Pack 7 - Exchange Flashcards
List 4 factors affecting diffusion
Surface area
Diffusion distance
Concentration gradient
Temperature
How do you calculate the surface area of a cube?
6side²
How do you calculate the volume of a cube?
side³
As an object gets larger which is happening to its surface area to volume ratio?
Decreases
What structures are present in the small intestine that help absorption?
Villi
Why do elephants need large ears?
To have a larger surface area:volume ratio for increased heat loss
Do animals with a larger SA:Vol require a higher or lower rate of metabolism?
Higher: higher SA:Vol leads to more heat loss
More respiration is therefore required to maintain the animal’s temperature
Define respiration
The release of energy (ATP synthesis) from food
eg. glucose/fats and proteins if desperate
What is respiration with O2 called?
Aerobic respiration
What is respiration without O2 called?
Anaerobic
What is the word equation for aerobic respiration?
Glucose + oxygen -> CO2 + H20 + Energy (ATP and heat)
What is the word equation for anaerobic respiration?
Glucose -> lactate + energy (ATP and heat)
Which type of respiration produces more ATP?
Aerobic
Aerobic Anaerobic
38 ATP : 2 ATP
Do all organisms need to respire?
Yes
List 6 features of an effective gas exchange surface
And why (think Fick’s law)
- Moist - To dissolve gases
- Large SA:Vol - SA
- Thin - DD
- Permeable to gases - To allow gas exchange
- Ventilation - CG
- Movement of internal medium - CG
What will happen to the rate of diffusion if diffusion distance is increased?
It will fall
What will happen to the rate of diffusion if SA:Vol is increased?
It will increase
What will happen to the rate of diffusion if the concentration gradient is decreased?
It will fall
Give an example of a single-celled protoctista?
Amoeba
How do amoeba get their O2 in and CO2 out?
Simple diffusion
Why do amoeba not need a specialised gas exchange system?
They are single-celled and therefore have a small diffusion distance for gases to travel
Why do bigger animals develop specialised respiratory surfaces/transport systems?
Most cells are far from the surface and so receive inadequate oxygen
Many larger animals have an increased metabolic rate, increasing oxygen demand
Give an example of a respiratory pigment
Haemoglobin
Give an example of a ventilation movement
Breathing
Why is spongy mesophyll made up of irregular cells?
Increased surface area due to more exposed CSM
Therefore a faster rate of diffusion
Do plants photosynthesise or respire at a higher rate at night?
Respire
Lack of sunlight means ineffective/no photosynthesis
Do plants photosynthesise or respire at a higher rate at in the day?
Photosynthesise
What is the function of stomata?
Open in light/close in dark
When open gas exchange is able to occur through them
-For metabolic needs eg. photosynthesis, respiration
Close (shrunken guard cells) if the plant looses too much water
-Reducing water loss through transpiration through open stomata
If a leaf is losing too much water, what will it do and how will this affect gas exchange in the leaf?
Close the stomata
Reduce gas exchange
-lower volume of gases diffusing in and out of the leaf
What is transpiration?
Evaporation of water from a plant leaf
Give 4 factors that will increase transpiration rate
Hot
Windy
Dry
Sunny
Define hydrophyte
Live in environment with LOTS of water availability
Define mesophyte
Live in environment with MODERATE water availability
Define xerophyte
Live in environment with LOW water availability
How does water potential gradient affect water loss from stomata?
More water is lost when there is a greater water water potential gradient between the inside and outside of the stomata
List 5 ways xerophytic plants are adapted to reduce water loss
And link to Fick’s law
Thick cuticle - DD
Rolled up leaves - CG (traps moist air on inside)
Hairy leaves - CG (traps moist air)
Stomata on pits/grooves - CG
Reduced SA:Vol of the leaves - SA (traps moist air)
Trapping moist air lowers the ψ gradient, lowering rate of diffusion, reducing water loss from the plant
Why do insects have a waterproof cuticle?
