Topic 4: Bioenergetics Flashcards
Why are plants autotrophs?
Make their own food using light, water and carbon dioxide
What is photosynthesis?
Endothermic reaction in which energy is transferred from the environment to the chloroplast by light
Where does most photosynthesis take place?
Leaves of plant, in specialised mesophyll cells which are packed with chloroplasts containing chlorophyll to absorb as much light energy as possible
What is produced in photosynthesis?
Glucose, sugars, used to make all the substances a plant needs, as well as being used in respiration to release energy
What is the word equation for photosynthesis?
Carbon Dioxide + Water –> Glucose + Oxygen
(Arrow has light and chlorophyll)
What is the balanced symbol equation for photosynthesis?
6 CO₂ + 6 H₂O –> C₆H₁₂O₆ + 6O₂
How are the reactants of the photosynthesis equation obtained?
Carbon Dioxide - Diffuses into the leaf through the stomata
Water - Taken up by the roots and transported through the xylem to the leaves
How are the products of the photosynthesis equation used or released?
Glucose - Used to make substance needed by plant; used in respiration to release energy
Oxygen - Diffuses out of the leaf through the stomata; used in respiration
What does a plant need in order for photosynthesis to occur?
- Light
- Water
- Carbon Dioxide
Why is water not a limiting factor for photosynthesis?
Amount needed is relatively small compared to amount of water transpired from a plant so there is hardly a situation where there is not enough water for photosynthesis
How does temperature affect the rate of photosynthesis?
- Temp. of environment affects amount of kinetic energy particles have
- Affects speed at which CO₂ and H₂O move through plant
- Lower temp. , the less kinetic energy particles have, resulting in fewer successful collisions occurring
- High temp. , increase kinetic energy of particles, increasing likelihood of collision between reactants and enzymes which results in formation of products
- However, at high temp. enzyme that control photosynthesis can be denatured
How does light affect the rate of photosynthesis?
- Intensity of light available to the plant will depend on the amount of energy that it has to carry out photosynthesis
- More light a plant receives, the faster the rate of photosynthesis
- The trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
How does carbon dioxide concentration affect rate of photosynthesis?
- One of the raw materials required for photosynthesis
- More carbon dioxide, the faster the reaction can occur
- Trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
How does chlorophyll affect rate of photosynthesis?
- Number of chloroplasts
- More chloroplasts a plant has, the faster rate of photosynthesis
- Amount of chlorophyll can be affected by:
> Diseases
> Lack of nutrients
> Loss of leaves
What does the inverse square law describe in relation to light?
The inverse square law describes the relationship between light intensity and distance, showing they are inversely proportional to each other.
How does light intensity change as distance increases?
As distance increases, light intensity decreases. Specifically, when distance doubles, light intensity decreases by a factor of four.
What is the equation for the inverse square law relating to light intensity?
Light intensity = 1/d² (where d is the distance from the light source)
Calculate the light intensity when a plant is placed 30cm from a lamp.
Light intensity = 1/30² = 0.001 au (arbitrary units)
What does ‘au’ stand for when measuring light intensity?
‘au’ stands for arbitrary units.
Why do commercial horticulturists grow plants in greenhouses?
To control as many of the limiting factors of photosynthesis as possible.
What limiting factors can be controlled in a greenhouse?
Heat, light, water, carbon dioxide, and nutrients.
Why are limiting factors important in greenhouse economics?
They’re important for enhancing conditions to gain maximum photosynthesis rates while still maintaining profit.
How do greenhouses help farmers make more money despite their costs?
Through increased crop yield and more frequent harvests.
Why do farmers carefully control resource levels in greenhouses?
To use only the smallest amounts needed and avoid wasting money.
Give an example of a wasteful practice in greenhouse management.
Spending money on increasing CO₂ concentration beyond the point where some other factor limits photosynthesis.
What is glucose produced in photosynthesis used for?
- Used for respiration
- Converted into insoluble starch for storage in stems, leaves and roots
- Used to produce fat or oil for storage
- Used to produce cellulose
- Combined with nitrate ions absorbed from the soil to produce amino acids for protein synthesis
How is starch tested to show a plant is photosynthesising?
- Iodine solution test
- Boil leaf
- Place in ethanol for 10 minutes and turn off Bunsen burner to remove chlorophyll from leaf
- Wash leaf in water to soften
- Place leaf on white tile and cover in iodine solution and if areas turn blue/black starch is present
What is cellular respiration?
An exothermic reaction which is continuously occurring in living cells.
What does the chemical process of cellular respiration release?
Energy.
What does the energy from respiration supply?
