Unit 3- Gas Exchange =) Flashcards
- water used in photos
- water produced in respiration
- water used for support
- water used in hydrolysis
What does the standard deviation show?
- variation in data
- around the mean
Explain the movement of oxygen into the gas exchange system of an insect when it is at rest. (3)
- O2 used in resp
- O2 gradient established
- O2 diffuses in
Explain what causes the oxygen concentration in the trachae to fall when the spiracles are closed. (2)
- O2 diffuses to tissues in resp.
- O2 x able to enter organism
Some insects live in dry conditions.
Suggest an advantage of the movement of spiracles. (2)
- x open all the time
- ∴ ↓ water loss by diffusion thru spiracles
Describe a method you could use to find the surface area of a leaf. (3)
- draw around leaf on graph paper
- count squares
- multiply by 2 (upper + lower leaf surface)
In large cells of U. marinum, most mitochondria are found close to the
cell-surface membrane. In smaller cells, the mitochondria are distributed
evenly throughout the cytoplasm. Mitochondria use oxygen during aerobic
respiration.
Use this information and your knowledge of surface area to volume ratios
to suggest an explanation for the position of mitochondria in large U.
marinum cells. (2)
- size ↑ sa : vol ↓
- longer for O2 to diffuse/ ↓ O2 diffuse/ ↑ diffusion distance
Explain the advantage for larger animals of having a specialised system
that facilitates oxygen uptake. (2)
- larger organism ↓ sa : vol
- overcomes ↑ diffusion pathway (=> faster diffusion)
Model A: Fish gills are developed outside the body for oxygen uptake.
Model B: Human lungs are developed inside the body.
Suggest how the environmental conditions have resulted in adaptations of
systems using Model A rather than Model B. (2)
- water has ↓ O2 conc
- ∴ system outside–> ↑ s.a. in contact w/ H2O (=> ↑ O2 absorbed)
//
- water- denser than air
- supports gills
How does having hollow tubes relate to the function of xylem tissue? (1)
- water flows easily in a continuous column
- maintains transpiration stream
How does lignin in xylem cell walls help the function of xylem tissue? (1)
- resists tension in water
- support
The stomata close when the light is turned off.
Explain the advantage of this to the plant. (2)
- water loss through stomata
- ↓ water loss
- maintains water content of cells
The uptake of carbon dioxide falls to
zero when the light is turned off.
Explain why. (2)
- x photos ∴ x use of CO2
- diffusion gradient into leaf x maintained
- new diffusion gradient out of leaf ∵ resp.
One theory of translocation states that organic substances are pushed from a high pressure in the leaves to a lower pressure in the roots.
Describe how a high pressure is produced in the leaves. (3)
- as sugars enter the phloem, Ψ ↓
- water enters by osmosis
- ↑ vol of water ↑ Pa in phloem
Explain how a stoma prevent water loss. (2)
- sunken- traps layer of saturated air–> ↓ Ψ gradient
- stoma can close- ↓ area for evaporation
Suggest appropriate units the students should use to compare the distribution of stomata on leaves. (1)
Stomata per mm2
The pieces of leaf tissue to be examined under an optical microscope were very thin.
Explain why this is important.
- single layer of cells
- light can pass through
Give 2 reasons why it is important to count the number of stomata in several parts of each piece of leaf tissue. (2)
- calculate mean
- non-uniform distribution–> representative
Explain the effect of temperature on the rate of carbon dioxide release. (3)
- enzymes work faster
- ↑ rate of resp. + CO2 release
- spiracles open ↑ often
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf. (3)
- CO2 enters through the stomata
- opened & closed by guard cells
- diffuses through (interconnected) air spaces w/ mesophyll cells
- down the diffusion gradient
Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish. (3)
- water & blood flow in opp. directions
- O2 conc. gradient maintained
- along the whole lamellae
- ↑ O2 will diffuse into the blood
The volume of water passing over the gills increases if the temperature of the water increases. Suggest why. (1)
- ↑ resp
- ↓ O2 dissolved in water
- ↑ water needs to pass over gills
Explain how the structure of the gill makes oxygen uptake efficient. (2)
- many filaments–> ↑ s.a. for diffusion
- large no. of capillaries–> maintains conc. gradient
- thin epithelium–> short diffusion pathway
There is a one-way flow of water over the gills of a fish whereas there is a two-way flow of air in the lungs of a mammal.
