UNIT 4 - B 3.1 - Gas Exchange Flashcards
What does it mean for an organism to be aerobic?
They require oxygen to metabolize energy from organic substances such as glucose
What do organisms need to remove in addition to their aerobic needs?
remove metabolic waste products such as carbon dioxide
How do some organisms, such as single-celled life forms exchange oxygen and carbon dioxide directly with the atmosphere?
Through their plasma membranes
Why have larger multicellular organisms evolved complex adaptations involved in gas exchange between the atmosphere or water habitat and other tissues?
because of their metabolically active tissues which may lie deep within the organism and far away from their environment
What is the problem of getting gases directly to and from an organism’s interior cells compounded by?
the surface area-to-volume ratio
When does the surface area-to-volume ration decrease?
when the size of the cell increases
What is the volume of an organism a reflection of?
its metabolic need to exchange respiratory gases
What is an organism’s ability to take in and release substances limited by?
its outer layer surface area
What do organisms with evolved adaptations for gas exchange must have?
specialized tissues designed for molecular exchange
Where are the specialized tissues required for gas exchanged found?
in the skin of some small organisms, gills of aquatic organisms, and lungs of some larger terrestrial organisms
What are gas exchange surfaces characterized by?
being thin, being moist, having a large surface area, and being permeable to respiratory gases
Why are gas exhange surfaces thin?
to keep diffusion distances short
Why are gas exchange surfaces moist?
to encourage gas diffusion
What does the large surface area of gas exchange surfaces allow?
for maximum diffusion
What are the respiratory gases?
oxygen and carbon dioxide
What do the properties of gas exchange surfaces allow for?
the max volume of gases to be exchanged across the surface in the shortest amount of time
What must be maintained for oxygen to diffuse into the blood and carbon dioxide to diffuse out of the blood?
concentration gradients
What has blood recently been within when it is first circulated to the gills, for example?
capillaries of the muscles and other body tissues
What are body cells continuously doing, utilizing oxygen and producing carbon dioxide?
respiring
What does the blood that leaves body tissues contain a higher and lower concentration of compared to before the blood reached the active body tissues?
higher levels of carbon dioxide and lower levels of oxygen
What do the numerous dense capillaries within lungs contain?
blood that has recently come from respiring body tissues
What events must occur in order to maintain concentration gradients for gas exchange?
- water must be continuously passed over the gills/air must be continuously refreshed in the lungs
- there must be a continuous blood flow to thh dense network of blood vessels in both the body tissues and the tissues of the gills/lungs
How do lungs expose air to a large surface of gas exchange tissue?
by subdividing their volume into alveoli
Where are each alveolus located?
at a terminal end of one of the branches of tubes that started as the trachea
What does it mean to inspire?
breathe in
What does it mean to expire?
breathe out
What happens within millions of alveoli when we inspire or expire?
most of the air is replaced inside
What lines each alveolus?
surfactant
What is the surfactant lining each alveolus?
a thin phospholipid and protein film
What does the surfactant inside alveoli do?
reduces the surface tension of the moist inner surface and helps prevent each alveolus from collapsing each time air is expired
What are bronchioles?
small tubes that connect alveoli and the trachea
Why are all of the bronchioles ultimately connected to the trachea?
for access to inspired and expired air
What does the spherical shape of alveoli provide?
a vast surface area for the duffusion of oxygen and carbon dioxide
What is the diffusion of respiratory gases also helped by?
the dense network of capillaries surrounding the alveoli
How do the concentrations of respiratory gases compare in air inspired into the alveoi to the blood in a nearby capillary?
air inspired into teh alveoli has a higher concentration of oxygen and a lower concentration of carbon dioxide compared to the blood in a nearby capillary
What do oxygen and carbon dioxide diffuse according to?
their concentration gradient
Why to respiratory gases only need to diffuse through two cells to enter or exit the blood stream?
because capillaries are one cell thick and so are each alveolus
Why are lungs themselves not capable of purposeful movement?
because the tissues making up the lungs is passive and not muscular
What are some of the muscles surrounding our lungs?
the diaphram, muscles of the abdomen, and the external and internal intercostal muscles surrounding the ribs
What do all the muscles around the lungs work collectively to do?
