Gas Exchange

Question 1

Explain how the body surface of a single celled organism is adapted for gas exchange

Answer 1

Thin flat shape and large surface area to volume ratio
Short diffusion pathway to all parts of cell for rapid diffusion of o2 and co2

Question 2

Describe the tracheal system f an insect

Answer 2

Spiracles-pores on surface that can open and close to allow diffusion
Trachea-large tubes full of air that allow diffusion
Trancheoles-smaller branches-permeable to allow gas exchange with cells

Question 3

Define gas exchange

Answer 3

Diffusion of oxygen from the air In the alveoli into the blood and carbon dioxide from the blood into the air in the alveoli

Question 4

Describe the gross structure of the human gas exchange system

Answer 4

-air is pulled into the lungs through the trachea
-the trachea divides into 2 bronchi and further divides into bronchioles and terminate in millions of sacs the aveoli

Question 5

How do humans ventilate

Answer 5

Internal and external intercostal muscles work in antagonistic pairs
Inspiration-breathing in:
-external intercostal muscles contract and internal intercostal muscles relax(antagonistic)
-rib cage pulled up and out
-diaphragm contracts and flattens
-increasing volume but decreasing pressure in Thoracic cavity
-air moves into lungs down pressure gradient
Expiration-breathing out
-internal intercostal muscles contract and external intercostal muscles relax
-ribcage moves down and in
-decreasing volume but increasing pressure in thoracic cavity
-air moves out of lungs down pressure gradient

Question 6

What happens in the external intercostal muscles during inspiration(inhalation) and expiration(exhalation)

Answer 6

Inspiration
-contracts moves the Ribs up
Expiration
-relax move ribs down

Question 7

What happens in the internal internalcostal muscles during inspiration(inhalation) and expiration(exhalation

Answer 7

Inspiration
-they relax
Expiration
-contract to pull the ribs in

Question 8

What happens in diaphragm during inspiration (inhalation) and expiration (exhalation)

Answer 8

Inspiration
Contracts and flattens
Expiration
-relaxes and moves up

Question 9

What happens to the lung volume in inspiration(inhalation) and expiration (exhalation)

Answer 9

Inspiration
-increases
Expiration
-decreases

Question 10

What happens to the pressure in thoracic cavity in inspiration(inhalation ) and expiration(exhalation

Answer 10

Inspiration
- decreases
Expiration
-increases

Question 11

What happens to the movement of air inspiration(inhalation) and expiration (exhalation)

Answer 11

Inspiration
-into the lungs
Expiration
-out of the lungs

Question 12

Define pulmonary ventilation

Answer 12

Is the total volume of air that is moved into the lugs during one min(d

Question 13

What is the equation of pulmonary ventilation

Answer 13

Tidal volume (dm3) x ventilation rate ( min-1)

Question 14

What is the essential features in the alveolar epithelium as a surface of which gas exchange takes place

Answer 14

-epithelium is one cell thick to reduce diffusion distance
-permeable to allow diffusion of oxygen and carbon dioxide
-folded so large surface area
-good blood supply from large network of capillaries to maintain concentration gradient

Question 15

Insects don’t have lungs but they do have a tracheal system for gas exchange
Explain how they do this

Answer 15

-trancheoles have thin walls to create a short diffusion distance to cells
- high number of highly branched trancheoles so large surface area for gas exchange
-tracheae provide tubes full of air so fast diffusion into insect tissues
-contraction of abdominal muscles changes pressure in body causing air to move in and out maintaining concentration gradient for diffusion

Question 16

How are insects adapted to prevent water loss and allow efficient gas exchange

Answer 16

-spiracles have valves which can close to prevent water being lost via evaporation and can open for gas exchange
-hairs around spiracles to trap moist air- reducing water potential gradient to reduce water loss-reduces evaporation
Thick waxy cuticle/Waterproof exoskeleton- increases diffusion distance so less water loss via evaporation- reduces evaporation

Question 17

What are the adaptations of gills in the fish for gas exchange

Answer 17

-many gill filaments covered with many lamellae so a large surface area for diffusion
-thin lamellae(surface) gives it a short diffusion pathway
-lamellae has large number of capillaries to remove O2 and bring CO2 so maintain concentration gradient

Question 18

What is the countercurrent flow mechanism

Answer 18

Water flows over the gills In the opposite direction to the flow of blood in the capillaries

Question 19

Explain how the leaves of dicotyledonous plants are adapted for gas exchange

Answer 19

Many stomata - large surface area for gas exchange when opened by guard cells-they close of plant is loosing too much water
Spongy mesophyll contains air spaces for gases to diffuse through
Thin- short diffusion distance

Question 20

What is a xerophytes

Answer 20

Plant adapted to live in very dry conditions

Question 21

How is xerophyte adapted to minimise water loss

Answer 21

-sunken stomata to trap water vapour/moist air so reduced water potential gradient between leaf and air so less evaporation
- curled leaves to trap moisture to increase local humidity
-hairs to reduce leaf surface area and to trap moisture
-thicker cuticle to increase diffusion distance so less evaporation
-fewer stomata

Question 22

Explain how the counter current mechanism in fish gills ensures the maximum amount of the oxygen passes into the blood flowing through the gills.

