chapter 10: respiration in human

Question 1

Why do living things respire?
How do living organisms get energy?

Answer 1

－ Need energy to move, excrete, grow and reproduce
- energy is locked up in food molecules like glucose
- living organisms release energy by consuming these molecules and breaking them down

Question 2

what is aerobic respiration?

Answer 2

• the breakdown of food substances in the presence of oxygen with the release of a large amount of energy
• carbon dioxide is released as waste products

Question 3

What is anaerobic respiration?

Answer 3

It is the breakdown of food substances in the absence of oxygen
- anaerobic respiration releases less energy than aerobic respiration

Question 4

What is the word equation of aerobic respiration of glucose?

Answer 4

Glucose+ oxygen > carbon dioxide + water + a large amount of energy

Question 5

What is the word equation of anaerobic respiration? in yeast

Answer 5

Glucose > ethanol + carbon dioxide+ small amount of energy

Question 6

What are the energy conversion in muscle cells?
(Muscular contractions)

Answer 6

• during muscular contractions
  > muscles first respire aerobically
  > may start panting in order to remove carbon dioxide and take in oxygen at a faster rate
• but there is a limit to the increase in the rate of breathing and heartbeat
• 400 m race, muscular contractions are so vigorous that maximum aerobic respiration is unable to release energy fast enough to meet the demand
• extra energy has to be released if vigorous muscular contractions continue
• muscle cells carry out anaerobic respiration to release this extra energy
• lactic energy is formed in the process

Question 7

What is the word equation for anaerobic respiration in human muscles?

Answer 7

Glucose > lactic acid + energy

Question 8

what is oxygen debt of the muscles and how is it repaid?

Answer 8

• when there is insufficient oxygen to meet the demand of vigorous muscular contractions,
  > muscles are said to incur oxygen debt
• lactic acid concentration builds up slowly in the muscles, and may eventually become high enough to cause muscular pains and fatigue
• the body then needs to rest and recover
• during the period of rest, the breathing rate continues to be fast for some time
  > to provide sufficient oxygen to the muscle cells to repay the oxygen debt
• lactic acid is also gradually removed from the muscles and transported to the liver
• in the liver, some of the lactic acid is oxidised to release energy
  > this energy is used to convert the rest of the lactic acid into glucose
• when all the lactic acid has been converted, the oxygen debt has been repaid
• glucose is then transported back to the muscles and the body is now ready for another race

Question 9

what type of respiration do runners use during sprint races?

Answer 9

• during a sprint race, athelete obtains most of their energy from anaerobic respiration
  > within the short period of time, the oxygen supply to the muscles is insufficient for aerobic respiration to meet the energy needs

Question 10

what is gas exchange?

Answer 10

• the exchange of gases between an organism and the environment

Question 11

how do unicellular organisms carry out gas exchange?

Answer 11

• unicellular organisms have a large surface area to volume ration
  > such organisms do not require any special gas exchange system or oxygen transport mechanisms
• carbon dioxide and oxygen can be efficiently exchanges between the organism and the surrounding water by diffusion
  > through the cell surface membrane

Question 12

how do large animals carry out gas exhange?

Answer 12

• fishes, amphibians and mammals have a comparatively smaller surface area to volume ratio
• external surfaces are often thickened for protection and to prevent water loss
  > surfaces are not suitable for gas exchange
• use special organs such as lungs and gills for gas exchange
• organs have enlarge surface areas and thin coverings
• more oxygen can be absorbed per unit time

Question 13

what are the structures and functions of the nose?

Answer 13

advantage of breathing through the nose are:

> air usually enters the body through the two external nostrils
walls of the nostrils bear a fringe of hairs
the nostrils lead into two nasal passages which are lined with a moist mucuous membrane

advantage of breathing through the nose are:
- dust and foreign particles, including bacteria in the air are trapped by the hairs in the nostrils and the mucus on the mucuous membrane
- as air passes through the nasal passages, it is warmed and moistened
- harmful chemicals may be detected by small sensory cells in the mucous membrane

Question 14

where does the air pass through from the nose to the trachea?