All the energy needed for living processes to occur within cells and organisms as a whole.
Name three things organisms need energy for.
1) Chemical reactions to build larger molecules from smaller molecules 2) Muscle contraction to allow movement 3) Keeping warm (to maintain a constant temperature suitable for enzyme activity).
What is aerobic respiration?
Respiration in cells that takes place using oxygen to transfer energy; glucose is reacted with oxygen in this process.
What is the word equation for aerobic respiration?
Glucose + Oxygen → Carbon dioxide + Water + Energy.
Where does most of aerobic respiration take place in the cell?
In the mitochondria.
What is anaerobic respiration in animals?
Respiration in cells without oxygen, involving the incomplete breakdown of glucose into lactic acid to transfer energy.
When does anaerobic respiration occur in the body?
When the body can’t supply enough oxygen for aerobic respiration, such as during vigorous exercise.
What is the word equation for anaerobic respiration in animals?
Glucose → Lactic acid + Energy.
How does the energy released in anaerobic respiration compare to aerobic respiration?
Much less energy is transferred in anaerobic respiration than in aerobic respiration.
How do plants and yeast respire without oxygen?
They break down glucose in the absence of oxygen to produce ethanol and carbon dioxide.
What is fermentation?
Anaerobic respiration in yeast cells.
Why is fermentation economically important?
In the manufacture of bread (carbon dioxide makes dough rise) and alcoholic drinks (as ethanol is a type of alcohol).
What is the main difference between aerobic and anaerobic respiration regarding oxygen?
Aerobic respiration requires oxygen while anaerobic respiration takes place without oxygen.
What are the different products of aerobic vs. anaerobic respiration?
Aerobic: carbon dioxide and water. Anaerobic (animals): lactic acid. Anaerobic (plants/yeast): ethanol and carbon dioxide.
How do the amounts of energy transferred differ between aerobic and anaerobic respiration?
Aerobic respiration transfers much more energy than anaerobic respiration.
Why do muscles need energy during exercise?
For muscle contractions to allow movement.
What happens to the demand for energy when exercising?
It increases as the number of muscle contractions increases.
How does the body react to increased oxygen demand during exercise?
The breathing rate and breath volume increase, and the heart rate increases.
What is the purpose of increased breathing rate during exercise?
To increase the amount of oxygen absorbed into the bloodstream by diffusion, and the amount of carbon dioxide removed.
What is the purpose of increased heart rate during exercise?
To increase the supply of oxygenated blood to the muscles.
What happens if the body cannot supply sufficient oxygen during vigorous exercise?
Some of the energy supplied to the muscles comes from anaerobic respiration.
What is an oxygen debt?
The ‘extra’ oxygen needed after exercising to react with the lactic acid produced via anaerobic respiration.
Why does an individual still breathe heavily after exercising vigorously?
To pay back the oxygen debt and to remove extra carbon dioxide from the body.
What causes muscles to become fatigued during long periods of vigorous activity?
Increased levels of lactic acid building up.
How can breathing rate be measured in an investigation?
By counting the number of breaths per minute.
How can heart rate be measured in an investigation?
By taking a pulse.
What are two ways the body can deal with lactic acid?
1) It can be oxidised to form carbon dioxide and water 2) It can be transported to the liver where it is converted back into glucose.
What is metabolism?
The sum of all the reactions in a cell or the body.
What does the energy released during respiration allow in cells?
Enzyme-controlled reactions to occur inside cells, e.g. to produce new molecules.
How do organisms gain organic molecules?
Either by consuming food (animals) or carrying out photosynthesis (plants).
What happens to molecules gained by organisms?
They can be broken down and used to produce, or synthesise, new molecules.
Name three types of molecules involved in metabolic reactions.
Carbohydrates, lipids, and proteins.
What are complex carbohydrates built from?
Sugars, e.g. glucose.
What are lipids built from?
Fatty acids and glycerol.
What are proteins synthesized from?
Amino acids.
Name three things glucose is used to synthesize in metabolism.
1) Starch (energy storage in plants) 2) Glycogen (energy storage in animals) 3) Cellulose (strengthens plant cell walls).
What happens to glucose during respiration?
It is broken down to release energy.
How are lipids formed in metabolism?
Glycerol is combined with three fatty acids in the synthesis of lipids.
What is the function of lipids in the body?
They can be used in energy storage.
What molecules are involved in the production of amino acids?
Glucose and nitrates.
What happens to excess proteins in the body?
They are broken down to produce urea, which is excreted from the body.
What is the difference between cellular respiration and breathing?
Cellular respiration is not breathing; it is a chemical process of transferring energy from glucose in all living cells.
