Molecules - WMS
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What is a nucleotide made up of?
Base + Sugar + Phosphate
What is a the difference between DNA and RNA?
- DNA contains deoxyribose
- RNA contains ribose
Name the 4 nitrogenous bases in DNA.
Name the 4 nitrogenous bases in RNA.
What is the difference between the adenine (A) and thymine (T) pairing and the cytosine (C) and guanine (G) pairing?
There are 2 hydrogen bonds between A and T whereas there are 3 between C and G
What are 2 of the main things required for DNA replication?
- DNA polymerase
- Deoxyribonucleotide triphosphate (dNTP)
Where does protein synthesis occur?
On the ribosomes in the cytosol
Name the phases in Mitosis.
Name the phases in meiosis.
- Prophase I
- Metaphase I
- Anaphase I
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II
Name 4 types of chromosomes
- Telocentric - non in humans
- Acrocentric e.g. 21
- Subcentric e.g. 17
- Metacentric e.g. 3
What is the difference between chromosomal disorders and DNA disorders?
Chromosomal disorders are ones where the numbers of chromosomes have changed or the chromosomes rearranged. Theses lead to loss or gain of genetic material.
DNA disorders involve changes in the base sequence of the DNA which leads to changes in the protein content and the cell behaviour.
From what do chromosomic disorders arise?
What do disomic gametes produce?
Trisomic cells (47 chromosomes)
What do nullisomic gametes produce?
Monosomic cells (45 chromosomes)
Name the only example of a monosomic disorder and give a brief description.
Turners syndrome (45, XO)
Individuals are female, but only contain one X chromosome. The fail to develop secondary sexual characteristics.
Name 3 autosomal trisomy conditions.
- Patau syndrome (trisomy 13)
- - Most die within hrs/days of birth
- Edwards syndrome (trisomy 18)
- - Most die within a few weeks of birth
- Down syndrome (trisomy 21)
- - Incidence ~ 1:700
Name 3 sex chromosome trisomy and give the effects on their life.
- Triplo-X-syndrome (47, XXX)
- - Some mile mental retardation and ~25% infertile
- Jacob's syndrome (47, XYY)
- - Usually asymptomatic - possible motor co-ordination problems
- Klinefelter's syndrome (47, XXY)
- - Mile learning difficulties and infertility
What is the philadelphia chromosome?
A reciprocal translocation between chromosome 9 and 22 produces the the Philadelphia chromosome, which results in the fusion of the ABL proto-oncogene on chromosome 9 with the BCR gene on chromosome 22. The fusion protein allows cells to escape control of the cell cycle, leading to chronic myelogenous leukemia (CML).
Some triplet repeat diseases exhibit anticipation.
What is meant by anticipation?
The condition gets worse as it goes through generations. Probably because the number of repeats gets larger.
Name 4 agents that can damage the DNA.
- Ionising radiation
- Chemical mutagens
- Viral genomes (or parts of)
- Spontaneous deamination of adenine or cystine.
Name 6 types of DNA mutations and explain what they are.
- THE FAT CAT SAT ONA MAT
- Missence - base has been substituted
- THE FAT CAT SAT ONA RAT
- Deletion - The T in FAT has been deleted which has caused a shift to the left.
- THE FAC ATS ATO NAM AT
- Insertion - A H has be inserted which has caused a shift to th right.
- THE FAT CAT SHA TON AMA T
- Nonsence - The codon chain has changed and has signaled for a STOP.
- THE FAT CAT
- Duplication - A set of 3 has been duplicated so an additional amino acid will be in the protein.
- THE FAT FAT CAT SAT ONA MAT
- Tanslocation - Half of the sentence has been translocated from another sentence.
- THE FAT DOG DID NOT EAT
Give a named example of a disease that is due to a base substition.
Sickle cell (A-T mutation)
Give a named example of a disease that is due to a base insertion.
Muscular Dystrophy (addition of a single base in dystrophin gene)
Give 2 named examples of diseases that are due to base deletions.
