Biology- gas exchange

• What is the thorax?


  - the space enclosed by the ribs

  - the lungs are enclosed in the thorax by the rib cage and diaphragm

  - the inside of the thorax and lungs are separated by the pleural membranes which form an airtight seal around the lungs

  - the ribs are joined by two sets of intercostal muscles
• What is the pleural cavity?


  - the space between the pleural membranes, filled with pleural fluid for lubrication so that the surfaces of the lungs don't stick to the inside of the thorax upon inhalation and exhalation
• What is the trachea?


  - the windpipe connecting the nose/mouth to the bronchi, one leading into each lung

  - the trachea has C-shaped rings of cartilage (keep the trachea open, food in the oesophagus doesn't catch on rings)
• What are the bronchi, bronchioles and alveoli?


  - each bronchus divides into smaller tubes, bronchioles, which lead into the alveoli, microscopic air sacs in which gas exchange takes place
• What is the bronchial tree?


  - the network of air passages in the lungs made up of the trachea, bronchi and bronchioles
• What is the epithelium?


  the tissue lining the inner surface of an organ
• What are the two epithelial tissues in the lungs?


  - simple squamous epithelium of alveoli is thin and flat for short distance and rapid diffusion

  - simple columnar epithelium of trachea/bronchi is composed of goblet cells (produce mucus to trap dust and pathogens keeping air ways/alveoli clear) and ciliated cells (cilia move the mucus up and out of the trachea)
• What is gas exchange?


  - the movement of oxygen into the blood from the alveoli and of carbon dioxide into the alveoli from the blood

  - oxygen diffuses into red blood cells to be carried to cells for aerobic respiration

  - carbon dioxide (acidic,toxic to cells) is a product of aerobic respiration and must be removed
• What is ventilation?


  - the movement of air into and out of the lungs for gas exchange

  - requires a difference in air pressure for air particles to move and equalise the pressure (Pa)

  - depends upon the thorax being an airtight cavity to change the volume of the thorax, changing the pressure inside for the movement of air
• How is pressure caused?


  - when a force is applied over an area
• What is the relationship between pressure and volume?


  - inverse relationship

  - pressure plotted against volume is a semi-u shape
• actions of structures during inhalation/exhalation


  external im : contract/relax

  internal im : relax/contract

  ribs : up,out/down,in

  diaphragm : muscles contract,flattens/muscles relax, dome shaped

  volume of thorax : increases/decreases

  pressure in thorax : decreases/increases

  volume of air in lungs : increases/decreases
• the movement of oxygen and carbon dioxide into the alveolus


  - oxygen diffuses across the layer of moisture, squamous cell wall of the alveolus, the two layers of cells that make the capillary wall and into the red blood cells inside the plasma (higher concentration in alveoli than blood)

  - carbon dioxide diffuses into the alveolus from the plasma (higher concentration in blood than alveoli)
• What are the adaptations of the alveoli?


  - 700 mil in lungs (large surface area)

  - wall is single cell thick/capillary and alveoli walls are close/thin and flat squamous cells (short distance)

  - breathing/movement of blood in capillaries (maintain concentration gradients)

  - lining of alveolus is moist (allows gases to dissolve) and permeable (allows gases to move into/out of blood)
• The composition of inspired vs expired air


  21% - 16% oxygen - diffuses into red blood cells from alveoli to be used by cells for respiration

  0.04% - 4% carbon dioxide - product of aerobic respiration that is toxic to cells so diffuses into alveoli from blood plasma

  78% nitrogen - no change, insoluble and doesn't dissolve

  water vapour - more in exhaled air as the lungs are moist, layer evaporates
• List the consequences of smoking in relation to the lungs

  - bronchitis

  - emphysema

  - lung cancer

  - coronary heart disease
• List the harmful chemicals found in cigarette smoke

  - carbon monoxide (binds to haemoglobin - carboxyhaemoglobin)

  - nicotine

  - carcinogens (cancerous)
• Bronchitis


  - cilia destroyed by chemicals in cigarette smoke

  - the reduction in cilia means that mucus is not moved away from the lungs leading to bacterial infections

  - the smoke irritates the lining of airways, causing the secretion of more mucus from the goblet cells, blocking the airways leading to 'smokers cough' (attempt to remove mucus from lungs)

  - the accumulation of mucus and the bacteria stuck to it causes inflammation of the bronchi

