Westminster bio question model answer

The journey of carbon atoms from atmospheric carbon dioxide to the koala’s muscular arm involves multiple
stages, starting with photosynthesis in eucalyptus trees, digestion, circulation, and cellular respiration.

First, carbon dioxide in the atmosphere is absorbed by the eucalyptus tree, which the koala feeds on. Through
the process of photosynthesis, chlorophyll in the tree's leaves uses sunlight to convert carbon dioxide and
water into glucose, a carbohydrate that stores carbon. This glucose is then transported to different parts of the
tree, including the leaves, which the koala consumes.

Once the koala eats the eucalyptus leaves, digestion begins. The leaves are broken down in the koala’s
digestive system, where enzymes break down the glucose molecules from the plant cell walls, allowing the
koala to absorb these sugars into its bloodstream.

Through the circulatory system, glucose is then transported via the blood to various cells, including those in
the muscles. In the muscle cells of the koala’s arms, cellular respiration occurs. Here, glucose combines with
oxygen to release energy, water, and carbon dioxide. This energy is stored in molecules of ATP (adenosine
triphosphate), which are essential for muscle function.

Finally, this energy in ATP enables the contraction of the muscles in the koala's arm, allowing it to climb trees.
Thus, the carbon atoms, which began in carbon dioxide, have completed their journey, contributing to the
koala’s ability to move and climb by providing energy at a cellular level.

This complex journey demonstrates the interconnectedness of photosynthesis, digestion, circulation, and
respiration in fueling the koala’s unique lifestyle.

Certainly! Here are some similar questions, each with a model answer that follows the IGCSE level style.

---

### Question 1
**"Describe the journey nitrogen takes to reach the protein in the muscles of a cow and explain how
this protein contributes to muscle function."**

---

**Model Answer:**

Nitrogen is an essential element for building proteins, and its journey to the muscles of a cow involves the
nitrogen cycle, digestion, and protein synthesis.

1. **Nitrogen Fixation in Plants**: Nitrogen gas in the atmosphere is converted into nitrates in the soil through
nitrogen-fixing bacteria. Plants, such as grass, absorb these nitrates through their roots and use them to create
amino acids, which build plant proteins.

2. **Consumption and Digestion**: When the cow eats grass, these plant proteins enter its digestive system.
Enzymes in the stomach and small intestine break down the proteins into amino acids, which are then
absorbed into the bloodstream.

3. **Circulatory System and Transport**: The amino acids travel through the bloodstream to various parts of
the cow’s body, including the muscles, where they’re reassembled into cow-specific proteins.
4. **Protein Synthesis in Muscle Cells**: In the muscle cells, these amino acids are used to build myofibrillar
proteins, essential for muscle contraction and strength.

5. **Muscle Function**: These proteins help the cow's muscles contract and support activities like walking,
grazing, and moving. Without adequate nitrogen and protein, the cow's muscles would lack strength and
durability.

This nitrogen cycle demonstrates the importance of nitrogen fixation, digestion, and protein synthesis in
providing the energy and structural support for muscle function in cows.

---

### Question 2
**"Describe how oxygen molecules in the air eventually reach the mitochondria in a fish’s tail muscle
cells, and explain how they contribute to the fish’s swimming ability."**

---

**Model Answer:**

The journey of oxygen from the air to the mitochondria in a fish’s tail muscles involves gas exchange,
circulation, and cellular respiration.

1. **Gas Exchange in Water**: Oxygen from the air dissolves into the water. Fish use their gills, which are
adapted with thin filaments and large surface areas, to extract oxygen from the water.

2. **Oxygen Transport in Blood**: Once the oxygen diffuses across the gill membranes, it binds to hemoglobin
in red blood cells. The blood carries oxygen through the fish's circulatory system to its tail muscles.

3. **Cellular Respiration**: In the tail muscle cells, oxygen enters the mitochondria, where it plays a vital role in
cellular respiration. Glucose and oxygen are used to produce ATP, the energy molecule, along with carbon
dioxide and water as by-products.

