IGCSE Biology: Breathing and Respiration

respiration

The process by which cells break down simple food molecules to release the energy they contain.

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

aerobic respiration

respiration in the mitochondria that requires oxygen

aerobic respiration equation

C6H12O6 + 6 O2 > 6 CO2 + 6 H2O + energy

anaerobic respiration

respiration without oxygen in the cytoplasm

animal anaerobic respiration equation

C6H12O6 > 2C3H6O3 + energy

glucose → lactic acid + energy released

lactic acid

product of fermentation in many types of cells, including human muscle cells

oxygen debt

the amount of oxygen required after physical exercise to convert accumulated lactic acid to glucose

The amount of oxygen required to remove the lactic acid, and replace the body's reserves of oxygen, is called the oxygen debt.

plants and fungi anaerobic respiration equation

C6H1206 > 2C2H5OH + 2CO2 + energy

fermentation

A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.

mitochondria

organelle that is the site of ATP (energy) production

thorax

chest

ribs

the bones in the chest that protect the heart and the lungs

epiglottis

a flap of cartilage at the root of the tongue, which is depressed during swallowing to cover the opening of the windpipe.

trachea

a large membranous tube reinforced by rings of cartilage, extending from the larynx to the bronchial tubes and conveying air to and from the lungs; the windpipe.

bronchi

two short branches located at the lower end of the trachea that carry air into the lungs.

pleural membrane

double-layered serous membrane that encloses and protects each lung

bronchioles

smallest branches of the bronchi

alveoli

tiny sacs of lung tissue specialized for gas exchange between air and blood

intercostal muscles

the muscles between the ribs that contract to lift and the ribs and move them out when we breath in.

lung

an organ found in air-breathing vertebrates that exchanges oxygen and carbon dioxide with the blood

heart

a hollow, muscular organ that pumps blood throughout the body.

diaphragm

dome-shaped sheet of muscle that separates the thoracic cavity from the abdomen

goblet cells

secrete mucus

mucus

a slimy substance produced in the nose and throat to moisten and protect them by trapping dirt and bacteria

Why do we cough and sneeze?

it is a way in which our body gets rid of foreign particles, irritants, microbes, mucus and bacteria - among other allergens from the throat.

cilia

hairlike projections on the outside of cells that move in a wavelike manner

How are the airways kept clean?

The trachea and larger airways are lined with a layer of cells, with some cells secreting mucus that traps dirt and bacteria. Other cells covered in cilia sweep the mucus and trapped particles out towards the mouth. This prevents dirt and bacteria entering the lungs to prevent infection.

ventilation of the lungs

volume and pressure changes caused by internal and external intercostal muscles, the diaphragm, and abdominal muscles

How does increased volume affect pressure in the lungs?

increasing the volume, decreases the pressure so therefore air enters the lungs

How does decreased volume affect pressure in the lungs?

decreasing the volume, increases the pressure so therefore air leaves the lungs

high air pressure in the lungs:

air moves out (breathe out)

low air pressure in the lungs:

air moves in (breathe in)

breathing in: intercostal muscles

contract causing the ribs to move up and out

breathing in: diaphragm

contract and flatten down

decrease in pressure, allowing air to rush in. Increasing the volume decreases the pressure

breathing out: intercostal muscles

relax causing the ribs to move down and in

breathing out: diaphragm

relax and returns to dome shape

increase in pressure, allowing air to rush out. Decreasing the volume increases the pressure

How does breathing work?

diaphragm contracts, rib cage rises, air inhaled, diaphragm relaxes, rib cage lowers, air exhaled, repeat.

breathing rate

12-20 bpm

Why does breathing rate increase during exercise?

It allows more oxygen to be delivered to the active muscles and extra carbon dioxide can be removed.

gases in the atmosphere

Nitrogen - 78 percent.

Oxygen - 21 percent.

Argon - 0.93 percent.

Carbon dioxide - 0.038 percent.

How does gas exchange occur in the alveoli?

Blood enters the lung through the pulmonary artery and enters the capillaries that surround the alveoli. Air entering the alveoli has a high concentration of oxygen compared to the blood in the capillary so thus oxygen diffuses into the blood. There is more carbon dioxide in the blood than in the air so CO2 diffuses out of the blood.

How do the alveoli maximize gas exchange?

two-cell layer, large surface area, ventilation, blood supply, moist surface

Why is the large surface area of the alveoli so important?

It maximises gas exchange

Why is the two-cell layer of the alveoli important?

It increases the rate of diffusion as there is a shorter distance

Why does the alveoli have a moist surface area?

Gases must dissolve in water before they diffuse across a cell membrane

Why does the alveoli have good blood supply?

The continual removal of oxygen by the capillaries and the arrival of carbon dioxide ensures a steep diffusion gradient for both gases

What does cigarette smoke contain?

nicotine, tar and carbon monoxide

nicotine

an addictive drug found in tobacco that causes a narcotic effect

How does nicotine damage the respiratory system?

It increases heart rate and blood pressures and also promotes the formation of fatty deposits in the artery wall, narrowing the lumen.

narcotic

drug that relieves pain and induces sleep by depressing the central nervous system

coronary heart disease

the clogging of the vessels that nourish the heart muscle; the leading cause of death in many developed countries

heart attack

a condition in which blood flow to part of the heart muscle is blocked, causing heart cells to die

carbon monoxide

a colorless, odorless toxic flammable gas formed by incomplete combustion of carbon.

Why is carbon monoxide dangerous?

As haemoglobin has more affinity to CO than to Oxygen, it causes less oxygen to be carried in the blood, preventing the maximum rate of respiration

tar

a thick, sticky, dark fluid produced when tobacco burns

How does tar damage the respiratory system?

paralyses cilia that moves mucus out of the lungs so thus mucus accumulates in the lungs

smoker's cough

this is a persistent hacking cough resulting from a build-up of mucus in the lungs which occurs when the cilia no longer function

cough

a reflex to keep the airway free of foreign matter.

bronchitis

inflammation of the bronchi with partial obstruction of bronchi due to excessive mucus secretion

emphysema

a condition in which the alveoli lose most of their ability to function because of excessive coughing damaging the walls

lung cancer

malignant tumor arising from the lungs and bronchi

Why is a smoker more likely to be out of breath running?

-Cigarettes contain carbon monoxide. Haemoglobin prefers to bind to carbon monoxide so thus reduces oxygen carried in the blood which prevents the maximum rate of respiration.

-Tar paralyses the cilia so thus mucus can only be removed by coughing. Coughing damages the alveoli.

When the alveoli are damaged, surface area for gas exchange is reduced. Muscles used for ventilation work harder to breathe deeper for gas exchange.

Why are smokers more likely to have a heart attack?

-Nicotine promotes the formation of fatty deposits in the artery wall which narrows the lumen. Less blood is able to flow which could cause blockages in the coronary artery. As less blood is able to flow, there is less oxygen for respiring heart muscle cells which kills cells.

microorganism

a small living plant or animal seen only with a microscope; a microbe