Gaseous Exchange Flashcards
What are 4 key features of exchange surfaces essential for rapid exchange?
- Large surface area to volume ratio
- Thin to allow short diffusion pathway
- Selectively permeable
- Maintain steep concentration gradient
What is Surface Area to Volume ratio?
The surface area of an organism divided by its volume, expressed as a ratio or decimal
What happens to the SA:Volume as the organism increases in size ?
The SA:Volume ratio decreases
What is the exoskeleton of an insect made from?
A hard ginormous material called Chitin
What is the purpose of Chitin exoskeleton?
It provides protection and a lipid layer to prevent water loss.
Impermeable to gas so not a good exchange surface
How do insects exchange gases?
They have a tracheal system (network or tube)
What is tracheae?
Microscopic air filled pipes that are held open by rings of chitin
What is the purpose of chitin in tracheae?
To prevent the collapse of the air filled tubes (strength)
What are tracheoles?
Smaller tubes that branch off the tracheae and extend deep into the abdomen, carrying oxygen directly to respiring cells and removing carbon dioxide
What is the diffusion distance like between the tracheoles and body cells?
Short diffusion pathway
What are spiracles?
Valve like openings that run the length of the abdomen (pores)
What is the purpose of spiracles?
Oxygen and carbon dioxide in and out via spiracles
Tracheae attach to the spiracles
How do gases move into the tracheal system?
- Concentration/diffusion gradient
- Contraction of muscles around the tracheal system
- Ends of tracheoles filled with water
How does the concentration/diffusion gradient enable gases to move in the tracheal system?
As cells respite they use 02 in the ends of tracheoles this caused oxygen to move down the concentration gradient and more atmospheric air enters the tracheal system
How does the contraction of muscles around the tracheal system enable gases to move in the tracheal system
As abdominal muscles contract and relax they squeeze the trachea/tracheoles speeding up gas movement in/out
How does the ends of tracheoles filled with water enable gases to move in the tracheal system
- During high/intense activity muscle cells respire anaerobically (as 02 levels are low) this produces lactic acid in muscle cells
- This lowers the water potential of cells and causes water to move from tracheoles into cells by osmosis
- This decreases volume in tracheoles so more air is drawn in
- Also speeds up diffusion of gases as gases diffuse faster in air than in water
What are adaptations of insects for efficient diffusion?
- Large number of tracheoles = large surface area
- Tracheoles are thin and short distance between spiracles and tracheoles leads to short diffusion pathway
- Use of O2 and CO2 production - steep diffusion gradient
What are an insect’s adaptations to prevent water loss?
Small surface area to volume ratio where water can evaporate
Chitin - waterproof exoskeleton
Spiracles - where gas enters and water evaporate - can open and close to reduce water loss (muscular sphincter)
What is the word equation for respiration?
Oxygen + Glucose —> Carbon dioxide + water + ATP
What is the purpose of guard cells in a plant?
They open and close the stomata to allow gases to diffuse in/out
How do guard cells open and close?
When they become turgid they bow outwards opening the stomata
When they are flaccid they shrink/shrivel closing the stomata
What are dictelydenous plant’s adaptations for gaseous exchange?
- Flat to provide a large surface area for the absorption of light/gases
- Stomata pores allow gas to diffuse in and out with a short diffusion pathway
- Mesophyll air space increase surface area for gas exchange and provide short diffusion pathway
- Eperdermis - transparent to allow light absorption
- Guard cells - open and close stomata to reduce water loss
What is a xerophyte?
Plants that are adapted to live in areas where water is limited
Name some adaptation which a xerophyte may have?
- Hairy leaves
- Thick Waxy Cuticle
- Rolling leaves
- Sunken Stomata
- Spines
Why do some xerophytes have a thick waxy cuticle ?
They are impermeable so less/no water can escape
Why do some xerophytes have rolled leaves/sunken stomata/hairy leaves?
It traps a region of still air which becomes saturated with water vapour leading to high water potential (this causes a low water potential gradient - by maintaining humidity to prevent water loss)
How do spines affect water loss?
Reduce the surface area for evaporation and transpiration
What are the similarities between gas exchange in plants and insects?