Water evaporates from their surfaces as they live on land and can become easily dehydrated
They conserve water by having waterproof coverings
How do insects respire?
Spiracles (pores) on their thorax and abdomen lead to
Tracheae (strengthened rings of chitin) dividing into
Tracheoles which bring atmospheric air directly into respiring cells
The spiracles can be opened and closed by valves which allow the insects to control water loss
What feature of respiratory surfaces is missing in an insect?
Permeable surface (exoskeleton)
How does oxygen enter the tracheal system?
Moving down the concentration gradient
Ventilation - moving muscles means air is taken in via the spiracles in the abdomen
Why are insects small?
To have short diffusion pathways for efficient respiration
What is the effect of exercise on the gas exchange of insects?
- Anaerobic respiration takes place
- Lactate increases
- Ψ decreases in muscle
- Water enters muscle via osmosis
- Air drawn into tracheoles
- Increases SA for gas exchange
- O2, CO2 diffuse faster through gases than liquids
- Increased respiration
What is the advantage of water entering insect’s muscle cells from the tracheoles?
O2, CO2 diffuse faster through gases than liquids, increasing respiration
How do insects limit water loss?
Hard, impermeable exoskeleton - reduces water loss from the whole body
Small SA: Vol - lower rate if diffusion of water
Valves around the spiracles - shut to reduce water loss from spiracles SA:Vol
Setae around the spiracles - hairs that trap most air reducing the concentration gradient therefore slower evaporation of water
What is Fick’s Law?
Diffusion rate ∝ Conc. Grad. × Surface Area
Diffusion Distance
Which areas of Fick’s Law do you want to keep large and small?
Big × Big
Small
How do fish move water over the gill?
Bony fish have four pairs of branchial arches supporting gill lamellae. These are covered by a muscular flap - the operculum.
- Fish open their mouth and lower the floor of the buccal cavity
- This increases the volume and decreases the pressure in the mouth, compared to outside, and so water enters down the pressure gradient
- The operculum is closed at this stage
- Then the fish closes its mouth and raises the floor of the mouth
- This has the effect of decreasing the volume and increases the pressure compared to outside and so forces water through the gills and out through the operculum
Why does water flow over the gills in only direction (and not pass in and out of the gills as air does in the lungs of a mammal)?
Water is more dense than air
What does afferent mean?
Conducted/conducting inwards or towards
What does efferent mean?
Conducted/conducting outwards or away from something
What is counter-flow system?
The blood and water flow in opposite directions.
This ensures a constant concentration gradient
Across the whole lamellae.
Present in bony fish for more efficient aerobic respiration
What shape is a counter-flow graph?
Distance across lamellae by % O2 in blood/water
blood \ water
What shape is a parallel flow graph?
Distance across lamellae by % O2 in blood/water
\____
/
What is the new spec name for a gill plate?
Gill lamellae
What are the two processes that make up respiration?
Cellular respiration
Gas exchange
Summarise cellular respiration
The process by which ATP is produced
What does cellular respiration involve?
- The breakdown of food (glucose and lipid) to release energy
- Some of this energy is used to make ATP from ADP and Pi
- The rest of the energy is released as heat
What gas exchange occurs in the mitochondria during aerobic respiration?
Mitochondria use O2 and release CO2
What is the word equation for aerobic respiration?
Glucose + Oxygen -> Water + Carbon Dioxide (+Energy; ATP + Heat)
What do increased organism size lead to?
Increased metabolic rate
∴ increased oxygen demand
This leads to:
- A specialised gas exchange system
- A transport system - usually a blood system
Give five characteristics of an effective respiratory surface
- Moist
- Permeable
- Thin
- High SA:Vol
- Maintained conc. grad.
What is the function of the larynx?
Allows air in and out and vocal cords to dilate
What is the role of the rings of cartilage in the trachea?
To keep the trachea open
What is the role of the bronchi and bronchioles?
To get air to the alveoli and back out again
Describe the structure of the alveoli
Like a bag of grapes
What is occurring in the alveoli?
