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True or False?
Diffusion is movement of particles from low to high concentration.
False.
Diffusion occurs from a region of higher concentration to a region of lower concentration.
What is gas exchange?
Gas exchange is the process of exchanging gases between an organism and its environment.
True or False?
Single-celled organisms exchange gases through complex processes involving specialised organs.
False.
Single-celled organisms, like amoeba, exchange gases by simple diffusion through the cell membrane; this is possible because they have a large surface area to volume ratio.
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True or False?
Diffusion is movement of particles from low to high concentration.
False.
Diffusion occurs from a region of higher concentration to a region of lower concentration.
What is gas exchange?
Gas exchange is the process of exchanging gases between an organism and its environment.
True or False?
Single-celled organisms exchange gases through complex processes involving specialised organs.
False.
Single-celled organisms, like amoeba, exchange gases by simple diffusion through the cell membrane; this is possible because they have a large surface area to volume ratio.
Define the term exchange surface.
Exchange surfaces are the surfaces across which exchange of substances occurs between organisms and their environment, e.g. the internal surfaces of the lungs and intestines.
True or False?
Multicellular organisms lack specialised organs for gas exchange.
False.
Multicellular organisms, like plants and animals, have specialised exchange surfaces to maximise the rate at which gases are exchanged with the environment
What are some features of efficient gas exchange organs?
Efficient gas exchange organs have a large surface area, short diffusion distance, and are well-ventilated to maintain steep concentration gradients. These features all serve to maximise rate of diffusion.
Name the gas exchange organ in plants.
The gas exchange surface in plants is the leaves.
Name the gas exchange organ in humans.
The gas exchange surface in humans is the lungs.
True or False?
Respiration occurs in plant cells.
True.
All living cells respire, including animal cells, plant cells, fungal cells and bacterial cells. There are just a few unusual exceptions to this rule.
True or False?
Oxygen concentration is high inside respiring plant tissues during respiration.
False.
Oxygen concentration is low inside respiring tissues because cells use oxygen in respiration. Oxygen will diffuse into these cells down its concentration gradient.
At night photosynthesis in plant cells stops while respiration continues. In which directions will gases be exchanged in plants at night?
At night oxygen diffuses into plant cells while carbon dioxide diffuses out. This is because respiration is taking place at a higher rate than photosynthesis so oxygen is being used faster than it is produced, while carbon dioxide is produced faster than it is used.
Describe the process of gas exchange in plant tissues where photosynthesis is taking place at a higher rate than respiration.
During photosynthesis carbon dioxide diffuses into photosynthesising tissues, and oxygen diffuses out. This is because photosynthesising plant tissues are carrying out photosynthesis at a higher rate than respiration.
Which gases are involved in gas exchange at the leaf?
Gases involved in gas exchange at the leaf are:
Carbon dioxide
Oxygen
Water vapour
What is the function of the spongy mesophyll in a leaf?
The spongy mesophyll is the region of the leaf where gas exchange takes place. Gases are exchanged between the cells of the spongy mesophyll layer and the surrounding air spaces.
Some photosynthesis also occurs here.
True or False?
The air spaces in a leaf are an adaptation for gas exchange.
True.
The air spaces increase contact between the cells of the leaf and the surrounding air. Gases can diffuse in and out of the spongy mesophyll cells from and into the air spaces.
What is the function of stomata in leaves?
Stomata are small pores present in the epidermis of leaves that allow the movement of gases into and out of leaves by diffusion.
True or False?
Leaves are thin, increasing the diffusion distance for gas exchange
False.
Being thin decreases the diffusion distance for gas exchange in leaves.
What are some adaptations of leaves for gas exchange?
Adaptations of leaves for gas exchange include:
They are thin, reducing the diffusion distance for gases
They are large and flat, increasing their surface area
Stomata allow gases to move in and out
Air spaces around mesophyll cells increase the contact between cells of the leaf and the surrounding air
Define the term stomata.
Stomata (singular stoma) are pores in the leaf epidermis through which gases can diffuse. Each stoma is surrounded by a pair of guard cells.
True or False?
Stomata are primarily located on the upper epidermis of the leaf.
False.
Stomata are predominantly found on the lower epidermis of the leaf in most plants.
What is the relationship between stomata being open or closed, and the rate of photosynthesis in a leaf?
When stomata are open the rate of photosynthesis will increase because carbon dioxide can diffuse into the leaf. When stomata close photosynthesis will stop due to low carbon dioxide availability.
Under what conditions are stomata likely to close?
Stomata close due to low water availability or at low light intensity.
True or False?
Stomata open when water availability is high.
True.
Stomata open when there is plenty of water; this allows gases to be exchanged, increasing the rate of photosynthesis.
