Topic 4 Bioenergetics

Question 1

What is Photosynthesis

Answer 1

• The process of plants producing their own food.
• The food it produces is Glucose
• Photosynthesis uses energy to change Carbon dioxide and water into Oxygen and Glucose
• Glucose is the used for making cell walls and proteins

Question 2

Which gas is used in photosynthesis

Answer 2

Carbon dioxide

Question 3

Which gas is produced by photosynthesis

Answer 3

Oxygen

Question 4

Name the part of the Plant cell that contains chlorophyll

Answer 4

Chloroplasts

Question 5

What role does chlorophyll play in photosynthesis

Answer 5

Chlorophyll is the green pigment found in chloroplasts and its role is to absorb light

• Energy is transferred to the chloroplasts from the environment by light making photosynthesis Endothermic

Question 6

what is the word equation for photosynthesis

Answer 6

Carbon Dioxide + water - light/chlorophyll - Glucose + Oxygen

Question 7

Write down the symbol equation for photosynthesis

Answer 7

6CO2 + 6H2O - light - C6 H12 O6 +6O2

Question 8

What chemical substance has the symbol C6 H12 O6

Answer 8

glucose

Question 9

3 identical plants were grown for a week.
Table shows the number of hours of sunlight exposure each plant received A =3, B=7, C= 10
Which plant produced the most glucose and why

Answer 9

Plant C as it received the most exposure to the sunlight so it was able to photosynthesis for a longer period of time. The Process of Photosynthesis produces glucose. The more photosynthesis the more glucose will have been produced

Question 10

Table below shows the average number of chloroplasts found in 3 different type of plant cells.
1 = 20, 2 = 0, 3 = 51
Which plant has the highest rate of photosynthesis

Answer 10

Plant 3 as it has the highest average number of chloroplasts per cell. Chloroplasts contain chlorophyll which absorbs sunlight an essential element of Photosynthesis

Question 11

By which process do plants breakdown glucose in order to transfer energy to their cells

Answer 11

Respiration - is a process where energy is released from the breakdown of glucose. This energy can then be used to convert the rest of the glucose into various different substances which they can use to build new cells and grow (cellulose)

Question 12

What do plants use cellulose for

Answer 12

• Glucose is converted into cellulose which is used to create cell walls especially in rapid growing plants.
• These cell walls support and strengthen the plant cells.

Question 13

What do plants absorb from the soil to make proteins with

Answer 13

Nitrate Ions

- Glucose combined with nitrate ions create Amino acids (the building blocks which make up proteins)

Question 14

What two substances can glucose be converted into for storage in plants

Answer 14

Lipids (Fats/Oils) - Plants store lipids in seeds e.g.sunflower seeds

Starch - glucose is stored as starch so it is ready for use when photosynthesis isn’t happening e.g.in the winter when sunlight is less. Starch is stored in roots, stems, seeds and leaves

Question 15

Why is starch better for storage than glucose

Answer 15

Starch is insoluble so it doesn’t draw up water and cause the cells to swell

Question 16

What is meant by the term limiting factor of photosynthesis

Answer 16

Anything that stops photosynthesis from happening any faster e.g. in winter Light intensity would be the limiting factor due to the lack of sunlight lowering the rate of photosynthesis

Question 17

Give three environmental conditions which can affect the rate of photosynthesis

Answer 17

Light Intensity - Light provides energy needed for photosynthesis therefore lack of light slows the rate of photosynthesis

Carbon dioxide concentration - The volume of CO2 in the air can sometimes affect the rate of photosynthesis. A plant cant synthesise if there is insufficient CO2 in the air.

Temprature - At low temperatures, the rate of photosynthesis is limited by the number of molecular collisions between enzymes and substrates. At high temperatures, enzymes are denatured

Question 18

What is used to investigate the rate of photosynthesis

Answer 18

• Using an aquatic plant such as canadian pondweed.