4. **Energy for Swimming**: ATP generated in the mitochondria powers the muscle contractions in the tail,
enabling the fish to swim efficiently. Oxygen is crucial for this energy production, as it allows the fish to
maintain strength and speed in swimming.

This journey from oxygen in water to ATP production in the tail muscles shows the vital role of oxygen in
supporting the fish's movement and overall survival.

---

### Question 3
**"Explain the path of glucose molecules from ingestion to their conversion into ATP in a human
muscle cell, and describe how this ATP helps in muscle contraction during physical activities."**

---

**Model Answer:**

Glucose’s journey to ATP in human muscle cells involves digestion, circulation, and cellular respiration.
1. **Digestion and Absorption**: Glucose enters the body through carbohydrate digestion, beginning in the
mouth with enzymes like amylase and continuing in the small intestine. Enzymes further break down
carbohydrates into simple sugars, mainly glucose, which is absorbed into the bloodstream.

2. **Transport in Blood**: The bloodstream carries glucose to cells throughout the body, including muscle cells.

3. **Cellular Respiration in Mitochondria**: Inside muscle cells, glucose enters mitochondria, where it
combines with oxygen during cellular respiration to produce ATP, carbon dioxide, and water.

4. **ATP and Muscle Contraction**: ATP molecules provide the energy needed for muscle fibers to contract.
During physical activities, ATP allows muscles to repeatedly contract and relax, supporting movement and
endurance.

This pathway from ingestion to ATP production highlights how glucose and oxygen work together to provide
essential energy for physical activities, emphasizing the role of cellular respiration in muscle function.

---

### Question 4
**"Describe how water from soil eventually contributes to photosynthesis in the leaf of a sunflower,
and explain the role of photosynthesis in the plant's growth and energy needs."**

---

**Model Answer:**

Water’s journey to support photosynthesis in a sunflower leaf involves absorption, transport, and light-driven
reactions in chloroplasts.

1. **Water Absorption**: Water in the soil is absorbed by the sunflower’s roots through osmosis. Root hairs
increase the surface area, helping the plant take in more water.

2. **Transport through Xylem**: The water moves upward through the plant’s xylem vessels, which carry it to
the leaves.

3. **Photosynthesis in the Chloroplasts**: In the leaf’s chloroplasts, water molecules participate in

4. **Energy and Growth**: The glucose produced is used by the sunflower for growth and as energy for cellular
activities. Excess glucose can be stored as starch for future energy needs.

Through this process, water from the soil supports photosynthesis, which in turn provides the energy and
building blocks for the sunflower’s growth and survival.

---

### Question 5
**"Describe how carbon dioxide moves from the blood to the alveoli in human lungs, and explain the
role of exhaling in maintaining oxygen levels in the blood."**

---

**Model Answer:**
The pathway of carbon dioxide from the blood to the alveoli is a part of respiration, helping to regulate oxygen
and carbon dioxide levels.

1. **Cellular Respiration and Carbon Dioxide Production**: During cellular respiration in body cells, glucose is
broken down, producing energy, water, and carbon dioxide as by-products. This carbon dioxide diffuses into
the bloodstream.

2. **Transport to the Lungs**: Carbon dioxide is carried in the blood, mainly dissolved in plasma, to the lungs.

3. **Gas Exchange in Alveoli**: In the alveoli, a high concentration of carbon dioxide in the blood diffuses
across the thin capillary walls into the alveolar air, where its concentration is lower.

4. **Exhalation**: When we exhale, carbon dioxide is removed from the lungs, maintaining a low level of
carbon dioxide in the blood. This process also ensures that oxygen can efficiently diffuse into the blood with
each new breath.

By removing carbon dioxide, exhaling helps maintain the balance of gases, allowing efficient oxygen uptake for
respiration and cellular function.