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Biology > B3.1 Gas Exchange > Flashcards

B3.1 Gas Exchange Flashcards

1
Q

Define gas exchange.

A

The exchange of oxygen and carbon dioxide between the alveoli and bloodstream

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2
Q

State the role of diffusion in gas exchange.

A

Gas exchange occurs via diffusion - the random net movement of particles from an area of higher conc. to an area of lower conc. leading to equilibrium (an equal distribution of particles)

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3
Q

Explain the need for structures of larger organisms to maintain a large enough surface area for gas exchange.​

A

As organisms increase in size, the SA:V ratio decreases thus, there is a greater need for specialised structures to facilitate efficient gas exchange having properties such as: being highly folded, branched, in structure, increasing the SA available across which gases can be exchanged.
- The larger the organism, the smaller the SA:V ratio, the greater the distance betw. the surface of the organism and the cells in the interior thus, rate of diffusion decreases.

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4
Q

Outline the function of the following properties of gas-exchange surfaces: permeability, thin tissue layer, moisture and large surface area.​

A
  • Permeability: The exchange surface must have pores allowing gases to be exchanged across its surface
  • Thin Tissue Layer: provides a short distance across which gases need to move
  • Moisture: helps dissolve gases before they diffuse across the exchange surface
  • Large SA: more membrane surface available for gases to diffuse across
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5
Q

State the reason why concentration gradients must be maintained at exchange surfaces.

A

The bigger the difference in the conc., the steeper the conc. gradient, the faster the rate of diffusion

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6
Q

Explain dense networks of blood vessels as a mechanism for maintaining concentration gradients at exchange surfaces in animals.

A
  • Dense network of blood vessels: Lots of opportunity for substances to be exchanged betw. the surface and the blood thus maintaining a low concentration gradient
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7
Q

Explain continuous blood flow as a mechanism for maintaining concentration gradients at exchange surfaces in animals.

A
  • Continuous blood flow: As soon as substances flow into blood, they’re transported away thus, ensuring a low conc. of that substance in the blood supply adjacent to the exchange surface.
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8
Q

Explain ventilation with air for lungs for maintaining concentration gradients at exchange surfaces in animals.

A
  • Ventilation: movement of air into and out of the lungs driven by respiratory muscles
  • MAMMALS WITH LUNGS: Inhale air into the lungs and exhale air out from the lungs
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9
Q

Explain ventilation with water for gills as mechanisms for maintaining concentration gradients at exchange surfaces in animals.

A
  • Ventilation: numberof breaths per minute
  • MAMMALS WITH GILLS: One of the various mechanisms is to pump water over the gills through the mouth.
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10
Q

Explain how mammals are able to maintain steep concentration gradients?

A
  • Double circulatory system separates oxygenated and deoxygenated blood
  • This ensures that blood transported to respiring cells is highly oxygenated
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11
Q

State the locations of gas exchange in humans.

A

Lungs

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12
Q

Outline the structures of mammalian lungs that are adapted to maximizing gas exchange.

A
  • Alveoli: Tiny air sacs w/ large surface areas
  • Bronchioles: Branches of bronchi leading into alveoli
  • Bronchi (plural for bronchus): Airways that lead from trachea into bronchioles
  • Trachea: Contains cartilaginous rings providing structure to the trachea, the smooth muscle regulates airflow, mucous membrane lining produces mucus trapping dust and bacteria before reaching the lungs
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13
Q

Describe the features of alveoli that adapt them to gas exchange (TRIM)

A

Thin wall: Made of a single layer of flattened cells so that diffusion distance is small

Rich capillary network: Alveoli are covered by a dense network of capillaries that help to maintain a concentration gradient

Increased SA:Vol ratio: High numbers of spherically-shaped alveoli optimise surface area for gas exchange

Moist: Pneumocytes type II in the lining secrete fluid to allow gases to dissolve and to prevent alveoli from collapsing (through cohesion)

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14
Q

State what pneumocytes are

A

Cells inside the lungs

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15
Q

Function of Type II Pneumocytes?