Gaseous exchange
What type of epithelium are alveoli and capillary cells made up of?
Squamous
Describe squamous (cells)
Very thin, flattened
How is squamous epithelium ideally suited to allow gas exchange?
Thin - short diffusion distance
Large SA: Vol - more diffusion at one time
Why is it an advantage to slow the blood down in capillaries?
More time for diffusion (CO2 and O2)
How are the lungs well-adapted for effective gas exchange
- Capillaries and alveoli lie very close to one another (resulting barrier approx. 0.3μm) - Short diffusion distance
- Both lungs possess many alveoli (approx. 700 million) - large surface area
- Capillaries are very small ∴ RBCs must squeeze through, slowing the blood flow
What is the function of surfactant?
A detergent-like substance reducing the epithelial moisture layer’s surface tension, preventing the alveolar walls bring pulled together and collapsing
What is a macrophage?
A type of phagocyte, WBCs
Why is it important that macrophages a present in the alveoli?
They destroy pathogens in the air
Define residual volume
The amount of air that remains in the lungs after the most forcible expiration possible
Define dead space
The air that does not reach the alveoli (stays in eg. trachea, bronchi and bronchioles)
How is partial pressure written?
pO2 or pCO2
Units kPa
Define partial pressure (for in an exam)
It is equivalent to concentration
How does oxygen diffuse inside the alveoli?
Down the pO2 gradient
Describe the six stages in the diffusion of oxygen from the alveolus to the red blood cells
- Diffuses through alveolar space
- Dissolves in mucus
- Diffuse through alveolar cell open bracket epithelium close bracket
- Diffuses through capillary cell
- Diffuses through plasma
- Diffuses through semi permeable membrane of red blood cells; joins with haemoglobin to form oxyhaemoglobin
Does the concentration of CO2 have any effect on the rate of diffusion of O2?
No. Both gases travel independently of each other and in opposite directions.
Answer exam questions only about the gas that is asked
Why is O2 transport on the alveoli not as efficient as it seems?
- Some blood entering the lungs does not go into the alveolar capillaries and therefore does get oxygenated
- Some alveoli are under-ventialted
Define inspiration
When air is breathed in
Define expiration
When air is breathed out
What happens when we inspire?
The diaphragm contracts and flattens
The external intercostal muscles contract moving the ribs up and out
The thorax volume increases, decreasing the pressure below atmospheric
Air moves into the lungs down the pressure gradient
What happens when we expire?
The diaphragm relaxes and bows upward
The internal intercostal muscles contract moving the ribs down and in
The thorax volume decreases, increasing the pressure above atmospheric
Air moves out of the lungs down the pressure gradient
What is the stretchy nature of the lungs called?
Natural elasticity
What muscles are used for forced expiration but not gentle breathing
Abdominal muscles
These contract, pushing the abdominal organs up against the diaphragm.
Thorax volume decreases
Lung pressure increases more
What is the function of pleural membranes?
Surrounds the pleural cavity around the lungs which is filled with pleural fluid.
The outer PM is attached to the inner wall of the thorax
The inner PM covers the lungs
What is the function of pleural fluid?
Allows pleurae to slide over one another easily during breathing
How would you describe the internal and external intercostal muscles?
Antagonistic
What are the short term effects of exercise on breathing?
Faster rate
Deeper breaths
Increased oxygen in
Increased carbon dioxide out
What are the long-term effects of regular exercise?
More alveoli
More capillaries
Diaphragm and intercostal muscles become stronger
What is the equation for pulmonary ventilation?
Pulmonary ventilation (cm3min-1) = tidal volume (cm3) × breathing rate (min-1)
Why will pulmonary ventilation increase with exercise?
Tidal volume and breathing rate are increased
Define pulmonary ventilation
The product of tidal volume multiplied by breathing rate
Define tidal volume
Volume breathed in and out in one cycle
Define breathing rate
Number of breaths in a minute
How does blood flow relate to Fick’s law?
