Bioenergetics

what happens in photosynthesis?

Light energy is absorbed by chlorophyll in chloroplasts in plant/algal cells

What type of reaction is photosynthesis and why?

Endothermic - energy transferred from environment to chloroplasts by light

Word equation for photosynthesis

Carbon dioxide + water → (light above arrow)(chlorophyll below arrow) glucose + oxygen

Symbol equation for photosynthesis

6CO2 + 6H2O -> C6H12O6 + 6O2

What does a limiting factor do?

restrict rate of photosynthesis (stop from increasing) if in low levels

How does temperature affect the rate of photosynthesis?

As temp increases, rate increases as enzymes controlling photosynthesis gain kinetic energy so temp is the limiting factor

Above an optimum temperature, rate decreases as enzymes denature/active site changes shape

How does light intensity affect the rate of photosynthesis?

As light intensity increases, rate increases as light provides energy needed for photosynthesis so light intensity is limiting factor

Above a certain light intensity, rate stops increasing so another factor is limiting

How does CO2 conc. affect the rate of photosynthesis?

As CO2 conc increases, rate increases as co2 is reactant/raw material needed for photosynthesis so co2 conc is limiting factor

Above a certain CO2 conc, rate stops increasing so another factor is limiting

How does chlorophyll affect the rate of photosynthesis?

Affects how much light energy can be absorbed

What is the inverse square law?

The law that describes the relationship between distance of a light source from a plant and light intensity

Light intensity ∝ 1/distance²

How can farmers use their knowledge of limiting factors to increase their profits?

Remove limiting factors - gain maximum rate of photosynthesis - increase plant yield

Profit from extra yield must be greater than the costs of providing conditions

uses of glucose from photosynthesis

1. Respiration to release energy

2. Converted into insoluble starch for storage

3. To produce fat/oil for energy storage

4. To produce cellulose to the strengthen cell wall

5. To produce amino acids for protein synthesis - combined with nitrate ions from soil to form amino aicds

What is cellular respiration?

A series of chemical reactions that release/transfer energy from glucose

Occurs continuously in all living cells

Exothermic reaction

How is the energy released in respiration used?

Chemical reactions to build larger molecules (e.g. metabolism)

Keeping warm (birds and mammals)

Movement (muscle contraction in animals)

Word equation for aerobic respiration

Glucose + oxygen → carbon dioxide + water (+energy)

Symbol equation for aerobic respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O

Word equation for anaerobic respiration in animals

Glucose → lactic acid (+some energy)

Word equation for anaerobic respiration in plants and yeast

Glucose → ethanol + carbon dioxide (+some energy)

What is the economic importance of anaerobic respiration in yeast?

Fermentation is used in production of bread - co2 makes dough rise

and production of alcoholic drinks - ethanol is a type of alcohol

How does the body react to increased energy demand during exercise?

Increased heart rate - increased blood flow to muscles/lungs

Increased breathing rate and volume - more air/oxygen enters lungs

To supply more blood containing more oxygen and glucose to muscles

For more aerobic respiration to release energy/to reduce anaerobic respiration and lactic acid build up

What happens when muscles are supplied with insufficient oxygen?

Anaerobic respiration - oxidation of glucose is incomplete causing a build up of lactic acid which causes oxygen det and muscles become fatigues and stop contracting efficiently

What is oxygen debt?

Amount of extra oxygen the body needs after exercise to react with lactic acid and remove it from cells

What is the role of the liver in recovering from vigorous exercise?

Blood flowing through muscles transports lactic acid to the liver where it is converted back to glucose

What is metabolism?

Sum of all chemical reaction in a cell or the body

What is metabolic rate?

Rate of all the chemical reactions in the body

How else do cells use energy transferred by respiration?

To continually carry out enzyme-controlled processes of metabolism that synthesise new molecules

Examples of smaller to larger molecules metabolic reactions

1. Many glucose molecules converted into starch, glycogen, cellulose

2. 1 glycerol molecules + 3 fatty acid molecules into a lipid molecules

3. Glucose + nitrate ions into amino acids used to synthesise proteins

Examples of larger to smaller molecules metabolic reactions

1. respiration

2. break down of excess proteins to form urea for excretion