Bionergetics Flashcards
What is photosynthesis?
Thr process by which plants syndthesis glucose using light energy from the sun (lighy energy is converted into chemical energy)
Where does photosynthesis take place?
Within chloroplasts in leaf palisade cells. They contain chlorophyll, a pigment which absorbs light energy.
What is the equation for photosynthesis?
6CO2 + 6H2O -> C6H12O6 + 6O2
Carbon dioxide + water -> glucose + oxygen
Is photosynthesis endergonic or exergonic reaction, and why?
Endothermic- energy is transferred from the environment to chloroplasts by light
How can you show that a plant gives off oxygen during photosynthesis?
Using a water plant (eg. Elodea), collect gas bubbles produced during photosynthesis. The gas will relight a glowing splint as it contains oxygen.
Give examples of leaf adaptations which maximise the rate of photosynthesis?
● Broad leaves - maximise surface area.
● Thin leaves - short diffusion distance.
● Chlorophyll present - trap light energy.
● Veins - transport water to leaves via xylem, remove photosynthesis products via phloem.
● Air spaces - allow CO2 to enter and O2 to leave.
● Guard cells - control opening of stomata for gaseous exchange and prevent water loss.
What are the four main factors that affect the rate of photosynthesis?
Temperature, light intensity, carbon dioxide concentration, amount of chlorophyll
How does temperature affect the rate of photosynthesis?
Increasing the temperature increases the rate of photosynthesis as the kinetic energy of particles is increased. The rate decreases past a certain temperature as enzymes become denatured.
How does light intensity affect the rate of photosynthesis?
Increasing light intensity increases the rate of photosynthesis, until another factor becomes limiting
How does carbon dioxide concentration affect the rate of photosynthesis?
Increasing the carbon dioxide concentration increases the rate of photosynthesis (until another factor becomes limiting) as CO2 is required to make glucose.
How does the amount of chlorophyll affect the rate of photosynthesis?
Decreasing the amount of chlorophyll (eg. due to a lack of magnesium) decreases the rate of photosynthesis as chlorophyll is required to absorb light energy.
What is a limiting factor?
An environmental factor which can restrict the rate of photosynthesis eg. light intensity.
Explain how you can calculate the rate of photosynthesis by measuring oxygen production
● Set up bubble potometer apparatus (pondweed in a sealed tube of water, attached to a capillary tube and a gas syringe).
● Oxygen gas produced causes the bubble in the capillary tube to move. The distance moved by the bubble is used to calculate the volume of oxygen produced.
How can farmers use their knowledge of limiting factors to increase their profits?
They can control temperature, light intensity and CO2 concentration to achieve the fastest possible rate of photosynthesis, leading to a greater yield.
State the law which describes the relationship between the distance of a light source from a plant and light intensity
Inverse square law - light intensity∝1 / distance^2
State 5 uses of glucose produced during photosynthesis
● Respiration
● Starch for storage
● Cellulose for strength
● Amino acid and protein synthesis (combined with nitrates)
● Lipids for energy storage in seeds
What is aerobic respiration?
An exothermic reaction in which glucose reacts with oxygen to release energy which can be used by cells.
What are the equations for aerobic respiration?
Glucose + oxygen -> carbon dioxide + water ( + energy)
C6H1206 + 6C02 -> 6CO2 + 6H20 ( + energy)
Where does aerobic respiration occur?
mitochondria
Why do organisms require the energy released by respiration?
● Synthesis of larger molecules
● Muscle contraction
● Maintenance of body temperature
● Active transport
What is anaerobic respiration?
An exothermic reaction in which glucose is broken down to release energy in the absence of oxygen.
What is the equation for anaerobic respiration?
glucose –> lactic acid (+ energy)
Why is anaerobic respiration less efficient than aerobic respiration?
Glucose is not completely broken down, so less energy is transferred.
Why can anaerobic respiration lead to muscle fatigue?
Lactic acid (product of anaerobic respiration) builds up in muscles, preventing efficient contraction.
What is an oxygen debt?
The amount of oxygen needed to convert lactic acid into back into glucose after anaerobic respiration.
What is fermentation?
A type of anaerobic respiration that occurs in yeast cells.
What is the equation for fermentation?
Glucose → ethanol + carbon dioxide ( + energy )
Why is the fermentation reaction important?
