Biology 6 Revision

Biology 6 Revision

The following are for an online biology assessment that I will take on Tuesday June 2, it is called B6 – Respiration and Gas Exchange, which covers Chapter 11 and Chapter 12 in the CIE Biology Textbook (Collins).

Chapter 11 – Gas exchange in humans

Questions

1. Explain as fully as you can why the lungs show adaptations for a rapid rate of diffusion.

Lungs show adaptations for a rapid rate of diffusion. Firstly, they have alveoli growing at the end of the bronchioles, which have a large total surface area of about 70 m2. This allows a lot of diffusion of oxygen and carbon dioxide to happen within the lungs. Secondly, they have thin permeable walls. This keeps the distance between the blood and the air to the minimum and makes it easier for the diffusion of oxygen and carbon dioxide to take place. Thirdly, there is a moist lining inside the alveoli, which dissolve the gases before they diffuse across the walls, again making diffusion easier. Fourthly, there is a high concentration gradient for the gases, delivering carbon dioxide out and taking oxygen in. The high concentration gradient is formed partly because of the diffusion that is happening all the time, and is also because of the ventilation of the lungs which refresh the air in the air sacs. Since diffusion is a passive process and no energy is required, it only occurs when there is a concentration gradient.

2. List the structures of the human respiratory system and, for each structure, explain its role in breathing.

The trachea is the windpipe located under the larynx and connects to the bronchi. The passage that provides air flow to the lungs for respiration. The bronchus are where the branch is divided into bronchioles and are supported by rings of cartilage to prevent collapsing during breathing. The bronchioles are the smaller branches of the bronchus and carry air to the alveoli. The alveoli are sacs that are adapted for the diffusion of oxygen and carbon dioxide into and out of blood.

3. What is the role of the cilia and mucus in the human respiratory system?

The motion fo the cilia forms a wave, which sweeps the sticky mucus produced by the goblet cells together with dust, bacteria and pathogens trapped in it out of the trachea and into the throat. This protects the lungs from damage and infection.

4. Describe what happens during the inhalation in terms of
a) movement of structures in the respiratory system and

During inhalation, the muscle around the diaphragm contracts and the diaphragm flattens (moves down). The external intercostal muscles (those that join the ribs together) contract and make the ribs move upwards and outwards.

b) pressure and volume changes in the thoracic cavity

The pressure inside the thorax decreases and the volume of it increases. This draws air into the lungs.

5. Describe what happens during exhalation in terms of
a) movement of structures in the respiratory system and

During exhalation, the muscle around the diaphragm relaxes so that the diaphragm returns to its normal shape (moves up). The ribcage moves downwards and inwards.

b) pressure and volume changes in the thoracic cavity

The pressure inside the thorax increases and the volume inside it to decreases. This causes air to leave the lungs.

6. Describe and explain the differences in composition between inspired air and expired air.

Inspired air contains a higher percentage of oxygen and a lower percentage of carbon dioxide. Expired air, on the other hand, contains a higher percentage of carbon dioxide (the product of respiration) and a lower percentage of oxygen. This is because the oxygen inside the inhaled air is used for respiration and is diffused into the body. At the same time, carbon dioxide, as the product of respiration, is diffused into the air inside the lungs and come out of the body as part of the expired air. There is also a higher percentage of water vapour in exhaled air than inhaled air because water evaporates from the moist linings of the alveoli due to the warmth of the body.

7. Describe the effects of exercise on the rate and depth of breathing.

The increase of exercising increases the rate and depth of breathing.

End of topic questions

1. a) Define the terms diffusion and gas exchange

Diffusion is the movement of particles from a place with higher concentration to a place with lower concentration. Gas exchange is the exchange of gases between the air and the body through a gas exchange surface such as the lungs.

b) Describe the role of diffusion in gas exchange in humans.

During gas exchange, diffusion happens at the alveoli at the end of bronchioles in humans’ lungs. In the process, oxygen diffuses into the blood from the air and carbon dioxide diffuses out into the air from the blood. This helps the body to get rid of the waste product of respiration and obtain oxygen for more respiration in order to produce energy.

c) Explain how the tissues and organs of the lungs are adapted to maximise the rate of gas exchange.

Firstly, the alveoli at the end of bronchioles have large surface areas of a total of 70 m2, allowing more diffusion to take place. Secondly, the walls of the alveoli are very thin so that diffusion can easily happen. Thirdly, there are moist linings inside the alveoli which dissolve gases before they diffuse, making diffusion easier too. Fourthly, a high concentration gradient is created due to the ventilation of the lungs and the diffusion that happens all the time.

2. Fig. 11.8 shows a model that can be used to demonstrate the role of the diaphragm in breathing.

a) Describe and explain what will happen to the balloon “lungs: when the rubber diaphragm is:

i) pulled down:

When the rubber diaphragm is pulled down, the air pressure inside the balloon lungs will decrease and their volume will increase. This will result in the balloon taking air into itself and become larger.

ii) pulled up.

When the rubber diaphragm is pulled up, the air pressure inside the balloon lungs will increase and their volume will decrease. The balloon will be pushing air out of it and become smaller.

b) Which parts of the body that can be involved in breathing are not included in this model?

The larynx, the trachea, the c-shaped cartilaginous rings and the ribs are all not included in the mode.

3. Fig 11.9 shows a few cells of the epithelium lining the trachea.

a) State where the trachea is found and explain its role in the body.

The trachea is found under the larynx and above the bronchus. It is the wind pipe that provides air flow to the lungs for respiration.

b) Name the type of cell shown by cell A and describe its function.

The cell shown by cell A is a ciliated cell. Its function is to create a wave in the mucus and to gradually sweep the mucus as well as the dirt and microorganisms trapped in it away from the lungs and into the throat.

c) name the type of cell shown by cell B and describe its function.

