Bioenergetics Flashcards
What is photosynthesis?
The process by which plants make glucose from sunlight
Light energy is converted into chemical energy
Where does photosynthesis take place?
Within chloroplasts in leaf palisade cells
They contain chlorophyll a pigment which absorbs sunlight
State equation for photosynthesis
Carbon dioxide +water light->glucose +oxygen
6CO2 + 6H2O -> C6H12O6 +6O2
Is photosynthesis an endothermic or exothermic reaction?
Endothermic- as energy is transferred from the environment to chloroplasts by light
How can you show that a plant gives off oxygen during photosynthesis?
Using water plant (elodea), collect gas bubbles produced during photosynthesis
The gas will relight a glowing splint as it contains oxygen
Give examples of leaf adaptions which maximise the rate of photosynthesis
-broad leaves- maximise surface area
-thin leaves- short diffusion pathway
-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 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 temperature increases the rate of photosynthesis as kinetic energy increases until it reaches optimum temperature
The rate decreases past a certain required as enzymes become denatured
If temp decreases too much the particles lack kinetic energy so there are fewer collisions so lower rate of photosynthesis
How does light intensity affect the rate of photosynthesis?
Increasing the light intensity increases the rate of photosynthesis until another factor becomes limiting
Then plateaus as chloroplasts can only absorb a certain amount of light and other factors like co2 or temperature are limiting factors meaning reaction can’t continue
How does carbon dioxide concentration affect the rate of photosynthesis?
Increasing co2 concentration increases rate of photosynthesis until another factor becomes limiting as co2 is required to make glucose
Then plateaus as other factors like light or temperature are limiting it further, are limiting factors
How does the amount of chlorophyll affect the rate of photosynthesis?
Decreasing the amount of chlorophyll (due to lack of magnesium) decreases the rate of photosynthesis as chlorophyll is required to absorb light energy
What is a limiting factor?
When a process depends on 2 or more factors the rate of a process is limited by the factor which is in shortest supply
Is an environmental factor which can restrict the rate of photosynthesis( light intensity)
How can you calculate the rate of photosynthesis by measuring oxygen production?
-pondweed is placed in a test tube full of water. The top is raked with bung. A capillary tube also containing water leads into a test tube and is attached to a syringe
- a lamp is placed at a measured distance from test tube
- as it photosynthesises oxygen is produced forming a gas tube into the capillary tube
- the distance the bubble has moved is measured using a ruler to calculate the volume of oxygen produced
-many variables can be changed to observe their effect on photosynthesis: the temp (using water bath) , time pondweed is left, the light intensity (varied by distance of lamp from plant)
How can farmers use their own knowledge of limiting factors to increase their profits?
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 described the relationship between the distance of a light source from a plant and light intensity
The light intensity is inversely proportional to the square of the distance
Inverse square law - light intensity inversely proportional 1/distance squared
State uses of the glucose produced during photosynthesis
Respiration
Starch for storage
Cellulose for strength
Amino acid and protein synthesis
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)
C6H12O6 + 6O2 -> 6CO2+ 6H2O
Where does aerobic respiration take place?
In the 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 then aerobic respiration?
Glucose is not completely broken down, so less energy is transferred
Why can anaerobic respiration lead to muscle fatigue?
Lactic acid (production of anaerobic respiration) builds up in muscles, preventing efficient contraction
What is an oxygen debt?
The amount of oxygen needed to convert lactic acid 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
Why is the fermentation reaction important?
It’s used in the production of bread and alcoholic drinks
What are the differences between aerobic and anaerobic respiration?
Aerobic requires oxygen
Aerobic produced co2 and water, anaerobic produces lactic acid
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 to increase the flow of oxygenated blood to muscles
-breathing rate increases and breathing so 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’s 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 tit he synthesis of new molecules
Give examples of metabolic processes
-glucose into starch/glycogen/cellulose by being joined together
-glycerol and fatty acids into lipids
-glucose and nitrate ions into amino acids
-photosynthesis
-respiration
- breakdown of excess proteins into urea
What is the difference between breathing and respiration
Breathing- physical process which occurs at lungs, exchange of gases
Respiration- chemical reaction, occurs on every cell and relies on diffusion
What are tree roots important?
Phloem- transports sugars which cells need for photosynthesis
Anchorage- support the plant and keep it in ground
Xylem water- needed for photosynthesis to produce glucose which is needed for respiration. For new cell walls and for amino acids
