respiration

Question 1

aerobic respiration

Answer 1

-the breakdown of food substances in the presence of oxygen, resulting in the release of a relatively large amount of energy. carbon dioxide and water are formed as waste products.
-the energy released is stored in the form of ATP molecules
-in eukaryotic cells, aerobic respiration occurs in the mitochondria
-C6H12O6 + O2 —> 6CO2 + 6H2O + relatively large amount of energy

Question 2

anaerobic respiration

Answer 2

-the breakdown of food substances without oxygen, resulting in the release of a relatively small amount of energy
-anaerobic respiration occurs in the cytoplasm of cells

Question 3

anaerobic respiration in yeasts

Answer 3

-C6H12O6 —> 2C2H5OH + 2CO2 + relatively small amount of energy
-production of wine and beer

Question 4

anaerobic respiration in humans

Answer 4

-C6H12O6 —> 2C3H6O3 + relatively small amount of energy
-during exercise, the muscles contract vigorously to enable movement. this results in high energy demand.
-both the rate of breathing and heart rate increase to enable more oxygen to reach the muscles (so that rate of aerobic respiration can be increased to meet the high energy demand) and carbon dioxide to be removed effectively.
-if the increased oxygen intake is not able to meet the oxygen demand, anaerobic respiration takes place to provide the additional energy required.
-results in the accumulation of lactic acid in the muscle, causing fatigue and muscular pains
-in the liver, lactic acid is oxidised and converted to glucose. the oxygen required to oxidise the lactic acid is the oxygen debt.

Question 5

nostrils

Answer 5

-air from external environment enters the nasal passage through the nostrils

Question 6

nasal passages

Answer 6

-the fringe of hair and mucous layer on walls of nostrils trap dust and foreign particles
-as the air passes through the nasal passages, it is warmed and moistened

Question 7

pharynx

Answer 7

-throat area containing openings to both the trachea and oesophagus

Question 8

larynx

Answer 8

-cartilaginous structure, contains elastic vocal cords

Question 9

trachea

Answer 9

-contains c-shaped rings of cartilage, prevents trachea from collapsing and keeps airways open

Question 10

bronchi

Answer 10

-trachea divides into bronchi

Question 11

inner walls of the trachea and bronchi

Answer 11

-gland/ goblet cells secrete mucus that trap dust particles and bacteria in the air that is inhaled
-ciliated cells have cilia that sweep the mucus containing dust particles and bacteria upwards and out of the airways

Question 12

alveoli

Answer 12

-are the site of gaseous exchange
-numerous alveoli in the lungs increase the total surface area for gaseous exchange
-are well-supplied with blood capillaries to enable the efficient exchange of gases
-alveolar surface is coated with a thin film of water
-epithelium of an alveolus is only one cell thick

Question 13

inspiration

Answer 13

-diaphragm contracts and flattens down
-external intercostal muscles contract and internal intercostal muscles relax
-the rib cage is raised upwards and outwards
-thoracic volume increases
-pressure in thoracic cavity decreases below atmospheric pressure, so air is drawn into the lungs

Question 14

expiration

Answer 14

-diaphragm relaxes and arches up
-external intercostal muscles relax and internal intercostal muscles contract
-the rib cage moves downwards and inwards
-thoracic volume decreases
-pressure in thoracic cavity increases above atmospheric pressure, lungs are compressed and air is pushed out of the lungs

Question 15

stimulus for breathing

Answer 15

-carbon dioxide
-oxygen concentration in blood has no effect on breathing rate

Question 16

composition of inhaled air

Answer 16

-oxygen 21 %, carbon dioxide 0.03 %, nitrogen 78 %, water vapour variable, room temperature, dust particles variable

Question 17

composition of exhaled air

Answer 17

-oxygen 17 %, carbon dioxide 4 %, nitrogen 78 %, water vapour saturated, body temperature, dust particles absent

Question 18

adaptations of alveoli

Answer 18

-large numbers of alveoli increases the total surface area for quick diffusion of gases during gaseous exchange
-alveoli epithelium and blood capillary wall is one cell thick so short distance allows quick diffusion of gases between alveoli and blood capillary
-thin layer of moisture on the surface of alveoli allows gases to dissolve in and easily diffuse into the blood in the capillaries
-maintenance of a steep concentration gradient between alveoli and blood so that diffusion of substances can occur more quickly

Question 19

transport of carbon dioxide

Answer 19

can be transported in 3 ways,
-majority transported in the form of bicarbonate ions dissolved in blood plasma to be transported to the lungs
-a small percentage dissolves directly in blood plasma
-a small percentage can bind to haemoglobin

-carbonic anhydrase catalyses the first reversible reaction CO2 + H2O —> H2CO3 (carbonic acid) —> HCO3- (bicarbonate ion) + H+

Question 20

components of tobacco smoke

Answer 20

-nicotine stimulates release of adrenaline, increased heart rate and blood pressure. makes blood clot more easily, hence increased risk of coronary heart disease. highly addictive.
-tar has cancer causing chemical. usually lung cancer, paralysing cilia, hence dust particles trapped in mucus cannot be removed. increased risk of bronchitis and emphysema.

Question 21

chronic bronchitis

Answer 21

-caused by prolonged exposure to dust particles in tobacco smoke
-cilia are paralysed, so mucus and dust particles cannot be removed
-persistent coughing to clear air passages in order to breathe
-excessive mucus is secreted by epithelium
-airways become inflamed

Question 22

emphysema

Answer 22

-persistent and violent coughing due to bronchitis may lead to emphysema
-walls between alveoli break down due to persistent and violent coughing
-results in a decreased total surface area for gaseous exchange
-breathing becomes difficult, constantly breathless