Topic 4 - Respiration and Gas Exchange

• Respiration definition


  Chemical reaction that takes place in all living beings. It is the process of transferring energy FROM glucose.
• Respiration


  - energy released from glucose either in presence of oxygen (aerobic respiration) or in absence (anaerobic respiration)
• Aerobic respiration word equation


  glucose + oxygen --> carbon dioxide + water
• Energy transferred in form of?

  ATP
• What does ATP provide for in cells?


  - Chemical reactions = to build large molecules from small molecules

  - Muscle contraction = movement

  - Maintain constant temp suitable for enzyme activity

  - Protein synthesis

  - Active transport
• Cellular respiration is exothermic or endothermic?

  Exothermic - heat energy released into atmosphere
• Where is ATP produced?

  In respiration in the mitochondria
• aerobic


  - oxygen needed

  - complete breakdown of glucose

  - products = carbon dioxide and water

  - a lot of energy is released
• anaerobic


  - oxygen NOT needed

  - incomplete breakdown of glucose

  - products in animals: lactic acid

  - products in yeasts: carbon dioxide + ethanol

  - little energy released
• Aerobic respiration chemical equation (backwards photosynthesis)

  C6H12O6 + 6O2 --> 6H2O + 6CO2
• Anaerobic respiration in PLANTS word equation

  glucose --> ethanol + carbon dioxide
• Anaerobic respiration in ANIMALS word equation

  glucose --> lactic acid
• Anaerobic respiration in ANIMALS chem equation

  C6H12O6 --> 2C3H6O3
• what is anaerobic respiration in yeast cells called?


  fermentation
• PRACTICAL: Investigating respiration CO2


  1. measure 10cm^3 of hydrocarbonate indicator into 3 boiling tubes

  2. add a layer of cotton wool

  3. place 10 germinating seeds in boiling tube A

  4. place 10 boiled seeds in tube B

  5. place 10 glass beads in tube C

  6. seal each rube with a rubber bung

  7. observe the colour change of the indicator after a few hours

  
  

  Results:

  - Tube A should turn yellow as the GERMENATING seeds are respiring and producing carbon dioxide

  
  

  - Tube B should remain orange as the DEAD seeds produce no carbon dioxide.

  
  

  - Tube C should remain orange as there is no living material in there
• Colour results for hydrogen-carbonate indicator (practical)


  High CO2 = yellow

  Atmospheric CO2 level = orange

  Low CO2 = purple
• PRACTICAL: Investigating respiration HEAT

  1. set up 2 thermal flasks - flask A with boiled/dead seeds and flask B with germinating seeds

  2. hold a thermometer in place with cotton wool

  3. record initial temperature of each flask

  4. after a few days, record the final temperature

  
  

  Results:

  - The thermometer in the flask with the germinating seeds (Flask B) should show an increase in temperature (respiring + producing heat energy in process = respiration is exothermic)

  - Flask A should remain at room temperature (not respiring)
• describe the structure of the thorax


  - RIBS --> bone structure that protects internal organs (on diagram it is white balls)

  - INTERCOSTAL MUSCLE --> muscles between the ribs that control movement for inhalation and exhalation

  - DIAPHRAGM --> SHEET of connective tissue and muscle at bottom of thorax that helps change volume of thorax to allow inhalation + exhalation

  - TRACHEA --> windpipe that connects mouth/nose to lungs

  - LARNYX --> voice box, air passes through here = sounds

  - BRONCHUS --> bronchi (pl) is a large tube branching off the trachea with one bronchus in each lung. The bronchi split to form smaller tubes called bronchioles that connect to the alveoli

  - ALVEOLI --> tiny air sacs where gas exchange takes place

  - PLEURAL CAVITY --> fluid filled space between pleural membranes which reduce friction, allowing lungs to move freely

  - PLEURAL MEMBRANES --> the 2 layers on diagram that forms lung shape
• Inhalation


  - Intercostal muscles + diaphragm contract

  - Volume in thorax increases

  - Pressure decreases

  - Diaphragm FLATTENS
• Exhalation


  - Intercostal muscles and diaphragm relax

  - Volume decreases

  - Pressure increases

  - Diaphragm moves up
• Experiment to see CO2 released from respiration


  - mouthpiece on top of boiling tube

  - boiling tube contains limewater

  - breathe in = limewater clear BUT breathe out = limewater turns cloudy = CO2 present
• Cilia cells


  Passage down to lungs are lined with cilia cells.

  - cells have little hairs on the end of them that beat and push mucus up the passages towards the nose and mouth

  - the mucus is created by goblet cells and they trap particles, pathogens and dust to prevent them from entering the lungs (may damage cells there)
• Expired air gas percentage

  Oxygen - 16%

  Nitrogen - 78%

  Carbon dioxide - 4%
• Inspired air gas percentage

  Oxygen - 21%

  Nitrogen - 78%

  Carbon dioxide - 0.04%
• Alveoli adaptations


  - Many microscopic alveoli = HUGE SA to volume ratio

  - Good blood supply = steep concentration gradient

  - Moist linings = gas can easily dissolve

  - Thin single-celled thick walls = short distance for diffusion

  - Permeable walls = gas can diffuse across easily

  - Ventilation meaning high lvls oxygen and low lvls carbon dioxide = steep concentration gradient
• Alveoli carries out gas exchange


  - blood passing next to alveoli returns to lungs from rest of body (contains lots of CO2 + very little oxygen)

  - oxygen diffuses out of alveolus (high concentration) + into blood stream

  - CO2 diffuses out of blood into alveolus to be breathed out

  - blood reaches body cells, oxygen is released form red blood cells and diffuse into them. CO2 diffuses out
• How does smoking affect the respiratory system?


  Emphysema (disease):

  - smoking damages the walls inside the alveoli, reducing the SA to volume ration = lower rate of diffusion

  - tar in cigarettes damage the cilia in lungs + trachea. They are unable to catch mucus (containing dust + pathogens) well leading to chest infections

  
  

  Smokers cough + Bronchitis:

  - tar irritates the bronchi + bronchioles encouraging mucus to be produced

  - damaged cilia cannot sweep this mucus out through mouth = can't be cleared very well

  
  

  Cancer:

  - tobacco smoke contains CARCINOGENS - chemicals that lead to cancer

  
  

  Coronary heart disease:

  - carbon monoxide in cigarette smoke binds to haemoglobin in blood = cannot carry as much oxygen. Body makes up for this by increasing heart rate = increase in blood pressure

  - high blood pressure damages artery walls = blood clots are more likely = coronary heart disease
• What is inside tobacco smoke that leads to cancer?

  Carcinogen (chemicals)
• Arteries


  blood vessels that bring oxygen-rich blood from your heart to all of your body's cells
• PRACTICAL: investigate breathing in humans - effect of exercise


  EFFECT OF EXERCISE

  - record breathing rate when stationary

  - carry out a specific exercise at the same intensity for a fixed period of time

  - measure breathing rate after exercise

  - compare results of before and after

  - more energy is required for respiration during exercise --> rate of breathing will increase to allow more oxygen to flow in the blood so movement can occur

  - if the demand for energy exceeds oxygen intake, then energy may be produced via anaerobic respiration, producing lactic acid as a waste product after exercise, breathing rate may continue to increase as extra oxygen is needed to break down the lactic acid (oxygen debt)