either increase or decrease the volume of the thoracic cavity, leading to pressure changes in the lungs
What is the mechanism of breathing based on?
the inverse relationship between pressure and volume
What does Boyle’s law state?
that an increase in volume will lead to a decrease in pressure and vice versa
What is the thoracic cavity also called?
the thorax
Where are lungs located?
in the thorax
What is the thoracic cavity closed to?
outside air
What is the only opening in the lungs?
through the trachea (via mouth and nasal passages)
What is the diaphram?
a large dome shaped muscle that forms the “floor” of the thoracic cavity
What happens when the diaphram contracts?
it flattens the dome shape and increases the volume of the thoracic cavity
What are the steps of inspiration?
- the diaphram contracts, increasing the volume of the thoracic cavity
- at the same time, the external intercostal muscles and one set of abdominal muscles contracts to help raise the rib cage, also increasing the volume of the thoracic cavity
- due to the increase in volume of the thoracic cavity, the pressure inside decreases
- The lung tissue responds to the lower pressure by increasing its volume
- this leads to a partial vacuum - air comes in through the open mouth/nasal passages to counter the partial vacuum within the lungs and fills the alveoli
What is a partial vacuum?
the decrease in pressure inside the lungs
What leads to deeper breathing and more air moving into the lungs during exercise?
the abdominal muscles and intercostal muscles acheive a greater initial thoracic volume
What is a spirometer?
a device that measures lung volume
What kind of air volumes can be measured using a spirometer?
tidal volume, inspiratory reserve volume, expiratory reserve volume, vital capacity
What is tidal volume?
volume of air breathed in/out during typical cycle when person is at rest
What is inspiratory reserve volume?
max volume of air that a person can breathe in
What is expiratory reserve volume?
mac volume of air that a person can breathe out
What is vital capacity?
the sum of the inspiratory reserve volume, tidal volume and expiratory reserve volume
What advantages are there to leaves being thin, only a few cells thick?
the diffusion of gases is quick and efficient, allows for a large surface area-to-volume ratio for efficient diffusion
What are the two primary energy-related processes within plants?
cell respiration and photosynthesis
What are plant cells producing through aerobic cell respiration?
ATP molecules for energy-requiring reactions
Why do plants use photosynthesis when light is available?
to make sugars as fuel for cell respiration
What is the summary reaction for cell respiration within plants?
glucose + oxygen = carbon dioxide + water
What is the summary reaction for photosynthesis within plants?
carbon dioxide + water = glucose + oxygen
How do rates of cellular respiration and photosynthsis compare within plants?
cellular respiration is fairly constant while photosynthesis rate depends heavily on light availability
How does the rate of cell respiration compare to the rate of photosynthesis in plants when conditions are optimal for photosynthesis?
the rate of photosynthesis is far greater than the rate of cell respiration
What is a waxy cuticle in plants?
a wax lipid layer that covers the surface of leaves and prevents uncontrolled and excessive leaf water loss by evaporation
What are upper epidermis in plants?
small cells on the upper surface of leaves that secrete a waxy cuticle
What is the palisade mesophyll in plants?
a densely packed region of cylindrical cells in the upper portion of the leaf which contains numerous chloroplasts and are located to recieve max sunight for photosynthesis
What is the spongy mesophyll in plants?
loosely packed cells located below the palisade layer and above the stroma which have few chloroplasts and many air spaces, providing a large surface area for gas exchange
What are veins in plants?
structures that enclose the fluid transport tubes called xylem and phloem, veins are located centrally within a leaf to provide access to all cell layers
What do xylem allow water to do?
move up from the root system to the leaves
What do phloem allow water and dissolved sugars to be?
distributed to other parts of the plant
What is a lower epidermis in plants?
small cells on the lower surface of leaves that secrete waxy cuticle
Where are guard cells forming stomata embedded?
in the lower epidermis
What are stomata in plants?
numerous microscopic openings on the lower surface of leaves
What are each stoma composed of?
two guard cells which can create an opening or close it when needed
What happens when a stoma is open?
it permits carbon dioxide to enter the leaf and at the same time water vapour and oxygen to exit the leaf
Why does the location of stomata on the lower surface of leaves limits water loss as a result of transpiration?
because the lower surface of leaves experiences lower temperatures compared to the upper surface
What is the evaporation of water through open stomata called?
