Chapter 7: Respiration in Humans

Question 1

Define respiration.

Answer 1

Respiration refers to the oxidation of food molecules to release energy.

Question 2

Define aerobic respiration.

Answer 2

Aerobic respiration refers to the breaking down of glucose in the presence of oxygen with the release of a large amount of energy.

Carbon dioxide and water are released as waste products.

Question 3

Chemical equation for aerobic respiration?

Answer 3

C6H12O6 + 6O2 -> 6CO2 + 6H2O (+large amount of energy)

C6H12O6 is the chemical equation for all monosaccharide, incl. glucose

Question 4

Word equation for aerobic respiration?

Answer 4

glucose + oxygen -> carbon dioxide + water (+large amount of energy)

Question 5

Where does aerobic respiration occur (in the cell)?

Answer 5

Mitochondria

Question 6

Can aerobic respiration be catalysed by enzymes?
(Yes / No)

Answer 6

Yes

Catalysts-catalyse CHEMICAL REACTIONS (e.g. respiration)

Question 7

Examples of energy-consuming processes?
(6 pts.)

Answer 7

• Synthesis of new protoplasm for growth & repair
• Synthesis of proteins from amino acids
• Active transport in the absorption of food substances by the small intestine
• Muscular contractions (e.g. heartbeats, respiratory movements, etc.)
• Transmission of nerve impulses
• Cell division (growth)

Question 8

How is energy also released?

Answer 8

As heat, heat energy is circulated around the body by blood to keep you warm (body temperature).

Question 9

What are the differences between breathing and respiration?

Answer 9

1. Breathing-> Physical process of moving air in and out of lungs + gaseous exchange with the environment + intake of oxygen and removal of carbon dioxide
   Respiration-> Chemical process of releasing energy from glucose
2. Breathing-> occurs in the respiratory system
   Respiration-> occurs within cells

Question 10

Define anaerobic respiration.

Answer 10

Anaerobic respiration refers to the breaking down of glucose in the absence of oxygen.

It releases less energy than aerobic respiration, with lactic acid as a waste product.

Question 11

Chemical equation for anaerobic respiration?

Answer 11

C6H1206 -> 2C3H6O3 (+small amount of energy)

Question 12

Word equation for anaerobic respiration?

Answer 12

glucose -> lactic acid (+small amount of energy)

Question 13

Differences between aerobic and anaerobic respiration?
(3 pts.)

Answer 13

1. Aerobic respiration-> Occurs in the presence of oxygen
   Anaerobic respiration-> Occurs in the absence of oxygen
2. Aerobic respiration-> A large amnt of energy is released
   Anaerobic respiration-> A small amnt of energy is produced
3. Aerobic respiration-> Carbon dioxide and water are produced
   Anaerobic respiration-> Only lactic acid is produced (in muscle and liver cells)

Question 14

Define oxygen debt.

Answer 14

Oxygen debt refers to the volume of oxygen needed to convert lactic acid back into glucose.

Question 15

What happens during exercise and why?
(15 pts.)

Answer 15

1. During vigorous muscular contractions, muscle cells first respire aerobically.
2. Panting occurs to remove carbon dioxide and take in oxygen at a faster rate.
3. The heart begins to beat faster so that oxygen and glucose can be transported to muscles at a faster rate.
4. There is a limit to the increase in the rate of breathing and heartbeat.
5. When aerobic respiration alone is unable to release energy fast enough to meet the energy demands of muscle cells, muscle cells also carry out anaerobic respiration to release extra energy.
6. Lactic acid is formed in the process.
7. Energy released from anaerobic respiration and aerobic respiration together helps the muscles to keep contracting.
8. Lactic acid concentrations build up slowly (accumulate) in the muscles, and may disrupt enzyme activity.
9. The body then needs to rest and recover.
10. During the period of rest, breathing rate and heart rate continues to be high for some time.
11. This is to provide sufficient oxygen to muscle cells to repay the oxygen debt (that is incurred due to the need to oxidise lactic acid that is produced from anaerobic respiration).
12. Lactic acid is removed from the muscles via blood and transported to the liver.
13. In the liver, some of the lactic acid is oxidised to release energy, which is then used to convert the remaining lactic acid into glucose.
14. ALL lactic acid is used up-> oxygen debt is repaid.
15. Glucose is then transported back to muscles and the body is ready for another race.

note: all 15 pts are unlikely to come out in the same qn, but it is better to know all
4: phrasing
5: phrasing

Question 16

Basis for studying aerobic respiration in experiments?

