Answer Key to Lab 6 Cellular Respiration

University: John Jay College of Criminal Justice

Course: Cell Biology (BIO 205)

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Lab 6: Cellular Respiration

Metabolism is the sum of all chemical reactions in a living organism. These reactions can be catabolic or

anabolic. Anabolic reactions use up energy to actually build complex biomolecules (think of anabolic steroids

building muscle mass). The energy for anabolic reactions usually comes from ATP, which is produced during

catabolic reactions. Catabolic reactions break down complex biomolecules, such as carbohydrates and lipids

and release the energy stored within.

1. Is cellular respiration anabolic or catabolic? Explain.

Cellular respiration is a catabolic reaction, because this process breaks down carbohydrates to release energy.

2. Is photosynthesis anabolic or catabolic? Explain.

Photosynthesis is anabolic, because this process uses energy to build carbohydrates.

Enzymes are proteins that facilitate chemical reactions in living systems by acting as catalysts in biochemical

reactions. Enzymes speed the rate of the reaction by either bringing the reactants into close proximity or by

binding to a single reactant and splitting it into smaller parts. Enzymes have a property known as specificity,

which simply means that each enzyme catalyses a specific biochemical reaction. Enzymes are indispensable

molecules of life. Enzymes are functional within a given range of temperatures and pH values for that enzyme.

Part 1: Starch Synthesis and Storage

Using energy from the sun, photosynthetic organisms convert carbon dioxide and water molecules into glucose.

Plants don’t store this chemical energy as glucose. Using enzymes, plants link the glucose molecules together

and store them as the polysaccharide starch. Potatoes are the primary starch storage site for the potato plant.

Iodine reacts with starch to form a bluish color. You can see the starch stored in a potato cell by staining the

cells with iodine.

M a terials

Microscope slide Coverslip Iodine Potato cells Tap water

P r oce d ure

1. Cut a thin slice or scrape a few cells from the surface of a potato.

2. Make a wet mount of the potato cells and stain them using a drop of iodine.

3. Observe your cells under high power.

4. Draw a few cells and label the following structures:

A. cell wall

B. plastid with starch grains (stains purple)

1. Where did the starch in the potato cells come from?

Enzymes inside of plant plastids link glucose molecules together to form a

polysaccharide starch. The glucose came from photosynthesis.

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