Met Flashcards
Formula for BMI
weight(kg)/height(m)^2
= BMI in kg/m^2
Give the BMI range for classification as clinically obese.
30-34.9 kg/m^2
Give the BMI range for classification as clinically underweight.
<18.5kg/m^2
Give the BMI range for classification as clinically normal.
18.5-24.9 kg/m^2
Give the BMI range for classification as clinically overweight.
25.0-29.9 kg/m^2
Describe the order fuel molecules are mobilised and utilised on an exended period of fasting.
Glucose from plasma Glycogenolysis Gluconeogenesis FA and glycerol from AT KB from FA via acetyl CoA aa from muscle protein
Define homeostasis
the maintenance of the body’s internal environment within set limits, in a dynamic equilibrium.
Define and BMR and state factors which may affect it.
basal energy required to maintain life and so necessary for the functioning of various TOB at physical, digestive and emotional rest.
- thyroid status
- pregnancy/lactation
- body weight
- gender
Describe the effects of thyroid hormones T3 and T4.
- Increase metabolic rate, catabolic effects generally, increase BMR: increase in size and no. of mit., increase O2 consumption and heat prod. and increase nutrient utilisation.
- promote normal growth and devel.-increase synthesis of specific proteins. Directly affect bone mineralisation and increase synthesis of heart muscle protein.
- CNS: hormones required for development of cellular processes of nerve cells, hyperplasia of cortical neurones and myelination of nerve fibres. Lack of T3 and T4 in adults characterised by poor conce., memory and lack of initiative.
- Stimulate hormone and neurotransmitter receptor synthesis e.g. heart muscle, GI tract. Heart more sensitive to adrenaline and noradrenaline. Increased motility in GI tract.
- Allow actions of FSH and LH. Necessary for ovulation.
- Increase turnover of proteins and glycoproteins in skin and subcutaneous tissue.
Describe lactose intolerance
Low lactase activity necessary to digest lactose to glucose and galactose. Lactose not absorbed is fermented by gut bacteria, producing lactic acid, methane gas and hydrogen. Water potential of gut lumen is lowered so fluid and electrolytes are secreted, causing diarrhoea. Gases cause stomach cramps, and flatulence and nausea may also be experienced. Condition may also affect galactose met.
How are thyroid hormones transported in the bloodstream?
Thyronine binding globulin, also pre-albumin and albumin. T4 binds with a greater affinity and so has a longer 1/2 life.
What is the mechanism of action of thyroid hormones?
T3 and T4=hydrophobic, so cross PM of cells, and interact with specific receptors in nucleus and possibly mit. Binding to hormone-binding domain of receptor induces a conformational change in receptor, unmasking the DNA binding domain. Interaction of hormone-receptor complex with DNA increases rate of transciption of specific genes translated into proteins. Increased rate of protein synthesis stimulates oxidative energy met. in target cells to provide extra energy required for protein synthesis- this also produces increased amounts of functional proteins so increased cell activity.
What treatment can be given for alcoholism and how does it work?
Disulfiram- inhibits the aldehyde dehydrogenase enzyme in alcohol metabolism, so toxic acetaldehyde accumulates, causing hangover symtpoms e.g. nausea for a week.
Anatomical location of the thyroid gland
base of neck, anterior to lower larynx and upper trachea
Describe thyroid hormone synthesis
ATE ICE
Why does a patient with hyperthyroidism suffer heat intolerance?
Excess thyroid hormones in bloodstream increase metabolic rate, so increased respiration in cells, and energy produces is dissipated as heat, so core temp. rises.
What test can be used to diagnose Cushings disease from cushings syndrome
High dose Dexamethasone suppression test
Describe the Dexamethasone suppression test
Dexamethasone=potent synthetic steroid which when given orally, normally suppresses secretion of ACTH and thus cortisol by feedback inhibiton. Suppression of plasma cortisol by >50% is characteristic of Cushing’s disease, as though diseased pituitary is relatively insensitive to cortisol, it is still sensitive to potent synthetic steroids. Suppression does not normally occur with adrenal tumours or ectopic ACTH secretion.
How can synacthen be used to test adrenocorticol functin?
Synacthen=ACTH analogue, given intramuscularly, which would normally increase plasma cortisol by >200nmol/l. A normal response usually excludes Addison’s disease.
Why can a person with Addison’s disease suffer from increased skin pigmentation?
Lack of cortisol- stimulates release of ACTH from the anterior pituitary via -ve feedback. The MSH sequence is contained with the primary sequence of ACTH so when ACTH is present at high levels, it can exert similar effects to MSH, stimulating melanocytes to produce and secrete melanin, so increased secretion of melanin by melanocytes in the skin which gives skin its pigmentation.
Where is glucokinase found and why does it have a high Km?
Liver
High Km=low affinity, so glucokinase only converts glucose to G6-P when glucose is at very high concentrations which is important as G6-P formed in the liver will be converted to glycogen for storage, and so we only want this when glucose is in excess.
List 2 functions of glucose 6P-dehydrogenase.
- NADPH production
- production of ribose sugars for nucleotide synthesis.
Describe the use of carbimazole in treating hyperthyroidism.
Carbimazole prevents the iodination of thyroglobulin when forming thyroid hormones, by inhibiting the thyroid peroxidase enzyme.
Why would a patient with G-6P dehydrogenase deficiency present with jaundice?
Enzyme catalyses Pentose Phosphate pathway respnsobile for NADPH prod. So reduced NADPH, meaning increased disulphide bond formation between adjacent Cys residues on aa in Hb bolecule, forming Heinz bodies. Therefore, increased rbc lysis, producing lots of bilirubin, unable to all be conjugated by liver fast enough so remains in bloodstream, causing jaundice.