Answer 16

If it can be shown that an organism takes in oxygen and gives off carbon dioxide and heat energy, it can be said that it respires aerobically.

Question 17

Basis for studying anaerobic respiration in experiments?

Answer 17

If it can be shown that a [micro]organism
(usually yeast) gives off carbon dioxide in the absence of oxygen, it can be said that it respires anaerobically.

Question 18

State the flow of air in the respiratory system.

Answer 18

Nasal cavity->
Pharynx->
Larynx->
Trachea->
Bronchi->
Bronchioles->
Alveoli

Question 19

State the features and functions of the nasal cavity.
(3 pts.)

Answer 19

-Fringe of hair and mucous layer on the walls of the nasal cavity-> traps dust and foreign particles

-Air is warmed and moistened as it passes through the air passages

-Sensory cells in mucous membrane-> detect harmful chemicals

Question 20

State the features and functions of the trachea.

Answer 20

-Supported by C-shaped rings of cartilage-> ensure that the trachea is always open

-Epithelium of inner walls consist of 2 types of cells:
* Gland cells: secrete mucus-> trap dust particles and bacteria in the air that is channelled to the lungs
* Ciliated cells: have hair-like structures (cilia)-> sweep trapped particles and bacteria in mucus up the trachea and into the pharynx

Question 21

State the features and functions of the bronchi and bronchioles

Answer 21

-Epithelium of inner walls (of bronchi) consist of 2 types of cells:
* Gland cells: secrete mucus-> trap dust particles and bacteria in the air that is channelled to the lungs
* Ciliated cells: have hair-like structures (cilia)-> sweep trapped particles and bacteria in mucus up the bronchi and trachea into the pharynx

-Each bronchus carries air into a lung (similar structure to trachea)

-Each bronchus branches repeatedly, giving rise to numerous bronchioles

-Each bronchiole ends in a cluster of alveoli

Question 22

State the features and functions of the alveoli
(4 pts. for both parts)

Answer 22

Features:
-Inner alveolar surface coated with thin film of moisture-> allows oxygen to dissolve in it

-Alveolar wall and capillary wall only one-cell thick-> shorter diffusion distance for gases, for faster rate of diffusion

-Numerous alveoli in lungs-> increase surface area to volume ratio for gaseous exchange

-Surrounded by numerous blood capillaries-> maintain steep concentration gradient
Conc. gradients of gases between alveolar air and blood maintained by:
* Continuous flow of blood in blood capillaries surrounding alveolus
* Movement of air in and out of alveoli due to breathing

Functions:
-Site of gaseous exchange
1. Oxygen dissolves in thin film of moisture lining alveolar wall
2. Oxygen diffuses through one-cell thick wall of alveoli and blood capillaries into bloodstream
3. Oxygen combines reversibly with haemoglobin to form oxyhaemoglobin in red blood cells
4. Carbon dioxide diffuses from blood into alveolar cavity, which is removed during exhalation

-Conc. gradient of oxygen maintained such that conc. of oxygen in alveolar air > conc. of oxygen in blood

-Conc. gradient of carbon dioxide maintained such that conc. of carbon dioxide in alveolar air < conc. of carbon dioxide in blood

Question 23

How is oxygen transported in red blood cells?

Answer 23

Oxygen molecules bind to haemoglobin reversibly in red blood cells to form oxyhaemoglobin.

Question 24

State the features and functions of the intercostal muscles

Answer 24

Two sets of muscles found between ribs:
* External intercostal muscles
* Internal intercostal muscles

-Antagonistic muscles

-Move ribcage up and down during breathing

Question 25

Describe the events that occur during **inspiration (inhalation)**. (8 pts.)

Answer 25

1. Diaphragm muscles **contract** and diaphragm **flattens** 2. _Internal_ intercostal muscles **relax**, _external_ intercostal muscles **contract**(R.I.C.E) 3. _Ribs_ move **upwards and outwards** 4. _Sternum_ moves **up and forward** 5. Volume of _thoracic cavity_ **increases** 6. Lungs *expand*-> _air pressure_ inside **decreases** as _volume_ **increases** 7. _Atmospheric pressure_ is now **higher** than pressure within the lungs 8. This **forces** _atmospheric air_ into the lungs

Question 26

Describe the events that occur during **expiration (exhalation)**. (8 pts.)

