NST1502
ASSIGNMENT 4
ANSWERS 2025
NST1502 ASSIGNMENT 4 ANSWERS
2025
,NST 1502
Natural Science and Technology in the Classroom 2
ASSIGNMENT NUMBER 04 (Portfolio)
ASSIGNMENT DUE DATE: 02 October 2025
QUESTION 1
1.1 Kinetic energy
- The energy an object has due to its motion. For a moving object with mass m and
speed v, KE = 1/2 m v^2.
1.2 How energy is transferred in an ecosystem
- Energy from the sun is captured by producers (photosynthesis) and converted to
chemical energy.
- This energy flows through the food chain as organisms eat each other (producers
→ consumers → decomposers).
- At each transfer, energy is lost as heat due to metabolic processes; only a portion
is passed to the next trophic level (roughly about 10% is often cited as the transfer
efficiency).
1.3 Main purpose of photosynthesis in plants
- To convert light energy into chemical energy stored as glucose (a sugar) and to
release oxygen as a byproduct. This stored chemical energy powers the plant and
supports other organisms higher up the food chain.
, 1.4 What is cellular respiration?
- The process by which cells break down glucose (and other molecules) with oxygen
to release energy, producing ATP, carbon dioxide, and water. It includes glycolysis,
the citric acid cycle, and oxidative phosphorylation (electron transport chain).
1.5 Compare aerobic and anaerobic respiration
- Oxygen requirement: Aerobic uses O2; anaerobic does not.
- Location: Aerobic largely occurs in mitochondria; anaerobic occurs in the cytoplasm
(and includes fermentation).
- ATP yield: Aerobic yields about 36–38 ATP per glucose; anaerobic yields about 2
ATP per glucose.
- End products: Aerobic produces CO2 and H2O; anaerobic produces lactate
(animals) or ethanol and CO2 (yeast/microorganisms).
- Efficiency: Aerobic is much more efficient at extracting energy from glucose.
1.6 Role of ATP in cellular processes
- ATP is the cell’s immediate energy currency. It powers most energy-requiring
processes (active transport, muscle contraction, biosynthesis, signal transduction,
etc.) by releasing a phosphate group when hydrolyzed to ADP and Pi.
1.7 How ATP is synthesized in the mitochondria
- Through oxidative phosphorylation (electron transport chain and chemiosmosis).
Electrons are transferred through the inner mitochondrial membrane, creating a
proton gradient. Protons flow back through ATP synthase, driving the synthesis of
ATP from ADP and inorganic phosphate (Pi). Oxygen acts as the final electron
acceptor.
ASSIGNMENT 4
ANSWERS 2025
NST1502 ASSIGNMENT 4 ANSWERS
2025
,NST 1502
Natural Science and Technology in the Classroom 2
ASSIGNMENT NUMBER 04 (Portfolio)
ASSIGNMENT DUE DATE: 02 October 2025
QUESTION 1
1.1 Kinetic energy
- The energy an object has due to its motion. For a moving object with mass m and
speed v, KE = 1/2 m v^2.
1.2 How energy is transferred in an ecosystem
- Energy from the sun is captured by producers (photosynthesis) and converted to
chemical energy.
- This energy flows through the food chain as organisms eat each other (producers
→ consumers → decomposers).
- At each transfer, energy is lost as heat due to metabolic processes; only a portion
is passed to the next trophic level (roughly about 10% is often cited as the transfer
efficiency).
1.3 Main purpose of photosynthesis in plants
- To convert light energy into chemical energy stored as glucose (a sugar) and to
release oxygen as a byproduct. This stored chemical energy powers the plant and
supports other organisms higher up the food chain.
, 1.4 What is cellular respiration?
- The process by which cells break down glucose (and other molecules) with oxygen
to release energy, producing ATP, carbon dioxide, and water. It includes glycolysis,
the citric acid cycle, and oxidative phosphorylation (electron transport chain).
1.5 Compare aerobic and anaerobic respiration
- Oxygen requirement: Aerobic uses O2; anaerobic does not.
- Location: Aerobic largely occurs in mitochondria; anaerobic occurs in the cytoplasm
(and includes fermentation).
- ATP yield: Aerobic yields about 36–38 ATP per glucose; anaerobic yields about 2
ATP per glucose.
- End products: Aerobic produces CO2 and H2O; anaerobic produces lactate
(animals) or ethanol and CO2 (yeast/microorganisms).
- Efficiency: Aerobic is much more efficient at extracting energy from glucose.
1.6 Role of ATP in cellular processes
- ATP is the cell’s immediate energy currency. It powers most energy-requiring
processes (active transport, muscle contraction, biosynthesis, signal transduction,
etc.) by releasing a phosphate group when hydrolyzed to ADP and Pi.
1.7 How ATP is synthesized in the mitochondria
- Through oxidative phosphorylation (electron transport chain and chemiosmosis).
Electrons are transferred through the inner mitochondrial membrane, creating a
proton gradient. Protons flow back through ATP synthase, driving the synthesis of
ATP from ADP and inorganic phosphate (Pi). Oxygen acts as the final electron
acceptor.
