1.5 The Respiratory System

Human respiratory system

A system of organs, functioning in the process of gas exchange between the body and the environment, consisting of the trachea, bronchi, alveoli and lungs

Need for a respiratory system

Large organisms require a complex respiratory system in order to obtain a sufficient volume of oxygen to maintain a high level of aerobic respiration and to remove an equivalent volume of waste carbon dioxide

Gaseous exchange

The process where oxygen is taken in and exchanged for carbon dioxide which is a waste product of respiration

Sites of gas exchange

The alveoli of the lungs and respiring cells around the body

Oxygen

A gas that is needed for aerobic respiration to release energy, oxygen is transported into the body by the respiratory system and around the body by the circulatory system

Carbon dioxide

A waste product of respiration that needs to be removed from cells via the blood and removed from the body via the respiratory system

Lungs

The main organs of the respiratory system, responsible for gas exchange where oxygen is exchange with carbon dioxide in the blood

Nasal cavity

A hollow space behind the nose that regulates the flow of air into the respiratory system

Trachea

Allows air to pass to and from lungs

Bronchi

Two short branches at the lower end of the trachea that carry air into the lungs

Bronchioles

Airways in the lungs that are made up of multiple branches, leads from the bronchi to the alveoli

Alveoli

Tiny sacs of lung tissue where gaseous exchange takes place with the blood

An effective exchange surface

Has a large surface area, a good blood supply, is well ventilated for gas exchange and has a thin membrane for diffusion

Capillary network

An interconnecting network of capillaries surrounding the alveoli for optimised gas exchange

Capillaries

Small and thin blood vessels where the exchange of molecules such as oxygen and carbon dioxide takes place, they consist of a single layer of cells

Diaphragm

A large muscle at the bottom of the chest cavity that helps control breathing, when the diaphragm pulls down and contracts to become flat, air can easily enter the lungs

Intercostal muscles

Muscles in between the ribs which move the rib cage during breathing

Pleural membrane

Double-layered membrane that encloses and protects each lung

Pleural fluid

Fluid necessary to prevent friction between the pleural membranes

Mucus and cilia

Help protect the respiratory system, particles and bacteria stick to mucus and the cilia moves the mucus out of the respiratory system to the back of the throat

Surface area to volume ratio

The amount of surface area in relation to how large something is, a larger surface area to volume ratio leads to faster diffusion rates

Diffusion

The movement of substances such as gas particles or substances in solution, from a higher concentration to a lower concentration

Adaptations of the respiratory system

Large surface area due to multiple branches of bronchioles and many alveolar sacs, good blood supply for quick diffusion, well ventilated, ventilation is optimised by effective involuntary muscular action

Need for transport and exchange systems

Larger organisms have smaller surface area to volume ratios and are unable to directly obtain useful substances from their environment like single-celled organisms can

Surface area

The total area of the surface of an object

Surface area to volume ratio

The amount of surface area in relation to how large something is

Large surface area to volume ratio

Leads to faster diffusion rates, as there is more room for particles to diffuse through a membrane

Gas exchange

When oxygen and carbon dioxide move in and out of cells by diffusion

Purpose of gas exchange

Organisms need oxygen for aerobic respiration, they also need to remove carbon dioxide which is a waste product in some organisms

Alveoli adaptations

Has a large surface area, a good blood supply, is moist, is well ventilated for gas exchange and has a thin membrane for diffusion

Moist lining of alveolus

The lining of the alveolus is moist, which increases the rate of diffusion

Wall of capillary

The capillary walls are thin and one cell thick to optimise diffusion between the alveoli and the blood

Many blood vessels surrounding the aveoli

Provide a constant blood supply to maintain a constant diffusion gradient for gas exchange

Specific cells, tissue and sacs adapted for exchange

Alveoli in mammal lungs, guard cells in plants, spongy mesophyll cells in plants

Respiratory system

A system of organs, functioning in the process of gas exchange between the body and the environment, consisting of the trachea, bronchi and lungs

Carbon dioxide

A waste product of respiration that needs to be removed from the body via the circulatory system, also an essential reactant in plants that is transported in to plant leaves via the stomata

Gas exchange in plants

Carbon dioxide diffuses into the plant in exchange for oxygen that diffuses out of the plant, this process is regulated by guard cells in the leaves that can open and close the stomata efficiently

Leaf adaptations as a respiratory surface

Leaves have pores called stomata that can open and close to regulate gas exchange, they also have a layer of cells called the spongy mesophyll that is very spacious allowing room for diffusion and gas exchange

Spongy mesophyll

Loose tissue beneath the palisade layer of a leaf, has many air spaces between its cells and an increased surface area for diffusion

Lungs

Are specialised in gas exchange due to the presence of many tiny sacs called alveoli that are adapted for diffusion due to being moist, one cell thick and surrounded by capillaries

Aerobic respiration

Cell respiration which happens in the presence of oxygen in the mitochondria of the cell, in animals and plants

Anaerobic respiration

Cell respiration which happens in the absence of oxygen

Fermentation

Anaerobic respiration in plant and yeast cells which produces ethanol and carbon dioxide

Word equation for fermentation

Glucose -> carbon dioxide + ethanol (+energy)

Uses of fermentation

The manufacture of bread and alcoholic drinks

Glucose

A simple sugar that is an important energy source in living organisms, the only reactant for the fermentation reaction

Carbon dioxide (CO2)

A byproduct of fermentation, can be used to make bread and contributes to alcohol production

Anaerobic respiration in yeast practical

Anaerobic respiration can be demonstrated by removing oxygen from the surroundings of yeast, the products of fermentation can then be observed

Removing oxygen

Adding an oil layer will prevent a solution of yeast obtaining oxygen from the air

