chapter 10: respiration in human Flashcards
Why do living things respire?
How do living organisms get energy?
- 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
what is aerobic respiration?
- 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
What is anaerobic respiration?
It is the breakdown of food substances in the absence of oxygen
- anaerobic respiration releases less energy than aerobic respiration
What is the word equation of aerobic respiration of glucose?
Glucose+ oxygen > carbon dioxide + water + a large amount of energy
What is the word equation of anaerobic respiration? in yeast
Glucose > ethanol + carbon dioxide+ small amount of energy
What are the energy conversion in muscle cells?
(Muscular contractions)
- 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
What is the word equation for anaerobic respiration in human muscles?
Glucose > lactic acid + energy
what is oxygen debt of the muscles and how is it repaid?
- 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
what type of respiration do runners use during sprint races?
- 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
what is gas exchange?
- the exchange of gases between an organism and the environment
how do unicellular organisms carry out gas exchange?
- 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
how do large animals carry out gas exhange?
- 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
what are the structures and functions of the nose?
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
where does the air pass through from the nose to the trachea?
- air in nasal passages enters the pharynx
- air then passes through the larynx then into the trachea
> through an opening known as the glottis
what are the structures and functions of the trachea?
- 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
what are bronchi and bronchioles?
- 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
what are the structures and functions of aveoli?
- 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
how are the lungs adapted for efficient gas exchange?
- 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
How is gas exchanged in the alveoli?
- 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
How is oxygen absorbed in your lungs?
- 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
how is carbon dioxide removed from your lungs?
- 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
what is the thoracic cavity?
- 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
what happens during the process of inspiration/ inhalation?
- 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
what happens during the process of expiration/exhalation?
- 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