Topic 2 - Genes + Health Flashcards
1
Q
Lungs
A
Lungs allow rapid gas exchange between the atmosphere and blood.
One bronchus extends into each lung, they branch into smaller air pathways called bronchioles. They each connect to alveolar ducts, that connect directly to alveoli (sites of gas exchange).
2
Q
Epithelial cells
A
They line the outer surface of many animals. They line cavities and tubes within animals along with covering sufaces of internal organs.
Basement membrane attaches epithelium to connective tissue below.
3
Q
Basal membrane
A
Membrane surface of epithelial cell that faces basement membrane
4
Q
Apical membrane
A
Membrane surface of epithelial cell that faces away frkm the basement membrane
5
Q
Types + location of epithelial cells
A
Squamous = epithelium in walls of alveolus
Columnar = epithelium in small intestine
Ciliated = found in airways, lungs
6
Q
Role of cilia, no CF
A
Mucus is swept by a beating of cilia into the mouth cavity where it is either coughed or swallowed (stomach acid can kill it)
7
Q
Cilia, with CF
A
People with CF produce stickker mucus, cilia cannot move this so jt builds up in airways
Pathogens can be trapped in sticky mucus and cause diseases
- white blood cells can fight infection but when they die they release DNA - making mucus stickier
- Low O2 levels in mucus as it diffuses slower due to thickness
- epithelial cells use more O2 as cilia are working harder, requiring more energy.
- anerobic environments perfect for bacteria to thrive
8
Q
SA:V
A
Surface area ÷ volume
As an organism increases in size:
- Surface area increases by factor of 4
- Volume increases by factor of 8
SA:V VALUE DECREASES BY A HALF
9
Q
Unicellular organism’s exchange surface
A
The whole cell surface membrane is the exchange system
Substances that diffuse into or out of cell move down the concentration gradient (high to low)
10
Q
Multicellular (larger) organism’s exchange surface
A
Require more gas exchange in order to meet metabolic needs, harder for them to absorb substances due to the size of their surface compared to their volume
11
Q
Why cant large organisms rely on simple diffusion
A
Inner most tissues would be too far from gas exchange site meaning it would not be fast enough.
Organism would die, dehydrate
12
Q
Gas exchange system features
A
Large surface area from alveoli
Numerous capillaries associated with each alveolus
One cell thick capillaries and thin alveoli walls reduces distance of air in the alveolus and blood in the capillaries
Cocentration gradient maintained by constant blood flow
13
Q
Fick’s law
A
Rate of diffusion = (Surface area x concentration gradient) ÷ thickness of exchange system
14
Q
Surface area
A
Directly proportional to rate of diffusion
15
Q
Concentration gradient
A
Directly proportional to the difference in concentration across the exchange system
16
Q
Thickness of gas exchange system
A
Inversely proportional to the thickness of the gas exchange system
17
Q
Amino acid structure consists of
A
amine group (-NH2) carboxylic acid group (-COOH) Hydrogn group (-H) Residual group (R)
18
Q
Primary structure of protein
A
The sequence of amino acids in a polypeptide chain
- Amino acids join in condensation reaction to form dipeptide
- Peptide bond formed between two subunits
- Process continues till polypeptide chain is formed
- Proteins consist of two or more polypeptide chains
19
Q
Secondary structure of protein
A
Protein folds and coils
- Interactions between R groups of amino acids in polypeptide chain cause it to fold and coil
- They either coil into a-helices or b-pleated sheets
Within a protein molecule there may be sections of both a-helic and b-pleated, and some that are not twisted in any ordered manner
20
Q
