GCSE Edexcel Biology Plant structure and their functions Complete Revision Summary

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GCSE Exdecel Biology Plant structure and their functions Complete Revision Summary

Plant structure and their functions

Plant structure and their functions

  • Photosynthesis
  • Factors affecting photosynthesis
  • How plants use glucose
  • Greenhouses
  • Respiration
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PHOTOSYNTHESIS

It is the process by which green plants prepare their own food by using water, carbon dioxide in presence of sunlight to form glucose and oxygen.
  • Only leaves can photosynthesize as they have chloroplast which contains chlorophyll.
  • Chlorophyll is the green pigment that traps light for the leaves and helps them to photosynthesis.
  • Photosynthesis is ENDOTHERMIC
  • Endothermic as it takes in heat from the sunlight.
  • The energy released in making glucose and oxygen is less than the energy required to break the bonds of carbon dioxide and water.

LEAF ADAPTATIONS FOR PHOTOSYNTHESIS

Mesophyll – Photosynthetic cells lies parallel to the surface to absorb maximum light and are closed to the stomata for quick diffusion of gases. Chloroplast – They have chloroplast which contains chlorophyll and traps light for photosynthesis Guard cell – They have stomata which are the pores for gas exchange

FACTORS AFFECTING PHOTOSYNTHESIS

  • As the light intensity increases the rate of photosynthesis increases and then it levels off.
  • Initially the rate increases an€ then it has no effect as at that point other factors become limiting.
    • As the light intensity increases the rate of photosynthesis increases and then it levels off.
    • Initially the rate increases and then it has no effect as at that point other factors become limiting
    • As the temperature increases the rate increases as the particles gain kinetic energy and moves faster causing greater collision and increase reaction rate.
    • Beyond optimum the rate decreases as at the higher temperature the enzymes get denatured. The enzyme changes shape and is not functions if the shape changes
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    Plant structure and their functi

    LAW OF LIMITING FACTORS

    • The factor that limits the rate OF photosynthesis
    • Limiting factor is that factor that is present in a least amount than required and affect the rate of photosynthesis.
    As the pH increases the rate increases upto optimum. Beyond optimum the rate decreases as enzymes get denatured.

    Measuring Photosynthesis

    FATE OF GLUCOSE

    • Glucose is soluble in water and if present longer will disturb osmotic balance of the cell Starch is complex molecule which is insoluble and can store large amount of glucose.
    • Also starch being insoluble does not disturb the osmotic balance of the cell.
    GLUCOSE
    • Principle source of energy.
    • It broken down during respiration and produces energy for the plant to grow and reproduce.
    STARCH
    • Excess glucose is stored in the plant as starch and is used by the plant when needed.
    CELLULOSE
    • Excess glucose can be converted into structural carbohydrate called Cellulose
    • Cellulose is the component of the cell wall which provide shape and support to the plant.
    PROTEINS
    • Glucose is combined with nitrates and other mineral ions from the soil to form protein.
    • Proteins are responsible for growth and also to make enzymes for metabolic reactions.
    LIPIDS
    • Glucose can be converted to fats and oil to serve as energy source.
    • Fats and oil can form the component of the cell membrane
    • They are also stored in seeds as an energy store for germination.
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    TEST FOR STARCH

    • Add Iodine Solution
    • If the solution turns blue black it indicates the presence of starch.

    GREENHOUSE

    • It controls all the limiting factors to provide maximum yield of photosynthesize
    • Temperature, light, carbon dioxide and other factors affecting photosynthesis are controlled and monitored.
    • It works on the principle of greenhouse effect in which light is allowed to enter but is not allowed to escape thereby increasing light and temperature inside the greenhouse.
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    RESPIRATION

    It is the process of breaking down food to release energy. AEROBIC RESPIRATION
    • Takes place in the presence of Oxygen
    • Releases more energy and the food is completely broken down.
    • Takes place in the mitochondria
    • It is opposite of photosynthesis
    ANAEROBIC RESPIRATION
    • Takes place in absence of oxygen.
    • Releases less energy and food is not completely broken down.
    • Takes place in the Cytoplasm
    • Glucose + Oxygen Carbon Dioxide + Water
    • C6H12O6 +602 6CO2 + H2O
    PLANTS
    • known as fermentation
    • forms ethanol and carbon-dioxide
    • Glucose Ethanol + Carbon Dioxide
    ANIMALS
    • takes place in muscles
    • Glucose Lactic Acid
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    BREATHING AND RESPIRATION

    BREATHING RESPIRATION
    It is a physical process. It is chemical process.
    Does not involve enzyme Involve Enzymes
    It is breathing in oxygen and breathing out carbon dioxide It is breaking of food in presence of oxygen for energy
    No energy is released Energy is released
    Takes place outside the cells Takes place inside the cells
    EXOTHERMIC As it releases heat. The energy released in making carbon dioxide and water is more than the energy taken in to break glucose and oxygen Cristae are the folding of the inner membrane of the mitochondria to increase the surface area for the attachment of the enzymes

