Topic 4: Bioenergetics Flashcards
Define photosynthesis
A process found in plants that uses light energy to change carbon dioxide and water into glucose and oxygen
Is photosynthesis an exothermic or endothermic reaction?
Endothermic - energy is transferred from the environment in the process
Where does photosynthesis take place?
Mainly in the chloroplasts containing chlorophyll of the plant’s leaves and a smaller amount on the stem (basically anywhere that’s green)
How does water reach the leaf for photosynthesis?
Through the roots (root hair cells) then up through the xylem via transpiration and to the leaf
What is the word equation for photosynthesis?
carbon dioxide + water ——-light——> glucose + oxygen
What is the symbol equation for photosynthesis?
6CO(2) + 6H(2)O ——-light——> C(6)H(12)O(6) + 6O(2)
What role does chlorophyll play in photosynthesis?
Chlorophyll absorbs light energy needed for photosynthesis
In what 5 ways is glucose used in a plant?
- Respiration
- Making cellulose
- Making amino acids
- Fatty acids (lipids)
- Starch
What role does glucose have in respiration in plants?
Plants use glucose as a reactant in respiration, which is where energy is released from the breakdown of glucose
What role does glucose have in making cellulose in plants?
Glucose is converted into cellulose for making strong cell walls especially in a rapidly growing plant to support and strengthen the cells
What role does glucose have in making amino acids in plants?
Glucose is combined with nitrate ions (absorbed from the soil) to make amino acids which are the building blocks for proteins
How is glucose stored in plants?
As lipids - plants convert some glucose into lipids (fats an oils) and store these in seeds eg sunflower seeds contain a lot of oil
As starch - plants can convert glucose into starch so it’s ready for use when photosynthesis is not happening as much such as in winter eg potato and parsnip plants store a lot of starch underground over winter
Where is starch stored in the plant?
In the roots, stems, seeds and leaves
Why is starch better for storage than glucose?
Starch is insoluble which makes it much better for storing starch than glucose: a cell with lots of glucose would draw in lots of water and swell up
What 4 things is the rate of photosynthesis affected by?
Light intensity
Concentration of CO(2)
Temperature
Amount of chlorophyll
What happens when one of the factors affecting photosynthesis becomes too high or too low?
It becomes a limiting factor
Why would an increase in light intensity only increase the rate of photosynthesis up to a certain point?
Another limiting factor will be affecting it
What happens to the rate of photosynthesis when light intensity increases?
As the light level is raised the rate of photosynthesis increases, but only up to a certain point, where it will plateau due to the presence of other limiting factors
What happens to the rate of photosynthesis when carbon dioxide concentration increases?
As the carbon dioxide level is raised the rate of photosynthesis increases, but only up to a certain point, where it will plateau due to the presence of other limiting factors
How does the presence of enzymes affect the rate of photosynthesis?
Enzymes increase the rate of photosynthesis in plant cells
What is an enzyme?
Enzymes are proteins which increase the speed of chemical reactions in living things.
What limiting factor affects the speed at which enzymes work?
Temperature
What happens to the rate of photosynthesis when the temp gets too low and why?
The rate will decrease as the enzymes needed for photosynthesis work slower at low temperatures
What happens to the rate of photosynthesis when the temp gets too high and why?
It will decrease (around 45 degrees) as the enzymes needed for photosynthesis and other reactions will be denatured (destroyed)
Describe a graph showing how the rate of photosynthesis is affected by light intensity and temperature
At the start, both of the lines show that as the light intensity increases, the rate of photosynthesis increases steadily. But the lines level off when light is no longer a limiting factor. The line at 25 degrees c levels off higher than the line at 15 degrees c, implying that temperature must have been a limiting factor at 15 degrees c
(see pg 174)
What practical would be used to investigate the rate of photosynthesis?
Using an aquatic plant moved further and closer from a light source where the rate at which the pondweed produces oxygen corresponds to the rate of photosynthesis
Describe the pondweed experiment
White light is placed a specific distance from the pondweed
Leave the pw for a couple of mins to adjust to the light intensity
The pondweed is left to photosynthesise for a set amount of time
As it reacts, the gas produced will be collected in a capillary tube
A syringe is used to draw the gas bubble(s) from the tube and this is measured against a ruler, representing the volume of O(2) produced
Take repeats
Move the light source at different distances from the pondweed
What is the independent variable of the pondweed experiment?
The light intensity
What is the dependent variable of the pondweed experiment?
The amount of oxygen produced (amount or length of bubble)
How would you calculate the rate of photosynthesis using your results from the pondweed experiment?
Divide the total length of the bubble (or the no of bubbles produced) against (per) of the set amount of time
How are distance and light intensity in the pondweed experiment related?
As the distance increases, the light intensity decreases in proportion to it: they are inversely proportional
What is the equation for the inverse square law?
light intensity (fishy symbol) 1/distance squared
If you halved the distance in the pondweed experiment, how would this affect the light intensity?
It would be four times greater
Light intensity =
1/d squaredc
How are the rates of photosynthesis managed by commercial growers?
