Respiration

ATP - adenosine triphosphate

1. all living organisms carry out cellular respiration.

2. glucose is broken down and releases energy.

3. this energy is carried as a chemical substance - ATP.

where is ATP produced

mitochondria

aerobic and anaerobic respiration

glucose can be respired in different ways. this depends on whether oxygen is available.

aerobic respiration

• uses oxygen

• most efficient way to transfer energy from glucose

aerobic respiration equations

glucose + oxygen → carbon dioxide + water (+energy)

C6H12O6 +6O2 → 6CO2 +6H20

anaerobic respiration

• no oxygen used

• glucose only partially broken down, so little energy released.

• build up of lactic acid in the muscles causes cramp.

anaerobic respiration (animals) equation

glucose → lactic acid (+ energy)

anaerobic respiration (plants) equation

glucose → ethanol + carbon dioxide (+ energy)

explain a practical to investigate the evolution of carbon dioxide from respiring seeds

1. hydrogen-carbonate indicator in 2 test tubes.

2. place gauze into the test tubes (to make a platform.)

3. place germinating beans into one test tube.

4. place dead beans into the second test tube.

5. seal test tubes with a rubber bung.

6. leave for 1 hour.

7. carbon dioxide produced by germinating beans will turn indicator yellow.

   note: put one test tube with just indicator in, to act as a control

explain a practical to investigate temperature change caused by respiration

1. add germinating beans to one vacuum flask, and dead beans to the other.

2. ensure some air is left in tanks (so beans can respire aerobically.)

3. place thermometer in each flask and seal top with cotton wool.

4. record temperature at start, and daily for a week.

   germinating beans will respire, and temperature will increase.

what is fermentation?

fermentation is when microorganisms break sugars down in order to release energy - usually by anaerobic respiration.

why is yeast used in bread production?

• the enzymes in the yeast break down the carbohydrates in the flour into sugars.

• the yeast then uses these sugars in aerobic respiration.

• this aerobic respiration produces carbon dioxide.

• the carbon dioxide is trapped in bubbles in the dough.

• these pockets of gas expand, and enable the dough to rise.

why is yeast used in beer production?

• When yeast cells are reproducing rapidly during beer production, the oxygen runs out. The yeast switches to anaerobic respiration.

• Ethanol and carbon dioxide are produced.

• ethanol is an alcohol.

describe an experiment to investigate the production of carbon dioxide by yeast under different conditions

1. add sugar, yeast and distilled water to a test tube.

2. create anaerobic conditions: add a layer of oil on top of yeast mixture.

3. attach a bung with a tube leading to a second test tube of water.

4. place the yeast tube into a water bath of a set temperature.

5. leave the tube to warm up a little, then count how many bubbles are produced in one minute.

6. calculate the respiration rate:

   • CO2 bubbles produced/time taken for them to be produced (in seconds.)

7. repeat experiment, with the water bath at different temperatures.

explain how bacteria is used in the production of yogurt

1. the equipment is sterilised to kill any unwanted microorganisms.

2. the milk is pasturised (heated to 72 degrees for 15 seconds) and then cooled.

3. lactobacillius bacteria is added and the mixture is incubated at 40 degrees in a fermenter.

4. the bacteria ferments the lactose sugar in the milk to form lactic acid.

5. lactic acid causes the milk to clot, and solidify into yogurt.

fermenters - culture medium

nutrients needed by the microorganisms for growth are provided in the liquid culture medium.

fermenters - pH probe

• the pH is monitored and kept at the optimum level for the microorganism’s enzymes to work efficiently.

• so that the rate of reaction and product yield are as high as possible.

fermenters - temperature recorder

• temperature kept at optimum level.

• a water-cooled jacket ensures the fermenter doesn’t get too hot, and the enzymes denature.

fermenters - sterilising the vessel

• vessels are sterilised between uses with superheated systems that kill unwanted microbes.

• having aseptic conditions increases the product yield because the microorganisms aren’t competing with other organisms.

fermenters - oxygen tube

• some microorganisms need oxygen to respire.

• it’s added by pumping in sterile air.

• this increases product yield because the microorganisms can respire more, and therefore have more energy for growth.

fermenters - paddles

• microorganisms are kept in contact with fresh medium by paddles that circulate/agitate the medium around the vessel.

• this increases product yield, because microorganisms always have access needed to respire and grow.