a-helix (secondary structure)
A
Regularly spaced hydrogen bonds form between amine and carbolxylic groups on different amino acids in the polypeptide chain
21
Q
b-pleated sheets (secondary structure
A
Amino acid chains may fold back on themselves or may kink together with the hydrogen bonds holding the parallel chains
Each hydrogen bond is weak but cumulative effect makes structure stabel
22
Q
Tertiary structure of protein
A
Protein folds into more precise 3D shape
Chemical bonds and hydrophobic reactions between R groups maintain final tertiary structure
Depression (active site) formed in tertiary structure
Reactions between R groups:
Polar R groups attract other polar molecules
Some amino acids have ionised R groups so ionic bonds can form between + and - R groups
23
Q
Quaternary structure of protein
A
Protein has more than one polypeptide chain
24
Q
Conjulated proteins
A
Contains other chemical group within their polypeptide chain
25
Globular protein
Polypeptide folded compactly into spherical shape
Soluble as hydrophillic side chains project on the outside of the molecule
3D structure vital for binding to other substances, such as enzymes and antibodies
26
Fribrous proteins
Do not fold, remain as long chains
Insoluble proteins
Several polypeptide chains can be cross-linked for strength
Keratin in hair, collogen in bone and tendons
27
Phospholipid bilayer
Structure of cell surface membrane
Basic structure = two layers of phospholipids
2 fatty acids, 3rd replaced by negatively charged phosphate group
Phosphate heads are polar, hydrophillic
Fatty acid tails are non-polar, hydrophobic
28
Why do phospholipids arrange themselves in the bilayer
Cells are filled with aqueous cytoplasm and aqueous tissue fluid
Cell surface phospholipids adopt most suitable structure - bilayer
Hydrophobic fatty acid tails have no contact with water on either side of the membrane
Hydrophillic phosphate heads are constantly in an aqueous environment
29
Fluid mosaic model
Model refers to arrangement of proteins in cell surface membrane
Suggests some proteins are fixed witin the membrane, but some are not and are free to move in the fluid bilayer
30
Evidence 1 (fluid mosaic model)
Experiment showed two types of proteins:
- Those that can be easily separated from membrane by increasing ionic conc of solution
- Those that required more drastic measures like detergents
This supports the model:
Peripheral proteins are loosely attached to the outer surface membrane
Integral proteins are fully embedded in the phospholipids
31
Evidence 2 (fluid mosaic model)
Evidende for integral proteins = freeze fracture electron microscopy studies
1) Frozen membrane sections were fractured along weak points between lipid layers
2) Inner fractured surface was coated in heavy metal
Smooth mosaic surfaces were revealed, interspersed with large integral proteins
32
Evidence 3 (fluid mosaic model)
Mouse/human cell fusion:
1) specific membrane protein in each cell was marked by a colour before fusion
2) light mìcroscope was used to follow protein movement, after fusion no immediate movement
3) after 40 mins at 37°c there was complete intermixing of proteins
4) only way to mix was by diffusion, showing membrane had fluid components
33
Unsaturated phospholipids + bilayer fluidity
More phospholipids with unsaturated fatty acids, more fluidity
Kinks in the hydrocarbon tails of unsaturated phospholipids prevent them packing closely together - more movement possible
34
Cholesterol + bilayer fluidity
Cholesterol between phospholipids maintains fluidity of membrane by affecting movement of phospholipids
35
Diffusion
Passive, no metabolic energy required
Net movement of molecules or ions from a region of high conc to a region of low conc.
