) and can become a fatal airway obstruction.
- This can lead to heart and nerve damage.
69
What disease is caused by spirochaetes? (LO5)
- Helicobacter pylori.
- Spread through food, water, utensils or infected people.
- Causes a stomach infection, enters the GI tract.
- Management by antibiotics - amoxicillin, clarithromycin, metronidazole, tetracycline or tinidazole.
70
What classification (shape) of bacteria causes Strep throat? Which specific bacteria causes it? Gram stain status? (LO5)
- Coccus.
- Group A Streptococcus.
- Gram positive.
71
What classification (shape) of bacteria causes infections in newborns? Which specific bacteria causes it? Gram stain status? (LO5)
- Coccus.
- Group B Streptococcus.
- Gram positive.
72
What classification (shape) of bacteria causes diphtheria? Which specific bacteria causes it? Gram stain status? (LO5)
- Bacillus.
- Corynebacterium diphtheriae.
- Gram positive.
73
What classification of bacteria causes a H. pylori infection? (LO5)
- Spirochaetes.
74
Describe the process of gram staining. (LO5)
1. Take a clean, grease-free slide.
2. Prepare the smear of suspension on the slide with a loop.
3. Air dry and heat fix.
4. Crystal violet poured on the slide and kept for 30 seconds to a minute then rinse with water.
5. Flood the gram's iodine for 1 minute and wash with water.
6. Wash with 95% alcohol or acetone for 10-20 seconds and rinse with water.
7. Add safranin, leave for 1 minute then wash with water.
8. Air dry, blot dry and observe under the microscope.
75
Define infection. (LO6)
Infection is when a virus or microorganism invades the host cells and duplicates, leading to an immune response.
76
Define infectious disease. (LO6)
An infectious disease is when a pathogen or immune response is able to cause illness or damage (symptoms).
77
Describe the definition between communicable disease and endogenous disease. (LO6)
Not all infections are transmissible. Communicable infections are transmissible since the causative organism is a "foreign pathogen".
However, endogenous infections are non-transmissible since the causative organism is a commensal organism and so cannot be spread from person to person.
78
List the types of spread of infection. (LO6)
- Airborne.
- Droplet.
- Direct contact.
- Faecal-oral.
- Sexual transmission.
- Blood to blood.
- Vertical.
79
Describe the airborne transmission of disease. (LO6)
- Tiny particles - 1-5μm.
- Spread by cough aerosol.
- Remain suspended in air for a long time.
- Able to reach the alveoli of lungs.
- Ineffective to prevent with just handwashing.
- Low numbers but high virulence organisms, e.g. TB, measles.
80
Describe the transmission of disease via droplets. (LO6)
- Larger particles.
- Common method of transmission.
- 1 metre spread.
- Organisms of 10μm remain suspended in air for 17 minutes.
- Impact on mucous membrane (10μm organisms are deposited in upper airway.
- Handwashing is useful.
81
What is meant by direct contact with regards to disease transmission? (LO6)
Skin-to-skin contact.
82
What is meant by vertical transmission of a disease? (LO6)
There are two types of vertical transmission:
1. Mother to foetus - passed through the placenta and umbilical cord.
2. Mother to baby - at mother's genital tract during birth, breastfeeding.
83
What factors are needed to describe outbreak in epidemiological terms? (LO6)
- Number of people infected.
- Time they were admitted to hospital.
- Time when their infection develops.
- Whether they are all on the same ward or not.
- Whether they have a common medical or surgical team for treatment.
- Whether they have all been exposed to the same treatment or not.
84
What are the steps taken once an outbreak has been identified in the clinical setting? (LO6)
1. Appropriate specimens are collected from patients, from healthcare staff if they were involved.
2. Possible sources of contamination such as equipment, water, should also be sampled.
3. Samples are processed by the microbiology lab team to identify the organism.
4. While this is happening, containment should be taking place:
- Isolate the infected patients and treat appropriately.
- Infected healthcare workers to be sent home until they have been treated.
5. After the investigation, the situation needs to be reviewed so it can be prevented.
85
Define and list some of the factors affecting endemic disease. (LO6)
Endemic disease has a consistent existence within a specific geographical region or population.
