Science 8th grade
UNIT 4: Respiration 4.3 Aerobic respiration
Science 8th grade
UNIT 4: Respiration 4.3 Aerobic respiration
Living cells need energy to stay alive. They get their energy from nutrients, especially glucose.
Glucose contains chemical potential energy. Inside cells, glucose takes part in a chemical reaction called respiration. In this reaction, the glucose combines with oxygen. The chemical potential energy in the glucose is released, so that the cells can use it.
glucose + oxygen carbon dioxide + water
The oxygen that combines with the glucose in this reaction comes from the air. So this is sometimes known as aerobic respiration. We can define aerobic respiration like this:
Aerobic respiration is the release of energy from glucose by reacting it with oxygen inside living cells.
Questions
1) Name the two new substances that are made when glucose reacts with oxygen inside a cell.
2) Use what you know about digestion and the human circulatory system to describe how glucose gets to a cell in a muscle.
3) Use what you know about gas exchange and the human circulatory system to describe how oxygen gets to a cell in a muscle.
4) Explain the difference between respiration and breathing.
Respiration and heat production
Some of the energy that is released from glucose during respiration is heat energy. Everything that respires releases heat energy.
Questions
5) Which are the hottest parts in the photograph? How can you tell?
6) Explain why these parts are hotter than their surroundings.
Activity 4.3 (Respiring peas)
SE: All living things respire, even seeds Seeds respire especially quickly when they are germinating. You can make pea seeds start to germinate by soaking them in water for about an hour.
1) Set up your apparatus as in the diagram. Take care to make everything exactly the same for the two pieces of apparatus, except that one contains dead peas and the other contains live, germinating peas.
2) Take the temperature inside cach flask, and record the two temperatures in a results table.
3) Continue to take the temperature inside both flasks at regular intervals. Your teacher will suggest when you can do this.
4) Draw line graphs to show how the temperature in each flask changes over time. Put time on the x-axis and temperature on the s-axis. Draw both lines on the same pair of axes. Remember to label the lines to say which is which.
Questions
${A_1}$: What was the variable that you changed in this experiment?
${A_2}$: What was the variable that you measured in this experiment?
${A_3}$: State two variables that you kept the same in this experiment.
${A_4}$: Suggest an explanation for the results that you obtained.