91 atory Review 7 I. What molecule is mostly typically broken down during cellul

Question

91 atory Review 7 I. What molecule is mostly typically broken down during cellular fermentation? What organelle, present in animal and plant cells, completes the during cellular respiration? respiration and breakdown of coe 3. What kind of biomolecule is glucose? at reactant must be present for cellular respiration to occur but is absent from fermentation? 5. What gas is produced by cellular respiration and et molecule is formed using energy in hanol fermentation? glucose and ADP + dining cellular 6. What respiration? 7. Where does fermentation take place in a cell? 8. what molecule is made when animal cells do fermentation? 9. What were the contents of the vial that served as the negative control for the soybenm experiment? What were the contents of the vial used to correct for changes in volume caused by atmospheric pressure or temperature changes? 10. 11. What does movement of the marker in the side arm of a respirometer toward a containing germinating soybeans indicate? 12. What biomolecule is the product of fermentation done by yeast? 13. What was measured in the yeast fermentation experiment to determine the an produced? What kind of biomolecule is the sucrose used during the fermentation exper 14. Thought Questions 15. Mature plants do photosynthesis mak s to make glucose, which is then used to make the ATP needed to germinating soybe reproduce. Where does the an get the glucose it needs for making ATP soybean experiment if you i cotton with KOH? 17. Why is it reasonable to hypothesize that sucrose will be more difficult than glucose for yea fermentation experiment?

Explanation / Answer

Answers and their corresponding explanations:

1. What molecule is mostly typically broken down during cellular respiration and fermentation?

Ans. Glucose

Explanation: Either it is cellular respiration or fermentation, the main difference lies in the presence or absence of oxygen respectively. The fist main step in any of the processes is mostly breaking down Glucose, by glcyolysis which can be regarded as a universal process. It produces Pyruvic acid, whose further fate is decided upon by the availability or unavailability of the oxygen. In the absence of Oxygen, fermentation occures which either produces lactic acid or ethanol. While, availability of oxygen, makes pyruvic acid to enter into citric acid cycle leaving end products of Carbon dioxide and water. Availability of Oxygen, makes the cellular respiration process more energy yielding as it generates 36 ATP molecules

2. What organelle, present in animal and plant cells, completes the breakdown of glucose during cellular respiration?

Ans. Mitochondria

Explanation: Glycolysis occurs in the cytoplasm of the cell as the enzymes required for the pathway are located in cytoplasm. It is major energy source of many cells. As described in the first question when glycolysis occurs in the presence of Oxygen, pyruvic acid is formed. Thus formed pyruvic acid is then converted to acetyl coA and through a series of steps called as Krebs cycle or Tricarboxylic acid cycle or citric acid cycle, it is finally oxidised to Carbon dioxide and water.

Thus breakdown of glycolysis in aerobic conditions is completed by Krebs cycle which occurs in the Mitochondria, since, all the enzymes which are required for the cycle are present in the mitochondrial matrix near to the electron transport chain.

So, the breakdown of glucose is completed in the organelle Mitochondria in cellular respiration.

It is for this reason brain cells lacking mitochondria solely depend on glycolysis as source of energy, although it is low energy yielding

3. What kind of biomolecule is glucose?

Ans. Carbohydrate

Glucose is having a molecular formula of C6H12O6 which is tallied with the general formula of carbohydrates i.e., Cm (H20)n. Carbohydrates as the name is suggesting they are hydrates of carbon. To define, carbohydrates are polyhydroxyaldehydes or ketones or substances which produce them on hydrolysis. They are divided into Monosaccharides, Disaccharides, Oligosaccharides and Polysaccharides

Glucose is a monosaccharide, aldo-hexose sugar. So, glucose can be termed as carbohydrate

4. What reactant must be present for cellular respiration to occur but is absent from fermentation?

Ans. Oxygen

Explanation: As described in the que 1 and 2, Oxygen is the determining step between cellular respiration and fermentation. Lactate or ethanol is formed under anaerobic(absence of oxygen) conditions which is termed as fermentation. On the other hand, pyruvate which is formed in last step of glycolysis, in the presence of oxygen, is ultimately oxidised to carbon dioxide and water in cellular respiration

So, the reactant which is present in cellular respiration and absent in fermentation is OXYGEN

5. What gas is produced by cellular respiration and ethanol fermentation?

Ans. Carbon dioxide

Explanation: As seen from the previous discussion, Carbon dioxide is formed in cellular respiration by Citric acid cycle as shown below (overall reaction):

Acetyl coA(from pyruvic acid of glycolysis) + 3NAD+ + FAD + GDP + Pi + H20 --------> 2CO2 + 3NADH + 3H+ + FADH2 + GTP + coA

Ethanol fermentation overall reaction is :

C6H12O6 ---------> 2(CH3CH2OH) + 2 CO2 + Energy

As we can see from the above two pathways Carbon dioxide is the gas produced in cellular respiration and alcohol fermentation and hence it is the answer