- The agent responsible would possibly have a vector, reservoir or intermediate host which is locationally restricted.
- The agent itself could have environmental requirements (e.g. humidity, temperature).
- The population affected may be isolated geographically.
- Outbreaks may be isolated to unvaccinated populations.
86
Can the geographical limitations of any particular endemic disease change? (LO6)
Yes. Factors affecting this could be climate change, or migration.
87
Define pandemic. (LO6)
A pandemic is an endemic which is so widely spread that large populations in different countries are affected.
Example: H1N1 in 2009 which emerged in North America and then spread and affected over 200 countries.
88
Define epidemic. (LO6)
A widespread occurence of an infectious disease in a community at a particular time.
89
What are the 3 aspects of measures used in infection prevention and control (IPC)? (LO6)
- Personal aspect.
- Hospital aspect.
- Public health/global health.
90
List some of the personal aspects of measures used in infection prevention and control. (LO6)
- Good hygiene (handwashing).
| - Wash and cook thoroughly for fish, chicken, beef, seafood and eggs.
91
What are the four categories of the hospital aspect of measures used in infection prevention and control? (LO6)
- Institution.
- Health-care staff.
- Clinical practice.
- Response to infections.
92
What can the institution (hospital aspect) do to prevent and control infection? (LO6)
- Handling, storage and disposal of clinical waste.
- Containment and safe removal of spilled blood and body fluids.
- Cleanliness of environment and medical equipment.
- Specialised ventilation (e.g. laminar flow, air filtration, controlled pressure gradients).
- Sterilisation and disinfection of instruments and equipment.
- Food hygiene.
- Laundry management.
93
What can health-care staff (hospital aspect) do to prevent and control infection? (LO6)
- Education.
- Hand hygiene.
- Sharps management and disposal.
- Use of PPE (masks, sterile and non-sterile gloves, gowns and aprons).
- Screening health care workers for disease (e.g. tuberculosis, hepatitis B virus, MRSA).
- Immunisation and post-exposure prophylaxis (PEP).
94
What can be done in clinical practice (hospital aspect) to prevent and control infection? (LO6)
- Antibiotic stewardship.
- Aseptic technique.
- Perioperative antimicrobial prophylaxis.
- Screening patients for colonisation or infection (e.g. MRSA, GRE, CPE).
```
MRSA = methicillin-resistant Staphylococcus aureus.
GRE = glycopeptide-resistant enterococci.
CPE = carbapenemase-producing Enterbacteriaceae.
```
95
How can we respond to infections (hospital aspect) to control spread. (LO6)
- Surveillance to detect organism outbreaks and antimicrobial resistance.
- Antibiotic chemoprophylaxis in infectious disease contacts.
- Isolation.
- Reservoir control.
- Vector control.
96
How does public/global health work to prevent and control infections? (LO6)
- Public health addresses the underlying risk factors that increase risk of disease.
- Part of public health is to provide health protection, health promotion and health services.
- Offering vaccination programmes to the public.
- Educating the public for preventing infectious diseases (e.g. using mosquito nets to prevent malaria in endemic areas).
97
What does a healthy cell need to be able to to do in order to survive? (LO7)
- Protection.
- Nutrition.
- Communication.
- Energy.
- Movement.
- Recycling and renewal.
98
Describe the function of the plasma membrane. (LO7)
- Acts as protection.
- Selectively soluble.
- Doesn't allow passive diffusion of ions or large molecules.
- Contains molecules like phosphatidylserine which usually faces the inside and helps regulate apoptosis.
- Also has glycoproteins and glycolipids which act as receptors and allow cell-cell and cell-matrix communication.
99
What disease is caused by a malfunctioning plasma membrane? (LO7)
Cystic fibrosis.
A defect in the transmembrane chloride channel causes thick mucus production. In the lungs, the mucus traps bacteria and causes repeated infections.
100
Describe the function of the cytoskeleton. (LO7)
- Helps the cell keep its shape.
- Can act as tracks for vesicles to move on for transport around the cell.
- Three main components: actin, microtubules and intermediate filaments.
- Fourth component is specific to nuclear membranes and is called lamins.
101
Describe the function of actin in the cytoskeleton. (LO7)
- Most abundant cytoskeleton component.
| - Controls cell shape and movement.