Using a greenhouses to control the limiting factors
How do greenhouses help to manage temperature?
Help to trap the suns heat, and make sure that the temp does not become limiting through the use of ac, shades, and ventilation in the summer and a heater in the winter
How do greenhouses help to manage light?
Farmers often supply artificial light after the sun goes down
Light is needed for photosynthesis, so the glass helps to supply as much light as possible
Shades can be used to shield the plants from extra light
How do greenhouses help to manage carbon dioxide concentration?
Paraffin heaters can be used to both heat the greenhouse and release co2 a day by product
co2 can be transported to the plants through tubes moving throughout the greenhouse
How do greenhouses help to manage the general health of plants?
Keeping plants enclosed in a greenhouse makes it easier to keep them free from plants and diseases
Fertilisers can also be added to the soil to provide all the minerals needed for healthy growth
How are greenhouse costs controlled?
Using enough to provide the plants with the perfect conditions for photosynthesis but not more than needed as this would be wasting money
What is respiration?
The process of transferring energy from glucose, which goes on in every cell
What process does respiration provide energy for?
All loving processes
Is respiration exothermic or endothermic?
Respiration is exothermic - transfers energy to the environment
Where do most reactions of aerobic respiration take place?
In the mitochondria
What is aerobic respiration?
Respiration using oxygen which is the most efficient way to transfer energy from glucose
What is the word equation for aerobic respiration?
glucose + oxygen—-> carbon dioxide + water
What is the symbol equation for aerobic respiration?
C(6) H(12) O(6) + 6O(2) —-> 6CO(2) + 6H(2)O
In what ways is the energy from respiration used in mammals?
- Building up larger molecules from smaller ones (proteins from amino acids)
- To allow muscle contractions
- To keep steady body temps
When does anaerobic respiration take place?
When you do vigorous exercise and your body can’t supply enough oxygen to your muscles, they start to do anaerobic as well as aerobic
Define anaerobic respiration
Respiration that takes place in the absence of oxygen; it is the incomplete breakdown of glucose making lactic acid
What is the word equation for anaerobic respiration in muscle cells?
glucose —-> lactic acid
What is the difference in energy output of aerobic and anaerobic respiration?
Anaerobic respiration does not transfer nearly as much energy as aerobic
What does anaerobic respiration not transfer as much energy as aerobic respiration?
Glucose is not fully oxidised in anaerobic respiration bcs it does not combine with oxygen.
What is the consequence of carrying out anaerobic respiration m?
Oxygen debt
What is an oxygen debt?
The amount of extra oxygen needed by the body after extensive exercise to react with the buildup of lactic acid and remove it from the cells to form harmless co2 and water
Why do the pulse and breathing rate stay high for a while after a period of extensive excersise?
There will be high levels of lactic acid and carbon dioxide
To deliver more oxygen to the cells and take away the co2 and lactic acid
Other than reacting with the buildup, how are the high levels of lactic acid dealt with?
The blood that’s enters your muscles transports the lactic acid to the liver, where it is converted back to glucose
What is the word equation for anaerobic respiration in plants and yeast?
glucose —-> ethanol + carbon dioxide
What is another way to say anaerobic respiration in plants and yeast?
Fermentation
How is fermentation important in industry?
Fermentation by yeast is used to make bread and alcoholic drinks
In bread making, the co2 is needed for the bread to rise
In wine and beer making, it’s the fermentation process that produces alcohol
What are the main differences between anaerobic and aerobic respiration?
Aerobic respiration requires oxygen, whereas anaerobic does not
The products
Amount of energy transfer
Why does physical activity increase your breathing rate?
Some of the muscles contract more frequently—> increased energy needed —> increased respiration——> increased oxygen ——-> blood flows faster ——> breathing rate increases to meet the demand for extra oxygen
Why does physical activity increase your heart rate?
Some of the muscles contract more frequently—> increased energy needed —> increased respiration——> increased oxygen & glucose needed and more co2 needs to be taken away ——-> faster blood flow thus heart needs to pump faster
What is muscle fatigue?
When the muscles get tired and stop contracting efficiently
What is the recovery period?
After anaerobic respiration stops, the heart rate and breathing rate stay high for a while so that the oxygen debt can be paid back
Card on investigating the effect of excersise
When larger molecules are made from smaller ones, is this endothermic or exothermic?
Endothermic- energy is taken in from the environment
When larger molecules are broken down into smaller ones, is this endothermic or exothermic?
Exothermic- energy is transferred to the environment
What is metabolism?
The combination of smaller reactions controlled by enzymes to form bigger reactions: the total of all reactions that happen in a cell or body
How do you get from glucose to cellulose?
Glucose molecules joined together in a reaction to form starch
Starch forms glycogen
Glycogen makes up cellulose
What are lipid molecules made up of?
One molecule of glycerol and 3 fatty acids
How are proteins made?
Glucose is combined with nitrate ions to make amino acids m, which form proteins
How is excess protein dealt with?
It is broken down to produce urea which is then excreted through the urine
Is metabolism endothermic or exothermic?
Endothermic