Suggest one advantage to a fish of this one-way flow of water over its gills. (1)
- ↓ energy needed/
- ✔️ continuous flow of water/ O2
The ends of tracheoles connect directly with the insect’s muscle tissue and are filled with water. When flying, water is absorbed into the muscle tissue.
Removal of water from the tracheoles increases the rate of diffusion of oxygen between the tracheoles and muscle tissue.
Suggest one reason why. (1)
- ↑ s.a. exposed to air
- gases diffuse faster through air than water
- ↑ vol of air
Suggest 2 precautions that should be taken to ensure the mean FEV1 value (taken from a group of 25 y.o.) is reliable. (2)
- Large sample size;
- Individuals chosen at random;
- Healthy;
- Equal number of males and
females; - Repeat readings;
The mean FEV1 value of non-smokers decreases after the age of 30.
Use your knowledge of ventilation to suggest why. (1)
Internal intercostal muscles ↓ effective/
↓ elasticity of lungs
One of the severe disabilities that results from emphysema is that walking upstairs becomes difficult.
Explain how a low FEV1 value could cause this disability. (3)
- ↓ CO2 removed
- ↓ O2 uptake
- ↓ aerobic respiration
The reduced elasticity of the lungs causes breathing difficulty.
Explain how. (2)
- alveoli x inflate/ deflate fully –> ↓ lung capacity
- breathing out x longer passive
- conc. gradient ↓
Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli. (3)
- ↓ CO2 removed (↑ remain in lungs)
- ↓ conc. gradient between blood & alveoli
- ↓ / slower movement of CO2 out of blood –> ↑ CO2 stays in blood
Describe and explain the mechanism that causes lungs to fill with air. (3)
- external intercostal muscles contract + diaphragm contracts & flattens
- vol ↑ pressure ↓
- air moves down PRESSURE GRADIENT
Two solutions often used to stain tissues are haematoxylin solution and iodine solution.
* Haematoxylin solution stains DNA a blue colour.
* Iodine solution stains starch a blue-black colour.
The scientist used haematoxylin solution and not iodine solution to stain the lung tissue.
Suggest why. (2)
- x starch in lung tissue
- nucleus visible- DNA in nucleus
If alveolar epithelium cells die inside the human
body they are replaced by non-specialised, thickened tissue.
Explain why death of alveolar epithelium cells reduces gas exchange in human lungs. (3)
- ↓ s.a.
- ↑ diffusion distance
- ↓ RATE of gas exchange
When a person starts to breathe out, the percentage of oxygen in the air first exhaled is the same as the percentage of oxygen in the atmospheric air.
Explain why. (2)
- air is from nose (x been in alveoli)
- gas exchange only in alveoli
Describe and explain one feature of the alveolar epithelium that makes the epithelium well adapted as a surface for gas exchange.
Do not refer to surface area or moisture. (2)
- single layer of cells
- ↓ diffusion distance
:) - permeable
- ✔️ diffusion of O2 & CO2
Describe and explain the mechanism that causes forced expiration. (4)
- internal intercostal muscles contract
- diaphragm relaxes (/ external intercostal muscles)
- vol of thoracic cavity ↓
- air pushed down pressure gradient
The volume of water passing over the gills increases if the temperature of the water increases.
Suggest why. (1)
- ↑ metabolism/ respiration/ enzyme activity
- ↓ O2 dissolved in water
Abdominal pumping increases the efficiency of gas exchange between the tracheoles and muscle tissue of the insect.
Explain why. (2)
- ↑ O2 enters/ quicker
- maintains a conc. gradient
Explainthe importance of determining a mean value in an investigation.