102
Describe the function of microtubules in the cytoskeleton. (LO7)
- Microtubules and their associated motors form cilia and flagella.
- They also participate in chromatid separation during mitosis.
103
Describe the function of intermediate filaments in the cytoskeleton. (LO7)
- Intermediate filaments give strength to the cells.
| - Cytokeratin is an intermediate filament found in the cytoplasm of epithelial cells.
104
How can cytokeratin help with the management of cancer? (LO7)
- Cytokeratin is an intermediate filament found in the cytoplasm of epithelial cells.
- Epithelial cells from different tissues have different cytokeratin type profiles and we can use this knowledge to determine the likely origin of a cancer which has spread.
- This allows us to know how to manage and treat the cancer better.
105
Describe the function of lamins in the cytoskeleton. (LO7)
- Lamins maintain nucleus structure and regulate gene transcription.
106
What happens when there's a defect in the cytoskeleton? (LO7)
Progeria.
A disease which causes premature aging, caused by the collapsing of the nuclear membrane. This is caused by a mutation on the lamin A gene.
107
Describe the function of the rough endoplasmic reticulum (RER) in the cell. (LO7)
- Ribosomes on the RER convert mRNA to protein.
| - RER is the primary production site for proteins and lipids and addition of sugar groups also happens here.
108
Describe the function of the smooth endoplasmic reticulum (SER) in the cell. (LO7)
- SER produces lipids, phospholipids for plasma membrane and steroids.
- SER also stores and releases calcium ions which enable muscles to contract and relax.
109
Describe the function of the golgi apparatus in the cell. (LO7)
- Golgi apparatus is responsible for protein modifications
- Also responsible for adding sugars to proteins and lipids.
- Plasma cells have lots of Golgi as they produce lots of antibodies.
110
What happens when proteins misfold or are no longer needed by the cell? (LO7)
- They are degraded into peptides by proteosomes.
| - If there is excess, a stress response can be triggered which leads to apoptosis.
111
What are two possible diseases resulting from protein malfunctions? (LO7)
- Creutzfeldt-Jakob disease = synthesis gone wrong.
| - Alzheimer's disease = degradation gone wrong.
112
What happens when there's a defect in protein synthesis? (LO7)
Creutzfeldt-Jakob disease, a degenerative brain disorder.
| Prions (misfolded proteins) that build up in the brain cause brain cells to die.
113
What happens when there's a defect in protein degradation? (LO7)
Alzheimer's disease.
- Thought to be caused by the abnormal build-up of proteins in and around brain cells.
- Amyloid is one of the proteins involved. Deposits of it form plaques around brain cells.
- The other protein is called tau, deposits of which form tangles within brain cells.
114
Describe the function of waste disposal in cells. (LO7)
- To get rid of organelles and denatured proteins.
- Autophagy is when a cell gets rid of its own waste.
- Heterophagy allows cells to ingest foreign material from outside the cell.
- Neutrophils and macrophages ingest material to form phagosomes.
- Normal cells can ingest material which binds to the surface receptors, forming membrane-bound endosomes.
- Lysosomes contain chemicals and enzymes (
115
What disease is associated with a defect in autophagy? (LO7)
Alzheimer's, Huntington's and Parkinson's.
- Deregulated autophagy at different steps of the pathway, whether excessive or downregulated, has been associated with these neurodegenerative disorders known for their intracellular accumulation of protein aggregates.
116
Describe the function of energy production in a cell (LO7)
- Energy is needed to survive.
- The mitochondria is the powerhouse.
- ATP produced mainly by oxidative phosphorylation using glucose and fat.
- Rapidly growing cells can make intermediates so that lipids, proteins and nucleic acids can be produced instead but reactive H2O2 free radicals are produced.
117
Describe the function of mitochondria in the cell. (LO7)
- The mitochondria is the powerhouse.
- Mitochondria also controls apoptosis and contain their own DNA (maternally linked).
- Mitochondrial diseases can also be autosomal or maternally inherited caused by a mutation in the DNA.
118
What disease can be caused by a defect in the mitochondria? (LO7)
Mitochondrial myopathy.
- Related to mitochondrial mutations.
