B4-Bioenergetics Flashcards
What is photosynthesis?
The biochemical reaction that fixes light energy into organic compounds. It is an endothermic reaction as energy is taken in.
What are the reactants and products in photosynthesis?
Reactants: Carbon Dioxide and Water
Products: Glucose and Oxygen
What is the relationship between light intensity and the rate of photosynthesis?
As light intensity increases, the rate of photosynthesis increases until different limiting factors come into play
What could the limiting factors be other than light intensity for rate of photosynthesis?
- carbon dioxide
- temperature
- amount of chlorophyll
Describe the method for the required practical which investigates the relationship of light intensity and the rate of photosynthesis:
1) Collect boiling tube of bicarbonate solution and elodea
2) Fix boiling tube into clamp stand, low down
3) Set up lamp 5cm from the tube and switch on
4) Wait 3 minutes
5) Count the number of bubbles being produced from the elodea in 3 one minute intervals
6) Repeat measurements with lamp at different distances
How could the validity of the light intensity and rate of photosynthesis required practical be improved?
- Reduce other light sources, so lamp is only one
- Add more bicarb to the tube for each test so there is an excess of carbon dioxide
- Use an LED bulb or heat sink so the heat emitted from the bulb doesn’t affect the results
- Measure volume of oxygen produced as bubbles could be different sizes
How is carbon dioxide a limiting factor in photosynthesis?
If there is no carbon dioxide available, there is a lack of the reactants carbon and oxygen to reactant with the hydrogen and oxygen from water so no more glucose will be produced. Therefore, photosynthesis doesn’t take place
How is temperature a limiting factor in photosynthesis?
If the temperature is low, the rate of photosynthesis is low since the enzymes controlling the reactions are below their optimum temperature and there is a low thermal energy transfer to kinetic energy stores of the reactants. If the temperature is too high, the enzymes denature.
How is light intensity a limiting factor in photosynthesis?
In the absence of light, there is not enough energy to allow for the activation energy to be reached to initiate the reaction between carbon dioxide and water
What are the main ways in which living organisms use energy from respiration?
- Movement (muscle contraction)
- Keeping warm (homeostasis)
- Synthesis
- Active transport
- Nerve impulses
What is metabolism?
The sum of all the chemical reactions that occur inside a cell or an organism
What is an anabolic reaction?
A reaction which joins (makes) stuff
What is a catabolic reaction?
A reaction which breaks stuff
What are the six main ways in which plants use glucose?
- Respiration: transferring energy from glucose
- Making cellulose: glucose is converted into cellulose
- Making amino acids: Glucose is combined with nitrate ions to make amino acids which are then made into proteins
- Stored as oils or fats: glucose turned into lipids for storing in seeds
- Stored as starch: glucose turned into starch, ready to use when photosynthesis isn’t happening because starch is insoluble(stores better as it doesn’t effect osmosis)
- Making fructose: attract animals to eat their fruit
Why can chlorophyll be a limiting factor in photosynthesis?
The amount of chlorophyll in a plant can be affected by disease or environmental stress. This can lead to chloroplast damage or lack of chlorophyll production in them. Therefore, not as much light can be absorbed for photosynthesis
Define respiration:
The process of transferring/releasing energy from glucose, which goes on in every cell. It is an exothermic reaction.
What is the relationship between light intensity and distance?
the light intensity decreases in proportion to the square of the distance. light intensity ∝ 1/distance^2
Describe some anabolic reactions:
- Glucose molecules are joined together to form starch, cellulose and glycogen
- A lipid molecule can be made from one molecule of glycerol and three fatty acids
- Glucose is combined with nitrate ions to make amino acids, which are then made into proteins
Describe some catabolic reactions:
- Glucose is broken down in respiration. (Respiration transfers energy to power all reactions in body which make molecules)
- Excess protein/ amino acids are broken down to produce urea which is excreted as urine
What is aerobic respiration?
Respiration which utilises oxygen- it is the most efficient way to transfer energy from glucose. It happens all the time in plants and animals (particularly in mitochondria)
What are the reactants and products in aerobic respiration?
Reactants: -Glucose -Oxygen Products: -Carbon dioxide -Water
What is anaerobic respiration?
The incomplete breakdown of glucose without utilising oxygen, making lactic acid.
Why does anaerobic respiration transfer less energy than aerobic respiration?
Because the glucose isn’t fully oxidised (doesn’t combine with oxygen)
What are the products and reactants for anaerobic respiration in muscle cells?