Concentration gradient - difference in concentration between two areas, diffuse occurs where there is a gradient
Un-charged molecules like O2 ca diffuse across membrane
36
Osmosis
Net movement of water molecules from an region of high conc to region of low conc through partially permeable membrane
- If solute is present, H20 will form bonds with them reducing the movement of the water
- More solute means fewer molecule collions and less movement across membrane
Osmosis continues till isotonic conditions are met
37
What cannot diffuse through the membrane
Polar (hydrophillic) molecules and ions larger than CO2
38
Facilitated diffusion
No metabolic energy needed
- Ions can diffuse across within channel proteins, which have specific shape allowing molecule to pass
- Gated channels open and close depending on signals
- Ions/molecules can bind to specific site on carrier proteins, protein changes shape allowing substance to diffuse actoss
-
39
Active transport
Energy required when moving substances again concentration gradient, specific carrier proteins used
- Energy supplied from ATP (adenosine triphosphate)
- Substance to be moved across binds to carrier protein
- One phosphate is removed from ATP by hydrolysis forming ADP
Small amount of energy needed when breaking bonds between ATP and phosphate group
- Phosphate group is then hydrated
Energy released as bonds form between phosphate group and water
- This energy changes carrier protein shape, substance is released on the other side of membrane
Moving substance against the concentration gradient
40
Active transport
Energy required when moving substances again concentration gradient, specific carrier proteins used
- Energy supplied from ATP (adenosine triphosphate)
- Substance to be moved across binds to carrier protein
- One phosphate is removed from ATP by hydrolysis forming ADP
Small amount of energy needed when breaking bonds between ATP and phosphate group
- Phosphate group is then hydrated
Energy released as bonds form between phosphate group and water
- This energy changes carrier protein shape, substance is released on the other side of membrane
Moving substance against the concentration gradient
41
Exocytosis
Bulk transport of substances out of cell
| Vesicles fuse with the cell surface membrane releasing their contents
42
Endocytosis
Bulk transport of substances into the cell
| Vesicles are created from the cell surface membrane bringing substances into the cell
43
Water content regulation achieved by
Transport of sodium and chloride ions across the epithelial cells
Water then follows by osmosis
44
Excess water in mucus
1) Sodium ions are constantly pumped across the basal membrane
2) Sodium ions diffuse across sodium channels in the apical membrane
3) Chloried ions diffuse down electrical gradient
4) Water is drawn out of cells by osmosis due to high salt content in fluid
5) Water is drawn out of mucus by osmosis
45
Too little water in mucus
1) Chloride ions are pumped into cell across basal membrane
2) Chloride ions diffuse across open CFTT channels
3) Sodium ions diffuse down electrical gradient into mucus
4) Elevated aalt conc in mucus drains water out of cell by osmosis
5) Water is drawn into cell by osmosis
46
Regulating water content with CF
1) CFTR channel is absent or not functioning, chloride ions cannot be secreted across apical membrane
2) Epithelial sodium ion channels are open, sodium ions are constantly absorbed from mucus by epithelial cells
3) High levels of sodium ions drains chloride ions and water from mucus into cell by osmosis
4) Makes mucus more viscous, water is constantly being removed
47
Digestive system
Groups of pancreatic cells produce enzymes that help breakdown carbohydrates + lipids. These enzymes are released through the pancreatic duct and delivered to the gut in pancreatic juice
48
Digestive system with CF
Pancreatic duct blocked by mucus
- Digestive enzymes cannot be released
- Low conc of enzymes in small intestine
- Low rate of digestion
Food not fully digested = higher % of undigested food in feces meaning energy is lost - leads to malabsorption syndrome
Enzymes trapped in mucus in the duct can lead to a form of diabetes
49
Enzymes
Enzymes are biological catalysts that speed up the rate of reactions, they are globular proteins.
Specific 3D shape, has a depression on the surface of the molecule, known as the active site.
Only a few amino acids may be involved in the active site.
The active site of an enzyme has a particular shape in which only a specific substrate can fit in.
50
Lock and key theory
Only one molecule with complimentary shape, or two molecules that join to form a complimentary shape can fit into the active site.
Substrate molecules form a temporary bond with the amino acids in the active site to produce an enzyme substrate complex.
When the reaction has occurred, the products are released leaving the enzyme unchanged.
Each enzyme will only catalyse one specific reaction
51
Activation energy
Energy needed at the start of a reaction to break
52
Activation energy + enzymes
In cells, enzymes reduce the amount of energy needed to start reactions so they can occur at lower temperatures.
Attraction of oppositely charged groups on enzyme active site and complimentary substrate distort shape of substrate and assist in breaking or forming bonds.
53
Induced fit theory
Active site is slightly flexible, when substrate enters the active site the enzyme molecule changes shape slightly, fitting closely around substrate.
Only a specific type of substrate can induce the correct change in the enzymes active site.
54
Metabolism
The metabolism of an organism is the sum of all the enzyme catalysed reactions occurring within it.
55
Anabolic reactions
'Building up' reactions
e.g synthesis of glycogen from glucose
56
Catabolic reactions
'Breaking down' reactions
e.g enzyme breaking down substrates
57
Enzyme conc + rate of reaction
Initial rate of reaction is directly proportional to enzyme concentration.