- The faster the rate at which the plant produces oxygen the faster the rate of photosynthesis will be

Question 19

How do you investigate the rate of photosynthesis

Answer 19

• Place a white light at a specific distance away from teh pond weed and leave for 2min for the plant to adjust to the light
• The pond weed is left to photosynthesise for a set amount of time
• Oxygen released by the plant will collect in a capillary tube
• At the end of the time a syringe is used to draw the gas bubble up the tube and a ruler is used to measure the length of the bubble (This is proportional to the volume of O2 produced
• Repeat twice and take the mean volume of O2
• Then repeat the whole experiment with the light source at a different distance

Question 20

In the rate of photosynthesis experiment what is the dependant variable

Answer 20

Dependant variable is the length of the gas bubble

The dependant variable refers to what it is your measuring or the outcome of the experiment

Question 21

In the rate of photosynthesis experiment what is the independant variable

Answer 21

The independent variable will be the light intensity

The independent variable is the variable which you change in an experiment

Question 22

How do you calculate the ate of photosynthesis

Answer 22

Divide the total length of the bubble by the time taken to produce it e.g.
- After 5min a gas bubble measuring the length of 25mm was taken
Firstly convert 25mm into cm
25/10 = 2.5cm

• Then divide the length by the time taken
  Rate = 2.5cm /5min = 0.5cm/min

Question 23

Why do farmers use artificial environments in order to grow plants

Answer 23

It allows them to create an ideal environment for plant growth. Maximise the rate of photosynthesis which in turn maximises the rate of plant growth

Question 24

What conditions can be controlled using a greenhouse

Answer 24

Light - using artificial light after the sun goes down to maximise their potential photosynthesis time

Carbon dioxide - Paraffin heaters can be used to heat the green house. As the paraffin burns Carbon Dioxide is produced as a by product

Temperature - Greenhouses help trap the suns heat in turn making sure that temperature doesn’t become a limiting factor for photosynthesis

Question 25

What is respiration

Answer 25

Respiration is the process of transferring energy from the breakdown glucose which goes on in every cell.

Respiration is Exothermic meaning it releases heat /transfers energy to the environment e.g. breathing out warm air

Question 26

What is aerobic respiration

Answer 26

Aerobic respiration is respiration which uses oxygen and is the most efficient way to transfer energy from glucose

Question 27

What do organisms use energy from respiration for

Answer 27

Organisms use energy from respiration to build up larger molecules from smaller ones (like proteins from amino acids)

Question 28

What do Animals use energy from respiration for

Answer 28

Animals including humans use energy from respiration to allow their muscles to contract allowing them to move

Question 29

What do Mammals and Birds use energy from respiration for

Answer 29

Mammals and Birds use energy from respiration to maintain their body temperature keeping their temperature at a constant

Question 30

What is anaerobic respiration

Answer 30

Anaerobic respiration is the process of producing cellular energy from glucose without oxygen.

Question 31

When does the body use anaerobic respiration

Answer 31

The body uses anaerobic respiration during exercise or increased physical activity when the body cant get enough oxygen to the muscles

Question 32

What is produced by anaerobic respiration

Answer 32

Lactic acid is a by product of anaerobic respiration. Anaerobic respiration is the incomplete breakdown of glucose making lactic acid.

Question 33

What is the word equation for anaerobic respiration in muscle cells

Answer 33

Glucose - Lactic acid

Question 34

What is oxygen debt

Answer 34

Oxygen debt is the amount of extra oxygen the body needs after exercise in order to react with the lactic acid and remove it from the cells.

Question 35

How does the liver help get rid of lactic acid in the muscles

Answer 35

The blood that enters your muscles transports the lactic acid to the liver where it is oxidised and broken down back into glucose.

