Topic 4 Core questions - Bioenergetics

Question 1

State the word equation for photosynthesis.

Answer 1

Carbon dioxide + water -> glucose + oxygen (light above the arrow)

Question 2

State the balanced chemical symbol equation for photosynthesis

Answer 2

6CO₂ + 6H₂O -> C₆H₁₂O₆ + 6O₂

Question 3

Is photosynthesis an endothermic or exothermic reaction?

Answer 3

Endothermic

Question 4

What energy transfer occurs in photosynthesis?

Answer 4

Light energy to chemical energy

Question 5

Where does photosynthesis occur in a plant or algal cell?

Answer 5

Chloroplasts

Question 6

What are chloroplasts filled with?

Answer 6

Chlorophyll

Question 7

What is the function of chlorophyll?

Answer 7

Captures light energy

Question 8

Name the three factors which affect the rate of photosynthesis.

Answer 8

Temperature, light intensity, carbon dioxide concentration

Question 9

What is the formula for the inverse square law (for light intensity)?

Answer 9

light intensity∝1/distance²

Question 10

Describe how the inverse square law applies to light intensity and distance.

Answer 10

The intensity of light is inversely proportional to the square of the distance from the light source.
E.g. if you halve the distance, the light intensity will be 4 times greater

Question 11

What does the inverse square law mean in practice when considering how plants grow?

Answer 11

When the light is moved twice as far from the plant it will receive a quarter of the energy

Question 12

Why can’t a commercial grower of plants just increase all three limiting factors of photosynthesis to maximum levels to obtain optimum growth?

Answer 12

Light, temperature and CO2 all cost money to supply – a balance between expenditure and income must be struck for a profit to be made

Question 13

Name the ways glucose produced in photosynthesis is used in plants.

Answer 13

Used for respiration
Converted into insoluble starch for storage
Used to produce fat or oil for storage
Used to produce cellulose which strengthens the cell wall and/or used to produce amino acids for protein synthesis.

Question 14

What else, other than glucose, do plants need to produce proteins?

Answer 14

Nitrate ions

Question 15

Where are mineral ions absorbed from and through which plant organ?

Answer 15

From the soil, through the roots

Question 16

What is aerobic respiration and where does it occur in cells?

Answer 16

Respiration WITH oxygen, in the mitochondria

Question 17

What is anaerobic respiration and where does it occur in cells?

Answer 17

Respiration WITHOUT oxygen, in the cytoplasm

Question 18

Is respiration an endothermic or exothermic reaction?

Answer 18

Exothermic

Question 19

State the balanced symbol equation for aerobic respiration.

Answer 19

C₆H₁₂O₆ + 6O₂ -> 6CO₂ + 6H₂O

glucose + oxygen -> carbon dioxide + water

Question 20

State the word equation for anaerobic respiration in animal cells.

Answer 20

Glucose -> lactic acid

Question 21

State the word equation for anaerobic respiration in plant and yeast cells.

Answer 21

Glucose -> ethanol + carbon dioxide

Question 22

Which transfers more energy, aerobic or anaerobic respiration?

Answer 22

aerobic respiration

Question 23

How have humans used our understanding of anaerobic respiration in plant and yeast cells in manufacturing?

Answer 23

Production of bread and alcoholic drinks

Question 24

Name three physical ways in which the human body reacts to an increased demand for energy.

Answer 24

increased heart rate, increased breathing rate and increased breathing volume

Question 25

Why do heart rate, breathing rate and breathe volume increase when the body needs more energy?

Answer 25

To increase the oxygenation of the blood and to supply the muscles with more oxygenated blood

Question 26

What does a build-up of lactic acid cause in muscles?

Answer 26

Muscle fatigue

Question 27

What is an oxygen debt?

Answer 27

The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells

Question 28

Where is lactic acid converted back into glucose?

Answer 28

The liver

Question 29

How is lactic acid transported to the liver?

Answer 29

Via the blood

Question 30

What is produced when enzymes chemically break down carbohydrates?

Answer 30

Simple sugar monomers

Question 31

What is produced when enzymes chemically break down a lipid?

Answer 31

1 glycerol, 3 fatty acids

Question 32

What is produced when enzymes chemically break down proteins?

Answer 32

Amino acids

Question 33

What is “metabolism”?

Answer 33

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

Question 34

Name three cellular reactions which could be included under the term “metabolism”.

Answer 34

• Conversion of glucose to starch, glycogen and cellulose;
• The formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids;
• The use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins;
• Respiration;
• Breakdown of excess proteins to form urea for excretion