RESPIRATION Summarized

RESPIRATION RELEASES ENERGY FROM FOOD

Respiration is the chemical reactions that break down nutrient molecules in living cells to release energy. In humans, our cells need energy (ATP) for:
• muscle contraction
• making protein molecules: linking together amino acids into long chains
• cell division: to repair damaged tissues and so that we can grow
• active transport
• transmitting nerve impulses
• maintenance of constant body tº
All this energy comes from the food we eat. Water soluble molecules are absorbed from the intestine into the blood. The main energy-providing nutrient: glucose (contains a lot of chemical energy).
There are 2 types of respiration:
1) Aerobic (with O₂)
2) Anaerobic (without O₂)

AEROBIC AND ANAEROBIC RESPIRATION

Respiration releases energy from food.
There are 2 kinds of respiration: Aerobic and Anearobic. The main difference between them is that aerobic respiration involves oxygen and anaerobic respiration does not!

A. Aerobic respiration

The release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of O₂.

B. Anaerobic respiration
Anaerobic respiration: the release of a relatively small amount of energy by the breakdown of food substances in the absence of 0₂.
Anaerobic respiration in muscles during exercise:

Anaerobic respiration in yeast:

Muscles respire anaerobically when exercising vigorously, because the blood cannot supply enough oxygen to maintain aerobic respiration. Howerver, the formation and build-up of lactic acid in muscles causes cramp (muscle fatigue).

The lactic acid that is made is transported to the liver, and later is broken down by combining it with O₂. This extra O₂ is breathed in after the exercise has stopped, and it is known as the oxygen debt.

Bread making

- yeast is mixed with water to activate it then added to flour to make dough
- mixture -----> warm place ------> rise
- yeast releases CO₂ ------> dough rises a warm tº is important because fermentation is controlled by enzymes
- when dough is cooked, high tº kills yeast and evaporates any formed ethanol
- air spaces are left where CO₂ was trapped

Brewing

-yeast is added to a source of sugar (fruit juice or germinated barley grains) and kept in warm conditions
- fermentation (yeast respires the sugar) occurs> ethanol is formed making the drink alcoholic
- CO₂ makes the drink fizzy + sharp flavour

GASEOUS EXCHANGE, ROLE OF MUCUS AND CILIA

Gas exchange usually involves 2 or more gases transferred in opposite directions across a respiratory surface.

1. Structure of the breathing system: the larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries.

2. Gaseous exchange relies on diffusion. To be efficient, the gaseous exchange surface must:
- thin (shorter distance to diffuse)
- moist (allow gases to dissolve)
- large surface area
- have a concentration gradient across surface maintained by movement of air and transport use of gas.

These features are present in gills (fish) and alveoli (lungs).

3. The role of mucus and cilia

-Inside the nose, thin turbinal bones are covered with a layer of cells. Some of which are goblet cells.
- Goblet cells produce a liquid (water + mucus) ---> evaporate ---> moisten nose.
- Cilia: tiny hair-like projections; constantly moving
- Bacteria + dust particles are trapped by cilia and mucus as to not move further inside the gas exchange system.

Try this

State how each feature labeled on the diagram of an alveolus makes the process of gaseous exchange efficient. [5 marks]

Answer
Wall of alveolus - one cell thick (or very thin) so that diffusion happens quickly.
Moist surface- allow O₂ to dissolve making diffusion faster.
Blood is moving - so that's concentration gradient is maintained for O₂ and CO₂
Wall of capillary - one cell thick (or very thin) so that's diffusion happens quickly.
Red blood cells - contain haemoglobin to transport O₂ away from the lungs.

INSPIRED AND EXPIRED AIR, BLOOD PH AND BREATHE RATE

(inspired air: air we breath in
expired air: air we breath out)

The composition of inspired and expired air Testing for CO₂

To investigate the differences in composition between inspired and expired air, we use limewater because it change 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).

Effects of physical activity on breathing
*tidal volume: amount of air during normal, relaxed breathing vital capacity; maximum amount of air breathed in or out in one breath*

During normal breathing:
-depth (tidal volume) : 0.5
- rate: 12 breaths/ minute

During exercise:
-depth:
- rate: over 20 breaths/ minute 5t (depending on age, sex, size & fitness of person)

The total lung volume is greater than vital capacity (some air always remains in the lungs). If not, alveoli walls would stick together, the lung would collapse.

Link between physical activity and rate and depth of breathing

• when you run, muscles in your legs use up a lot of energy.
• cells in the muscles need a lot of O₂ very quickly.
• they combine O₂ + glucose as fast as they can, to release energy for muscle construction ---> a lot of O₂ is needed
• you breath deeper and faster to get more O₂ into your blood.
• your heart beast faster to get O₂ to the leg muscles as quickly as possible.
• a limit is reached the heart and the lung can not supply O₂ to the muscles any faster.
• some extra energy (not much) is produced by anaerobic respiration: some glucose is broken down without combing with 0₂: Glucose ---> lactic acid + energy.
• CO2 and lactic acid concentration in tissue and in the blood † ---> blood pH
• Brain sens the change ---> nerve impulses sent to the diaphragm and the intercostal muscles, stimulating them to contract harder and more often ---> faster and deeper breathing.