True or False?
Plants photosynthesise all the time.
False.
Plants can only photosynthesise when they have access to light, but plant cells respire all the time.
Define the term net diffusion.
Net diffusion is the overall movement of molecules when they move from an area of higher concentration to an area of lower concentration.
How does gas exchange differ between night and day in plants?
There is net diffusion of carbon dioxide into the plant and net diffusion of oxygen out of the plant during the day.
There is net movement of oxygen into the plant and net diffusion of carbon dioxide out of the plant during the night.
True or False?
During the daytime there is net diffusion of carbon dioxide into the leaves of plants.
True.
During the daytime there is net diffusion of carbon dioxide into the plant. This is because light intensity is high and photosynthesis is occurring at a higher rate than respiration.
Why does gas exchange in plants differ between night and day?
Gas exchange in plants is different during the night and day time because of changing light intensity. When light intensity is high during the day plants photosynthesise faster than they respire, but the reverse of this is true at night.
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator, what is the purpose of the hydrogen carbonate indicator?
Hydrogen carbonate indicator is used to study the effect of light intensity on gas exchange in plants by indicating changes in carbon dioxide levels.
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator, what does purple hydrogen carbonate indicator signify?
Purple hydrogen carbonate indicator shows that there is less carbon dioxide than atmospheric levels, suggesting that carbon dioxide is being used in photosynthesis faster than it is being produced in respiration.
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator, what does yellow hydrogen carbonate indicator signify?
Yellow hydrogen carbonate indicator shows an increase in carbon dioxide above atmospheric levels. This suggests that carbon dioxide is being produced faster than it is being used, therefore respiration is occurring at a higher rate than photosynthesis.
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator, what does orange/red hydrogen carbonate indicator signify?
Orange/red hydrogen carbonate indicator shows that carbon dioxide remain at atmospheric levels, suggesting a balance between photosynthesis and respiration rates.
True or False?
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator, the purpose of a control tube is to show the effect of light intensity.
False.
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator a control tube is to show that any colour change occurs due to the effect of light intensity on gas exchange and not any other factor (e.g. that the indicator wouldn't just change colour on its own).
True or False?
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator, the tube wrapped in foil is expected to turn yellow.
True.
The tube is wrapped in foil to block out light, so we would expect it to turn yellow. This indicate an increase in carbon dioxide above atmospheric levels, which occurs because respiration will be taking place faster than photosynthesis.
True or False?
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator, a tube covered in gauze would be expected to remain orange/red.
True.
A tube wrapped in gauze will be exposed to low light intensity, so would be expected to remain orange/red. This indicates no net change in carbon dioxide levels due to balanced photosynthesis and respiration.
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator, what is the variable that is changed? (CORMMS)
The variable that is changed when investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator is the light intensity received by each tube.
This is part of the CORMMS criteria for planning an investigation.
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator, what is the variable that is measured? (CORMMS)
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator the variable being measured is the colour of the hydrogen carbonate indicator after 30 minutes.
This is part of the CORMMS criteria for planning an investigation.
When investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator, what variables should be kept the same? (CORMMS)
The factors that should be kept the same when investigating the effect of light intensity on net gas exchange in plants using hydrogen-carbonate indicator are:
Volume of hydrogen carbonate indicator
Number of leaves
Temperature of the environment
This is part of the CORMMS criteria for planning an investigation.
True or False?
The lungs allow gas exchange in humans.
True.
The lungs are the gas exchange surface in humans.
What is the function of the trachea?
The trachea, or windpipe, connects the nose and mouth to the lungs.
What are the alveoli?
Alveoli are tiny air sacs surrounded by a network of capillaries, serving as the site of gas exchange between the air and the blood.
Describe the role of the bronchi.
The bronchi (singular bronchus) branch off the trachea and carry air into the right and left lungs. They contain mucus to trap dust and pathogens.
True or False?
The only role of the ribs is to protect the organs of the chest cavity.
False.
The function of the ribs is to protect the lungs and heart, and to aid in ventilation.
What is the function of the pleural membranes?
Pleural membranes surround the lungs inside the ribs. They provide protection by reducing friction between the lungs and the ribs during breathing.
Where are the intercostal muscles located?
The intercostal muscles are located between and around the ribs. There are two layers of intercostal muscles; the external intercostals are outside the rib cage and the internal intercostals are inside the ribs.
True or False?
The diaphragm is located at the top of the lungs.
False.
The diaphragm is a sheet of connective tissue located beneath the lungs. It is involved with changing the volume inside the thorax during breathing.
What is the function of the external intercostal muscles?
