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Minerals and vitimin
Option A: Human Nutrition and Health
| Question | Answer |
|---|---|
| Minerals | elements in their ionic form: eg sodium, pottasium, Calcium |
| Vitimins | Organic compounds that cannot be synthesized by the body. eg vitamins A,B,C,D, E |
| what is vitimin C required for? | collagen synthesis |
| what is collagen | tough fibrous protein used to strengthen tissues such as skin and bone |
| what does a lack in vitimin C cause | Scaurvy |
| what foods are rich in vitimin C | citrus fruits |
| RDA | recommended daily amount, is the approximate amount that should be taken daily though the precise amount will vary depending on state of health. also raises from country to country |
| why are guinea pigs used to determine RDA? | it is unable to synthesise DNA (laboratory rats can) |
| symptoms of scury | bleeding gums, slow rate of reppair, brittle bones |
| determining RDA using guinea pigs | guinea pigs fed just grain → symptoms of scurvy. Further groups fed grain +different amounts of cabbage and lemon juice. Blood plasma and urine analysed. skin and bone samples tested for strength. results used to find guinea pig RDA. scaled up for humans. |
| why have there been questions about how DNA determined | RDA varies from country to country |
| Determining RDA using humans | 20 concientous objectors used in trials. given diet lacking in vitimin c but different amounts of daily suplements for initial 6 weaks and then 8 month trial. |
| how much vitimin c were they given in initial 6 weeks | 70mg |
| volunteers with 0mg of vitimin C | 10 volunteers, developed signs of scurvy within 6-8months. Wound healing slow. repair was weak and would easily break |
| volunteers with 10mg and 70mg of vitimin C | no symptoms of scurvy, wound healing normally, strength normal. no differences in health in these 2 groups |
| what were results of determining RDA using humans | indicated 10mg is sufficient to prevent scurvy. Recommended RDA from this work was 30mg to allow for differences in body mass and efficiency of absorbtion |
| what happens to excess dietrt vitamin C | it is excreted |
| rebound malnutrition | if persson takes in a large excess of vitimin c for a long time the body becomes used to excreting large amounts. If you stop taking suplement and level of intake fall vitimin c continues to be excreted so that levels in the body may fall too low. |
| current RDA in the UK | 65mg for females, 75mg for male |
| function of vitimin D | promotes absorbtion of calcium from the gut |
| deficiency of vitimin D | failure to absorb calcium leads to poor bone growth and the development of rickets. (eg bone deformities) |
| sources of vitimin D | fish, eggs, milk and dairy products. tablets and certain manufactured goods such as cereals to which it has been added (artificially maniifactured). also made in skin when exposed to UV light |
| risk of UV light | UV light can cause mutatations in DNA resulting in skin cells becoming cancerous and forming malignant melanomas which can be fatal. |
| what can protect skin from uv light | suncream and clothing |
| what can a lack of uv light cause? | A Vitimin D deficiency. |
| what balance needs to be struck about uv ligh | enough exposure to UV light to allow synthesis of vitamin D and protection of skin to prevent melanoma development |
| where can vitamin D be stored | in the liver, allowing people who live in high latitudes to store the excess made in the summer which can be released in winter month when less uv light and more of skin covered by clothing |
| what is the point of dietry supplements | restore health and prevent lack of development. |
| function of iodine | required for the synthesis of the hormone thyroxin by the thyroid gland in neck. throxin regulates growth and controls metabolism |
| Deficiency if iodine | IDD (Iodine deficiency disease). The thyroid gland swells (called a goitre). during pregnacy the fetal brain fails to develop normall. during childhood mental development and intelligence are reduced. |
| source of iodine | marine fish and seaweed. small amounts in plants grown in soils that contain iodine. sometime drinking water. |
| dietary supplement for iodine | iodised table salt (cheap and easy to obtain) |
| Main source of dietry fibre | cellulose from plant cell walls, also chitin from fungi, insects and crustaceans |
| functions of fibre in reducing risk of becoming overweight | reduces absorbtion of sugar by increasing the rate of movement of food through the gut so less time for absorbtion. this lowers the risk of becoming overweight |
| other functions of fibre | fire can't be digested so acts as bulk material against which the gut muscels work. this strengthens the gut muscles - improves peristalsis, reduces constipation. also can lower risk of cancer of large intesting fibre |
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Nel.bio