Chapter 9 - Respiration

Question 1

What do we need energy for?

Answer 1

• Movement
• To keep warm
• For chemical reactions to build larger molecules - e.g. proteins are made by chemically joining amino acids

Question 2

What is the energy we need supplied by?

Answer 2

A process called (cellular) respiration.

Question 3

Is respiration an exothermic or endothermic reaction?

Answer 3

Exothermic as it releases energy.

Question 4

Where does it take place?

Answer 4

Continually in all living cells.

Question 5

What is the word equation for aerobic respiration?

Answer 5

glucose + oxygen -> carbon dioxide + water.

Question 6

What does aerobic respiration release and why?

Answer 6

A lot of energy, as the glucose molecule has been fully oxidised.

Question 7

What is the symbol equation for aerobic respiration?

Answer 7

C6H12O6 + O2 -> CO2 + H2O
(all numbers small)

Question 8

When is anaerobic respiration carried out?

Answer 8

When there is a shortage of oxygen.

Question 9

What do muscle cells need a great deal of energy for?

Answer 9

Contraction.

Question 10

Under certain conditions…

Answer 10

…the amount of oxygen is limited - in these conditions, anaerobic respiration is carried out in muscle cells.

Question 11

What is the word equation for anaerobic respiration in muscles?

Answer 11

glucose -> lactic acid

Question 12

How much energy does anaerobic respiration release in comparison to aerobic respiration and why?

Answer 12

Much less energy is released as in anaerobic respiration the oxidation of glucose is incomplete.

Question 13

What is the word equation for anaerobic respiration in plant and yeast cells?

Answer 13

glucose -> ethanol + carbon dioxide

Question 14

What is anaerobic respiration called in yeast cells?

Answer 14

Fermentation.

Question 15

What is fermentation used for?

Answer 15

• Making alcoholic drinks such as beer - the alcohol in these drinks is ethanol which is produced by fermentation.
• Making bread - here, the carbon dioxide produced by fermentation is useful, as it creates bubbles in the dough causing it to rise.

Question 16

Energy when relaxing vs. when doing exercise

Answer 16

• When relaxing, our body does not need a great deal of energy, as we are not moving.
• When exercising, the body needs a great deal of energy for muscle contraction, and the body has to react to the increased demand for energy. Because the body needs more energy, aerobic respiration increases. This means that the body cells need more oxygen.

Question 17

How is the extra oxygen needed when exercising provided for?

Answer 17

• Both the breathing rate and breathing volume increase - we breathe more frequently, and take deeper breaths, getting more oxygen into the bloodstream.
• The heart rate also increases to pump this oxygenated blood around the body.

Question 18

In what situations can not enough oxygen be supplied to the muscles?

Answer 18

When the exercise is vigorous and/or prolonged. In these situations, anaerobic respiration now takes place in the muscles.

Question 19

What does the oxidation of glucose being incomplete during anaerobic respiration lead to?

Answer 19

A build-up of the chemical lactic acid.

Question 20

What does the lactic acid do to muscles after long periods of vigorous exercise?

Answer 20

Makes them become fatigued, causing them to stop contracting efficiently.

Question 21

How is oxygen debt created?

Answer 21

When the body has to remove the lactic acid from the muscles.

Question 22

How does the body remove lactic acid from muscles?

Answer 22

• The lactic acid is transported out of the muscles by the blood.
• The lactic acid is then taken to the liver and converts back to glucose in a series of chemical reactions.
• Reacting with the accumulated lactic acid and removing it from the cells requires oxygen.

Question 23

Oxygen debt definition

Answer 23

The amount of extra oxygen the body needs after exercise to deal with the accumulated lactic acid (that is why people continue breathing rapidly for some time after finishing exercise).

Question 24

How is the energy from respiration used by enzymes?

Answer 24

To synthesise new molecules in the cell.

Question 25

Metabolism definition

Answer 25

The sum of all the chemical reactions in a cell or in the body.

Question 26

Uses of glucose in plants

Answer 26

• Converted into cellulose which strengthens the plant cell wall.
• Converted into starch - a storage form of glucose.
• Reacts with nitrate ions to form amino acids, which are then used to synthesise proteins.

Question 27

Uses of glucose in humans

Answer 27

• Converted into the molecule glycogen - a storage form of glucose.

Question 28

1 glycerol molecule + 3 molecules of fatty acids ->

Answer 28

lipid molecule - found in the cell membrane.

Question 31

Proteins

Answer 31

• Humans don’t need to eat a large amount of protein.
• Excess proteins are broken down into the chemical urea.
• Urea is then excreted by the kidneys.