A
  • Surfactants Secrete alveolar fluid that moistens the surface of the alveoli allowing gases to dissolve into the surfactant before diffusing across the wall of the alveoli and capillary into the blood.
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16
Q

Function of Type I Pneumocytes

A
  • Very thin cells (also called epithelial cells) forming a single layer that make up the wall of each alveolus thus, they are adapted for gas exchange due to a short diffusion distance from the alveolar air space into the bloodstream
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17
Q

How does a highly branched network of bronchioles increase SA

A
  • Each bronchiole branches into many alveoli (the exchange surface of the lungs)
  • This increases SA available for gas exchange and thus, increasing the rate of gas exchange
  • A high degree of branching ensures air is distributed throughout the lungs
  • The small diameter of bronchioles compared w bronchi & trachea helps slow down the rate of airflow increasing the efficiency of gas exchange
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18
Q

Draw a diagram showing the structure of an alveolus and an adjacent capillary.​

A

pk

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19
Q

Identify the structure of the airway that connects the lungs to the outside of the body.

A

Trachea

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20
Q

Define ventilation, inspiration and expiration.

A

Ventilation:
- The process of inhaling and exhaling into the lungs. Helps to maintain concentration gradients

Inspiration:
- Inspiration is the intake of air into the lungs

Expiration:
- Expiration is the expulsion of air from the lungs.

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21
Q

State the relationship between gas pressure and volume.

A
  • Inversely proportional; as the volume of gas increases, the pressure of gas decreases
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22
Q

Explain why internal and external intercostal muscles are defined to be “antagonistic”

A

They are opposing pairs of muscles that work in opposite directions during breathing

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23
Q

Explain the mechanism of inspiration of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles (DETTA)

A

Inspiration:
- Diaphragm muscles contract and flatten downwards
- External intercostal muscles contract, pulling ribs upwards
- Internal intercostal muscles relax, pulling ribs outwards
- This increases the volume of the thoracic cavity (and therefore lung volume)
- The pressure of air in the lungs is decreased below atmospheric pressure
- Air flows into the lungs by moving down its pressure gradient to equalise the pressure

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24
Q

Explain the mechanism of expiration of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles. (DAEITTA)

A

Expiration:
- Diaphragm muscles relax and the diaphragm curves upwards
- External intercostal muscles relax, allowing the ribs to fall
- Internal intercostal muscles contract, pulling ribs downwards
- This decreases the volume of the thoracic cavity (and therefore lung volume)
- The pressure of air in the lungs is increased above atmospheric pressure
- Air flows out of the lungs by moving down its pressure gradient to equalise the pressure

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25
Q

Define tidal volume, vital capacity, and inspiratory and expiratory reserve.

A

Tidal volume: vol of air that moves into and out of your lungs with every normal breath

Vital Capacity: Volume of air you can exhale with max effort after inhaling the maximum possible vol. of air

Inspiratory reserve: The extra vol of of air can be inhaled with maximum effort beyond the volume of air inhaled in a normal inspiration

Expiratory reserve: The extra vol of air that can be exhaled with a maximum effort beyond the vol. of air exhaled after a normal exhalation

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26
Q

List methods for measuring tidal volume, vital capacity, and inspiratory and expiratory reserve.

A
  • A pulmonary function test called spirometry; a person breathes into a machine called a spirometer and the volume & speed of exhaled air are measured
  • Simple observation; counting the number of breaths per minute
  • Breathing into a balloon: measuring the volume of air in a single breath by submerging the balloon in water and measuring the vol. displaced.
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27
Q

formula for ventilation rate

A

number of ventilations / time

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28
Q

State the direction of movement of gases exchanged in leaves.

A

Gases move from the inside of the leaves to the outside

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29
Q

Outline adaptations for gas exchange in leaves; Epidermis

A

Epidermis: Regulates the exchange of gases betw. the leaf and external air through small pores called stomata

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30
Q

Outline adaptations for gas exchange in leaves; epidermis

A

Epidermis: Regulates the exchange of gases betw. the leaf and external air through small pores called stomata

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31
Q

Outline adaptations for gas exchange in leaves; waxy cuticle

A

Waxy Cuticle: Forms a protective water-proof layer to reduce water loss

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32
Q

Outline adaptations for gas exchange in leaves; guard cells

A

Guard cell: Regulate the opening and closing of stomata by changing shape.

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33
Q

Outline adaptations for gas exchange in leaves; air spaces

A

Air spaces: allow gases to diffuse from one part of the leaf to another and a greater SA

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34
Q

Outline adaptations for gas exchange in leaves;, spongy mesophyll

A

Spongy mesophyll: Provides many air spaces

35
Q

Outline adaptations for gas exchange in leaves; veins.