6. What molecule is formed using energy in glucose and ADP + P during cellular respiration?

Ans. ATP (Adenosine Triphosphate)

ADP + P (inorganic phosphate) + energy ----Phosphokinases----> ATP

The formation of ATP is an endergonic reaction (which requires energy) and non spontaneous. ATP thus formed is used as energy currency to drive the other reaction which require energy which can be yielded by breaking up the phosphoanhydride bond in ATP

So, the molecule formed using energy in glucose in cellular respiration is ATP

7. Where does fermentation take place in a cell?

Ans. Cytoplasm

Just like glycolysis, fermentation also takes place in the cytoplasm of the cell as the enzymes are present in the cytoplasm and it also favors transport of the substances formed

8. What molecule is made when animal cells do fermentation?

Ans. Lactic acid

When fermentation occurs in animal cells or some bacterial cells, it yields lactic acid as shown below:

Pyruvic acid + NADH <------> Lactic acid + NAD +

But in yeast cells fermentation yields alcohol:

Pyruvic acid <------> CO2 + Acetaldehyde

Acetaldehyde + NADH ------------> Etahnol + NAD +

9. What were the contents of the vial that served as the negative control for the soybean experiment

Ans. Plastic beads

Explanation: Inorder to have a control, one vial is filled with beads alone which serves the reference for no respiration is carried out in the vial. Inorder to know the respiration rate, the experimental set up is made to avoid all the possible errors and make simulation of the natural process. One vial with beads ensure that it serves as a mark for no respiration with which reference and test can be measured

10. What were the contents of the vial used to correct for changes in volume caused by atmospheric pressure or temperature changes?

Ans. Plastic / Glass beads

This also serves as one of the controls as explained in the previous question. Beads (irrespective of material plastic /glass) ensures that each vial in the experimental setup has same volume and make sure that volume of vial donot effect the respiration rate

11. What does movement of the marker in the side arm of a respirometer toward a containing germinating soybeans indicate

Ans. Cellular respiration

Respirometer (Gilson respirometer) can be used to measure the oxygen produced during photosynthesis. As oxygen is used up, the pressure of gases inside the respirometer decreases causing the movement of marker in the side arem of the respiromenter which is taken as a measure of photosynthesis rate

12. What biomolecule is the product of fermentation done by yeast?

Ans. Ethanol

In yeast cells, fermentation yields alcohol:

Pyruvic acid <------> CO2 + Acetaldehyde

Acetaldehyde + NADH ------------> Ethanol + NAD +

Hence the biomolecule produced in fermentation is ethanol

13. What was measured in the yeast fermentation experiment to determine the amount of CO2 produced?

Ans. Bubbles

In yeast cells, fermentation yields alcohol:

Pyruvic acid <------> CO2 + Acetaldehyde

Acetaldehyde + NADH ------------> Ethanol + NAD +

As seen in the step 1 of fermentation, Carbon dioxide is first formed in fermentation which appears as effervescence (bubbles). So this was taken as a measure to determine the amount of carbondioxide produced

14. What kind of biomolecule is the sucrose used during the fermentation experiment?

Ans. Disaccharide

Sucrose is a disaccharide (carbohydrate) with a molecular formula of C12H22O11 and consists of two monosaccharide units glucose and fructose which are linked by alpha 1,4 glycosidic bond

15. Mature plant do photosynthesis to make glucose, which is then used to make the ATP needed to reproduce. Where does the germinating soybean get the glucose it needs for making ATP

Ans. Photosynthesis

The overall reaction of photosynthesis can be written as follows:

CO2 + H2O + Sunlight -----------> Carbohydrates (Glucose) + oxygen + water

The water molecule formed in the above step of photosynthesis is split to release Hydrogen which is used for the making of ATP and NADPH. Thus glucose is produced by photosynthesis and further ATP molecules are produced

16. Why would no net change for vial 1 have been the results in the soybean experiment if you cotton with KOH?

Ans. KOH absorbs Carbon dioxide

Potassium hydroxide is used to absorb Carbon dioxide to form Potassium carbonate. It is very important in the reaction, because if carbon dioxide is present it will alter the values of respirometer, but as CO2 is removed by KOH, the amount of oxygen consumed is directly proportional to volume of gas in the respirometer

17. Why is it reasonable to hypothesize that sucrose will be more difficult than glucose for your fermentation experiment?

Sucrose is a disaccharide

Explanation: Sucrose is a disaccharide (carbohydrate) with a molecular formula of C12H22O11 and consists of two monosaccharide units glucose and fructose which are linked by alpha 1,4 glycosidic bond

Hence, it would be difficult for sucrose to be used for fermentation rather than simple sugar like glucose which easily undergoes hydrolysis. Sucrose has to be hydrolyzed to give glucose to be continued to fermentation through glycolysis. If sucrose is used some other enzyme which hydrolyzes it is to be present in the test organism which is not the case in all times.

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