    WHY WE NEED ENERGY

    MOVEMENT
    • Energy is required by the muscles to contract.
    • Respiration provides energy for muscle contraction.
    • Muscle cells have loads of mitochondria and glycogen for efficient respiration.
    TRANSPORT
    • Transport of substance in an out of the cell against the concentration gradient via active transport required energy.
    THERMOREGULATION
    • Respiration produces heat which helps to maintain the body temperature.
    CATABOLISM
    • Breaking of large substances to smaller ones like digestion requires energy.
    ANABOLISM
    • Building of bigger molecules from smaller ones like making proteins fats and lipids from minerals ions require energy

    RESPONSE TO EXERCISE

    Demand for oxygen and glucose increases as more energy is needed BREATHING RATE
    • The breathing rate increases so that more oxygen is inhaled to meet the demands of oxygen by the muscles.
    • Increased breathing rates also increases the rate of removal of carbon dioxide.
    HEART RATE
    • Increase heart rate pumps more blood to the muscles.
    • Increase blood supply increases the supply of both glucose and oxygen via blood to the muscles cells.
    GLYCOGENOLYSIS
    • Glycogen       Glucose
    • Stored carbohydrates, glycogen is converted to glucose in the muscles during exercise to meet the demand for increased glucose.

    WHY BREATHlNG RATE Б НОН AFTER STOPPlNG ТНЕ EXERClSE

    Extra Oxygen needed by the body after exercise to recover. OXYGEN DЕВТ*
    • During Exercise the body switches to anaerobic respiration. So glucose is broken down into lactic Acid
    • Glucose        Lactic Acid
    • The lactic acid needs to be broken down into carbon dioxide. The breathing rate is still high to get maximum oxygen to break lactic acid.
    • Lactic acid + O2                       CO2 + H2O
    METABOLISM It is the sum of all the reactions of the body CATABOLISM Breakdown reaction in which bigger molecule is broken down into smaller ones.
    1. a) Breakdown of glycogen
    2. b) Breakdown of proteins
    3. c) Breakdown of lipids
    4. d) Respiration
    ANABOLISM It is the synthesis reaction in which bigger molecule js formed from the smaller ones.
    1. a) Synthesis of cellulose from glucose
    2. b) Synthesis of starch and glycogen from glucose
    3. c) Synthesis of fats and lipids
    4. d) Synthesis of proteins
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    LIVER

    DETOXIFICATION
    • The alcohol or any poisonous substance taken in the body is detoxified in the liver as liver contains enzymes for detoxification
    BREAKDOWN OF BLOOD CELLS
    • Old and work out blood cells are broken down in liver.
    BREAKDOWN OF HARMFUL SUBSTANCES FOR EXCRETION
    • Excess proteins is broken down into urea in the liver which is excreted by kidney as Urine
    BREAK DOWN OF LACTIC ACID
    • Lactic acid produced during anaerobic respiration in the muscles is transported into the liver via blood and liver converts it into carbon dioxide and water by taking in more oxygen which is inhaled as oxygen debt.

    PHOTOSYNTHESIS VERSUS RESPIRATION

    PHOTOSYNTHESIS RESPIRATION
    Only in plant cells Occurs in all living cells
    It is endothermic reaction It is exothermic reaction.
    Oxygen is produced Oxygen is used up
    Takes place in chloroplast Takes place in Mitochondria
    Anabolic reaction, glucose is made Catabolic reaction, glucose is broken down.
    Light dependent Light independent
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    Key Terms

    Photosynthesis – It is the process by which green plants prepare their own food carbon dioxide and water are combined to form glucose and oxygen in presence of sunlight Respiration – breakdown of food to release energy Limiting Factors — Factor that limits the rate of photosynthesis Endothermic Reaction— Reaction that takes in heat Exothermic Reaction — Reaction that releases heat Glucose — product of photosynthesis and fuel for respiration Starch — Storage carbohydrate in plants Glycogen — Storage carbohydrate in animals Aerobic Respiration – Breaking down of food in presence of oxygen Anaerboic Respiration – breaking down of food in absence of oxygen Fermentation – Anaerobic respiration in plants that produces ethanol and carbon dioxide Greenhouse – A glass or a plastic house to control the limiting factors and increase the rate of photosynthesis. Metabolism – Sum Of all the catabolic and anabolic reactions of the body. Liver – An organ involved in metabolism. Lactic Acid — The product of anaerobic respiration in animals Oxygen Debt —The extra oxygen needed exercise to break down lactic acid and recover to pre exercise state. Banner 9

    Disclaimer:

    I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it. References: BBC Bitesize Wikipedia Wikimedia Commons Image Source: Wikipedia Wikimedia Commons Flickr Pixabay

    Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.

    Photosynthesis

    Respiration