1. CHAPTER 3
SCIENCE QUEST 9
Compiled by: M Nortje Year 9 Science/2012 1

2. BLOOD AND
CARBON DIOXIDE
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3.  Did you know that your body is more
sensitive to changes in levels of carbon
dioxide than oxygen?
 Ifthere is too much carbon dioxide in your
body, it dissolves in the liquid part of blood
and forms an acid.
 The resulting acidic blood can affect the
functioning of your body.
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4.  The amount of carbon dioxide in your blood
influences your breathing rate.
 The level of carbon dioxide in the blood is
detected by receptors in the walls of some
arteries and in the brain.
 Ifthe levels of carbon dioxide in your blood
increase, your breathing rate will be
increased so that carbon dioxide can be
exhaled from your lungs and passed out of
your body.
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5.  If you were to climb up high on a mountain, you
would need time for your body to adjust.
 Initially you would feel tired and out of breath
because you would be restricted by the limited
amount of oxygen available to your cells.
 Your breathing and heart rate would increase in
an effort to get more oxygen around your body.
In time, your body would begin to produce more
red blood cells and hence more haemoglobin.
 After this, your breathing and heart rate would
return to normal.
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6.  Glucose is an example of a nutrient that may
be released from digested food.
 Itis absorbed in your small intestine and
then taken by the capillaries to cells for use
in cellular respiration.
 In this process the glucose is combined with
oxygen, and is then broken down into carbon
dioxide (a waste product that needs to be
removed from the cell) and water.
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7.  During this reaction energy, in the form of
ATP (adenosine
triphosphate), is also released.
 ATP provides the cells with the energy
needed to perform many of its activities, and
is essential to life.
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8.  Glucose+ oxygen → carbon dioxide
+ water + energy (ATP)
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9.  This is an example of systems working together.
Glucose is supplied via the digestive system and
oxygen is supplied via the respiratory system.
 The circulatory system transports nutrients
(such as glucose) and oxygen to your cells and
removes wastes (such as carbon dioxide) from
your cells.
 These wastes are then removed from your body
by your excretory systems.
 Without a supply of glucose and oxygen, cellular
respiration could not occur.
 Without removal of wastes, your cells may die.
 If you systems did not work together like they
do, you would not be able to stay alive.
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13. A supply of energy to keep it working
efficiently.
 During exercise the body needs more energy
than usual.
 Energy for the cells of the body comes from
chemical reactions.
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14. The energy is stored in a chemical called ATP.
 Muscles use ATP as a source of energy.
 →glucose + oxygen  carbon dioxide +
water + (36–38) ATP
 The glucose comes from the food we eat and the
oxygen comes from the air we breathe.
 Endurance sports like running a marathon or
playing netball or football use energy released
by aerobic respiration.
 The body has another chemical reaction called
anaerobic respiration:
 glucose  lactic acid + (2) ATP
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15. →glucose + oxygen  carbon dioxide + water + (36–38) ATP
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16.  makes a lot of energy in cells
 uses oxygen and glucose
 makes large amounts of energy over a long
period of time.
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17. glucose  lactic acid + (2) ATP
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18.  gives less energy than aerobic respiration
 gives energy to cells quickly
 does not use oxygen
 makes lactic acid which builds up in our
muscles.
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19.  Lacticacid build-up makes our muscles feel
sore after exercise.
 During
a 1500 m race, 55% of the ATP used
would be made by anaerobic respiration.
 ATP can be stored in the cells of the body for
a short time.
 This gives us an energy source that is very
good for sports that do not last too long, like
100 m sprints or high jumping.
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