respiration in humans (chap 7) -olevel pure bio

what is respiration

the breaking down of food molecules such as glucose to release energy

what is aerobic respiration

• the release of energy by the breakdown of glucose in the presence of oxygen

• produces carbon dioxide and water as waste products

• generates large amount of energy

• some of the energy is converted into heat energy circulated around your body to keep warm

what is the equation for aerobic respiration

examples of energy consuming processes

• synthesis of new protoplasm for growth and repair

• synthesis of proteins from amino acids

• active transport in the absorption of food substances by the small intestine

• muscular contractions such as heartbeats and respiratory movements

• transmission of nerve impulses

• cell division

what is anaerobic respiration

• the breakdown of glucose in the absence of oxygen

• generates small amount of energy

word equation for anaerobic respiration

glucose —> lactic acid

what happens during vigorous activity

• muscle cells need more energy to contract

• aerobic respiration in muscle cells increased

• increased breathing rate to remove carbon dioxide and take in oxygen at a faster rate

• increased heart rate so that oxygen can be transported to muscles at a faster rate

when vigorous activity continues, muscular contracts are so vigorous that maximum aerobic respiration is not enough to release energy fast enough to meet the demands

• muscle cells carry out anaerobic respiration to meet the increased energy demand and lactic acid is formed in the process

what is oxygen debt

• when there is insufficient oxygen to meet the demands of the vigorous muscular contractions, an oxygen debt is incurred

• oxygen debt is the amount of oxygen required to remove lactic acid

how is oxygen debt removed

1. continuation of fast heart rate after activity - continuation of fast transport of lactic acid from the muscle cells to the liver and oxygen from the lungs to the liver for removal

2. continuation of deeper and faster breathing after activity - for fast intake of oxygen by the lungs to obtain oxygen for supply to the liver

3. once lactic acid is removed, oxygen debt is paid.

adaptations of the nasal passage for respiration

• nostrils has a fringe of hairs and is lined with a moist mucous membrane

• dust and foreign particles, including bacteria in the air, are trapped by the hairs in the nostrils as well as by the mucus on the mucous 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

adaptations of the trachea for respiration

epithelium of trachea contains 2 types of cells

• gland cells: secrete muscles to trap dust particles and bacteria

• cillated cells: have hair like particles called cilia on their surfaces. cilia sweep dust-trapped mucus up the trachea towards the pharynx to be coughed out or swallowed.

adaptations of the lungs for efficient gas exchange

• numerous alveoli - large surface area

• walls of the alveoli is only one cell thick - short diffusion distance for gases for higher rate of diffusion

• thin film of moisture covers inner wall of alveolus - allows oxygen to dissolve in it

• walls of alveoli are richly supplied with blood capillaries - flow of blood maintains steep concentration gradient of gases

how does gas exchange occur in the alveolus

• gas exchange in the lungs occur by diffusion

• blood entering the lungs has a lower concentration of oxygen and a 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 alveolar air

• oxygen dissolves into the thin film of moisture on the wall of the alveolus

• the dissolved oxygen then diffuses through the wall of the alveolus and the wall of the blood capillary into the red blood cells

• the oxygen combines with haemogoblin to form oxyhaemogoblin

• carbon dioxide diffuses from the blood into the alveolar air

how is the concentration gradient between the alveolus and blood maintained

• continuous flow of blood through the blood capillaries

• continuous breathing, which causes air in the lungs to be continuously refreshed

what happens during inspiration

• diaphragm muscle contracts and the diaphragm flattens

• external intercostal muscles contract and internal intercostal muscles relax

• ribs and sternum move upwards and outwards

• volume of thoracic cavity increases

• lungs expand and air pressure decreases as the volume increases

• atmospheric pressure is now higher than the pressure within your lungs

• air moves into the lungs

what happens during expiration

• diaphragm muscles relaxes and the diaphragm arches upwards

• internal intercostal muscles contract while the external intercostal muscles relax

• ribs and sternum move downwards and inwards

• volume of thoracic cavity decreases

• lungs are compressed and air pressure increases as the volume decreases

• pressure within the lungs is now higher than atmospheric pressure

• air is forced out of your lungs to the exterior environment

what effects does nicotine have on health

• increases heartbeat rate and blood pressure

• increases risk of blood clots in the arteries, which leads to increased risk of coronary heart disease

• increases risk of arteries to narrow

  • in a pregnant mother, narrow arteries decrease the amount of food substances reaching the fetus, affecting fetal development and may cause miscarriage

what effects does carbon monoxide have on health

• reduces ability of blood to transport oxygen as carbon monoxide binds permanently with haemogoblin. thus, there will be less haemogoblin available to transport oxygen

  • in a pregnant mother, less oxygen reaches the fetus through the placenta which may affect fetal development

• increases risk of coronary heart disease

effects of tar on health

• increases risk of cancer in the lungs as tar can cause uncontrolled cell division

• increases risks of chronic bronchitis and emphysema.

  • tar paralyses cilia lining the air passages. hence, dust particles trapped in the mucus lining cannot be removed

what is chronic bronchitis

• prolonged exposure to irritants from smoking

• causes inflamed lining of bronchus

• excessive mucus secreted by epithelium

• cilia on the epithelium become paralysed

• dust-trapped mucus cannot be removed

• airways become blocked

• persistent coughing to clear the air passages

• increases risk of lung infection

what is emphysema

• persistent and violent coughing due to bronchitis may lead to emphysema

• partition walls between the alveoli break down due to persistent and violent coughing

• decreased surface area for gaseous exchange

• lungs lose elasticity and become inflated with air

• breathing becomes difficult, wheezing and severe breathlessness occurs