B3.1 Gas Exchange

Question 1

properties of gas exchange surfaces

Answer 1

1 cell thick walls, large surface areas, moist, permeable to O and CO2, concentration gradients

Question 2

how are concentration gradients maintained for gas exchange?

Answer 2

1. continuous movement of air/water
2. continuous blood flow

Question 3

exothermic animal

Answer 3

uses gills, “cold-blooded”

Question 4

endothermic animal

Answer 4

uses lungs, “warm-blooded”

Question 5

describe structure of lungs

Answer 5

trachea branches into bronchi, into bronchioles, into alveoli embedded in capillary bed

Question 6

surfactant in alveoli

Answer 6

phospholipid/protein film lining inner alveoli; decreases surface tension and adhesion, and collapse upon expiring

Question 7

boyle’s law

Answer 7

increased volume results in decreased pressure

Question 8

thorax

Answer 8

chest cavity containing lungs; diaphragm as “floor” and only opening is mouth and nasal passages

Question 9

steps to inspiration

Answer 9

1. diaphragm and external intercostal and ab muscles contract to increase thorax volume
2. increased volume results in decreased pressure, allowing lungs to expand
3. expansion creates partial vacuum, air flows in

Question 10

steps to expiration

Answer 10

1. diaphragm relaxes and internal intercostal muscles contract to decrease thorax volume
2. decreased volume results in increased pressure, pushing air out lungs

Question 11

device used to measure lung volume

Answer 11

spirometer

Question 12

types of lung volume

Answer 12

• tidal volume: difference in max and min air at rest
• inspiratory reserve volume: difference in max air and max tidal volume
• expiratory reserve volume: difference in min air and min tidal volume
• vital capacity: difference in max air and min air

Question 13

adaptations of leaves for efficient gas exchange

Answer 13

thin with high surface area, cuticle, epidermis, mesophyll, veins, stomata

Question 14

what is the waxy cuticle of a leaf and what is its purpose?

Answer 14

lipid layer covering leaf secreted by upper and lower epidermis, prevents water loss

Question 15

what is palisade mesophyll and what is its purpose?

Answer 15

densely packed cylindrical cells under upper epidermis, many chloroplasts for photosynthesis

Question 16

what is spongy mesophyll and what is its purpose?

Answer 16

loosely packed cells under palisade mesophyll, few chloroplasts but air spaces for gas exchange

Question 17

veins in plants

Answer 17

• xylem: dead cells forming tubes that transport water
• phloem: living cells forming tubes that distributes water and sugars

Question 18

stomata

Answer 18

non-selective microscopic openings on bottom of leaf allowing gas exchange; opened and closed by guard cells embedded in lower epidermis

Question 19

draw and label a cross section of a leaf

Answer 19

top to bottom: waxy cuticle, upper epidermis, palisade mesophyll, spongy mesophyll with vein to the right, lower epidermis with guard cells embedded

Question 20

factors affecting rate of transpiration

Answer 20

1. higher temperature = more transpiration
2. more light = more transpiration
3. more humidity = less transpiration
4. faster wind = more transpiration

Question 21

what makes haemoglobin saturated?

Answer 21

having each of their 4 Fe atoms bonded to an O

Question 22

cooperative binding

Answer 22

when O binds to haemoglobin, it changes the haemoglobin’s shape, increasing its affinity for O

Question 23

allostery

Answer 23

when CO2 binds to haemoglobin on allosteric sites of the polypeptide regions, it decreases the haemoglobin’s affinity for O

Question 24

allosteric inhibitor

Answer 24

molecule that binds to enzyme’s allosteric sites, preventing it from performing its function

Question 25

how does the Bohr shift increase effectiveness of gas exchange?

Answer 25

if more CO2 binded to haemoglobin results in its lower affinity for O, it will release more O to the body tissues that need it while retrieving more CO2 waste; especially effective with muscle tissue/tissue that respires most

Question 26

what do the x- and y-axes of O dissociation curves represent and what units are used?

Answer 26

partial pressure of O in pO2/mm Hg or kPa and percent haemoglobin saturation

Question 27

what patterns does an O dissociation curve show?

Answer 27

the more O in blood, the more haemoglobin that will be saturated; exponentially increases at first because of cooperative bonding but then plateaus because of 100% saturation

Question 28

what is the percent haemoglobin saturation where tissues undergo cell respiration?

Answer 28

65%

Question 29

what is the percent haemoglobin saturation at the lungs?

Answer 29

95%