Unit 5: Respiration, exchange, and transport Flashcards
(47 cards)
Define respiration
A chemical process which involves the breakdown of nutrient molecules (specifically glucose) in order to release the energy stored within the bonds of the molecule. Cellular respiration just means the same thing as respiration. Respiration can take place with oxygen (aerobically) or without oxygen (anaerobically).
Define aerobic respiration
The chemical reactions in cells that uses oxygen to break down nutrient molecules to release energy.
Define anaerobic respiration
Chemical reactions in cells that breakdown nutrient molecules to release energy without using oxygen.
State the balanced chemical equation for aerobic respiration (as well as the word equation):
Glucose + Oxygen —> Carbon dioxide + Water
C6H12O6 + 6O2 —-> 6CO2 + 6H2O
(recognise that this is the backwards reaction of photosynthesis)
What processes require energy in the human body?
- Muscle contraction (so that we can move parts of our bodies)
- Protein synthesis (by linking amino acids into long chains)
- Cell division (so that we can repair damaged tissues and grow)
- Growth(by making new cells)
- Nerve impulse
- Maintenance of a constant body temperature (37 *C) - so that we can adapt to the changes in external temperature
What is the equation for anaerobic respiration in muscles during vigorous exercise / in animals?
Glucose —> Lactic acid
It does produce energy too but you cant put this in the equation.
What is the equation for anaerobic respiration in microorganism yeast?
Glucose — alcohol + carbon dioxide
In anaerobic respiration in muscles this toxic chemical is produced…
Lactic acid builds up in muscles and blood during vigorous exercise causing a oxygen debt. Lactic acid provides a more acidic environment for you muscle cells - this is what leads to the burning sensation. The lactic acid needs to be oxidised to carbon dioxide and water later. The amount of oxygen required to remove the lactic acid, and replace the body’s reserves of oxygen, is called the oxygen debt. This is why, when the period of activity is over, a person’s breathing rate and heart rate do not return to normal straightaway.
Name and identify (in the human respiratory system):
- lungs
- diaphragm
- ribs
- intercostal muscles
- larynx
- trachea
- bronchi
- bronchioles
- alveoli
- associated capillaries
State and explain the differences in composition between inspired and expired air
Inspired gas (during inhalation):
- More oxygen
- Less CO2
- Less water vapour
Expired gas (during exhalation):
- Less oxygen
- More CO2
- More water vapour
What is the test/practical to see the difference in inspired vs expired air
Use limewater as a test for carbon dioxide
to investigate the differences in composition
between inspired and expired air.
Lime water changes colour when the gas is bubbled through, from colourless to milky. There is more CO2 present in expired air —> it makes limewater change colour more quickly (than inspired air).
List the features of gas exchange surfaces in humans…
… limited to large surface area, thin
surface, good blood supply and good ventilation
with air.
- Alveolar walls are very thin – only a single cell thick – reducing the diffusion distance.
- Capillary walls are very thin – only a single cell thick – reducing diffusion distance.
- Alveolar walls are moist, to prevent the cells from drying out and to allow the gases to dissolve in the water on the alveolar walls. This reduces diffusion distance.
- Alveoli have a very high surface area: volume ratio, making diffusion easier.
- Collectively, the alveoli have a huge surface area, making it possible for large amounts of gas to diffuse at the same time.
- Good blood supply and proper ventilation ensure that steep carbon dioxide and oxygen concentration gradients are maintained. Ventilation, or breathing, is the movement of air through the conducting passages between the atmosphere and the lungs. The air moves through the passages because of pressure gradients that are produced by contraction of the diaphragm and thoracic muscles.
- Gas exchange surfaces are close to an efficient transport system to take gases to and from the exchange surface
- Gas exchange surfaces have a good supply of oxygen (mainly brought in by breathing movements)
Investigate and describe the effects of physical activity on rate and depth of breathing
During exercise there is an increase in physical activity and muscle cells respire more than they do when the body is at rest. The heart rate increases during exercise. The rate and depth of breathing increases - this makes sure that more oxygen is absorbed into the blood, and more carbon dioxide is removed from it.
What is the route that gasses take in the human body?
Pathway of air: nasal cavities (or oral cavity) > pharynx > larynx > trachea > primary bronchi (right & left) > secondary bronchi > tertiary bronchi > bronchioles > alveoli (site of gas exchange)
During gas exchange, oxygen diffuses from the alveoli, across the alveolar membrane and capillary wall, into the bloodstream, to be picked up by the RBCs. Carbon dioxide diffuses from the blood into the alveoli. This causes the partial pressure of oxygen in the alveoli to dwindle and the partial pressure of carbon dioxide in the alveoli to increase.
Note: partial pressure is the pressure of one gas in a mixture of gases. It is proportional to its concentration.
Therefore, inspiration allows the dwindling supply of oxygen in the alveoli to be replenished, and expiration enables the maintenance of a low carbon dioxide concentration.
The steady flow of blood prevents oxygen from building up and keeps bringing more carbon dioxide close to the alveoli.
These two processes help maintain the steep oxygen and carbon dioxide concentration gradient.
Explain the differences in the composition of inspired and expired air
When you inspire air, you are breathing in the air in our atmosphere. This is why inspired air has 21% oxygen, 0.04% carbon dioxide and variable water vapour levels.
While that air is in your alveoli, it loses oxygen to your blood and picks up carbon dioxide from your blood. Because the inside of your body is moist – your mouth has saliva, your nasal cavity and airways are lined with mucus, and your alveoli have a thin layer of water inside – a lot of the water evaporates into the air that you inspired.