The function of the external intercostal muscles is to pull the ribcage up. This occurs when the external intercostal muscles contract during inhalation.
What is the diaphragm?
The diaphragm is a thin sheet of muscle that separates the chest cavity (thorax) from the abdomen and plays a crucial role in ventilation.
True or False?
During inhalation the volume of the chest cavity decreases.
False.
During inhalation the volume of the chest cavity increases.
What happens to the diaphragm during exhalation?
During exhalation the diaphragm relaxes and moves upwards into its domed shape, decreasing the volume of the chest cavity.
What happens to the pressure inside the chest cavity during exhalation?
During exhalation the pressure inside the chest cavity increases as the ribs move down and in and the diaphragm moves up. This causes air to be forced out of the lungs.
What is the function of the internal intercostal muscles?
The function of the internal intercostal muscles is to pull the ribcage down. This occurs when the internal intercostal muscles contract during forced exhalation.
Which process takes place at the alveoli?
The process that takes place in the alveoli is gas exchange.
True or False?
Alveoli and surrounding capillaries are surrounded by multiple layers of cells to minimise diffusion distance.
False.
Alveoli and surrounding capillaries are surrounded by single layers of cells to minimise diffusion distance.
True or False?
A layer of moisture on the surface of the alveoli aids diffusion.
True.
Gases dissolve in the layer of moisture on the surface of the alveoli, aiding diffusion.
What are the features of alveoli that make them an efficient exchange surface?
Alveoli are an efficient gas exchange surface because:
They have a large total surface area
They provide a short diffusion distance
They have a good blood supply and good ventilation, maintaining a steep concentration gradient
They are lined with a layer of moisture in which gases can dissolved
How is a steep concentration gradient for both oxygen and carbon dioxide maintained in the alveoli?
A steep concentration gradient for both oxygen and carbon dioxide is maintained in the alveoli as follows:
Good ventilation means that a high concentration of oxygen and a low concentration of carbon dioxide is maintained inside the alveoli
A good blood supply ensures that blood is constantly flowing; this means that the blood immediately next to each alveolus is always low in oxygen and high in carbon dioxide
Smoking can result in emphysema. How does emphysema affect the lungs?
Emphysema can affect the lungs as follows:
Reduce the surface area of the alveoli, so reducing gas exchange
Reduce the elasticity of the alveoli, meaning that breathing is less efficient
Thicken the alveolar lining, increasing the diffusion distance for gas exchange
How does carbon monoxide in cigarette smoke affect the body?
Carbon monoxide binds to haemoglobin and reduces the oxygen-carrying capacity of the blood.
True or False?
Smoking reduces incidence of lung infections such as bronchitis.
False.
Smokers tend to have a higher incidence of lung infections than non-smokers. This is because tar can damage the cilia in the airways, leading to a build-up of mucus and pathogens which can cause infection.
Define the term carcinogen.
A carcinogen is a substance that causes cancer. E.g. tar in cigarette smoke is known to be a risk factor in the development of lung cancer.
True or False?
Smoking is a risk factor in coronary heart disease.
True.
Smoking is one of multiple risk factors in coronary heart disease. This is because smoking can raise blood pressure, increasing the chance of damage to the blood vessel walls.
True or False?
Exercise causes the frequency of breathing to increase.
True.
Exercise causes the frequency of breathing to increase in order to provide more oxygen for respiration.
How can a student's breathing rate at rest be calculated?
Breathing rate is measured in breaths per minute. To calculate a student's breathing rate at rest, either:
Count breaths over a minute
Count breaths for 30 seconds and multiply by 2
Count breaths for 15 seconds and multiple by 4
Repeat several times to obtain an average.
When investigating the effect of exercise on breathing rate, what is the purpose of repeating the investigation for each student several times?
When investigating the effect of exercise on breathing rate, repeating the investigation for each student allows several measurements to be taken. This allows any anomalies to be identified and missed out when calculating a mean.
When investigating the effect of exercise on breathing rate, which variables should be kept the same? (CORMMS)
Variables that should be kept the same when investigating the effect of exercise on breathing rate include:
The age and general fitness level of the students
Students have all eaten similar meals at the same time prior to exercise
The type of exercise
The temperature of the room
This forms part of the CORMMS criteria for planning an investigation.
When investigating the effect of exercise on breathing rate, how can consistency of exercise intensity be ensured for each repeat?
To replicate exercise intensity consistently, give students an exercise type where intensity can be measured, such as running at a certain speed on a treadmill or cycling with a specific power output on a watt bike.
When investigating the effect of exercise on breathing rate, how can the effects of fatigue on results be limited?
When investigating the effect of exercise on breathing rate the effects of fatigue on results can be limited by ensuring that students take a period of rest in between each repeat.