The cell shown by cell B is a goblet cell. Its function is to produce a sticky fluid called mucus that can trap dirt and microorganisms.

d) Explain the role of these cells in protecting the body.

Together, with the dirt and microorganisms trapped by the mucus produced by the goblet cells and being swept away from the lungs into the throat by the ciliated cells, the lungs will be protected from being damaged or infected and the trachea will be clear without anything blocking it.

Image from MedicalXpress

Chapter 12 – Respiration

Questions

Be clear in your answers that you are using the term respiration to mean cellular respiration, and to use ventilation not respiration when talking about breathing.

1. a) b) c)

oxygen (from ventilation) + glucose (from digested food) –> carbon dioxide (breath out into the air from the alveoli) + water (through sweating, urination) (+ energy) (used in muscles constrictions, keep a balanced temperature in the body, active transport, form chemical bonds during the synthesis of new protein molecules, producing chemical needed for cell growth and division, movement of nerve impulses along neurones)

d) Describe how your answer to part (c) might differ for a camel on a long journey without water, and explain your answer.

The respiration reaction of a camel differs to the respiration reaction of a human. Firstly, camels use fats in their humps instead of glucose. Secondly, the water, as a product of aerobic respiration, isn’t excreted (or very little excreted) by camels but instead is consumed.

2. Where does respiration take place in the body?

Respiration take place in all cells everywhere in the body. (Sample answer: inside cells)

3. Give three examples of the use of energy from respiration in the human body.

Energy from respiration is used on the contraction of muscles, active transport and the synthesis of protein molecules.

4. Write the balanced symbol equation for aerobic respiration.

C6H12O6 + 6O2 –> 6H2O + 6CO2

5. Explain why muscle cells sometimes need to respire anaerobically.

Sometimes muscle cells need to respires anaerobically, for example, during vigorous exercises. Since the oxygen in the muscle cells is rapidly used up, and the cells still requires a large amount of energy so oxygen in the blood is not enough. In this case, humans start to breath anaerobically.

6. Describe the similarities and differences between anaerobic respiration in yeast cells and in animal cells.

In both animal and yeast cells, glucose molecules are broken down to release energy and no oxygen is needed. However, while animal cells directly break glucose into lactic acids and energy, yeast cells break glucose into ethanol, carbon dioxide and energy.

7. Compare the amount of energy released during aerobic respiration and anaerobic respiration of glucose in a muscle cell. During aerobic respiration, a large amount of energy is released with glucose and oxygen. On the other hand, when a muscle cell is respiring anaerobically, no (or little) oxygen is used and a small amount of energy is produced with the same amount fo glucose molecules (for one mole of glucose molecules, only about 150 kJ is produced for anaerobic respiration while 2900 kJ of energy are released when the muscle cell is using aerobic respiration).

8. Explain why bread dough rises and becomes soft and spongy if it is kept warm.

The bread dough rises, becomes soft and spongy because when it is kept warm, yeasts are no longer able to respire aerobically. Therefore, they start to do anaerobic respiration, which produces carbon dioxide as one of the products. Since carbon dioxide is a gas and has very low density, the bubbles of it trapped in the bread dough allows the bread dough to rise in water and become soft and spongy.

End of topic questions

1. a) List the body systems in a human that are involved in supplying the reactants of cellular respiration.

Digestive system (for glucose), respiratory and circulatory system (for oxygen).

b) List the body systems in a human that are involved in removing the products of cellular respiration.

The circulatory system, the respiratory system (to carry carbon dioxide to the alveoli), and the excretory system (for urination).

2. Draw up a table to summarise the similarities and differences between aerobic and anaerobic respiration.

SimilaritiesDifferences
Both produces energyOne requires oxygen, the other does not
Both requires glucoseOne is efficient, the other not so much
Both occur in mitochondriaOne is long-lasting, the other does not last long
Differences and similarities between aerobic and anaerobic respiration

3. a) What was the role of the second set of apparatus? Explain you answer.

By having two sets of apparatus, the state of the limewater can be easily compared. Or else it might be quite hard to identify the limewater as cloudy or not.

b) Suggest what happened to the limewater in the two sets of apparatus.

In the set of apparatus with some woodlice, the limewater will gradually turn cloudy and in the set without woodlice, limewater will remain clear.

c) Explain as fully as you can your answer to part (b).

Apparatus with some woodlice will make the limewater turn cloudy, because since woodlice are organisms, they will respire inside the boiling tube. Carbon dioxide, as one of the waste products of cellular respiration, is released from the woodlice and into the tube of limewater through the delivery tube. As limewater turn cloudy when it meets carbon dioxide, it will do so here as it encounters carbon dioxide from the woodlice. On the other hand, the limewater of the apparatus with no woodlice inside will remain clear, because no respiration had taken place inside those apparatus and therefore no carbon dioxide is formed in the boiling tube and the tube of limewater.

4. A whale takes a deep breath of air and then dives for half an hour. Suggest how energy would be generated in the whale’s muscles over the period of the dive.

The whale will be respiring aerobically because it has enough oxygen stored in its lungs (or close to its lungs).

5. a) Explain why sugar solution is added to the yeast at the start.

Sugar solution is added to the yeast at the start so that the yeast will form ethanol as it breaks down the sugar solution added to it as it is breathing aerobically.

b) i) Explain what would happen if the temperature was lower than this.

At a low temperature yeast will not be used to the environment. It will slow down respiring but will not die either.

ii) Explain what would happen if the temperature was higher than this.

When the temperature was higher than this the cells will become stressed meaning that their content becomes damaged. This might lead to little or no respiration at all and the bread might not become soft and spongy.

Good luck to myself and hope this helps you too!

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