- Muscle fatigue is a common symptom because your muscles aren't getting enough energy.
119
Define homeostasis. (LO8)
"The intracellular milieu of cells is normally tightly regulated such that it remains fairly constant."
120
What can damage cells? (LO8)
- Hypoxia.
- Physical agents (e.g. mechanical trauma, temperature, pressure, radiation, electric shock).
- Chemical agents (e.g. arsenic, cyanide, insecticides, alcohol).
- Infections.
- The immune system (e.g. autoimmune disease).
- Genetic abnormalities (e.g. sickle cell anaemia - genetic abnormality in haemoglobin genes).
- Nutritional imbalances (e.g. starvation, vitamin deficiency, excess nutrition).
121
Describe hypoxia in cells. (LO8)
- Hypoxia refers to a lack of oxygen.
- Common cause of cell injury or death.
- Often occurs in conjunction with ischaemia (lack of blood supply).
- Ischaemia also starves cells of necessary nutrients and prevents removal of toxic waste products.
- Hypoxia can occur in several ways; most common is arterial blockage resulting in ischaemia.
122
Name a disease that can cause hypoxia in cells and explain how this happens. (LO8)
- Sickle cell anaemia.
- Inherited disease.
- Blood cells that are not normal biconcave disc shape.
- Results in hypercoagulation.
- Therefore, ischaemia and hypoxia can cause long-term stress on body cells.
- Lack of functional proteins.
- Lack of functional enzymes.
- Build-up in damaged proteins or DNA.
All of this results in cell death when beyond repair, triggering apoptosis and/or necrosis.
123
List some of the negative effects of hypoxia in cells. (LO8)
- Lack of functional proteins.
- Lack of functional enzymes.
- Build-up in damaged proteins or DNA.
All of this results in cell death when beyond repair, triggering apoptosis and/or necrosis.
124
Describe some environmental factors that could cause hypoxia in cells. (LO8)
Toxic agents are consumed or inhaled from the environment everyday. These can result in cell injury or death.
E.g. carbon monoxide, cigarette smoke and alcohol.
Carbon monoxide permanently binds to haemoglobin which can result in hypoxia.
125
Describe how the stress response (cortisol) is mediated. (LO8)
The hypothalamic-pituitary-adrenal (HPA) axis mediates the stress response.
- Stress induces nerve cells in the hypothalamus to stimulate the production of proopiomelanocortin.
- Proopiomelanocortin serves as a basis for a number of stress-related hormones including adrenocorticotropic hormone.
- This stimulates the adrenal gland to produce the hormone cortisol.
126
Describe the function of cortisol. (LO8)
The function of cortisol is to control the stress response. The stress response constitutes:
1. Blood pressure.
2. Blood glucose.
3. Inflammatory response.
The presence of glucocorticoid receptors in almost every cell and the fat-soluble nature of cortisol means it affects a wide range of body systems.
127
Give some examples of cell adaptations. (LO8)
- Hypertrophy.
- Hyperplasia.
- Atrophy.
- Metaplasia.
128
Describe hypertrophy. (LO8)
Increase in cell size and therefore organ size but not cell number.
In pure hypertrophy, there is only an increase in organelles and structural proteins. The massive enlargement of the uterus during pregnancy happens because of hypertrophy and hyperplasia.
129
Describe hyperplasia. (LO8)
Increase in the number of cells.
Can only occur when the cells in a tissue are capable of replication. Hyperplasia can be caused by growth factors, e.g. papillomavirus causes skin warts and mucosal lesions. In this case, the growth factors may be encoded by viral genes.
130
Describe atrophy. (LO8)
The reduction in size of cells by the loss of cell substance.
This can occur due to lack of blood supply or lack of endocrine stimulation. The atrophied cells have reduced function although they are not dead.
131
Describe metaplasia. (LO8)
The replacement of one adult cell type by another adult cell type.
Example: in a smoker, where normal ciliated columnar epithelial cells are replaced by rugged stratified squamous cells which can survive the harsh environment.
132
How does the immune system damage our own cells? (LO8)
Despite the immune system generally protecting against disease, it can cause damage to cells.
Example: autoimmune reactions against one's own tissues, allergic reactions against environmental substances, and excessive or chronic immune responses to microbes.
