Human Gas Exchange (AQA A Level Biology): Flashcards

The alveoli are tiny sacs with structural adaptations that maximise gas exchange.

A scalpel is a sharp blade used for precise cutting during dissection.

Dissecting scissors are used for lower-precision cutting or for separating layers of tissue during dissection.

During dissection, tweezers/forceps are used for manipulating the specimen, while dissecting pins are used for pinning sections in place.

False.

Scalpel blades should always cut away from the body to prevent injury during dissection.

Responsible use of biological materials means using specimens from a reputable source and ensuring they are disposed of correctly.

A lab coat, gloves and eye protection should be worn to avoid contamination with biological material.

The cartilage rings support the trachea and prevent it from collapsing.

In a dissected mammalian lung, the bronchi can be seen branching into each lung, and the bronchi divide further into smaller bronchioles.

An operculum is a bony flap that covers and protects the gills on each side of a fish's head.

Gill filaments are feathery structures that increase the surface area for gas exchange, while the gill arch supports the gill and can be cut to remove the gill from the fish.

To examine the tracheal system in a large insect, cut along the exoskeleton of the abdomen and add saline solution to highlight the silvery tracheae.

An alveolus is a small air sac in the mammalian lung where gas exchange occurs between the air and the blood.

The walls of alveoli are one cell(s) thick and made up of flattened cells.

Alveolar walls are one cell thick, which provides a short diffusion distance for efficient gas exchange.

A gill filament is a thin projection from the gill arch in fish, providing a large surface area for gas exchange.

The gill arch provides structural support for the gill filaments, holding them in place for efficient gas exchange.

Insect gas exchange structures such as spiracles can be clearly imaged using an electron microscope.

True.

Nuclei are stained and appear as dark dots in thin sections of lung tissue under the microscope.

Lamellae are thin plates on fish gill filaments that increase the surface area available for gas exchange.

The palisade mesophyll contains tightly packed cells for photosynthesis, while the spongy mesophyll has loosely arranged cells for gas exchange.

Stomata allow gas exchange between the inside of the leaf and the atmosphere, enabling uptake of carbon dioxide and release of oxygen and water vapour.

True.

Blood vessels run between alveoli to transport gases to and from the lungs.

A respirometer is an experimental apparatus used to measure oxygen consumption in living organisms by detecting changes in air pressure.

A respirometer measures the volume of oxygen consumed by living organisms.

A respirometer measures oxygen consumption by detecting changes in air pressure.

The movement of the coloured liquid is caused by a decrease in air pressure as oxygen is consumed inside the respirometer.

A three-way tap is a device in a respirometer that can be opened to allow air into the system, resetting the internal pressure and enabling repeat measurements.

Respirometers often include a three-way tap to allow air into the apparatus and a manometer to measure air pressure changes.

A manometer is a narrow tube containing liquid that measures the difference in air pressure between two sealed containers in a respirometer.

True.

The movement of liquid in a manometer reflects the change in gas volume due to pressure differences.

The alveolar epithelium is a layer of thin, flattened cells lining the alveoli that functions as an exchange surface for gases between the alveoli and blood.

The primary function of the alveolar epithelium is to act as an exchange surface for oxygen and carbon dioxide between the alveoli and capillaries.

The alveolar epithelium serves as an exchange surface for gas exchange.

True.

The alveolar walls are only one cell thick, which reduces the diffusion distance for gases.

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration, as occurs during gas exchange in the alveoli.

The lungs contain many alveoli, which increases the surface area available for gas exchange.

The constant flow of blood in capillaries maintains a steep concentration gradient for oxygen and carbon dioxide, which is necessary for efficient diffusion across the alveolar epithelium.

Alveolar epithelium cells are flattened in shape, allowing gases a very short diffusion distance.

The pulmonary ventilation rate is the volume of air an individual breathes per minute.

Tidal volume is the volume of air inhaled or exhaled in one normal breath.

Breathing rate is the number of breaths taken per minute.

Pulmonary ventilation rate = tidal volume × breathing rate

Tidal volume is measured in cm³ (or mL), breathing rate is measured in breaths per minute, and pulmonary ventilation rate is measured in cm³/min.

Pulmonary ventilation rate is calculated by multiplying tidal volume by breathing rate.

Their tidal volume is 0.5 dm³, calculated by dividing pulmonary ventilation rate by breathing rate: 8.0 ÷ 16 = 0.5 dm³.

Ventilation is the process of moving air in and out of the lungs.

During inhalation the diaphragm contracts and flattens and the external intercostal muscles contract.

Gas exchange in the lungs occurs when oxygen diffuses from the air into the blood and carbon dioxide diffuses from the blood into the air.

False.

Breathing out is usually a passive process at rest, but can become active during forced exhalation.

During inhalation, chest volume increases and pressure decreases, causing air to move into the lungs.

