Topic 2 Ford Flashcards
What is Cystic Fibrosis?
- a genetic disease that’s caused by inheriting a recessive allele
- it results in stickier mucus
Structures in the lungs
- trachea
- bronchus (bronchi)
- bronchioles
- alveolus (alveoli) –> where gas exchange occurs
- diaphragm
Endothelium
a single layer of squamous epithelial cells to create a short diffusion distance
Types of epithelium
- columnar –>tall cells
- squamous –> flat cells
- cuboidal –> square cells (large SA)
- stratified –> multiple layers
What type of epithelial cells are found in the lungs?
pseudostratified ciliated columnar epithelium
fake - has layers, has cilia, tall
Cilia
hair like structures beat and move mucus up and out of lungs
Basement membrane
holds cell in position, touching connective tissue
Goblet cell
produces mucus which is released into the airway
Apical membrane
in touch with gases and mucus
How does the structure of alveoli and surrounding capillaries ensure there is rapid diffusion across the gas exchange surface?
- large surface area –> lots of alveoli
- plentiful blood supply –> numerous capillaries which maintains the concentration gradient
- short diffusion pathway –> one cell thick
How does the rate of diffusion change as an object gets bigger?
the rate of diffusion doesn’t change we just expect it to travel further
Diffusion
the net movement of particles from a high concentration to a low concentration (down a concentration gradient) until equilibrium is achieved
PASSIVE
Factors affecting diffusion
-concentration gradient
-surface area
-diffusion distance
(-temperature –> not relevant as body temperature)
How do we maintain the concentration gradient?
- continuous blood flow
- lots of ventilation (breathe in/out)
Fick’s Law
the rate of diffusion is proportional to the (surface area x concentration difference) / membrane thickness
What happens in the lungs of a CF sufferer?
- mucus is normally move up by cilia
- the mucus isn’t moved as the mucus is stickier
- gas exchange becomes less efficient
- this can cause less oxygen in and carbon dioxide out so there is a smaller concentration gradient
- also if it becomes blocked the overall surface area of the lungs will be reduced
- sometimes pathogens will get caught
Typical cell membrane
phospholipid bilayer
Phospholipid
has a phosphate head and 2 fatty acid tails (is made by removing a fatty acid from a triglyceride and replacing it with a phosphate)
Why does a bilayer form?
- because both fluids (the cytoplasm and tissure fluid) are aqueous
- the phosphate head is hydrophilic and the fatty acid tail is hydrophobic so to satisfy both parts of the phospholipid it creates two layers so the water loving heads are in the aqueous solutions and the fatty acid tails are separated from it
What is the most stable arrangement for phospholipids?
a bilayer
Phospholipid bilayer function
provides stability, fluidity and selective permeability (to small non-polar molecules)
Proteins and glycoproteins function (protein and carbohydrate)
many diverse functions: channels, transporters, receptors, enzymes
Glycolipid function (lipid and carbohydrate)
involved in cell cell recognition
Cholesterol function
reduces membrane fluidity
Glycolipids
attached to phosphate heads
Glycoproteins
attached to proteins
Cholesterol
within the membrane
Integral membrane protein
embedded within the membrane
Transmembrane proteins
these are integral proteins which span all the way across the membrane
Peripheral proteins
attached to the surface of the membrane
Facilitated diffusion
-diffusion with the aid of proteins either channel or carrier
-channel –> transport different molecules with a specific shape allowing them through, has an aqueous environment (some are gated)
-carrier –> proteins change shape to allow the specific molecule to pass through them
PASSIVE
Osmosis
the net movement of free water molecules from a high concentration to a low concentration of free water molecules through a partially permeable membrane
PASSIVE
Active Transport
the net movement of molecules from a low concentration to a high concentration of molecules through a partially permeable membrane
ACTIVE –> REQUIRES ENERGY FROM ATP
Exocytosis
vesicles fuse with the cell membrane and release their contents out of the cell
Endocytosis
vesicles are created from the membrane to bring contents into the cell
Vesicle
small membrane bound sacs
How can you treat CF?
you can’t really but to make it easier you can take antibiotics to kill bacteria as you’re more prone to bacterial infection. Also physiotherapy is used to dislodge mucus
Why is extra sticky mucus produced?
because the epithelial cells don’t regulate the water content of the mucus correctly
How might a CFTR protein be faulty?