It is used in the production of bread and alcoholic drinks.
What are the differences between aerobic and anaerobic respiration?
● Aerobic requires oxygen; anaerobic does not.
● Aerobic produces CO2 and water; anaerobic produces lactic acid or ethanol + CO2.
● Aerobic transfers a greater amount of energy.
How do muscles store glucose?
as glycogen
What changes take place when muscular activity increases in the body?
● Heart rate increases and arteries dilate - increases flow of oxygenated blood to muscles.
● Breathing rate increases and breathing is deeper - increases the rate of gaseous exchange.
● Stored glycogen is converted back into glucose
How is lactic acid transported away from the muscles?
Blood flow through the muscles transports lactic acid to the liver, where it is oxidised back to glucose.
What is metabolism?
The sum of all the reactions that take place in a cell or an organism
How do cells use the energy transferred by respiration?
To continuously carry out enzyme-controlled processes which lead to the synthesis of new molecules.
Give examples of metabolic reactions
● Glucose into starch/glycogen/cellulose
● Glycerol and fatty acids into lipids
● Glucose and nitrate ions into amino acids
● Photosynthesis
● Respiration
● Breakdown of excess proteins into urea
What is the photosynthesis rate?
The rate at which plants take in carbon dioxide, water and the energy from sunlight to produce glucose and oxygen
What is light intensity?
A factor that typically increases the rate of photosynthesis
What is the LED light source?
Is used as it releases less heat compared with other light bulbs
What is pondweed?
A species of aquatic plant such as Cabomba or Elodea
What is the role enzymes in photosynthesis?
Photosynthesis is an enzyme-controlled reaction where the enzymes are needed to convert carbon dioxide into glucose
What is sunlight?
Is needed as an energy source for photosynthesis to occur
What is carbon dioxide?
Enters the plant through the stomata during gas exchange and is the source of carbon needed to make glucose
What is a plateau?
Where a graph levels off and no longer increases past a certain point
What is the inverse-square law?
Light intensity is inversely proportional to the square of the distance from a light source
What is the inversely proportional relationship?
As the distance of light from a plant increases, the light intensity decreases
What is glucose?
The main chemical product of photosynthesis that has many different uses in a plant, including respiration
What is oxygen?
A waste product of photosynthesis that leaves the plant through the stomata of the leaves or can be used for respiration
What is water?
A reactant needed for photosynthesis to take place, water is absorbed by the roots and is transported by the xylem to reach the leaves where photosynthesis occurs
What do you do to test leaves for starch?
Plant leaves can be tested for the presence of starch using iodine solution, after the leaf has been intensely heated and submerged in ethanol
What are fats and oil?
Lipids which can be made from the products of photosynthesis for storage
What does metabolism include?
The synthesis of new molecules, the breakdown of existing molecules and the process of respiration
What is the energy transferred by cellular respiration used for?
Is used by organisms for the continual enzyme-controlled processes of metabolism
What do enzyme and metabolism do?
Enzymes regulate most cellular reactions and are essential for the synthesis and breakdown of molecules
How do convert glucose to complex carbohydrates?
Glucose can be converted into starch, glycogen and cellulose
What is formation of lipid molecules?
One molecule of glycerol joins with three fatty acids
What is amino acids production?
Glucose and nitrate ions form amino acids which are used to make proteins
What is protein synthesis?
Amino acids join together in specific arrangements to form proteins
What is urea excretion?
Excess proteins are broken down to form urea for excretion
What does digestion need?
Requires energy from respiration to break down large insoluble molecules into smaller soluble molecules
What does carbohydrates provide?
Provide energy for chemical reactions and can break down into sugars
What is protein?
The building blocks of cells and tissues that can break down into amino acids
What is lipids?
An energy store of fats and oils that can break down into glycerol and fatty acids
What is cellular respiration?
Process that releases energy by breaking down glucose and other food molecules
What is an exothermic reaction?
A reaction that releases energy to its surroundings, usually in the form of heat
What is lactic acid?
A toxic waste product that is produced during anaerobic respiration in humans and can cause muscle fatigue
What is incomplete oxidation?
Occurs during anaerobic respiration causing a build up of lactic acid in the muscles
What is oxygen debt?
The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid
What do organisms need energy for?
Movement, keeping warm and chemical reactions to make larger molecules
