B4 - Bioenergetics

Question 1

What is photosynthesis?

Answer 1

The use of energy to change carbon dioxide and water into glucose and oxygen

Question 2

Where does photosynthesis take place?

Answer 2

Chloroplasts in green plant cells - they contain pigments like chlorophyll that absorb light

Question 3

What transfers energy to the chloroplasts?

Answer 3

Light

Question 4

Photosynthesis is endothermic - what does this mean?

Answer 4

This means energy is transferred from the environment in the process

Question 5

What is the word equation for photosynthesis?

Answer 5

carbon dioxide + water (light)> glucose + oxygen

Question 6

What is the symbol equation for photosynthesis?

Answer 6

6CO2 + 6H2O (light)> C6H12O6 + 6O2

Question 7

What are the main ways plants use glucose?

Answer 7

• Respiration
• Making cellulose
• Making amino acids
• Stored as oils or fats
• Stored as as starch

Question 8

What is cellulose?

Answer 8

For making strong plant wall cells

Question 9

How are amino acids formed?

Answer 9

Nitrate ions (from the soil) and glucose combine to form amino acids (which then turn into proteins)

Question 10

How does a plant use fat or oil?

Answer 10

Storing in seeds

Question 11

How does a plant use starch?

Answer 11

Used for when photosynthesis isn’t happening (winter) and because it is insoluble, it is much better for storing than glucose, so it stop the plant from swelling

Question 12

What are the limiting factors that affect the rate of photosynthesis?

Answer 12

• Light
• Concentration of CO2
• Temperature

Question 13

Give examples where the rate of photosynthesis could be affected

Answer 13

• Night
• Winter
• Warmth

Question 14

What else can be considered a limiting factor?

Answer 14

Chlorophyll which can be affected by disease or environmental stress (lack of nutrients)

Question 15

How does light intensity affect the rate of photosynthesis?

Answer 15

As the light level is raised, the rate of photosynthesis increases steadily, but only up to a certain point. Beyond that it won’t make any difference because it’ll either be the temperature or CO2 level which is now the limiting factor

Question 16

How does carbon dioxide affect the rate of photosynthesis?

Answer 16

Similarly to light intensity, as the amount of CO2 increases, the rate of photosynthesis steadily increases as well to a certain point. Beyond that, it won’t make a difference so as long as a plant has plenty of CO2 and light, temperature should be the limiting factor.

Question 17

How does temperature affect the rate of photosynthesis?

Answer 17

Enzymes work faster with more heat (usually most efficient around 37) but if they get too hot, then they can become denatured (usually happens around 45)

Question 18

What law links light intensity and distance?

Answer 18

The Inverse Square Law

Question 19

Inverse Square Law

Answer 19

light intensity ∝ 1 / distance(d)^2

Question 20

Why does light intensity decrease with distance?

Answer 20

Light intensity decreases in proportion to the square of the distance

Question 21

What is the most common way to create the ideal environment for plants to grow?

Answer 21

In a greenhouse

Question 22

What are some different methods to artificially create ideal conditions for farming?

Answer 22

• Greenhouse
• Heater
• Shades
• Ventilation
• Lamps
• Paraffin Heater
• Fertilised

Question 23

How does greenhouses work?

Answer 23

They help to trap the Sun’s heat, and make sure that the temperature doesn’t become limiting.

Question 24

What is a common misconception of respiration?

Answer 24

Respiration is breathing

Question 25

What is respiration?

Answer 25

The exothermic process of transferring energy from glucose and oxygen into carbon dioxide and water

Question 26

Why do we need respiration?

Answer 26

- To build up larger molecules from smaller ones - Allow the muscles to contract - Used to keep body temperature steady - Produce ATP

Question 27

What are the 2 different types of respiration?

Answer 27

Aerobic and anaerobic respiration

Question 28

Aerobic respiration word equation

Answer 28

glucose + oxygen --> carbon dioxide + water

Question 29

Aerobic respiration symbol equation

Answer 29

C6H12O6 + 6O2 --> 6CO2 + 6H20

Question 30

Aerobic respiration

Answer 30

- The most efficient way to transfer energy from glucose - It goes on all the time in plants and animals - Most of the reactions in aerobic respiration happen in the mitochondria

Question 31

Anaerobic respiration word equation in muscle cells

Answer 31

glucose --> lactic acid

Question 32

Anaerobic respiration in muscle cells

Answer 32

- The incomplete breakdown of glucose, making lactic acid - Anaerobic respiration happens if there is not enough oxygen - Anaerobic respiration does not transfer nearly as much oxygen as aerobic respiration because the glucose isn't fully oxidised - So it is only used when people do vigorous exercise

Question 33

Anaerobic respiration in plants and yeast word equation

Answer 33

glucose --> ethanol + carbon dioxide

Question 34

Anaerobic respiration in plants and yeast

Answer 34

- They produce ethanol and carbon dioxide instead of lactic acid - This is usually called fermentation - In the food industry, fermentation is used a lot (bread, cider, wine etc.)

Question 35

Why do you respire more during exercise?

Answer 35

Some muscles contract more frequently than normal so you need more energy. This energy comes from increased respiration.

Question 36

What happens if you need to respire more?

Answer 36

You need to get more oxygen which affects the breathing rate, breath volume and heart rate. This removes CO2 more quickly at the same time

Question 37

Anaerobic respiration during exercise

Answer 37

This is not the best way to transfer energy because lactic energy builds up in the muscles which gets painful. Long periods can cause muscles to get tired and then stop contracting efficiently

Question 38

What is oxygen debt and how is it repaid?

Answer 38

After resorting to anaerobic respiration, you will have an "oxygen debt". Oxygen debt is the amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from the cells. Oxygen reacts with the lactic acid to form harmless CO2 and water

Question 39

What usually happens when you are repaying your oxygen debt?

Answer 39

- Your pulse and breathing rate stay | - High levels of lactic acid and CO2

Question 40

What is another way your body copes with the high level of lactic acid?

Answer 40

Your blood transports the lactic acid to the liver, where the lactic acid is converted back into glucose

Question 41

What are the effects of exercise in the body?

Answer 41

Your breathing rate and heart rate increase

Question 42

What is metabolism?

Answer 42

All the chemical reactions in an organism

Question 43

Give some examples of metabolism

Answer 43

- Conversion of glucose to starch, glycogen and cellulose - Formation of lipid molecules from a molecule of glycerol and 3 fatty acid molecules - Reaction of respiration - Reaction of photosynthesis - Breakdown of excess proteins in the liver to form urea for excretion in the urine by the kidneys