So when you expire, the air that you expired has less oxygen, more carbon dioxide and more water vapour than atmospheric air. This is why expired air has 16% oxygen, 4% carbon dioxide and is saturated with water vapour.
Explain the effects of physical activity on rate and depth of breathing in terms of the increased carbon dioxide concentration in the blood, causing an increased rate of breathing
The brain constantly monitors the pH of the blood. If there is a lot of carbon dioxide or lactic acid in the blood, this causes the pH to fall. When the brain senses this, it sends nerve impulses to the muscles that cause breathing movements, the diaphragm and the intercostal muscles. The nerve impulses stimulate these muscles to contract harder and more often. The result is a faster breathing rate and deeper breaths.
Explain the concept of ‘repaying the oxygen debt’
- Frequency and depth of breathing increase when exercising
- This is because muscles are working harder and aerobically respiring more and they need more oxygen to be delivered to them (and carbon dioxide removed) to keep up with the energy demand
- If they cannot meet the energy demand they will also respire anaerobically, producing lactic acid
- After exercise has finished, the lactic acid that has built up in muscles needs to be removed as it lowers the pH of cells and can denature enzymes catalysing cell reactions
- It can only be removed by combining it with oxygen - this is known as ‘repaying the oxygen debt’
- This can be tested by seeing how long it takes after exercise for the breathing rate and depth to return to normal - the longer it takes, the more lactic acid produced during exercise and the greater the oxygen debt that needs to be repaid
Explain the role of goblet cells, mucus and ciliated cells
They protect the gas exchange system from pathogens and particles.
Some of the cells that line the passages through which air moves towards the alveoli are goblet cells. These cells secrete a sticky mucus. As the air passes over the mucus, microorganisms and particles of dust in the air get trapped in it.
There are other cells that have microscopic hair-like extensions called cilia. These beat in a synchronised wave, sweeping the mucus towards the back of the throat. Once there, it is swallowed.
This protects the lungs from any harmful microorganisms, pathogens, that might be in the air, reducing the chance of getting infections in the lungs. It also stops too many particles (eg soot,dust) getting to the lungs where they might cause inflammation.
State that tobacco smoking can cause…
chronic obstructive pulmonary disease (COPD), lung cancer and coronary heart disease.
A person may develop COPD - chronic obstructive pulmonary disease. This condition includes the diseases chronic bronchitis and emphysema . In COPD: smoking damages the bronchioles and can eventually destroy many of the alveoli in the lungs.
Describe the effects on the gas exchange system of tobacco smoke and its major toxic components, limited to carbon monoxide, nicotine and tar
- Chemicals in cigarettes include:
- Tar - a carcinogen (a substance that causes cancer)
- Nicotine - an addictive substance which also narrows blood vessels
- Carbon monoxide - reduces the oxygen-carrying capacity of the blood
Nicotine
- Nicotine narrows blood vessels leading to an increased blood pressure
- It also increases heart rate
- Both of these effects can cause blood clots to form in the arteries leading to heart attack or stroke
Carbon monoxide
- Carbon monoxide binds irreversibly to haemoglobin, reducing the capacity of blood to carry oxygen
- This puts more strain on the breathing system as breathing frequency and depth need to increase in order to get the same amount of oxygen into the blood
- It also puts more strain on the circulatory system to pump the blood faster around the body and increases the risk of coronary heart disease and strokes
Tar
- Tar is a carcinogen and is linked to increased chances of cancerous cells developing in the lungs
- It also contributes to COPD, which occurs when chronic bronchitis and emphysema (two different diseases which are frequently linked to smoking) occur together
-
Chronic bronchitis is caused by tar which stimulates goblet cells and mucus glands to enlarge, producing more mucus
- It destroys cilia and mucus (containing dirt, bacteria and viruses) builds up blocking the smallest bronchioles and leading to infections
- A smoker’s cough is the attempt to move the mucus
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Emphysema develops as a result of frequent infection, phagocytes that enter the lungs release elastase, an enzyme that breaks down the elastic fibres in the alveoli
- This means the alveoli become less elastic and cannot stretch so many burst
- The breakdown of alveoli reduces the surface area for gas exchange
- As it progresses, patients become breathless and wheezy - they may need a constant supply of oxygen to stay alive
Describe the role of anaerobic respiration in yeast during bread-making.
Yeast, a single celled fungus, can respire anaerobically. It breaks down glucose to alcohol. Bread is made from flour, which is made from grinding seeds from cereal crops. Most bread is made from wheat flour. Contains a lot of starch and protein - in particular, a protein known as gluten. The dough is made from mixing the flour with water and yeast.
Amylase enzymes break down some of the starch into maltose and glucose, which the yeast can use in anaerobic respiration. It produces bubbles of CO2. These get trapped in the dough. The gluten makes the dough stretchy. The CO2 bubbles cause the dough to rise.
Anaerobic respiration also produces alcohol, but when the bread is baked this is broken down. When the bread is baked, the yeast is also killed.
Differences between anaerobic and aerobic respiration
Describe 2 features of the trachea
- There is a piece of cartilage called the epiglottis, this either closes or opens up to let things into the trachea. It stops food from going into the trachea.
- The trachea has rings of cartilage around it which keep it open.
- Just below the epiglottis is the voice box, which contains vocal chords, the vocal chords can be tightened by muscles so that they make a noise when air passes over them.
Why do we end up having to resort to anaerobic respiration while doing exercise?
Because while doing intense exercise, our breathing rate increases (CO2 build up thingy), so then the muscles in our lungs must contract more and our heart must pump more. These movements by these muscles takes up energy in themselves. So as you can see our energy demands can grow quite large, just to get to that extra bit of energy we require anaerobic respiration.