Answer 14

• air in nasal passages enters the pharynx
• air then passes through the larynx then into the trachea
  > through an opening known as the glottis

Question 15

what are the structures and functions of the trachea?

Answer 15

• the trachea ( windpipe) is supported by C-shaped rings of cartilage
• the cartilage keeps the lumen of the trachea open
• the membrane next to the lumen is the epithelium

the epithelium consists of two types of cells:
- gland cells: secrete mucus to trap dust particles and bacteria
- ciliated cells: cells have hair like structures called cilia on their surfaces
> the cilia sweep the dust-trapped mucus up the trachea

Question 16

what are bronchi and bronchioles?

Answer 16

• the trachea divides into two tubes called bronchi (S: bronchus)
  > each bronchus carries air into the lung
• the bronchi are similar structures to the trachea
• each bronchus branches repeatedly, giving rise to numerous bronchioles
• bronchioles: very fine tubes which end in a cluster of air sacs or aveoli

Question 17

what are the structures and functions of aveoli?

Answer 17

• numerous aveoli are found in the lungs, providing a very large surface area for gas exchange
• aveolar walls are very thin, moist and well-supplied with blood capillaries
  -gas exchange between the aveoli and the blood capillaries takes place through the walls of the aveoli

Question 18

how are the lungs adapted for efficient gas exchange?

Answer 18

• the numerous aveoli in the lungs provide a large surface area
• the wall of the aveolus is only one cell thick
  > provides a short diffusion distance for gasses, ensuring a faster rate of diffusion
• a thin film of moisture covers the surface of the whole aveolus which allows oxygen to dissolve in it
• the walls of the aveoli are richly supplied with blood capillaries
  > the flow of blood maintains the concentration gradient

Question 19

How is gas exchanged in the alveoli?

Answer 19

• gas exchange occurs by diffusion
• blood entering the lungs has a lower concentration of oxygen and higher concentration of carbon dioxide
  > than the atmospheric air entering the alveoli in the lungs
• a concentration gradient for oxygen and carbon dioxide is set up between blood and aveolar air
• oxygen diffuses from the aveolar air into the blood capillaries
  > carbon dioxide diffuses in the opposite direction

Question 20

How is oxygen absorbed in your lungs?

Answer 20

• one cell thick aveolar wall that separates the capillaries from the aveolar air is permeable to oxygen and carbon dioxide
• since the aveolar air contains a higher concentration of oxygen than the blood
  > oxygen dissolves in the moisture lining the aveolar walls and diffuses into the blood capillaries
• oxygen combines with haemoglobin in the red blood cells to form oxyhaemoglobin
  > reversible reaction
  > the direction in which the reaction takes place depends on the amount of oxygen in the surroundings
• in the lungs where oxygen concentration is high, oxygen combines with haemoglobin to form oxyhaemoglobin
• when blood passes through oxygen-poor tissues
  > haemoglobin releases oxygen
  > which diffuses through the walls of the blood capillaries into the cells of the tissue

Question 21

how is carbon dioxide removed from your lungs?

Answer 21

• tissue cells produce a large amount of carbon dioxide as a result of aerobic respiration
• as blood passes through these tissues via blood capillaries,
  > C02 diffuses into the blood and enters the red blood cells
• the CO2 then reacts with the water in the RBC to form CARBONIC ACID
  > this reaction is catalysed by carbonic anhydrase which is present in blood cells
• the carbonic acid is then converted into HYDROGENCARBONATE IONS which diffuse out of the RBC
• most of the CO2 is carried as hydrogencarbonate ions in the blood plasma
• a small amount of C02 is also carried and dissolved in the RBC
• in lungs, hydrogencarbonate ions diffuse back into the RBC
  > converted back into carbonic acid and then into water and carbon dioxide
• the carbon dioxide then diffuses out of the blood capillaries and into the aveoli where it is expelled when you breathe out

Question 22

what is the thoracic cavity?

