Chapter Note: Gas Exchange in Humans | Biology for GCSE/IGCSE - Year 11 PDF Download

 Page 1


Respiration and gas exchange
? Every living cell needs energy for
? Contracting muscles
? Making protein molecules by linking together amino acids into long chains
? Cell division so that we can repair damaged tissues and can grow
? Active transport, so that we can move substances across cell membranes up their concentration
gradients
? Transmitting nerve impulses so that we can transfer information quickly from one part of the
body to another
? Producing heat inside the body to keep the body temperature constant even if the environment
is cold. Homeostasis
? The food is digested and broken down into smaller molecules which are absorbed from the intestine
into the blood. The blood transports the nutrients to all the cells in the body. The cells take up the
nutrients that they need
? Breathing is the muscular movement which keep the respiratory surface supplied with oxygen
? Respiration is a series of chemical reaction which happen in all living cells, in which food is broken
down to release energy, usually by combining it with oxygen
? Aerobic respiration
? The release of energy from glucose by combining with oxygen is called aerobic respiration,
takes place in the mitochondria
? Glucose + oxygen ? carbon dioxide + water (word equation)
? C6H12O6 + 6O2 ? 6CO2 + 6H2O (balanced equation)
? Anaerobic respiration
? The chemical reaction in cells that break down nutrient molecules to release energy without
using oxygen
? Single-celled fungus
¦ Glucose ? alcohol + carbon dioxide
? Humans
¦ Glucose ? lactic acid
Aerobic respiration Anaerobic respiration
Uses oxygen Does not use oxygen
No alcohol or lactic acid is made Alcohol or lactic acid is made
Large amount of energy released from each
molecule of glucose
Much less energy released from each molecules of
glucose
Carbon dioxide made Carbon dioxide is made by yeast and plants, but not
by animals
? When oxygen is inhaled, the waste product carbon dioxide has to be exhaled and for that to happen,
gas exchange takes place
? The surface have to be permeable for it to take place
Page 2


Respiration and gas exchange
? Every living cell needs energy for
? Contracting muscles
? Making protein molecules by linking together amino acids into long chains
? Cell division so that we can repair damaged tissues and can grow
? Active transport, so that we can move substances across cell membranes up their concentration
gradients
? Transmitting nerve impulses so that we can transfer information quickly from one part of the
body to another
? Producing heat inside the body to keep the body temperature constant even if the environment
is cold. Homeostasis
? The food is digested and broken down into smaller molecules which are absorbed from the intestine
into the blood. The blood transports the nutrients to all the cells in the body. The cells take up the
nutrients that they need
? Breathing is the muscular movement which keep the respiratory surface supplied with oxygen
? Respiration is a series of chemical reaction which happen in all living cells, in which food is broken
down to release energy, usually by combining it with oxygen
? Aerobic respiration
? The release of energy from glucose by combining with oxygen is called aerobic respiration,
takes place in the mitochondria
? Glucose + oxygen ? carbon dioxide + water (word equation)
? C6H12O6 + 6O2 ? 6CO2 + 6H2O (balanced equation)
? Anaerobic respiration
? The chemical reaction in cells that break down nutrient molecules to release energy without
using oxygen
? Single-celled fungus
¦ Glucose ? alcohol + carbon dioxide
? Humans
¦ Glucose ? lactic acid
Aerobic respiration Anaerobic respiration
Uses oxygen Does not use oxygen
No alcohol or lactic acid is made Alcohol or lactic acid is made
Large amount of energy released from each
molecule of glucose
Much less energy released from each molecules of
glucose
Carbon dioxide made Carbon dioxide is made by yeast and plants, but not
by animals
? When oxygen is inhaled, the waste product carbon dioxide has to be exhaled and for that to happen,
gas exchange takes place
? The surface have to be permeable for it to take place
? They have other characteristics which help the process to be quick and efficient
? They are thin and allow gases to diffuse across them quickly
? They are close to an efficient transport system to take gases to and from the exchange surface
? They have a large surface area, so that a lot of gas can diffuse at the same time
? They have a good supply of oxygen (often brought by breathing movements)
? The nose and mouth
? The air enters through nose and gets moist, warm and
filtered before it enters lungs
? Inside nose, turbinal bones are covered with thin layer of
cells
? Some cells are called goblet cells that secrete mucus and
others have hair like projection called cilia
? The moving cilia traps bacteria in the mucus
? Cilia are found at the trachea and bronchi so that they waft
the mucus
? Trachea
? From the nose the air passes into the trachea
? At the top of the trachea is a piece of cartilage called
epiglottis, this stops food from entering the trachea. Just
below the epiglottis is the voice box or larynx. This contains
vocal chords. The trachea has a ring of cartilages around it
which keep it open
Page 3