Try this
a) The composition of the air inside the lungs changes during breathing.
i) State three differences between inspired and expired air. [3 marks]
ii) Gaseous exchange in the alveoli causes some of the changes to the inspired air. Describe three features of the alveoli which assist gaseous exchange. [3 marks]
b) i) State what is meant by anaerobic respiration [2 marks]
ii)Where does anaerobic respiration occur in human? [1mark]

Answers
a) i) Inspired air contains more 02, less CO2, and less water vapor then expired air.
ii) Three features from: the wall of the alveolus is one cell thick (or very thin)
- there is a moist surface to the alveoli
- there are large number of alveoli
- the air in the alveoli is constantly being replaced.
b) i) The release of energy by cells without the use of oxygen.
ii) In muscle cells.

EFFECTS OF TABACCO SMOKE ON RESPIRATORY SYSTEM

Tobacco smoke contains irritants and carcinogens. Its 4 main toxic chemicals: carbon monoxide, nicotine, smoke particles and tar.

Carbon monoxide:
- combines with haemoglobin in RBC ---> prevents them transporting 02.

Nicotine:
- addictive ---> continual smoking

Smoke particles:
- irritate air passages ---> inflammation + increase mucus production ---> chronic bronchitis.
- presence of smoke particles in alveoli + coughing emphysema (breathlessness)

Tar:
- a carcinogen: increase risk of lung cancer (cell division out of control)
- lines air passages:
- increase mucus production
- paralysing + damaging cilia ---> bronchitis

Common misconceptions
Remember that only nicotine and carbon monoxide enter the blood. Tar and smoke particles do not they stay in the lungs.

Sample question

The table shows the percentage of haemoglobin which is inactivated by CO present in the blood of taxi drivers in a city.

i) Suggest two sources of the CO inhaled by these taxidrivers [2marks]
ii) Some daytime drivers have 5.8% of their Hb affected. Using information from the table, explain which source contributes most to this effect.[2 makrs]
iii) Suggest a reason for the differences, shown in the table, between daytime and night-time drivers. [1 mark]

Studen's answer
i) 1. cigarette smoke ✔
    2. breathing by passengers (wrong)
ii) It must be cigarette smoking because non-smokers have less of their Hb affected. ✔
iii) There could be less car exhaust fumes, containing CO, at night. ✓

Examiner's comments
In part (i), the second answer if biologically incorrect (we breath out CO₂, not CO. The other correct answer was car exhaust gases.
In part (ii), the answer and the explanation were correct.
Part (iii) war a good answer.

VENTILATION, ROLE OF INTERCOSTAL MUSCLES AND DIAPHRAGM

There are 2 sets of muscles which help you to breath:
- intercostal: between the ribs

- diaphragm: a large sheet of muscle and elastic tissue, underneath the lungs and heart.

Figure below shows the relationship between intercostal muscles, diaphragm and ribcage to achieve ventilation of the lungs.

Two set of intercostal muscles are attached to the ribes. They are antogonistic.

1. Breathing in (inhaling)
• The external intercostal muscles contract, they move the ribcage upward and outward---> ↑ volume of the thorax.
• The diaphragm muscles contracts ---> diaphragm moves down
• ↑ (goes up) volume of the thorax
• ↓ (goes down) air pressure in the thoracic cavity air rush into the lungs through the mouth or nose.

2. Breathing out (exhaling)
The opposite happens:
• The internal intercostal muscles contract
• The diaphragm muscles relax ---> diaphragm moves up
• ↓ (goes down) volume of the thorax
• ↑(goes up) air pressure in the thoracic cavity
• air rush out of the lungs.

Summary of Respiration

• Respiration is a series of metabolic reactions that takes place in every living cell. The purpose
of respiration is to release energy from glucose, so that the cell can make use of the energy.
• In aerobic respiration, the glucose is combined with O₂, forming CO₂ and H₂O.
• In anaerobic respiration, the glucose is broken down without being combined with 02. In plants and fungi, this produces alcohol and CO₂.
• In animals (including human) it produces lactic acid.
• Muscles respire aerobically when they are working so fast that they cannot be supplied with O₂ quickly enough. The lactic acid that is made is transported to the liver, and later is broken down by combining it with O₂. This extra O₂ is breathed in after the exercise has stopped, and it is known as the oxygen debt.
• All gas exchange surfaces need to be thin, have a large surface area, be kept moist, and have a good supply of O₂. In larger animals,
a transport system is needed to carry away the CO₂ and bring 0₂.
• The air we breath in travels down the trachea and bronchi, through the bronchioles and into the alveoli.
• Some of these tubes are lined with goblet cells which make mucus, and ciliated cells. The mucus traps dirt, bacteria and other particles
and the cilia sweep the mucus up and away from the lungs.
• Air is drawn into the lungs by the contraction of the external intercostal muscles and the muscles in the diaphragm. These muscle contractions increase the volume of the thorax, which decreases the pressure. Air flows down the pressure gradient and into the lungs.
• Tobacco smoke contains many different substances that harm health. Nicotine is an addictive stimulant, and its intake increases the
risk of developing heart diseases. Tar causes lungs and other cancers. CO₂ reduces the ability of red blood cells to transport O₂. Smoke particles irritate the lungs and can contribute to the development of emphysema.

THE END, SEE YOU ON THE NEXT POST. Posted by Mr James C.