A

Veins (phloem and xylem): Transport water from the roots to the leaves where:
- Xylem tissue transports water + dissolved minerals
- Phloem tissue transports sugars + amino acids

36
Q

State what a plan diagram shows

A

The distribution of tissues, but not individual cells.

37
Q

Draw and label a plan diagram to show the distribution of tissues in a transverse section of a leaf. Include upper and lower epidermis, palisade and spongy mesophyll, xylem and phloem.

A

pk

38
Q

Define transpiration.

A

The loss of water vapour from plant leaves by evaporation at the surface of the mesophyll cells

39
Q

Describe the process of transpiration

A
  • Light energy converts water in the leaves to vapour which evaporates from the leaf via stomata via diffusion
  • New water is absorbed from the soil by the roots, via osmosis, creating a difference in pressure between the leaves (low) and the roots (high)
  • Water flows, via the xylem, along a pressure gradient to replace the water lost from the leaves - this is the transportation stream that can function due to capillary action (adhesive and cohesive properties of water)
40
Q

Outline the relationship between water evaporation and transpiration.

A

As transpiration increases, water evaporation increases

41
Q

State the 4 abiotic factors that affect the rate of transpiration

A
  • Temperature
  • Humidity
  • Wind Intensity
  • Light Intensity
42
Q

Discuss the effect of abiotic factors on the rate of transpiration; Temp.

A

Temperature: The higher, the more kinetic energy water molecules have, the faster they evaporate and diffuse out the stomata.

43
Q

Discuss the effect of abiotic factors on the rate of transpiration; Humidity

A

Humidity: The higher, the more water vapour molecules in the air outside the air, the less steep the conc. grad. betw. the leaf and the surrounding air, therefore, decreased rate of diffusion of water vapour

44
Q

Discuss the effect of abiotic factors on the rate of transpiration; Wind Intensity

A

Wind Intensity: the higher, the faster water molecules are moved away from the leaf after transpiration resulting in increased conc. grad. betw. stroma and air outside leaf thus, increasing rate of diffusion of water molecules

45
Q

Discuss the effect of abiotic factors on the rate of transpiration; Light Intensity

A

Light Intensity: the higher, guard cells cause stomata to open WIDER to allow more CO2 into the leaf for photosynthesis (more water evaporates from plant to outside as water is absorbed into the leaves via osmosis at the roots, initially).

46
Q

Discuss the advantages of opening and closing stomata at different times of the day.

A
  • Stomata remain closed at night to prevent water loss and because the gas exchange required at night doesn’t occur via stomata pores and instead, occurs via other parts of the surface of the leaf through diffusion.
  • Stomata open during daytime to allow gas exchange; CO2 diffuses in and O2 diffuses out to allow photosynthesis to occur
47
Q

Define stomatal density

A

The number of stomata in a particular unit of area of a leaf or other plant organ

48
Q

Calculate stomatal density from a leaf cast or micrograph.

A
  • The diameter in mm
  • The number of stomata in FOV
  • Area = πr^2
  1. Calculate the mean number of stomata in FOV
  2. Divide value by the area (Area = πr^2)
49
Q

Describe the relationship between the rate of respiration / photosynthesis and diffusion of oxygen and CO2

A
  • When the rate of respiration is higher than the rate of photosynthesis (during night time), O2 diffuses into the stomata and CO2 diffuses out
  • When the rate of photosynthesis is higher than the rate of respiration (when exposed to intense light), CO2 diffuses into stomata and O2 diffuses out
50
Q

Describe the structure and function of haemoglobin.

A

Structure:
- The iron-containing protein present in red blood cells

Function:
- Binds to 4 O2 molecules to transport oxygen from the lungs to respiring tissues (then forming an oxyhemoglobin complex)
- Also transports CO2 from respiring tissues back to lungs where it can be exhaled

51
Q

State the unit for volume when measuring vol. of water in potometers and state what its the same as

A
  • Unit: mm^3
  • Same as ml
52
Q

Define affinity.

A

The degree to which two substances bind together

53
Q

Outline how cooperative binding alters haemoglobin’s affinity for oxygen.