The more enzymes present, the more active sites available to form enzyme substrate complex.
More enzymes mean more successful enzyme/substrate collisions.
Substrate in excess.
58
Substrate conc + rate of reaction
High substrate concentration means the enzyme concentration is limiting the rate of reaction.
The active sites are full and substrates cannot enter an active site until it is free.
59
Effect of CF on reproductive system
Females have a reduced chance of becoming pregnant. Mucus plug can develop in the cervix preventing sperm from reaching the egg.
It can make a male lack vas deferens (sperm duct) on both sides so sperm cannot leave the testes.
If vas deferens is present however, it can be blocked by a thick sticky layer of mucus. Means fewer sperm is present in each ejaculate.
60
Genes
Gene: sequence of bases on DNA molecule coding for sequence of amino acids in a polypeptide chain. It is a section of a DNA strand.
Genes make up a fraction of the DNA in chromosomes.
61
DNA
DNA= deoxyribonucleic acid. It is a long chain polymer made up of units called nucleotides or mononucleotides.
62
Mononucleotides consist of:
Deoxyribose (5-carbon) sugar.
Phosphate group.
Nitrogen containing base.
```
Only the base is variable between 4 types:
Adenine
Cytosine
Guanine
thymine
```
63
DNA molecule structure
Two polynucleotide strands twist to form double helix.
Sugar and phosphate groups form two sugar-phosphate backbones and are on the outside.
Base faces inwards horizontally and are held in pairs by hydrogen bonds.
Two nucleotide strands are described as antiparallel as they run in opposite directions.
64
Why does A pair with T and G with C
Adenine pairs with thymine. (2 Hydrogen bonds)
Cytosine pairs with guanine. (3 Hydrogen bonds)
65
Protein synthesis (basic outline)
Proteins are made in the cytoplasm; 1st stage is transcription which takes place in the nucleus.
A copy of the gene that codes for the required protein is made, made from RNA.
RNA leaves the nucleus into the cytoplasm; the original gene stays in the nucleus.
RNA carries the code from the nucleus to the cytoplasm, so it is called messenger RNA.
Correct sequence of amino acids are joined in the 2nd stage, translation. Where the protein is formed.
Involves transfer RNA (tRNA) and ribosomal RNA (rRNA).
66
RNA
Single stranded polynucleotide made of ribonucleic acid.
Contains phosphate, base and ribose sugar.
Uracil replaces thymine as a base.
67
Nature of genetic code
3-base code carried by DNA
3 bases (1 codon) codes for 1 amino acid
code is degenerate (several triplets can code for the same amino acid)
68
Transcription process
Enzyme RNA polymerase attaches to start of gene
Hydrogen bonds break between genes, DNA molecules unwinds at that point
One strand acts as a template to make mRNA copy
RNA polymerase lines up RNA mononucleotides along the template strand, complimentary base pairing means mRNA strand will be complimentary to template sttrand
Once paired, RNA polymerase joins the mononucleotides to form mRNA molecule
mRNA detaches from DNA and leaves nucleus through pore, original DNA remains in the nucleus
69
Translation process
mRNA attaches to ribosome, tRNA brings amino acid to ribosome
tRNA molecule with anticodon for start codon on mRNA attaches itself to mRNA by complimentary base pairing
Second tRNA molecule attaches itself to the next codon in the same way, two amino acids on tRNA form peptide bond through condensation reaction - first tRNA moves away
Another tRNA molecule attaches to the next codon, this process repeats forming a polypeptide chain until stop codon is reached and tRNA does not transfer another amino acid
polypeptide moves away from ribosome - transcription complete
70
Outline DNA replication
DNA double helix unwinds from one end and two strands split up as hydrogen bonds break by DNA helicase.
Free DNA nucleotides line up next to each single DNA strand and H2 bonds form between complimentary base pairs.
Enzyme DNA polymerase links adjacent nucleotides with phosphodiester bonds in condensation reaction forming new complimentary strands.