Answer 22

-water and blood flows in opposite directions
-blood is always passing water with a higher oxygen concentration-as oxygen concentration is higher in water - maintains oxygen concentration gradient between water and blood
-diffusion gradient is maintained through the entire length of the gill lamellae

Question 23

What are the advantages of a counter current mechanism in gas exchange accross gills

Answer 23

-water and blood flow in opposite directions
-maintains diffusion gradient along the entire length of lamellae
-maintains concentration gradient of oxygen as oxygen concentration is higher in the water

Question 24

Describe how oxygen is taken from the alveolus to the blood

Answer 24

-across alveolar epithelium
-into epithelium of capillary

Question 25

Describe how gas exchange occurs I’m the lungs

Answer 25

-Oxygen diffuses from alveolar air space into blood down it’s concentration gradient
-Across alveolar epithelium then across capillary endothelium

Question 26

Explain the importance of ventilation

Answer 26

• brings in air containing higher concentration of oxygen and removes air with lower concentration of oxygen
  -maintaining concentration gradients

Question 27

Suggest why expiration is normally passive at rest

Answer 27

● Internal intercostal muscles do not normally need to contract
● Expiration aided by elastic recoil in alveoli

Question 28

Suggest how lung disease reduce rate of gas exchange

Answer 28

Thickened alveolar tissue- increases diffusion distance
Alveolar wall breakdown reduces surface area
Reduce
Reduce lung elasticity- lung expand so less recoil which reduces concentration gradient of O2 abs CO2

Question 29

Suggest how different lung diseases affect ventilation

Answer 29

-reduce lung elasticity eg fibrosis-lungs expand ‘ and recoil less
-reduce volume in air in each breath
-reducing maximum volume of air breathed out in one breath
-narrow airway and reduce airflow in and out of lungs eg asthma inflamed bronchi
-reducing maximum volume of air breathed out in one second
-reduced rate of gas exchange- increased ventilation rate to compensate for reduced oxygen in blood

Question 30

Suggest how different lung diseases affect ventilation

Answer 30

-reduce lung elasticity eg fibrosis-lungs expand ‘ and recoil less
-reduce volume in air in each breath
-reducing maximum volume of air breathed out in one breath
-narrow airway and reduce airflow in and out of lungs eg asthma inflamed bronchi
-reducing maximum volume of air breathed out in one second
-reduced rate of gas exchange- increased ventilation rate to compensate for reduced oxygen in blood

Question 31

Suggest Ehy people with lung disease experience fatigue

Answer 31

Cells receive less oxygen
Rate of aerobic respiration reduced
Less ATP made

Question 32

Suggest how you can analyse and interpret data to the effects of pollution,
smoking and other risk factors on the incidence of lung disease

Answer 32

● Describe overall trend → eg. positive / negative correlation between risk factor and incidence of disease
● Manipulate data → eg. calculate percentage change
● Interpret standard deviations → overlap suggests differences in means are likely to be due to chance
● Use statistical tests → identify whether difference / correlation is significant or due to chance
○ Correlation coefficient → examining an association between 2 sets of data
○ Student’s t test → comparing means of 2 sets of data
○ Chi-squared test → for categorical data

Question 33

Suggest how you can evaluate the way in which experimental data led to statutory restrictions on the sources of risk factors

Answer 33

● Analyse and interpret data as above and identify what does and doesn’t support statement
● Evaluate method of collecting data
○ Sample size → large enough to be representative of population?
○ Participant diversity eg. age, sex, ethnicity and health status → representative of population?
○ Control groups → used to enable comparison?
○ Control variables eg. health, previous medications → valid?
○ Duration of study → long enough to show long-term effects?
Statistical tests used
● Evaluate context → has a broad generalisation been made from a specific set of data?
● Other risk factors that could have affected results?

Question 34

Explain the difference between correlations and causal relationships

Answer 34

● Correlation = change in one variable reflected by a change in another - identified on a scatter diagram
● Causation = change in one variable causes a change in another variable
● Correlation does not mean causation → may be other factors involved