- Alport syndrome (loss of a single base from collagen gene)
- Cystic fibrosis (loss of a triplet - F508)
What are the main patterns of inheritance in autosomal dominant conditions?
- Vertical inheritance (every affected child has an affected parent)
- Both sexes equally likely to get the condition
- Homozygotes for the condition are rare as both parents would have to be afftected
Give a named example of a disease that is due to a base substitution.
Sickle-cell (A-T mutation)
What are 2 main things required for DNA replication?
- DNA Polymerase
- Deoxyribonucleotide triphosphate (dNTP)
If a patient suffers from muscle stiffness and you suspect Paramyotonia (Eulenberg's), what effect does the mutation have on the Na+ channel?
Na+ is unable to close/is deffective
Use the Hardy-Weinberg equation to calculate the % of the population who are carriers for an autosomal recessive condition that affects 1 in 10,000 people.
- p2 + 2pq + q2 = 1 therefore p + q = 1
- q2 = 1/10000
- q = 1/100
- p = 1 - 1/100 = 99/100
- 2pq = 2 x 1/100 x 99/100 = 198/10000 = 2%
What assumptions are made when using the Hardy-Weinberg equation?
- Random mating
- No selection of alleles
- Mutation rate remains constant
- Population is large
- No migration in/out of the population
Explain how glucose is transported from the gut into a red blood cell and how important concentration gradients are maintained?
- Glucose and Na+ move into the epithelia cell down the concentration gradient via a Na+ driven symport.
- Glucose moves out of the epithelia cell into the blood down a concentration gradient via GLUT-2 transporter via facillitated diffusion.
- Glucose is then transported into the red blood cells via the GLUT-1 transporters via facillitated diffusion, down a conentration gradient.
- To maintain the low [Na+] in the epithelia cell, there is a Na+/K+ ATPase pump which transports 3 Na+ ions out into the blood and takes in 2 K+ ions.
What prevents an efflux of glucose from the red blood cell?
Glucose is converted to glucose-6-phosphate by hexokinase immediately in the the red blood cell and therefore the concentration of glucose remains low.
What is the Nernst equation?
- E = ln [ion]out / [ion]in * RT/ZF
- At 37 degrees use:
- E = 61/Z * log [ion]out / [ion]in
- Z = valance/charge of ion
What effect would increasing the extracellula [K+] have on the resting membrane potential?
Moves the resting membrane potential closer to the action potential, i.e. makes it more positive. This makes is easier for an action potential to occur.
What type of active transport is Ca2+-ATPase an example of?
What type of transporters are glucose transporters?
Name 5 physiological processes that transporters can influence.
- Uptake of metabolites
- Extrusion of waste products
- Maintenance of intracellular pH
- Generation of and use of ion gradients
- Regulation of cell volume
What are the main differences between passive transporters and active transporters?
- Passive transporters do NOT require energy, whereas active transporters DO.
- Passive transport is from [high] to [low], whereas active can be against concentration gradient.
What are the main differences between channel/pore transporters and carrier proteins?
Channel/pore transporters are faster and less specific that carrier transporters.
Name 5 different types of signals.
- Gap junction
- Direct contact
What is the name given to a ligand that does not activate a pathway?
What is the name given to a ligand that activates a pathway?
What are ligands?
Generic term for molecules that bind to specific sites on a protein.
How do effectors alter the gene transcription?
They change the protein composition which changes the cell behaviour. This can turn genes on or off.
What 3 mechanisms do effectors use to change cell behaviour?
- Alter gene transcription
- Alter ion balance across the plasma membrane
- Alter the activity level of existing enzymes
What can increase basal metabolic rate?
Trauma - Body needs to make more red blood cells
What are macronutrients?
- Nutrients needed in large amounts
- Essential fatty acids
Name 3 conditional nutrients.
What genetics are associated with obesity?