Answer 26

1. Diaphragm muscles **relax** and diaphragm **arches upwards** 2. _External_ intercostal muscles **relax**, _internal_ intercostal muscles **contract** (E.R.I.C) 3. _Ribs_ move **downwards and inwards** 4. _Sternum_ moves **down** to its original position 5. Volume of _thoracic cavity_ **decreases** 6. Lungs are *compressed*-> _air pressure_ inside **increases** as _volume_ **decreases** 7. _Atmospheric pressure_ is now **lower** than pressure within the lungs 8. This **forces** _air out of lungs_ into the exterior environment

Question 27

Differences between inspired and expired air? (6 pts.)

Answer 27

_OXYGEN:_ **Inspired air**-> ab 21% **Expired air**-> ab 16.4% _CARBON DIOXIDE:_ **Inspired air**-> ab 0.03% **Expired air**-> ab 4.0% _NITROGEN:_ **Inspired air**-> ab 78% **Expired air**-> ab 78% _WATER VAPOUR:_ **Inspired air**-> Variable (rarely saturated) **Expired air**-> Saturated (water evaporates from the surfaces of the alveoli) _TEMPERATURE:_ **Inspired air**-> Variable **Expired air**-> ab body temp., 36.9/37 'C _DUST PARTICLES:_ **Inspired air**-> Variable, but usually present **Expired air**-> Little, if any

Question 28

What is the stimulus for breathing?

Answer 28

High concentration of carbon dioxide in blood or alveolar air (NOT lack of oxygen) ## Footnote When there is too little carbon dioxide in lungs, breathing movements do not occur.

Question 29

State the chemicals in tobacco smoke

Answer 29

Nicotine Carbon monoxide Tar Irritants

Question 30

Properties and effects on body of **nicotine**?

Answer 30

_Properties:_ * **Addictive** drug, causes **release of adrenaline** (hormone) * **Makes blood clot** easily _Effects on body:_ * *Increases* **heartbeat rate** and **blood pressure** * *Increases* risk of **blood clots** in the **arteries**(incl. coronary artery)-> increased risk of coronary heart diseases-> stroke

Question 31

Properties and effects on body of **carbon monoxide**?

Answer 31

_Properties:_ * **Combines irreversibly** with *haemoglobin* to form _carboxyhaemoglobin_ * Increases rate of **fatty deposits** on *inner arterial wall* _Effects on body:_ * **Reduces oxygen-carrying capability** of *red blood cells* as there is *_less available haemoglobin to bind to oxygen_* * **Narrows lumen of arteries** (incl. coronary artery)-> increased risk of coronary heart disease

Question 32

Properties and effects on body of **tar**?

Answer 32

_Properties:_ *Causes **uncontrolled cell division** * **Paralyses cilia**, which line the air passages _Effects on body:_ * *Increases* **risk of cancer** in lungs * _Dust particles_ **trapped in** the _mucus_ lining the air passages **cannot be removed**-> increased risks of chronic bronchitis and emphysema

Question 33

Examples, properties and effects on body of **irritants**?

Answer 33

_Examples:_ - Hydrogen - Cyanide - Acrolein - Formaldehyde _Properties:_ * **Paralyses cilia**, which line the air passages _Effects on body:_ * _Dust particles_ **trapped in** the _mucus_ lining the air passages **cannot be removed**-> increased risks of chronic bronchitis and emphysema

Question 34

Description of **chronic bronchitis**? (incl. cause & symptoms)

Answer 34

***_Cause:_*** Prolonged exposure to tar and irritants ***_Description:_*** - _Epithelium lining the airways_ is **inflamed** - There is **excessive mucus secretion** - **Cilia** lining the airways are **paralysed** and **unable to move mucus and dust** up the bronchus and trachea and into the pharynx ***_Symptoms:_*** - **Breathing difficulties** (due to blocked airways) - **Persistent cough** (_as the body's response to clear blocked airways and breathe_)-> increased risk of lung infections

Question 35

Description of **emphysema**? (incl. cause & symptoms)

Answer 35

***_Cause:_*** Persistent and violent coughs from chronic bronchitis ***_Description:_*** - _Partition walls of alveoli_ **break down** due to persistent and violent coughs from bronchitis - This **reduces the surface area to volume ratio** for _gaseous exchange_ - _Lungs_ **lose their elasticity** and become **inflated with air** ***_Symptoms:_*** - **Breathing difficulties** (due to inflated lungs) - **Wheezing** and **severe breathlessness**

Question 36

Description of **cancers caused by smoking**? (incl. cause & examples)

Answer 36

***_Cause:_*** Uncontrolled division of cells caused by tar ***_Description:_*** - Uncontrolled division of cells produces outgrowths or lumps of tissues ***_Examples:_*** _Cancers of:_ - Mouth - Throat - Pancreas - Kidneys - Urinary bladder