transpiration
What is transpiration a natural consequence of?
a leaf’s function to accomplish photosynthesis
What happens when a leaf opens its stomata?
carbon dioxide enters as a reactant for photosynthesis while excess oxygen diffuses out
Why will water also evaporate through any open stomata?
becuase the mesophyll area is very humid
Where can water that evaporates through the stomata be traced back to?
water that entered the roots and has reached the upper sections of the plant
What can transpiration amount to when conditions are optimal?
a significant amount of water
Why does increased light increase the rate of transpiration in plants?
because light stimulates guard cells to open stomata
Why does increased temperature increase the rate of transpiration in plants?
becuase it increases molecular movement including increased evaporation of water
Why does increased wind speed increase the rate of transpiration in plants?
because wind removes water vapour at the entrance of stomata which leads to an increase in the water concentration gradient between the inside and outside of the leaf
Why does increased humidity lead to a decreased rate of transpiration in plants?
because it lessens the water concentration gradient between the inside and outside of the leaf
When would a change in temperature, wind speed and humidity not affect transpiration?
if there is too little light because the stomata would then be closed and the rate of transpiration would be zero
What is haemoglobin?
the protein molecule found within red blood cells
What are erythrocytes?
red blood cells
What is haemoglobin responsible for?
carrying most of the oxygen within the bloodstream
What is the basic construct of erythrocytes?
a plasma membrane surrounded by cytoplasm filled with haemoglobin molecules
What is the construct of each haemoglobin molecule?
composed of four polypeptides, quaternary structure, each polypeptide has a haem group near its center, each haem group has an iron atom inside
What is really binding with oxygen when haemoglobin reversibly binds to an oxygen molecule?
the iron atom within the haem group
Why is haemoglobin able to transport 4 oxygen molecules at once?
because haemoglobin has a total of 4 iron atoms within the 4 haem groups
When is haemoglobin said to be saturated?
when it is carrying its max 4 oxygen molecules
What is cooperative binding?
the phonomenon where there is an increase in affinity/attraction for oxygen when haemoglobin is already bound to an oxygen molecule(s)
When does haemoglobin have the greatist affinity for oxygen?
when it alread has 3 oxygen molecules
How does oxygen increase haemoglobin’s affinity for more oxygen?
it changes the haemoglobin’s shape
When will haemoglobin not have any affinity for oxygen?
when it alread has all 4 oxygens that it can carry
what is allostery?
the binding of carbon dioxide to the polypeptide chain(s) of haemoglobin and the resulting change in haemoglobin’s affinity for oxygen
Where does carbon dioxide bind to in haemoglobin instead of the iron atoms?
it binds to the polypeptide resgions of the molecule
What is the allosteric site of a polypeptide?
the area of each polypeptide where carbon dioxide binds
What do the structural differences in foetal haemoglobin allow for?
it to have a higher affinity for oxygen compared to the haemoglobin of the mother
Where do capillaries of the mother come very close to the capillaries of the foetus?
in the placenta of the mother
What does the mother’s and foetus’s capillaries being very close allow for?
molecular exchange between the mother and the foetus including oxygen and carbon dioxide
What encourages diffusion of the mother’s oxygen to the foetus?
the concentration gradient between the blood of the mother and the foetus, aided by the foetal haemoglobin’s greater affinity for oxygen
What happens when a haemoglobin molecule bonds to a carbon dioxide?
its affinity for oxygen decreases
When does haemoglobin have a greater tendancy to give up oxygen molecules?
in the presence of carbon dioxide
What is the Bohr shift?
the change in affinity of haemoglobin in the presence of carbon dioxide
What is the partial pressure of a gas?
the pressure exerted by a single gas within a mixture of gases
How could you calculate the percentage of oxygen released to tissue using an oxygen dissociation curve? (when y-axis = percentage of haemoglobin saturation and x-axis = partial pressure)
by subtracting the left y-axis intersect point (the lower percentage of haemoglobin saturation) from the right y-axis intersect point (the higher percentage of haemoglobin saturation)
What would a greater affinity for oxygen look like on a oxygen dissociation curve?
a shift to the left
What would increased carbon dioxide mean for oxygen dissociation curves?
it would shift to the right
