4.1) Respiration is a chemical reaction that happens inside cells.
a: Copy and complete the word equation for respiration.
glucose + ....................... > carbon dioxide + ........
b: This reaction is known as aerobic respiration. Explain why it is described as 'aerobic

4.2) In each of these groups of statements, only one is correct. Choose the correct statement and write down its letter.
a: A) Every living cell respires.
B) Only animal cells respire.
C) The way in which plant cells respire is called photosynthesis.
b: A) Expired breathed out air is carbon dioxide.
B) Expired air contains more carbon dioxide than inspired breathed in) air.
C) Expired air contains more oxygen than inspired air.
c: A) Respiration means moving your muscles to draw air into the lungs.
B) Respiration means the diffusion of gases between the air sacs and the blood.
C) Respiration means the release of energy from glucose, inside cells.

4.3) "The diagram shows an air sac and a blood capillary.

a: Copy the diagram. Label:
* the blood capillary
* the wall of the air sac.
b: Draw two red blood cells in the correct place on your diagram.
c: Draw an arrow to show the direction in which oxygen diffuses.
Label your arrow O.
d: Draw another arrow to show the direction in which carbon dioxide diffuses.
Label your arrow C.
e: The blood leaving the lungs in the capillary travels to another blood vessel and then to the heart. What are the names of the blood vessel and the part of the heart it will first enter?

4.4) Emile did an experiment to compare the rate of respiration in woodlice (small crustaceans) and maggots (the larvae of houseflies). The diagram shows how he set up his experiment.
Lamewater is a clear liquid. It goes cloudy when carbon dioxide is present.

a: Suggest why Emile used four tubes in his experiment, rather than two.
b: Describe three variables that Emile needed to keep the same in 
his experiment
c: Emile timed how long it took for the limewater to go cloudy in each tube.
These are his results.
A) 6 minutes
B) $6\frac{1}{2}$ minutes
C) $8\frac{1}{2}$, minutes
D) 9 minutes
Draw a results table, and write in Emile's results.
d: Write a conclusion that Emile can make from his results.