Answer 22

• the chest wall is supported by the ribs
• the ribs are attached dorsally to (at the back) vertebral column (backbone)
  > in a way that they can move up and down
• the ribs are attached ventrally to the sternum
  -humans have 12 pairs of ribs but only the first 10 pairs are attached to the sternum

Question 23

what happens during the process of inspiration/ inhalation?

Answer 23

• when you inspire:
• your diaphragm muscles contracts and the diaphragm flattens
• your external intercostal muscles contract, while your internal intercostal muscles relax
• your ribs move upwards and forward
• the volume of your thoracic cavity increases
• your lungs expand and air pressure inside them decreases as the volume increases
• atmospheric pressure is now higher than the pressure within your lungs
  > forces atmospheric air into your lungs

Question 24

what happens during the process of expiration/exhalation?

Answer 24

• when you expire,
• your diaphragm muscles relaxes and the diaphragm arches upwards
• your intercostal muscles contract while your external intercostal muscles relax
• your rib cage moves downwards and inwards
  > and the sternum also moves down to its original position
• the volume of the thoracic cavity decreases
• your lungs are compressed and air pressure inside them increases as the volume decreases
• pressure within the lungs is higher than the atmospheric pressure
  > forces air out of your lungs to the exterior environment

Question 25

what are the 4 chemicals of tobacco smoke?

Answer 25

• nicotine
• carbon monoxide
• tar
• irritants

Question 26

(chemicals in tobacco smoke)
what are the properties of NICOTINE and what are the effects on the body?

Answer 26

properties:
- addictive drug which causes release of adrenaline ( a hormone)
- makes blood clot easily

effects on the body:
- increases heartbeat rate and blood pressure
- increases the risk of blood clots in arteries
> increase risk of coronary heart disease

Question 27

(chemicals in tobacco smoke)
what are the properties of CARBON MONOXIDE and what are the effects on the body?

Answer 27

properties:
- combines with haemoglobin to form carboxyhaemoglobin
- increases rate of fatty deposits on the inner arterial wall
> increase risk of coronary heart disease

effects on the body:
- reduces the ability of blood to carry oxygen
- narrows the lumen of arteries and leads to increase in blood pressure

Question 28

(chemicals in tobacco smoke)
what are the properties of TAR and what are the effects on the body?

Answer 28

properties:
- causes uncontrolled cell division
- paralyses cilia lining the air passages

effect on the body:
- increased risk of cancer in the lungs
- dust particle trapped in the mucus lining the air passages cannot be removed, increasing risk of chronic bronchitis and ephysema

Question 29

(chemicals in tobacco smoke)
what are the properties of IRRITANTS and what are the effects on the body?

Answer 29

properties:
- it paralyses cilia lining the air passages

effects on the body:
- dust particles trapped in the mucus
> cant removed
> increasing risk of chronic bronchitis and emphysema

Question 30

what are diseases caused by tobacco smoke?

Answer 30

increase risk of lung diseases like:
> chronic bronchitis
> lung cancer
> emphysema

Question 31

what is chronic bronchitis?

Answer 31

when someone is exposed to irritant particles for a prolonged period
- the epithelium lining of air passages becomes inflamed
> excessive mucus is secreted by the epithelium
- the cilia on the epithelium > paralysed
> mucus and dust particles cannot be removed
- air passages become blocked > difficult to breathe
> persistent coughing to clear air passages to breathe
> increase risk of lung infections

Question 32

what is emphysema?

Answer 32

• persistent and violent coughing due to bronchitis > lead to emphysema
• the partition walls between the aveoli break down
  > cuz of persistent and violent coughing
  > decrease SA/V ratio for gaseous exchange
• lungs lose their elasticity and become inflated with air
  > breathing becomes difficult > wheezing and severe breathlessness

Question 33

what is it called when a person suffers from both chronic bronchitis and emphysema?

Answer 33

• chronic obstructive lung disease

‘COLD’

Question 34

what causes lung cancer and what is cancer?

Answer 34

• risk of lung cancer is increased when a person smokes tobacco
• cancer is the uncontrolled division of cells producing outgrowths or lumps of tissues
• smoking also increases risk of cancers of:
  > mouth, pancreas, kidneys, throat and urinary bladder