On air broadcast presented by Dr Andi on Sunday May 4, 2008
Online article written by Michelle Kovacevic
Q: If you fell over and ingested a spider web, could you digest it?
A: Spider silk is made of a form of keratin, the protein found in human hair, which can be broken down into its constituent amino acids by strong acid at high temperatures for a long period of time. As you may know, our stomachs contain very strong acid (hydrochloric acid with a pH of 1-2 to be exact!) but obviously are not at very high temperature, so human hair would pass through the stomach undigested. The protein chains of spider silk keratin are folded in a different way to human hair, forming flat sheets (only 2 micrometers thick) as opposed to ropes 60 micrometers thick for human hair. Even so, I don’t think spider silk would be my choice of entrée!
Q: Does eating celery make you lose weight?
A: An average stick of celery only contains about 6 calories because most of it is cellulose- a fibre that is indigestible by the human digestive system. To extract the energy from the celery stick and move it along our intestine to digest it, we actually use more energy than we get back, namely about 4 or 5 calories more than we gain. But before you jump on the new famed Celery Stick Diet, you’d have to eat at least 20 sticks of celery to even cancel out a single chocolate biscuit!
Q: If I eat uncooked red kidney beans, could I get sick?
A: Red kidney beans actually are quite harmful when not cooked. They are quite rich in a chemical called phytohaemagglutinin (PHA) a carbohydrate binding protein that causes red blood cells to clump together. The red blood cell clumping power is measure in haemagglutinin units (hau). A toxic dose of PHA, which would cause vomiting and diarrhoea, is 350,000hau and one raw red kidney bean contains about 70,000hau. Cooking kidney beans denatures the PHA protein, making it about 200 times less potent! Don’t forget though that kidney beans are high in fibre, B vitamins and other minerals so don’t knock them ‘till you try them (cooked of course!)
Q: Could my cat taste my lollipop?
A: Unfortunately your cat’s tongue has malformed sugar receptors which don’t bind to sugar properly and hence it won’t be able to taste sweet things. This is due to a unique genetic mutation: cats are missing 247 base pairs from the gene that codes for the one of the sweet receptor proteins. That means cats probably don’t get sugar cravings either!
Q: Whenever I go to a fish market it always smells so bad! Why is that?
A: Many cold water, surface dwelling fish contain trimethylamine oxide, an odourless chemical on it’s own but once the fish dies, bacteria in the fish’s body break this chemical down into it’s ammonia derived components that smell pretty bad to us! This sense of bad smell may have evolved to warn us off eating old fish.
Q: Can I get ink poisoning from writing my shopping list on my hand?
A: Although not always the case, ink nowadays is generally considered non-toxic which means that unless you swallow a large quantity (more than about 29 grams) you should not get sick. However, the epithelia lining your digestive tract and your skin are two very different surfaces- your skin epithelia is waterproof and quite resistant whereas the epithelia lining your intestines is coated with mucus and highly absorptive so obviously it would be more harmful for you to swallow ink as opposed to writing it on your hand!