Maintained concentration gradient
How does ventilation relate to Fick’s law?
Maintained concentration gradient
How does a large number of alveoli with many internal walls relate to Fick’s law?
Increased SA:Vol
Decreased diffusion distance
How does a large number of capillaries relate to Fick’s law?
Increased SA:Vol
Decreased diffusion distance
How does Plaza now being separated by only two cells (alveoli and capillary) relate to Fick’s law?
Decreased diffusion distance
Does correlation mean causation?
No as there may be other contributing factors
List the 5 major risk factors for lung disease
Smoking Air pollution Genetic disposition Infections Occupation
What are the causes/risk factors of fibrosis?
Unclear. Evidence suggests reaction to microscopic lung injury to which some are genetically more susceptible
What are the symptoms of fibrosis?
Shortness of breath
- reduced elasticity of lungs: DD SA
- lungs filled with fibrosis tissue: lower lung capacity
Chronic dry cough
- fibrous tissue blocks airway: cough reflex to attempt to move it (but immovable)
Chest pain
- pressure due to fibrous tissue
- damage and scarring due to coughing
Weakness and fatigue
- less oxygen intake therefore reduced cellular respiration and energy release
What are the long term effects of fibrosis?
Scars
- longer diffusion pathways
Reduced lung elasticity
- difficult to expire spent air
What are the causes/risk factors of asthma?
Localised allergic reaction
- air pollution
- exercise
- cold air
- infection
- anxiety
- stress
What are the symptoms of asthma?
Causes white blood cells to release histamine which
- inflames the linings of the Airways
- causes the epithelium to secrete more mucus
- causes fluid from the capillaries to enter the airways
- causes the muscles around the bronchioles to contract and constrict airflow
Breathing difficulty
- bronchi constricted
- lungs inflamed; filled with mucus and fluid
Wheezing
- air passing through constricted bronchi
Tight feeling in the chest
- unable to ventilate the lungs due to constrictions
Coughing
- attempt to clear the obstructed airways
What are the long-term consequences of asthma?
Restricted ventilation
Reduced cellular respiration
Lower concentration gradient across alveoli cells
What are the causes/risk factors of emphysema?
Elastin protein in lungs becomes permanently stretched
- cannot force out spent air
- surface area of the alveoli becomes reduced
- fewer alveoli
- thicker alveoli walls
- larger air space in each alveoli
What are the symptoms of emphysema?
Shortness of breath
- constant stale air
- lungs permanently inflated
- reduced surface area meaning the rate of diffusion therefore less oxygen available for cellular respiration
Chronic cough
- reflux cough to remove damaged tissue and mucus that are not removable
Blue skin tone
- low blood oxygen levels
What are the long-term consequences of emphysema?
Restricted ventilation
Lower concentration gradient across alveoli cells
Longer diffusion distances inside lungs
Reduced cellular respiration
What are the causes/risk factors of tuberculosis?
Mycobacterium tuberculosis or mycobacterium bovis
- bacteria attach the droplets of water/mucus from an infected person
Varying vaccination rates Immigration and different strains Living conditions Close contact Residential facilities Reduced immunity Cows Certain countries
What are the symptoms of tuberculosis?
Bacteria growing up a part of the lungs (where there is plenty of oxygen)
White blood cells accumulate to ingest the bacteria
Primary infection
- inflammation and enlargement of lymph nodes in the lungs
- occurs in children
Few symptoms and infection is controlled but the bacteria remain
What are the long-term consequences of tuberculosis?
Post primary tuberculosis
- bacteria re-emerge
- occurs in adults
Bacteria creates cavities in the lungs
- the lung repairs itself with scar tissue
Sufferer coughs up damaged lung tissue and blood containing bacteria
The infection can spread to the rest of the body and be fatal
Define pulmonary
Relating to the lungs
Why is an excess of carbon dioxide in the body a problem?
Creates carbonic acid
Carbonic acid denatures enzymes
H20 + CO2 -> H2CO3