Obtain gases they need from air by diffusion down a concentration gradient
Movement of gases controlled by pore like structure (spiracles/stomata)
What are the differences between gas exchange in plants and insects?
Insect deliver air to cells via a system of tubes that are not present in a leaf
Insect muscle contractions can assist with the movement of air
How does water enter a fish?
Water is taken in through the mouth and forced out over the gills. They do this by increasing the volume of their mouth to reduce pressure and force out the water
Where do fish extract oxygen form the water?
Gills are located within the body behind the head in a gill flap. They are made of gill filaments with gill lamellae on their surface at right angles
Describe counter current flow?
Blood flows through gill lamellae in the opposite direction to water flowing over the surface
How is counter current flow beneficial for fish’s gas exchange?
Water always meets blood at a lower concentration which maintains the concentration gradient along the whole gill lamellae surface.
Describe what parallel flow is?
Blood flows through the gill lamellae in the same direction to water flowing over the gills
Why is parallel flow bad for fish’s gas exchange
Equilibrium is reached halfway across the gill lamellae so no net movement of oxygen into the blood
Why is it easier to extract oxygen from air?
Water is more dense than air so requires more energy to push water back out.
What are the two different types of fish?
Bony
Cartilaginous
How do cartilaginous fish do gas exchange?
They have no ventilation mechanism so have to keep swimming in order for oxygenated water to flow over their gills (parallel flow in gill lamellae)
RAM VENTILATION
How do bony fish do gas exchange?
Use a ventilation mechanism and counter current flow in gill lamellae
Name all the structures associated with human gas exchange?
- Epiglottis
- Larynx
- Trachea
- Lungs
- Bronchi
- Bronchioles
- Diaphragm
- Pleural/Chest membrane
- Pleural Cavity
- Internal/External intercostals
- Ribs
What type of process is inspiration?
Active
What type of process is expiration?
Passive
Describe the process of inspiration?
- Ribs move up and Out
- External intercostals contract, internal intercostals relax whilst the diaphragm contracts and flattens
- This increases the volume of the thoracic cavity which causes a decline in pressure below atmospheric air
- Leading to air being drawn into the lungs
Describe the structure of the trachea?
A flexible airway supported by rings of cartilage to prevent collapse
Describe the structure of alveoli?
Microscopic, elasticated and very thin air sacs, closely associated with pulmonary capillaries to allow for gaseous exchange
Describe the structure of the bronchi?
Teo tube division leading to the left and right lung.
Lined with ciliates epithelium and mucus secreting cells to remove dirt particles
Describe how the alveoli are adapted for efficient gas exchange?
Ventilated from the bronchioles - maintains the concentration gradient for gas exchange
Thin, flat, one cell thick alveolar walls - short diffusion distance
Alveolar epithelium is folded to increase surface area
Moist - helps gases dissolve (oxygen/carbon dioxide)
Associated with many capillaries - large SA;VOL ratio for gas exchange with blood
Capillaries are thin and maintain concentration gradient
Describe the process of expiration?
- Internal intercostals muscles contract
- Diaphragm relaxes and the elasticated alveoli recoil
- The volume of the thoracic cavity reduces
- This increases pressure in the lungs
- Air pressure in the lungs is greater than the atmospheric air so air is forced out deflating the lungs
Write the equation for pulmonary ventilation?
Pulmonary ventilation = Tidal volume x Breathing Rate
What do scatter graphs show?
Relationships between two variables
Just because there is a correlation…
Does NOT mean there is a CAUSAL link and other factors may affect the variables
What is COPD?
Chronic Obstructive Pulmonary Disease
What are two types of COPD?
Emphysema
Bronchitis
What are the risk factors for COPD?
Smoking - 90% of COPD patients are/were heavy smokers
Air pollution- particulates and gases
Genetics
Infections
Occupation - exposure to dust/harmful chemicals
What is a risk factor?
Something that increases the chance/probability of something
How do you identify a strong correlation?
Large sample of data points with few outliers and most plots on/close to line of best fit
What were government acts/schemes used to minimise risk factors for lung disease?
- Promotion of electric vehicles- reduce diesel cars
- NHS free support to give up - nicotine patches and vaping
- Health warnings on packaging with graphic images
- Minimum age to buy tabaco is 18
- Increased cigarette tax
- Can’t smoke in public places
