(CIE A2 Biology) Test strips + biosensors

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10 Terms

1
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diabetes

a type of medical condition where blood glucose concentrations become uncontrollable

2
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how urine samples can be identified as coming from diabetics

by checking for the presence of unfiltered glucose in them

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the renal threshold

the blood glucose concentration above which glucose reabsorption from the PCT filtrate becomes abnormal

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test strips

contain two immobilized enzymes (glucose oxidase and peroxidase) on small pads at each of their ends so they can be immersed into urine samples for a short amount of time

<p>contain <strong>two immobilized enzymes (glucose oxidase and peroxidase) on small pads at each of their ends</strong> so they <strong>can be immersed into urine samples for a short amount of time</strong></p>
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how test strips can identify glucose levels in urine

  1. firstly the glucose oxidase in them catalyzes an oxidation reaction where glucose splits into gluconic acid and hydrogen peroxide

  2. then the peroxidase in them forms a brown compound (along with water) from the hydrogen peroxide + colorless pad-stored chemical

<ol><li><p>firstly the <strong>glucose oxidase</strong> in them <strong>catalyzes an oxidation reaction </strong>where <strong>glucose splits into gluconic acid and hydrogen peroxide</strong></p></li><li><p>then the <strong>peroxidase</strong> in them <strong>forms a brown compound (along with water)</strong> from the <strong>hydrogen peroxide + colorless pad-stored chemical</strong></p></li></ol><p></p>
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how higher glucose concentrations in urine affect test strip results

there’s a higher yield of the brown compound from the peroxidase-catalyzed reaction

<p>there’s a <strong>higher yield of the brown compound from the peroxidase-catalyzed reaction</strong></p>
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the main shortfall of the test strip method

it can’t display results based on current blood glucose concentration levels the way biosensors do due to it only working with urine samples

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biosensors

have a recognition layer impregnated w/ immobilized glucose oxidase molecules that’s covered by a partially-permeable membrane that only small blood-transported molecules can pass through

<p>have a <strong>recognition layer impregnated w/ immobilized glucose oxidase molecules</strong> that’s <strong>covered by a partially-permeable membrane</strong> that <strong>only small blood-transported molecules can pass through</strong></p>
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how biosensors calculate current blood glucose concentration levels

  1. firstly glucose oxidase-catalyzed reactions occur upon contact with human blood samples to form gluconic acid + hydrogen peroxide

  2. an electron transfer-detecting electrode then oxidizes the hydrogen peroxide at an electron flow proportional to blood sample glucose concentrations

  3. the electron flow’s current then gets biosensor-amplified and processed to produce digital blood glucose concentration readings within seconds

<ol><li><p>firstly <strong>glucose oxidase-catalyzed reactions occur upon contact with human blood samples </strong>to <strong>form gluconic acid + hydrogen peroxide</strong></p></li><li><p>an <strong>electron transfer-detecting electrode then oxidizes the hydrogen peroxide</strong> at an <strong>electron flow proportional to blood sample glucose concentrations</strong></p></li><li><p>the <strong>electron flow’s current then gets biosensor-amplified and processed </strong>to <strong>produce digital blood glucose concentration readings within seconds</strong></p></li></ol><p></p>
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what happens when solutions with non-glucose sugars get tested using test strips

glucose oxidase’s specificity leads to negative results