  - the inflammation and mucus reduces the laymen size of the bronchi so less air can reach the alveoli

  - condition is called bronchitis
• emphysema


  - smoke leads to the breaking down the walls of the alveoli and the fusion of the alveoli, decreasing surface area and the rate of gas exchange

  - the blood has a low oxygen concentration (inability to exercise)

  - condition called emphysema
• lung cancer


  - cigarette smoke contains over 7000 chemicals, some of which that collect in the tar that collects in smoker's lungs are carcinogens (cancerous)

  - cancer occurs when the DNA of cells mutates and the cells start to divide uncontrollably by mitosis forming a tumour due to the chemicals
• coronary heart disease


  - chemicals inhaled cause damage to the heart and blood vessels resulting in plaque build up in the arteries

  - restricts blood flow leading to resided blood pressure and increased clot risk, forcing heart to work harder

  - heart attacks
• What is aerobic respiration?


  - Glucose + oxygen » water + carbon dioxide

  - C6H12O6 + 6O2 » 6CO2 * 6H2O

  releases more energy than anaerobic respiration

  - test for carbon dioxide (limewater from clear to cloudy)
• What is anaerobic respiration?


  - Glucose » lactic acid

  - releases less energy than aerobic respiration
• Explain the effect of exercise on breathing in humans


  - breath rate and volume of each breath increases

  - muscles need energy to contract so the cells respire more than they do at rest

  - increased oxygen supply needed for aerobic respiration

  - more carbon dioxide produced that must be removed

  - insufficient oxygen supply causes anaerobic respiration

  - lactic acid (lactate) is produced from glucose (causing muscle fatigue and tiredness)

  - muscles contract but less efficiently

  - after exercise breath rate remains high

  - lactate in the muscles and blood must be broken down into water and carbon dioxide by oxygen

  - the quantity of oxygen needed is the oxygen debt
• How do doctors investigate breathing?

  - spirometry/spirometer tests

  - investigate lung function, diagnose lung disease, investigates effects of exercise

  - spirometer used to measure the volume of air breathed in and out

  - spirometer traces can be used to find out tidal volume, breathing rate, vital capacity and total lung capacity
• What is breathing

  rate?

  the number of breaths taken per minute (inspiration + expiration = one breath)
• What is vital capacity?


  the maximum volume of air breathed out after breathing in as much air as possible
• what is tidal volume?


  the volume of air breathed in with each normal breath (average - 500ml)
• What is ventilation rate?


  - the volume of air breathed into and out of the lungs in one minute

  - tidal volume x breathing rate
• What is total lung capacity?


  the total amount of air the lungs can hold after the biggest possible breath in (average - 6000ml)
• What is the function of a leaf?


  - an organ (group of tissues working together to perform a function)

  - photosynthesis for which a leaf must absorb light and exchange gases
• What is the cuticle?


  - thin layer of waxy material

  - reduce water loss by evaporation

  - barrier to microorganisms that cause diseases
• What is the upper epidermis?


  - tissue made from a single layer of transparent cells

  - no chloroplasts

  - allows light to the palisade mesophyll

  - produces the cuticle
• What is the palisade mesophyll?


  - tissue made from elongated cells containing hundreds of chloroplasts

  - chloroplasts contain chlorophyll to absorb the light energy needed for photosynthesis
• What is the spongy mesophyll?


  - tissue made from moist loosely packed cells with air spaces

  - main gas exchange surface

  - moisture allows gases to dissolve and enter cells

  - air space allows gases to diffuse to all of the cells in the layer
• What is the lower epidermis?


  - tissue at the bottom of the leaf containing many pores (stomata) (single pore = stoma)

  - pores allow carbon dioxide to diffuse into leaf for photosynthesis and oxygen and water vapour to diffuse out
• What are the guard cells?


  - specialised cells located in the lower epidermis forming the stomata

  - open and close the stomata
• What is xylem?


  - tissue of dead cells arranged end-to-end

  - strengthened with lignin (waterproof)

  - carries water and mineral ions to leaf
• What is phloem?


  - tissue of living cells joined end to end. Openings between cells to allow the movement of substances

  - carries sugars and amino acids to and from leaves to other parts of plant
• How is a lead adapted for absorption of light?

  thin - as much light as possible reaches chloroplasts (close to surface) for more photosynthesis

  large surface area - maximises area available to absorb light for more photosynthesis