UNIT6_Enzymes_lab

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Arizona State University *

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181

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Biology

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Apr 3, 2024

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docx

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ENZYMES W What variables affect hydrogen peroxide breakdown by p peroxidase enzymes? Introduction Today we are going to talk about enzymes! Before you keep reading, watch these 2 videos: https://www.youtube.com/watch?v=ok9esggzN18 https://www.youtube.com/watch?v=qgVFkRn8f10&vl=en Okay, so enzymes! Specifically, today we are going to talk about a specific enzyme called peroxidase. This enzyme is found inside a small and very simple organelle, called Peroxisome. This organelle is found in all eukaryotic cells. The principal function of peroxisomes is to house many metabolic pathways that are involved in various aspects of lipid metabolism. The peroxisome derives its name from the fact that many metabolic enzymes that generate hydrogen peroxide (H 2 O 2 ) as a by-product are sequestered here because peroxides are toxic to cell. Inside these organelles, the toxic hydrogen peroxide is degraded to water and oxygen by the peroxidase enzyme. The balanced equation is written here: peroxidase 2 H 2 O 2 2 H 2 O + O 2 a (Substrate.) b (Enzyme.) c (Product.) BIO 181 online

 Fill in the a, b, c blanks above with “Substrate” “Enzyme” and “Product”.  Is oxygen a gas? Yes  Based on the figure below, how will you observe that the tissue contains peroxidase? Bubbles will form. OBJECTIVE:  Learn how an enzyme works  Learn what effects may temperature of pH may have on an enzymatic reaction  Learn the function of the peroxisome EQUIPMENT Components from your lab kit :  5 test tubes  600 ml beakers x2  Scale  transfer pipettes  Graduate cylinder BIO 181 online

You will need to buy (or get from your kitchen):  3% Hydrogen peroxide (120 ml)  it can be purchased from any store. Here an example  1 potato  1 apple  Optional choice: raw meat (e.g. raw chicken, raw fish or raw hamburger) and raw fungi. If you are vegan or vegetarian use only the fungi option (mushroom and yeast) ASSIGNMENTS: You will have to complete 3 different experiments for today’s lab. Follow the instructions step by step. We are using chemicals today so remember to use closed toe shoes and to work with caution. Exercise #1 What tissues contain peroxidase?  Add 10 ml of 3% H 2 O 2 to four test tubes measuring it in your graduated cylinder (see figure 1 below) and lean them upright in a 600 ml beaker. Figure 1: Set up four test tubes in a beaker and add 10 ml H 2 O 2 to each. Add 2g of a different tissue to each.  Choose 4 living tissues. Use potato, apple and two tissues of your choice. If you don’t have them or you are vegan/vegetarian, go outside and grab a leaf (tissue#3) and a flower (tissue #4). Caution: BIO 181 online

Some plants can be allergenic or poisonous.  Write in the actual tissue names under “Tissue #3” and “Tissue #4” in Table 1 below.  Cut and weigh two grams (g) of each tissue.  Slice the tissue with a knife repeatedly to break open the cells inside and so it is small enough to fit in the tube.  Add the samples quickly to each of the tubes. Begin timing.  Record your observations in Table 1 at 1, 3 and 5 minutes using a scale of 0-5. The bubbles are often tiny and foamy. (0=no bubbles 5=lots of bubbles) Scale: No bubbles=0, 1, 2, 3, 4, 5= Lots of bubbles Time (minutes) Potato Apple Tissue #3 Mushroom Tissue #4 Raw ground beef 1 1 0 1 2 3 3 1 2 3 5 2 1 1 1 Table 1: Tissues in H 2 O 2  Take a picture of your test tubes at 5 minutes  When you are done list below your four tissues in order from the highest to the lowest peroxidase activity, and why you think this is the right order: Potato, raw ground beef, mushroom, apple. The peroxide activity for more active for the apple, the raw ground beef was bubbly and increased in activity at the 3 minute mark but slowed down, while the mushroom had the lowest amount of activity and nothing happened to the apples. BIO 181 online

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