Question 36

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

Answer 36

Glucose - Ethanol + Carbon dioxide

Question 37

What is anaerobic respiration also known as in yeast cells

Answer 37

Fermentation - In the beer industry the fermentation process produces alcohol.
In the bread making industry the fermentation process is what makes the bread rise

Question 38

Compare anaerobic and aerobic respiration

Answer 38

Aerobic:

• Oxygen needed
• C02 and water are made
• Produces large amounts of energy

Anaerobic Respiration:

• Does not require oxygen
• Produces Lactic Acid (in humans)
• Ethanol (in Plants and yeast)
• Produces small amount of energy

Question 39

How is lactic acid formed

Answer 39

Lactic acid is formed from the incomplete oxidation of glucose during anaerobic respiration (Energy is transferred from glucose to cells without using oxygen)

Question 40

What do muscle cells use oxygen for during exercise

Answer 40

Oxygen is used to transfer energy from glucose which is then use to contract the muscles

Question 41

The body has what three responses to increased respiration in cells when exercising

Answer 41

• Increase in breath rate and breath Volume to meet the demand for extra oxygen
• Increase in heart rate in order to make your blood flow more quickly delivering more oxygen and glucose to the cells for respiration and taking more carbon dioxide away.

Question 42

What are the two reactions from the body after vigorous exercise.

Answer 42

• The body cant supply oxygen to the muscles quickly enough so they start respiring anaerobically.
• Lactic Acid build up due to the transfer of energy from glucose without the presence of oxygen
• Muscle fatigue where muscles get tired and stop contracting efficiently

Question 43

What is meant by the term metabolism

Answer 43

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

Question 44

What is glucose used/converted into in plant cells

Answer 44

Cellulose = to strengthen plant cell walls

Starch = This is a storage form of Glucose e.g. potatoes

Glucose also reacts with nitrate ions to make amino acids which are then used to synthesise proteins

Question 45

What is glucose used/converted into in Humans and other Animals

Answer 45

Glycogen = converted into glycogen which is a storage form of glucose

Question 46

What are Lipid molecules made from

Answer 46

1 molecule of glycerol and 3 molecules of fatty acids

Question 47

What is formed when glucose combines with nitrates

Answer 47

Amino acids

Question 48

What component of urine is produced from the breakdown of excess protein

Answer 48

Urea

Question 49

Where in a plant cell does photosynthesis take place

Answer 49

chloroplasts

Question 50

Tim wants to measure the effect of light intensity on the rate of photosynthesis. He follows an experiment from a science mag where discs cut from leafs are put into a solution 0.2% concentrated (which serves as a carbon dioxide source) and put into a syringe under a light source. He then timed how long it took for the discs to float to the top. Results below:
Light Intensity A = 18 min for discs to float to top
Light Intensity B = 9 min
Light Intensity C = 11 min

Which Light intensity do you think was the highest, explain why

Answer 50

B because the discs floated to the top in a shorter time than the other Light intensities. This would indicate that more photosynthesis is taking place causing the cells to produce oxygen filling the air spaces in the leaf and causing them to float.

Question 51

Tim thinks that in an experiment measuring the effect of light intensity on the rate of photosynthesis, if he keeps increasing the light intensity the rate of photosynthesis will continue to increase.
Is he right? explain your answer.

Answer 51

• Increasing the light intensity will increase the rate of photosynthesis up to a point but once this point is reached the increase in light intensity will have no effect on the rate.
• Other limiting factors will need to be considered in order to increase the rate such as carbon dioxide concentration or temperature increase

Question 52

Tim wants to measure the effect of light intensity on the rate of photosynthesis. He follows an experiment from a science mag where discs cut from leafs are put into a solution 0.2% concentrated (which serves as a carbon dioxide source) and put into a syringe under a light source. He then timed how long it took for the discs to float to the top. Results below:
Light Intensity A = 18 min for discs to float to top
Light Intensity B = 9 min
Light Intensity C = 11 min

Tim conducts the experiment again using light intesity A but increases the solution (which serves as a carbon dioxide source) from a concentration of 0.2% to 0.8%

Do you think it will take less than 18 min for the discs to float? Explain why.

Answer 52

Yes because the increased carbon dioxide concentration will increase the rate of photosynthesis causing the discs to float to the top in a faster time

Question 53

Photosynthesis produces glucose explain fully how this glucose can be used

Answer 53

used for respiration
converted to cellulose to strengthen cell walls
converted to starch for storage
converted to lipids for storage
combined with nitrates to form amino acids which can be joined to form proteins