Sterilisation

It is important that the equipment and glucose solution is sterile, as this could lead to contamination which would affect the results of the experiment

Temperature

Should be controlled and kept warm for yeast fermentation, a set temperature condition can be achieved using a water bath

Yeast solution

The solution that is required for this practical consists of yeast, water and sterile glucose, with a suspended layer of oil above the solution

Acclimatisation

It is important that the yeast solution is given time to settle, particularly when there may still be oxygen present in the solution which would lead to aerobic respiration and affect the results

Bung and delivery tube

The yeast solution should be in a boiling tube with a bung attached to a delivery tube, this allows the gas products of fermentation to be collected

Limewater test

A solution that can confirm the presence of carbon dioxide, if CO2 is bubbled in limewater it will cause the solution to change from colourless to a milky or cloudy precipitate

Water displacement

A method that can be used to measure the rate of fermentation by how much carbon dioxide is produced, carbon dioxide will displace water from an inverted measuring cylinder that can be recorded

Carbon dioxide bubbles

Yeast will produce bubbles of carbon dioxide when undergoing fermentation, CO2 gas will travel down the delivery tube and will form bubbles in an inverted measuring cylinder that is full of water

Measuring rate of fermentation

By measuring how much water has been displaced from the measuring cylinder over a set period of time, the volume of carbon dioxide and the rate of carbon dioxide production (or fermentation) can be determined

Dependent variable

The variable that is measured, in this case it is the rate of fermentation or volume of carbon dioxide produced by yeast for a set duration

Independent variable

The variable that is changed, in this case it could be the temperature that the yeast is fermented at or the type of sugar that is used as a food source for yeast

Control variables

The variables that should be kept the same, in this case it could be the time each test is recorded for, the volume of solutions, the concentration of glucose

Expected results for changed temperature

The rate of fermentation, which is the amount of carbon dioxide produced over a set time, will be greatest when yeast is kept at an optimum temperature

Cellular respiration

Process that releases energy by breaking down glucose and other food molecules

Exothermic reaction

A reaction that releases energy to its surroundings, usually in the form of heat

Purpose of respiration

Releases energy in all cells that organisms can use for heat, movement, growth, reproduction and active uptake/transport

Aerobic respiration

Cell respiration which happens in the presence of oxygen in the mitochondria of the cell

Word equation for aerobic respiration

Glucose + oxygen -> carbon dioxide + water (+energy)

Balanced chemical equation for aerobic respiration

C6H12O6 + 6O2 -> 6CO2 + 6H2O

Word equation for anaerobic respiration

Glucose -> lactic acid (+energy)

Lactic acid

A toxic waste product that is produced during anaerobic respiration in humans and can cause muscle fatigue

Incomplete oxidation

Occurs during anaerobic respiration causing a build up of lactic acid in the muscles

Liver

Receives blood from the muscles with lactic acid and converts the lactic acid back into glucose

Oxygen debt

The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid

Effect of exercise

Increased heart rate, breathing rate and breath volume to supply the muscles with more oxygen

Organisms need energy for

Movement, keeping warm and chemical reactions to make larger molecules

Glucose (C6H12O6)

The main reactant of respiration that is obtained from the digestion of carbohydrates

Oxygen (O2)

A molecule that is essential for the complete oxidation of glucose in aerobic respiration

Carbon dioxide (CO2)

A waste product of respiration that is removed from cells and the body via gas exchange

Water (H2O)

A byproduct of respiration that is either used or removed from the body typically during exhalation or urination

Bell jar model

A simple model of the lung made up of a transparent jar and two balloons, demonstrates ventilation by pulling down on or pushing up on the elastic base which causes the balloons to automatically inflate or deflate due to changes in pressure

Limitations of the bell jar model

The glass jar is not flexible to show the action of intercostal muscles, the glass trachea are not flexible, the elastic base does not correctly show the shape of the diaphragm, the balloons contain open space as opposed to many small alveolar sacs

When breathing in

Intercostal muscles contract pulling the ribcage upwards and outwards, the diaphragm contracts pulling downwards, volume of the thorax increases and pressure decreases, air is drawn into the lungs down a pressure gradient

When breathing out

Intercostal muscles relax pulling the ribcage downwards and inwards, the diaphragm relaxes and domes upwards, volume of the thorax decreases and pressure increases, air is pushed out of the lungs

Ventilation

The movement of air in and out of the lungs in response to muscular action that changes the volume and internal pressure of the thorax or chest, needed to efficiently regulate the exchange of oxygen and carbon dioxide

Percentage composition of inspired air

21% Oxygen, 0.04% Carbon Dioxide, 78% Nitrogen, percentage of water vapour varies

Percentage composition of exhaled air

16% Oxygen, 4% Carbon Dioxide, 78% Nitrogen, saturated with water vapour

Exercise

Planned, structured, repetitive movement intended to improve or maintain physical fitness

Respiration

The process by which cells break down glucose, in order to release energy

Aerobic respiration

Respiration that requires inhaled oxygen, an efficient process that releases a lot of energy

Uses of energy from respiration

Muscular contraction and movement, synthesis of new molecules, metabolic processes

Muscle cells during exercise

Require significantly more energy from respiration

Effect of exercise on cells

Cells need more oxygen and will produce more carbon dioxide as a result of increased respiration

Demand on lungs during exercise

When blood reaches the lungs, a larger volume of air is needed to replace the oxygen used and remove the carbon dioxide produced by this extra respiration

Increased breathing rate

In order to supply more oxygen to the exercising cells, the body increases the rate and depth of breathing

Recovery time

The time taken for the breathing rate to return to normal, following exercise