B4 Bioenergetics

What is photosynthesis?

A reaction in plants where carbon dioxide and water react in the presence of light to form glucose and oxygen

Where does photosynthesis take place?

In chloroplasts in green plant cells

Where is the energy for photosynthesis taken from?

light radiation from the Sun

What type of reaction is photosynthesis?

Endothermic

What is the word equation for photosynthesis?

Carbon dioxide + water → glucose + oxygen

What is the symbol equation for photosynthesis?

6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂

What are the main limiting factors of photosynthesis?

Light

Concentration of CO2

Chlorophyll

Temperature

How does temperature affect the rate of photosynthesis?

• If the temperature is low, the enzymes work more slowly.

• If the plant gets too hot (around 45°C), the enzymes become damaged.

How do plants use glucose?

For respiration and to produce important molecules

What is cellulose used for in plants?

Making strong cell walls.

Why do plants store starch?

It is a source of stored energy ready for when photosynthesis isn't happening

Why do plants store energy as starch, rather than glucose?

Starch is insoluble

What is respiration?

an exothermic reaction which is continuously occurring in living cells to provide energy for living processes

Is respiration exothermic or endothermic?

Exothermic

How do organisms use energy from respiration?

chemical reactions to build larger molecules

movement

keeping warm

What is aerobic respiration?

Respiration using oxygen

What is anaerobic respiration?

Respiration without oxygen

Where does aerobic respiration happen?

in the mitochondria

Where does anaerobic respiration happen?

in the cytoplasm

What is the word equation for aerobic respiration?

Glucose + oxygen → carbon dioxide + water

What is the symbol equation for aerobic respiration?

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O

What is the word equation for anaerobic respiration in humans?

Glucose → lactic acid

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

Glucose → ethanol + carbon dioxide

What is the name given to anaerobic respiration in yeast cells?

Fermentation

When do human body cells start to respire anaerobically?

When you do vigorous exercise and your body can't supply enough oxygen to your muscles

Why is anaerobic respiration undesirable?

• It doesn't transfer as much energy as aerobic respiration

• It causes lactic acid to build up in the muscles, which is painful.

How is fermentation used in industry?

alcoholic drinks and bread making

How does your body increase the amount of oxygen that gets to your cells when you exercise?

• Breathing rate and depth increases (to get more oxygenated blood to cells)

• Heart rate increases (to get oxygenated blood to cells quicker, and to remove CO₂ quicker)

How could you measure breathing rate?

By counting the number of breaths taken in a certain period of time.

How could you measure heart rate?

Counting the number of pulses on your wrist/neck in one minute.

What happens to muscles after long periods of exercise?

Muscle fatigue (muscles get tired and stop contracting efficiently)

What is 'oxygen debt'?

After cells have respired anaerobically, it is the amount of oxygen need to react with the buildup of lactic acid to remove it from cells (forming CO₂ and water).

What is metabolism?

The sum of all the chemical reactions occuring in an organism.