Respiration and gas exchange
? Every living cell needs energy for
? Contracting muscles
? Making protein molecules by linking together amino acids into long chains
? Cell division so that we can repair damaged tissues and can grow
? Active transport, so that we can move substances across cell membranes up their concentration
gradients
? Transmitting nerve impulses so that we can transfer information quickly from one part of the
body to another
? Producing heat inside the body to keep the body temperature constant even if the environment
is cold. Homeostasis
? The food is digested and broken down into smaller molecules which are absorbed from the intestine
into the blood. The blood transports the nutrients to all the cells in the body. The cells take up the
nutrients that they need
? Breathing is the muscular movement which keep the respiratory surface supplied with oxygen
? Respiration is a series of chemical reaction which happen in all living cells, in which food is broken
down to release energy, usually by combining it with oxygen
? Aerobic respiration
? The release of energy from glucose by combining with oxygen is called aerobic respiration,
takes place in the mitochondria
? Glucose + oxygen ? carbon dioxide + water (word equation)
? C6H12O6 + 6O2 ? 6CO2 + 6H2O (balanced equation)
? Anaerobic respiration
? The chemical reaction in cells that break down nutrient molecules to release energy without
using oxygen
? Single-celled fungus
¦ Glucose ? alcohol + carbon dioxide
? Humans
¦ Glucose ? lactic acid
Aerobic respiration Anaerobic respiration
Uses oxygen Does not use oxygen
No alcohol or lactic acid is made Alcohol or lactic acid is made
Large amount of energy released from each
molecule of glucose
Much less energy released from each molecules of
glucose
Carbon dioxide made Carbon dioxide is made by yeast and plants, but not
by animals
? When oxygen is inhaled, the waste product carbon dioxide has to be exhaled and for that to happen,
gas exchange takes place
? The surface have to be permeable for it to take place
? They have other characteristics which help the process to be quick and efficient
? They are thin and allow gases to diffuse across them quickly
? They are close to an efficient transport system to take gases to and from the exchange surface
? They have a large surface area, so that a lot of gas can diffuse at the same time
? They have a good supply of oxygen (often brought by breathing movements)
? The nose and mouth
? The air enters through nose and gets moist, warm and
filtered before it enters lungs
? Inside nose, turbinal bones are covered with thin layer of
cells
? Some cells are called goblet cells that secrete mucus and
others have hair like projection called cilia
? The moving cilia traps bacteria in the mucus
? Cilia are found at the trachea and bronchi so that they waft
the mucus
? Trachea
? From the nose the air passes into the trachea
? At the top of the trachea is a piece of cartilage called
epiglottis, this stops food from entering the trachea. Just
below the epiglottis is the voice box or larynx. This contains
vocal chords. The trachea has a ring of cartilages around it
which keep it open
? The bronchi
? In the thorax, the trachea divides into 2
? The 2 branches are called right and left bronchi
? One bronchus goes to each lung, and then branches into smaller tubes called bronchioles
? The alveoli
? At the end of each bronchiole are many tiny air sacs called alveoli. This is where gas exchange
takes place
? Gas exchange in lungs
? These features of alveoli make it efficient for gas exchange
? They are only 1 cell thick so oxygen o=molecules can easily diffuse into the blood
? Large surface area
? Good supply of oxygen. Breathing movements keep lungs well supplied with oxygen
? Blood is constantly pumped into lungs by pulmonary artery
? Breathing in (inspiration)
? The diaphragm is lowered
? Ribcage is raised
? Volume of the thorax increases, so air is drawn into lungs
? Breathing out (respiration)
? The diaphragm springs up
? Rib cage is lowered
? The volume of thorax decreases, so air is forced out of the lungs
? Gas exchange
? The exchange of gases across a respiratory surface
? For example oxygen is taken into the body and Carbon dioxide is removed from it; gas
exchange also takes place during photosynthesis and respiration of plants
Thorax volume intercostal muscles Diaphragm
Inhalation Increases Contraction of external
intercostal muscles, up
and out
Dome shape to flatten
Exhalation Decreases Relaxation of intercostal
muscles, down and in
Goes back to dome
shaped appearance
? Oxygen uptake by respiring organisms
? A simple respirometer is used. An organism is placed in the boiling tube on top of the wire
gauze. A capillary tube connected to the boiling tube is measured against a ruler and a colored
dye is introduced into it
? With the starting point of the dye measured, the due will move towards the boiling tube as the
organism uses up oxygen in the air
? The carbon dioxide produced by the organism is eliminated by soda lime
? We can measure the rate of respiration by calculating distance traveled by the dye, dividing it by
time it took