07.Respiration

Answers to Pg 76-79
7.1  Anaerobic respiration in yeast
Aim : To investigate anaerobic respiration in yeast
Hypothesis : Anaerobic respiration by yeast produces carbon dioxide and ethanol
a) MV : Presence or absence of yeast
b) RV : Change in colour of bicarbonate indicator and smell of ethanol
c) FV : Temperature, volume of solution
Discussion :

1. To remove oxygen
2. To pevent oxygen from dissolving in the solution
3. Carbon dioxide is produced and it will turn limewater cloudy
4. Yes. Ethanol is produced and can be detected through the smell of alcohol.

Conclusion : The hypothesis is accepted. Anaerobic respiration by yeast produces carbon dioxide and ethanol.

7.2 : Effects of vigorous exercising on the rates of respiration and heartbeat

Aim : To study the effects of vigorous exercising on the rates of respiration and heartbeat
Hypothesis : The more vigorous the exercise, the higher the rates of respiration and heartbeat.
a) MV : At rest or vigorous activity
b) RV : Rates of respiration and heartbeat
c) FV : Temperature, student

Condition	Rate of respiration (counts per min)				Rate of respiration (counts per min)
	1	2	3	Mean	1	2	3	Mean
At rest	14	15	14	14	72	71	72	72
After vigorous exercise	27	27	28	27	88	86	88	87

Discussion

1. The rate of respiration increases when the exercise is more vigorous.
2. Vigorous exercise actually increases the rate of heartbeat.
3. An increase in the rate of respiration and the rate of heartbeat will increase the oxygen content in the body. Cell respiration increases due to an increase in oxygen content. This results in an increase in carbon dioxide content in the body as more carbon dioxide is released through cell respiration.

Conclusion

The hypothesis is accepted. The more vigorous the exercise, the higher the rates of respiration and heartbeat

2007 Biology Paper 3-Question 2

Anaerobic respiration is the process of releasing energy from the breakdown of glucose in the absence of oxygen. Yeast can carry out anaerobic respiration in a glucose solution.

Glucose ---> Ethanol + Carbon dioxide + Energy

The rate of anaerobic respiration is affected by several factors such as temperature, pH values and nutrients.

Based on the above information and equation, design a laboratory experiment to investigate the effect of temperature on the rate of anaerobic respiration in yeast.

The planning of your experiment must include the following aspects:

§ Problem statement

§ Aim of investigation

§ Hypothesis

§ Variables

§ List of apparatus and materials

§ Technique used

§ Experimental procedure or method

§ Presentation of data

§ Conclusion

ANSWER

:1. Aim of investigation

To investigate the effect of temperature on the rate of anaerobic respiration in yeast.

2. Problem statement

What is the effect of temperature on the rate of anaerobic respiration (in yeast)?

3. Hypothesis

The higher the temperature, the higher the rate of anaerobic respiration (in yeast).

4. Variables

Manipulated variable: Temperature

Responding variable: Rate of anaerobic respiration//No of bubbles released//Time taken for lime water to turn chalky

Fixed variable: Volume/conc. of yeast suspension/glucose/pH/Time taken

5. Apparatus:

Boiling tube, Manometer/Capillary tube, Water bath//Beaker + thermometer,

Stopwatch, Marker/thread, Rubber stopper, Ruler, Rubber tubing, Retort stand, measuring cylinder

Material :

Yeast suspension / Yeast, Glucose solution, Paraffin oil (Yeast & Glucose – must have)

6. Technique

Using a ruler to record the change in height of the colored liquid/Record the number of bubbles released (after 10 minutes) using a stopwatch

//Calculating the rate of anaerobic respiration (in yeast) by using the formula :

Number of bubbles / Change in height

Time taken

//Take and record the time taken for the lime water to turn chalky using a stopwatch.

7. Procedure :

1. Set up the apparatus as shown in diagram.

2. Place the boiling tube with 15 cm³ of glucose solution in a beaker at 20^oC for 5 minutes.

3. Add 15 cm³ of yeast suspension into the boiling tube.

4. Mark the initial height of coloured liquid in manometer.

5. Start the stopwatch and mark the level of coloured liquid in the manometer after 10 minutes.

6. Record all data in a table.

7. Repeat step l, 3, 4, 5 and 6 by placing the boiling tubes in a water bath at temperatures of 30^oC, 40^oC and 50^oC.

8. Make sure all the joints of the apparatus are air tight //Repeat the experiment for each temperature to get average readings.

9. Plot a graph of rate of anaerobic respiration in yeast against temperature.

Precaution :

1. Ensure the temperature is stablised at the fixed temperature before taking the reading if the height of the coloured liquid//counting the number of bubbles released.

2. Make sure all the joints of the apparatus are air tight //Repeat the experiment for each temperature to get average readings.

8. Result: Draw a table

9. Conclusion:

Hypothesis is accepted. The higher the temperature, the higher the rate of anaerobic respiration in yeast.

2004 Biology SPM SAMPLE ANSWERS
a) An athlete has just completed a 400 metre track event. His leg muscles are painful due to muscle fatigue. The athlete then carries out the following actions.

· Wears a track suit

· Takes a few long deep breaths

· Walks freely as a ‘cooling down’ activity.

Explain why the athlete carries out these actions.

b) Human and fish respiratory systems are adapted to function in their respective habitats. Compare and explain the adaptations.

Answer

a) The athlete wears a track suit so that there is no sudden decrease in temperature in his muscles.

A sudden decrease in temperature will cause the accumulation of lactic acid and muscles pain/cramp.

He draws a deep breath several times to oxidize lactic acid that has been accumulated and pays back the oxygen debt.

He walks freely so that his muscles take time to oxidize 1/6 of lactic acid to carbon dioxide, water and energy and 5/6 of the lactic acid is converted back to glucose.

b)

	Human	Fish
Organ	Human’s respiratory structure is the lungs	Fish’s respiratory structure is the gills
Habitat	Human lives on land	Fish lives in the water
Function	Lungs do not need a medium to function	Gills need flow of water through the gills for gaseous exchange
Adaptation	Human lungs have a lot of alveoli and covered with a large network of blood capillaries. Gaseous exchange occur by diffusion through the alveoli	Water is drank in and flows through the gills for absorption of oxygen to blood capillaries which are cross linked with the filaments of gills. Then water flows out through the operculum and absorbs carbon dioxide from the blood capillaries to the water to be released
Characteristics	Total surface area is big with 700 million alveoli/ many alveoli to increase total surface area for diffusion Thin alveolar wall which helps in the diffusion of gases, The wall of the alveolus is moist whereby respiratory gases can dissolve in it, The alveolus is well supplied by blood capillaries to facilitate diffusion and transportation of the gases.	Has thin epithelial wall of gill filaments to facilitate diffusion of gases. Many plate like projections (lamella) at gill filaments to increase the total surface area for diffusion A network of blood capillaries in the gill filaments to facilitate diffusion and transportation of the gas