Ventilation maintains the concentration gradients of oxygen and carbon dioxide necessary for efficient gas exchange in the lungs.

Lung diseases can reduce lung function by affecting the structure of the alveolar walls and/or by damaging the airways.

Tumours develop due to uncontrolled cell division.

They may interfere with the normal working of the lungs, e.g. by squeezing against blood vessels or blocking airways.

Chronic obstructive pulmonary disease (COPD) includes a range of conditions, such as chronic bronchitis and emphysema.

COPD causes damage to the lungs or airways, reducing air flow and/or the rate of gas exchange.

Fewer / larger alveoli mean the patient has a reduced lung surface area.

This reduces the rate of diffusion.

So less oxygen enters the blood, causing breathlessness.

Less oxygen enters the blood due to the reduced rate of diffusion.

This leads to a reduced rate of respiration.

So less energy is released, causing fatigue.

False.

Reducing the alveolar surface area decreases the rate of gas exchange, as there is less area over which diffusion can take place.

True.

COPD (chronic obstructive pulmonary disease) includes a range of conditions, including chronic bronchitis and emphysema.

No.

An exam question will provide any relevant information about a lung disease.

You are expected to apply your knowledge of the gas exchange system to explain the disease symptoms.

Lung tumours develop due to uncontrolled cell division, and may block the airways or squeeze against blood vessels.

A reduced alveolar surface area lowers the rate of diffusion of oxygen into the blood.

Exposure to pollution and cigarette smoke has been linked to lung disease.

Cigarettes contain:

Cancer-causing chemicals.

Chemicals that affect the blood's ability to transport oxygen.

Chemicals that increase mucus production in the airways.

Air pollution has been linked to:

Worsening COPD.

Asthma.

Lung cancer.

Smoking rates and cancer rates are both higher in men.

As smoking rates in men have decreased, cancer rates in men have also decreased.

Cancer rates in women have increased even though smoking rates in women have decreased.

The data shows a correlation, which does not prove a causal relationship.

It suggests that factors other than smoking may be contributing to the difference in lung cancer rates.

Therefore the data does not fully support the conclusion that smoking alone causes lung cancer.

False.

A correlation shows an association only; it does not prove a causal relationship between the two variables.

You are not expected to know the effects of smoking and air pollution on the lungs.

You need to be able to interpret data relating to their effects on the incidence of lung disease.

Some chemicals in cigarette smoke increase mucus production in the airways, while others reduce the blood's ability to transport oxygen.

Lung cancer rates have only been recorded since the 1970s, so there may not be enough data to draw firm conclusions.

A risk factor is any factor that is linked to an increased probability of suffering from a particular condition or disease.

Risk factors for lung disease include:

Smoking.

Air pollution.

Exposure to certain chemicals at work (genetics and asthma are also risk factors).

OR = 1: no association with the condition.

OR > 1: associated with an increased probability of the condition.

OR < 1: associated with a decreased probability of the condition.

An OR greater than 1 means the factor is associated with an increased probability of worsening COPD.

As 3.26 is the highest value in the study, it has the strongest association with worsening COPD.

A small sample size.

A lack of statistical testing.

A failure to control other variables, e.g. diet.

False.

You are not expected to know the risk factors, but you must be able to interpret data on their relationship to the incidence of lung disease.

Data from risk factor studies are often used to inform government policy.

Examples include health warnings on cigarettes and bans on smoking in public places.

Control variables: other variables such as diet may affect the outcome.

Sample size: must be large enough to represent the population.

Sample demographic: must represent the target group.

The sample does not represent other groups.

So it cannot be used to determine the effect of the risk factor on men, or on women aged 50-60.

It would be unethical to run a controlled experiment, e.g. asking one group to smoke 10 cigarettes daily for 10 years while another avoids smoking.

Instead, researchers ask people about their lifestyle factors and look for patterns in the data.

Statistical tests should be used to determine whether an association between variables is significant or due to chance.

A correlation is an association between two variables.

Positive correlation: as variable A increases, variable B increases.

Negative correlation: as variable A increases, variable B decreases.

A causal relationship (causation) is present when a change in one variable is caused by a change in the other.

Correlation does not equal causation.

The two variables may be linked by a third factor that has not been taken into account by the research.

See the same results repeated across many studies.

Demonstrate that the causal factor occurs before the resulting change.

Demonstrate the causal mechanism.

Carry out controlled trials (this is not always possible).

True.

A correlation coefficient can be calculated to determine the strength of a correlation.

There is an association between the two variables.

Increasing pollution levels are correlated with an increase in COPD (a positive correlation).

The data only shows a correlation, not a causal relationship.

More data would be needed before reaching this conclusion.

Correlation does not equal causation; the two variables may instead be linked by a third factor.

In a negative correlation, as variable A increases, variable B decreases.