A
  • As 1 O2 binds to 1 haemoglobin subunit, this changes the conformation of the molecule, increasing the affinity of haemoglobin to oxygen, making it easier for other O2 molecules to bind to the remaining haem groups
54
Q

Compare the oxygen affinity of adult (HbA) and fetal haemoglobin (HbF).​ Explain the result too.

A
  • HbF has a higher oxygen affinity than HbA due to the presence of gamma polypeptides
  • This increases the efficiency with which the foetus gains O2 from mother’s blood across placenta; high oxygen affinity in HbF is important for foetal development and survival as the O2 conc. in foetal’s blood is lower than O2 conc. in mother’s blood
55
Q

Describe the structures of foetal haemoglobin (HbF) and adult haemoglobin

A

HbA:
- Quaternary structure - 2 alpha & 2 beta polypeptide chains each containing its own haem group containing iron ion

HbF:
- Quaternary structure - 2 alpha & 2 gamma polypeptide chains each containing its own haem group containing iron ions

56
Q

Describe allosteric binding of CO2 to hemoglobin and the consequences for oxygen transport.

A
  • As CO2 binds to allosteric site of haemoglobin rather than the haem group, this causes haemoglobin to form carbaminohaemoglobin as a conformational change occurs

Consequences for O2 transport:
- The conformational change results in a decreased affinity for Oxygen
- This is important for Haemoglobin unloading Oxygen in areas of low partial pressure of Oxygen (like respiring tissues)

57
Q

Sketch what the oxygen dissociation curve looks like and how

A
  • X-axis: Oxygen partial pressure (concentration)
  • Y-axis: Percent Oxygen Saturated
  • Due to the cooperative binding of haemoglobin to oxygen, an S-shaped oxygen oxygen dissociation curve forms
58
Q

Describe the oxygen dissociation curve (don’t sketch)

A
  • Rate of oxygen uptake by haemoglobin increases rapidly as the partial pressure of Oxygen increases
  • Eventually levels off as the haemoglobin becomes fully saturated with oxygen in areas of higher partial pressures of oxygen (like lungs)
59
Q

Define the Bohr shift.

A

This shift to the right in the O2 dissociation curve

60
Q

Explain the mechanism and benefit of the Bohr shift.

A

Mechanism:
- respiring tissues produce more CO2 and require more O2
- CO2 binds to an allosteric site of Haemoglobin forming carbaminohaemoglobin
- CO2 that is dissolved in plasma reacts with water to form carbonic acid CATALYSED BY CARBONIC HYDRASE
- carbonic acid lowers the pH of the blood (blood becomes more acidic)
- carbonic acid then disassociates into H+ ions and HCO3-
- Haemoglobin undergoes a conformational change
- H+ ions react w Haemoglobin which releases Oxygen
- This causes a decreased haemoglobin affinity for Oxygen, therefore, causing a Bohr shift to the right
- Thus at any given partial pressure, the oxygen saturation for haemoglobin stays the same

Benefit:
- Hemoglobin releases more O2 into tissues with higher partial pressures of CO2 (like respiring muscles)
- It also loads up more O2 in areas with higher partial pressures of Oxygen (like lungs)
- This facilitates oxygen transfer from the mother to the foetus to help ensure proper foetal development

61
Q

Outline why the partial pressure curve is an S shape

A
  • Cooperative binding occurs
  • 1 O2 binds to 1 haemoglobin subunit forming oxyhaemoglobin
  • conformational change occurs
  • haemoglobin affinity for oxygen increases
  • makes it easier for Oxygen to bind to remaining haem groups
62
Q

Outline the reaction between Oxygen and haemoglobin

A

The binding of oxygen to haemoglobin results in oxyhemoglobin. This is a reversible reaction

63
Q

What is the haem group made of

A

an Iron ION
(not iron atom)

64
Q

State the effect of the Bohr shift on the oxygen dissociation curve.

A

Shifts to the right

65
Q

Define partial pressure.

A

The individual pressure exerted by a particular gas within a mixture of gases

66
Q

State the relative partial pressures of oxygen in the atmosphere at sea level, in the alveoli, in alveoli blood capillaries, and respiring tissue.

A
  • relative partial pressures of O2 in the atmosphere at sea level is
67
Q

Explain the difference in the oxygen dissociation curves of adult and fetal haemoglobin.