- never made
- folded wrong, not in membrane
- doesn’t function properly
- faulty opening
- breaks down quickly after being made
- made in smaller quantities than norma
Effects of CF on the reproductive system
- mucus plug develops in cervix –> stops the sperm getting past it at any point
- vas deferens are absent or blocked by sticky mucus –> stop sperm being produced
- in both cases sperm can’t reach the egg
Effects of CF on the digestive system
- the pancreas is where digestive enzymes and insulin and glycogen are made
- the pancreatic duct gets blocked by sticky mucus so digestive enzymes don’t get into the small intestine
- less food is digested so not absorbing nutrients
- maintaining body mass is difficult, diabetes, enzyme damage to pancreas tissue
Chromosomes in humans
46 chromosomes, 23 pairs
Homozygous
2 identical copies of the allele
Recessive
- the allele that will only code for a protein if the dominant allele is absent
- 2 of these need to be present for it to be expressed
Phenotype
the characteristic seen which is cause by the genotype
Dominant
- the allele that codes for a protein even if the recessive allele is present
- only one allele needs to be present for the characteristic to be expressed
Genotype
the combination of alleles that a person has
Heterozygous
2 different alleles - genotype containing different alleles with different instructions
Alleles
different versions (alternative form) of the same gene
Locus
the position of a gene on a chromosome
Gene
- the length of DNA that codes for a protein
- sequence of bases on DNA that codes for a sequence of amino acids in a polypeptide chain
Monohybrid inheritance
inheritance of a characteristic controlled by a single gene
Incomplete/Co-dominance
- when one allele is recessive and one is dominant - there’s an in between so this is what is seen as the phenotype
- neither allele is completely dominant and both effects of the alleles are shown in the phenotype
Dihybrid inheritance
inheritance of two independent characteristics controlled by two different genes
Example of co-dominance
blood type genotype I^AI^B –> phenotype AB
Sex linkage
the chance of getting a disease is linked to the XY chromosomes (if an allele for a disease is on the Y chromosome then women can’t pass it on, if the allele is on the X chromosome then a father can’t pass it to his son because he would pass on his Y chromosome, females have greater reduced chances of getting a dominant allele because they have 2 X chromosomes)
Genetic screening
allows you to identify carriers and diagnose a disease
Prenatal genetic testing
testing of DNA from an embryo or foetus
Amniocentesis
- insert a needle into the amniotic fluid to collect fetal cells that have fallen off the placenta and fetus or a sample of amniotic fluid
- usually at 15-17 weeks
- 1% risk of miscarriage
Chorionic Villus Sampling
- small sample of placental tissue removed either through abdomen wall or vagina
- usually at 8-12 weeks
- 1/2% risk of miscarriage
Genetic testing
-can confirm an initial diagnosis and identify carriers of ‘faulty’ genes
Testing before implantation (PGD)
- If there’s a family history of the disease then pre-implantation genetic diagnosis may be an option
- The couple undergo in vitro fertilisation
- Once embryos are created, they can be tested before being put into the uterus
- One cell can be removed without harming the embryo and can be tested for disease
- They can decide which embryo to put back into the uterus
In vitro fertilisation
- mix sperm and egg cells
- fertilisation
- create an embryo
- inserted into uterus
is expensive and stressful, also the success rates are quite low
IVF ethical issues
- embryo may be damaged and they have a right to life
- embryo may be destroyed
- false negative leading to parents preparing incorrectly emotionally and physically
Rights and Duties
we have certain rights and because of this we have duties towards people
Maximising the good in the world
always do whatever maximises the good in the world. Utilitarianism have no other moral absolutes
Making decisions for yourself
you get to decide what you want - informed decision and consent so able to think about yourself
Leading a virtuous life
the good life consists of acting virtuously, consider the virtues before deciding (justice, wisdom, faith, hope, courage, charity)
Prenatal testing ethical issues
- risk of damage to fetus and risk of miscarriage (fetus has right to life)
- false negative; parents not prepared emotionally/financially
- confidentiality issues; paternal DNA not match
Advantages of genetic screening
- can make informed decisions
- can prepare mentally and financially
- early diagnosis allows better treatments
Homologous
pairs of chromosomes (one from the male parent and one from the female parent)