- Prader-Willi synrome (gene cluster on chromosome 15) - predisposed to overeating ==> hyperphagia and obesity
- Human Leptin (chromosome 7) - RARE
- HOB1 (Chromosome 4) - familial obesity in women
- 300 proteins associated with diabetes type II
What are micronutrients?
- Nutrients required in small amounts
- e.g. vitamins, iron, zinc
Who are at risk from malnutrition in the west?
- Chronically ill patients
- Drug abuser/alcoholics
- Those on long term medication
- The homeless
- Those living in solitary
- Pregnant/lactating women
What are the factor which affect basal metabolic rate?
- Age - Increased in infants, declines with age
- Sex - higher in males
Basla metabolic rate is measured in terms of surface area. What is the advantage of this?
Comparison between infants and adults etc. can be made
What are the symptoms of vitamin A deficiency?
- Preventable blindness
- Increased risk of infection
What is the general water expenditure per day?
- 1-2 L/day
- 1/2 - 11/2 L through normal kidney function
- 1/2 L through respiration and sweating
Which drugs are cholesterol lowering drugs?
Why does a child suffering from Marasmus starvation look thin and bony?
Low calarie intake so the body is forced to break down fats and protein for energy which leads to muscle wastage.
Why does a child with kwashiokar starvation have oedema?
The child has too low a protein intake and so when the carbohydrates in the diet are converted to fat in the liver it cannot be removed. This leads to a fatty liver which leads to liver failure. this causes portal hypertension which leads to ascites.
What are the 5 lipoprotein classes?
- VLDL (very low density lipoprotein)
- IDL (intermediate density lipoprotein)
- LDL (low density lipoprotein)
- HDL (high density lipoprotein)
Name the 6 essential nutrients.
- Calaries (carbs/fats)
- 8-10 amino acids
- Essential fatty acids
What is the body water content of a lean body mass and where in the body is it?
- In 70kg person there is 42L - 28L intracellular, 10L interstitual and 4L serum
As a rough guide, how do you work out basal metabolic rate in:
- KJ/day ==> weight (kg) x 100
- Kcal/day ==> weight (kg) x 24
Name the two types of starvation.
What are the main differences between marasmus and kwashiokor?
- Marasmus ==> inadequate cal intake, inadequate protein intake, no oedeam, thin and bony
- Kwashiokor ==> poor/normal cal intake, inadequate protein intake, oedema present, thin with pot belly
What are the approx. clincal goals for a weight loss programme for an obese/overweight person?
What is cachexia?
Rapid fat and muscle wastage
What are the main diseases linked to obesity?
- Type II diabetes
- Cancers - endometrial, breast, prostate, colon
- Gall bladder disease
- Respiratory problems
How do you calculate BMI?
Weight (kg )/ Height (m2)
What are the clinical definitions of overweight and obese?
- Overweight ==> BMI>25<30
- Obese ==> BMI>30
How many joules are there in 1 cal?
What are the roles of proteins?
- Gene control
What is meant by the tertiary structure of proteins?
The overall structure formed by a polypeptide chain e.g. myoglobin
What is meant by the quaternary structure of protein?
The interaction of a number of polypeptide chains to forma multimeric protein complex e.g. heamoglobin
What is meant by the secondary structure of a protein?
- The local interactions of the amino acids in the polypeptide chain. These forces can include ==> van der waals, hydrogen bonds, hydrophobic forces, ionic interactions and disulphide bonds e.g. cysteine
- 3 types
- alpha helix
- beta sheets
- loop/turn or beta turn
What is meant by primary structure of a protein?
The order of amino acids
At what site in the DNA's double helix are enzymes/substances likely to act and why?
- Major groove of DNA
- More base pairs are exposed in the major groove and there is more space for enzymes/substances to reach and act upon them.
What bonds are present in primary proteins?
What is the general structure of an amino acid?
Name the positively charged and hydrophillic amino acids.
Name the negatively charged and hyrophillic amino acids.
Name the polar hydrophillic amino acids.
Name the non-polar hydrophobic amino acids.
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