Reactant:
-Glucose
Product:
-lactic acid
What are the products of anaerobic respiration in yeast and plant cells?
Ethanol and carbon dioxide
What is anaerobic respiration in yeast cells called?
Fermentation
In what industrial processes is fermentation used for?
Brewing (alcohol) Bread making (rise)
What happens to the glucose in aerobic respiration?
It is totally combusted (all energy is released from it)
What happens to the glucose in anaerobic respiration?
Only a fraction of the energy is released from the glucose and lactic acid is produced instead (incomplete combustion)
Symbol equation for photosynthesis:
6CO2 + 6H2O → C6H12O6 + 6O2.
Symbol equation for aerobic respiration:
C6H12O6 + 6O2 → 6CO2 + 6H2O
Symbol equation for anaerobic respiration in animals:
C6H12O6 → 2C3H6O3
Symbol equation for anaerobic respiration in plants and fungi:
C6H12O6 → 2CO2 + 2C2H5OH
Give some key examples of how organisms use the energy transferred from respiration:
- To build up larger molecules from smaller ones
- Allow muscles to contract in animals
- Mammals and birds use energy to maintain body temperatures
Why is there increased respiration when you exercise?
Your muscles contract more frequently than normal so you need more energy so you respire more
What is needed when respiration increases in your body?
Cells need to get more oxygen into them
How do we get more oxygen to our cells?
Our breathing rate and breath volume increase to get more oxygen to the blood and our heart rate increases to get the oxygenated blood around the body faster. This removes carbon dioxide more quickly at the same time
What happens to our muscles when we do long periods of exercise?
It can cause muscle fatigue (muscles get tired and stop contracting efficiently)
What happens to our muscle cells during vigourous exercise (ie. sprinting)?
Our bodies can’t supply oxygen to our muscles quickly enough, so they start respiring anaerobicallly
What is caused as a result of anerobic respiration post exercise?
Oxygen debt
What is oxygen debt?
The amount of extra oxygen a body needs to react with the build up of lactic acid and remove it from the cells.
What are the products of when oxygen reacts with lactic acid after oxygen debt?
Carbon dioxide and Water
As well as getting lots more oxygen into our blood, how else can our body cope with high levels of lactic acid?
The blood which enters our muscles transports the lactic acid to the liver where the liver converts the lactic acid to glucose.
As a result of exercise, our ventilation rate increases. What is ventilation?
It is something which determines how much oxygen can be taken in and how much carbon dioxide can be exhaled
What is the formula for calculating ventilation rate?
Ventilation rate = volume of each breath(dm^3) x number of breaths per minute
As a result of exercise, our cardiac output increases. What is cardiac output?
Something which provides oxygen to muscles and removes carbon dioxide, lactic acid and heat
What is the formula for calculating cardiac output?
Cardiac output = heart rate (bpm) x volume of blood in each beat (dm^3)
How do greenhouses provide the ideal environment for plants to grow in them?
- Greenhouses trap the Sun’s heat and when it’s cold they use heaters and when it is too hot, they have ventilators/shades. This makes sure temperature is not a limiting factor
- Artifical light is supplied to the plants so light intensity is not a limiting factor
- Carbon dioxide levels are increased in the greenhouse by using e.g. a paraffin heater so co2 isn’t limiting
- Plants are protected from pests and diseases in greenhouses
What are the bodies responses to increased demand of energy (ie. during exercise)?
- increase in heart rate, ventilation rate, breathing rate, breath volume and cardiac output
- Glycogen stores in muscles are converted to glucose for respiration
- Flow of oxygenated blood to muscles increases
- Blood vessels dilate (open wider)
Why is energy not included in the respiration equations?
Because equations include substances and energy is not a substance
How does a fitter person have a quicker recovery rate?
Because they have a bigger heart and lungs so can get more oxygen to their muscles quicker
CO2 concentration, light levels and temperature are all at optimum values. What might be the limiting factor of rate of photosynthesis, and why?
The concentration of mineral ions in the soil is probably the limiting factor.
Chlorophyll absorbs light energy and the production of chlorophyll requires these mineral ions (especially Mg2+).
What are some of the consequences for plants growing in mineral-deficient soil?
low absorption of minerals
low production of chlorophyll
low rate of photosynthesis
Why is it important for plants to take in more carbon dioxide than they give out?
- Means plant is photosynthesising quicker than it is respiring
- More carbohydrate made than used
- Plant can grow/survive