This way each original strand acts as a template on which new strand is built.
Over all two complete DNA molecules are formed, each identical to each other and the original strands.
Each of the two DNA molecules contain one “old” and “new” strand -> semi-conservative replication.
71
Define gene mutation
Sometimes as the “new” strand is being made, inaccuracies with base pairings can cause an incorrect base to slip into place. This is an example of a gene mutation.
72
Outline the basics of genes + chromosome pairs
Gene is a length of DNA that codes for protein, every cell apart from the sex cells contain two copies (one from each parent).
For any gene, the copies are located on the same locus (position) on the two paired chromosomes.
Humans have 23 pairs of chromosomes, chromosomes in each pair are called homologous chromosomes. one originally comes from the father the other from the mother.
73
Define allele/genotype/phenotype
Allele; different form of the same gene
Genotype: alleles a person has
Phenotype: characteristics caused by genotype
74
what is Thalassemia (single gene recessive disorder)
Genetic disorder affecting production of haemoglobin
Someone homozygous recessive for one of these alleles cannot produce, or produce functioning haemoglobin
75
What is Albinism (single gene recessive disorder)
Effects production of melanin, pigment that colours skin, hair and eyes
76
what is Phenylketonuria (single gene recessive disorder)
Rare metabolic disorder that effects breakdown of protein
77
What is Huntington's disease (single gene dominant disorder)
Inherited brain disorder, effects mid-life cognitive ability like walking and speech
78
Testing embryos - Amniocentesis
Invasive technique
needle inserted into amniotic fluid to extract foetal cells that have fallen off the foetus and placenta
cells are cultured and examined for faulty allele
carried out 12-17 weeks into pregnancy - 1% chance of miscarriage
79
Testing embryos - Chronic villus sampling
invasive technique
Using ultrasound guidance, tube is inserted through the cervix and sample of foetal villi is taken from placenta.
carried out 8-12 weeks into pregnancy - 2% chance of miscarriage
80
Testing embryos - non-invasive parental diagnosis
DNA fragments from mother’s blood plasma are analysed, 10-20% of this “cell-free” fetal DNA (cffDNA) belongs to the embryo not the mother.
cffDNA detectable at 4-5 weeks into pregnancy
81
IVF treatment
First an early embryo is placed into a culture till it is around 8 cells developed.
One can be removed for genetic testing without damaging the embryo.
DNA of cell is analysed and results of genetic screening are used to decide whether to put the embryo in the uterus.
IVF is expensive and can be a stressful process.
Low rates of success.
82
Ethical framework 1 - Rights and duties
Rights are social conventions, if you live in a society you must abide by these conventions.
Some in the same society as you may have a duty to get you these rights
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Ethical framework 2 - Maximising good in the world
Utilitarianism - no moral absolute beyond maximising good in the world.
Always do things that increase good in the world
84
Ethical framework 3 - Leading a virtuous life
A good life consists of acting virtuously
85
Treatments for CF - Dietary changes
Adults with CF are recommended high energy foods and double the normal protein intake
May be advised to take salt supplements
Digestive enzyme supplements help compensate for lack of enzymes in the small intestine
86
Treatments for CF - Physiotherapy
rhythmic tapping of chest and flutter devise can help loosen mucus + improve flow of air in/out of lungs
87
Treatments for CF - Medication
Bronchodilators -> drugs that are inhaled using nebulisers. Drug relaxes the muscles in the airways, opening them up and relieving the tension in the chest.
Antibiotics -> used to kill or prevent growth of bacteria in the lungs.
DNAase enzymes -> Infection in lungs accumulates white blood cells, when they break down they release DNA adding to the stickiness of the mucus. DNAase can be inhaled by a nebuliser and breaks down the DNA, making the mucus easier to rid of from the lungs.
Steroids -> used to reduce inflammation of lungs.
88
Treatments for CF - Future gene therapy
Gene therapy alters the genotype and therefor phenotype of cells affected by condition - remove genes that don't work and replace them with ones that do
In CF gene trials, healthy CFTR protein incorporates with cell membrane thus restoring ion channel + avoiding symptoms of CF