- comparison
- takes into account outliers/ anomalies
- // see effect of independent variable
Explain why molecules of oxygen and carbon dioxide are able to diffuse across membranes. (2)
- lipid is non-polar
- O2 + CO2 small & non-polar
- can diffuse through layer
- down conc. gradient
Describe two differences between active transport and facilitated diffusion. (2)
AT vs FD
1. against conc. gradient vs down
2. uses ATP vs x
3. uses carrier proteins vs channel proteins
Explain why ventilation of the lungs increases the efficiency of gas exchange. (2)
- brings ↑ O2, removes ↑ CO2
- maintains conc. gradient
- between alveoli & blood
Suggest and explain one way the leaf growth of xerophytic plants would be different from the leaf growth of sunflowers. (2)
- slow growth ∵ ↓ stomata
- growth may continue at ↓ ψ ∵ xerophytic adaptations in enzymes involved in photos
Use your knowledge of gas exchange in leaves to explain why plants
grown in soil with very little water grow only slowly. (2)
- stomata close
- ↓ CO2 for ↓ photosynthesis
Describe the gross structure of the human gas exchange system and how we breathe in and out. (6)
- order: trachea → bronchi → bronchioles → alveoli
- Inspiration: diaphragm contracts + flattens, external intercostal muscles contract
- vol ↑ pressure ↓ in thoracic cavity
- Expiration: diaphragm relaxes, internal intercostal muscles contract
- vol ↓ pressure ↑ in thoracic cavity
Explain three ways in which an insect’s tracheal system is adapted for
efficient gas exchange. (3)
- tracheoles w/ thin walls- short diffusion distance to cells
2.large no. of tracheoles (highly branched)- short diffusion distance+ ↑ s.a. - trachea w/ tubes full of air- faster diffusion
- fluid at end of tracheoles-** move out into tissues during exercise** –> faster diffusion through air to gas exchange surface
- muscles contract to move air–> maintains a diffusion gradient for O2
Some other species of insect have larvae that are a similar size and shape to damselfly larvae and also live in water. These larvae do not actively
hunt prey and do not have gills.
Explain how the presence of gills adapts the damselfly to its way of life. (2)
- ↑ metabolic rate
- uses ↑ O2
Explain how an asthma attack caused the drop in the mean FEV. (4)
- muscles in walls of bronchi contract
- walls secrete ↑ mucus
- diameter of airway ↓
- ∴ flow of air reduced
Describe how oxygen in air in the alveoli enters the blood in capillaries. (2)
- diffusion
- across alveoli epithelium
- capillary epithelium
Fire-breathers create a ball of fire by blowing a fine mist of paraffin oil onto a flame. Some of this mist can be inhaled and may eventually lead to fibrosis.
People who have been fire-breathers for many years often find they cannot breathe out properly. Explain why. (2)
- loss of elasticity
- x recoil properly
Describe the features of fish gills that give them a large surface area. (2)
- lamella on filaments
- lots of both
When first hatched, the young of some species of fish are less than 2 mm long.
Explain how these young fish get enough oxygen to their cells without having gills. (2)
- exchange across skin
- short diffusion distance
Explain why ventilation of the lungs increases the efficiency of gas exchange. (2)
- brings ↑ O2
- maintains conc. gradient
- between alveoli & blood
Explain the relationship between gill surface area and swimming speed (positive correlation). (2)
- ↑ O2 can be supplied
- for ↑ resp
Suggest why blood returning to the heart from the lungs contains some carbon dioxide. (2)
- conc reached equilibrium
- conc gradient needed for diffusion–> some remain in blood//
- lung cells respire
- produce CO2
Describe how ventilation helps to maintain the difference in oxygen concentration in the lungs. (2)
- brings in air containing ↑ conc of O2
- removes air w/ ↓ O2 conc
Give one way other than ventilation in the lungs that helps to maintain the difference in oxygen concentration. (1)
circulation of blood
Gas exchange in fish takes place in gills. Explain how two features of gills allow efficient gas exchange. (2)
- thin epithelium- short diffusion pathway
- many filaments + lamella–> ↑ s.a.
- countercurrent flow–>maintains conc gradient
The graph shows the volume of air he breathed out in the first 6 seconds of a breath.
You could use the curve to find the total volume of air that this person could breathe out in one complete breath. Describe how. (2)
- extrapolate the curve
- read off where it reaches a max/ plateau
The concentration of oxygen is higher in the surface waters than it is in water close to the seabed.
Suggest why. (2)
- air & water mix at surface
- O2 conc of air > water
- O2 diffuses into water
- surface closer to plants
- photosynthesise + produce O2
Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin. (2)
- ↑ dissociation
- by ↓pH (↑ acidity)
Explain why oxygen uptake is a measure of metabolic rate in organisms. (1)
O2 ised in resp, provides energy/ ATP
Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs.
Details of breathing are not required. (4)
- trachea, bronchi, bronchioles
- down pressure gradient
- down diffusion gradient
- across alveoli epithelium
- across capillary epithelium