A
  • HbA curve is more to the right –> requires a greater partial pressure of O2 to achieve the same level of saturation as HbF (at lower O2 conc., HbA releases O2 more readily than HbF)
  • HbF curve is more to the left –> has a higher oxygen affinity than HbA and at the same partial pressure of O2, HbF will be more saturated with O2 than adult Haemoglobin
68
Q

What name is given to muscles that have opposite effects?

A

Antagonistic

69
Q

State the 3 potometers to measure the rate of transpiration

A
  • Using a mass potometer
  • Using a bubble potometer
  • Using a pressure potometer
70
Q

State how to work out the area of a leaf

A
  • Draw around a leaf on graph paper and shade in the squares that the leaf covers
71
Q

State 3 ways to measure the ventilation rate

A
  • Strap a belt around the chest and measure the pressure from the contraction and expansion of the chest using a data logger.
  • Breathe into a mouthpiece connected to a spirometer and measure the volume of air inhaled and exhaled over a period of time.
  • Place hands on the chest and count the number of times the chest rises over a period of time.
72
Q

Explain why haemoglobin is described as an ‘allosteric protein’?

A

Changes in concentration of oxygen cause conformational changes in haemoglobin that influence the ability of oxygen to bind

73
Q

During the Bohr shift, when the curve shifts to the right, what does this mean for the affinity of Oxygen

A

The affinity of Oxygen decreases as it shows that higher concentrations of O2 are necessary for haemoglobin to become saturated (carries the max amount of oxygen) - opposite of the curve theory in economics

74
Q

Explain how the presence and absence of water affects guard cells (3)

A

Presence of Water:
- Guard cells absorb water via osmosis
- become turgid

Absence of water:
- Guard cells lose water via osmosis
- become flaccid

75
Q

Explain how the structure of normal haemoglobin enables cooperative binding (5)

A
  • Haemoglobin has 4 binding sites for O2
  • It’s hard for first O2 to bind
  • Conformational change occurs once first O2 binds making it easier for other O2 molecules to bind
  • Haemoglobin has 4 protein subunits arranged in a quaternary structure
  • In the absence of O2, binding sites for O2 have lower O2 affinity
76
Q

How would the oxygen dissociation curve look which represents the oxygen saturation of HBf? (1)

A

Shifts to the left (increased O2 affinity for HBf)

77
Q

Explain how intense exercise causes changes to the affinity of Haemoglobin for O2 (5)

A
  • Respiring tissues release CO2
  • This causes the pH of the blood to become more acidic
  • O2 dissociation curve shifts rightwards
  • Haemoglobin has lower affinity for O2 and releases O2 at respiring tissues
  • Intense exercise results in increased body temperature
78
Q

Describe the structure of bronchioles (2)

A
  • Branch from bronchi
  • Contain walls of smooth muscle fibres
79
Q

Distinguish between the external intercostal muscles and the internal intercostal muscles.

A

During inhalation:
- EIM contract whereas IIM relax

During exhalation:
- EIM relax whereas IIM contract

80
Q

Outline how the concentration gradients of oxygen and carbon dioxide are maintained in the lungs. (4)

A

Inhalation:
- EIM contract
- Alveoli have higher O2 conc.
- O2 diffuses into blood capillaries from alveoli
- Conc. gradients of gases maintained by blood flow in capillaries

81
Q

Explain why transpiration is an inevitable consequence of gas exchange in a leaf (2)

A
  • Both occur through stomata
  • Stomata open for gas exchange
  • Water loss increases by transpiration through stomata
82
Q

Why would the 1st measurement in each condition be discarded from the calculation of the mean rate of water uptake for each condition

A

To give the plant time to adjust to the temperature or humidity level

83
Q

State 3 adaptations of the spongy mesophyll for the intake of CO2 to photosynthetic leaf cells

A
  • a water layer on the cell surface
  • air spaces between mesophyll cells
  • a large surface area
84
Q

Explain the process of gas exchange in alveoli (7)

A
  • air in alveoli has high concentration in O2 and a low concentration in CO2
  • concentration gradients are maintained by ventilation
  • diffusion takes place due to concentration gradients
  • type I pneumocytes are thin which provides a short diffusion distance
  • rich supply of blood capillaries allows efficient gas exchange
  • increased surface area to volume ratio due to numerous alveoli
  • moist conditions created by type II pneumocytes that secrete surfactants to reduce surface tension
  • gases must dissolve in liquid lining of alveoli to be exchanged

Biology (20 decks)

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