Biology bioenergetics

• What is photosynthesis?

• Photosynthesis is an endothermic reaction that takes place in plants.

• It involves absorbing light energy to convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆) and oxygen (O₂).

What is the word equation for photosynthesis?

Carbon dioxide + Water → Glucose + Oxygen

What is the balanced chemical equation for photosynthesis?

6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂

Where in the plant cell does photosynthesis occur?

• Takes place in the chloroplasts, found in plant cells (mainly in the leaves).

• Chloroplasts contain chlorophyll, a green pigment that absorbs light energy

List the main factors that affect the rate of photosynthesis.

Light intensity, CO₂ concentration, temperature, chlorophyll levels.

How does light intensity affect photosynthesis?

More light increases the rate of photosynthesis because chlorophyll absorbs more energy.

How does carbon dioxide concentration affect photosynthesis?

Higher CO₂ levels increase the rate as more CO₂ is available for making glucose.

How does temperature affect photosynthesis?

• At low temperatures, the enzymes work slowly, reducing the rate.

• At higher temperatures (up to ~45°C), the rate increases as molecules move faster.

• Above 45°C, enzymes denature, stopping photosynthesis.

What is the definition of a limiting factor in photosynthesis?

A factor that restricts the rate of photosynthesis when in short supply.

How do plants use the glucose produced in photosynthesis?

• For respiration – Releases energy for cell functions.

• Stored as starch – Insoluble and used for energy when needed.

• Converted into fats/oils – Used for energy storage.

• Used to make cellulose – Strengthens cell walls.

• Used to make amino acids – Combined with nitrates to form proteins for growth.

What is respiration?

• A chemical reaction that releases energy from glucose.

• Happens in all living cells to provide energy for movement, growth, and repair.

What is the word equation for aerobic respiration?

Glucose + Oxygen → Carbon dioxide + Water

What is the balanced chemical equation for aerobic respiration?

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O

What is anaerobic respiration in muscles?

• Glucose is broken down without oxygen, producing lactic acid.

• This releases less energy than aerobic respiration.

What is the word equation for anaerobic respiration in muscles?

• Glucose → Lactic Acid + Energy

• Lactic acid builds up and causes muscle fatigue.

How does anaerobic respiration differ in plant and yeast cells?

• In plants/yeast: Glucose → Ethanol + Carbon Dioxide + Energy

• Used in fermentation (e.g., making bread and alcohol).

What is fermentation?

• Anaerobic respiration in yeast cells.

• Used in bread-making (CO₂ makes dough rise) and alcohol production (ethanol is the alcohol in drinks).

What is oxygen debt?

• The extra oxygen needed after exercise to remove lactic acid.

• Lactic acid is transported to the liver and broken down into CO₂ and water.

What changes occur in the body during exercise?

• Heart rate increases – More blood (oxygen + glucose) to muscles.

• Breathing rate & depth increase – More oxygen taken in and CO₂ removed.

• Anaerobic respiration occurs if oxygen is insufficient, leading to lactic acid buildup.

What is metabolism?

Sum of all chemical reactions in the body.