Respiration & the Respiratory System in Humans (WJEC GCSE Science (Double Award): Biology): Flashcards

As the molecule ATP (adenosine triphosphate).

The energy released during aerobic respiration is in the form of a molecule called ATP.

In the mitochondria.

True.

Aerobic respiration breaks glucose down completely, so it releases far more ATP per glucose molecule than anaerobic respiration.

The incomplete breakdown of glucose in the absence of oxygen to release energy and produce lactic acid.

glucose → lactic acid

Energy is released during the reaction.

During vigorous exercise, when the body cannot deliver oxygen to the muscles fast enough for aerobic respiration alone.

Anaerobic respiration in human cells produces lactic acid as its product.

The extra oxygen that must be taken in after exercise to break down the lactic acid built up during anaerobic respiration.

Lactic acid lowers the pH of the cells, making them more acidic. This could denature the enzymes inside them.

To take in the extra oxygen needed to break down the lactic acid that built up during anaerobic respiration. This is called repaying the oxygen debt.

The heart keeps pumping quickly to deliver oxygen to the muscles so the lactic acid can be broken down.

False.

In human cells anaerobic respiration produces lactic acid only. Carbon dioxide and water are products of aerobic respiration.

False.

Anaerobic respiration takes place in the absence of oxygen.

Glucose is only incompletely broken down in anaerobic respiration, so less ATP is released per molecule of glucose.

• Aerobic: glucose is broken down completely

• Anaerobic: glucose is broken down incompletely

Anaerobic respiration produces less ATP per molecule of glucose than aerobic respiration.

False.

Aerobic respiration releases many more ATP molecules per glucose molecule, because the glucose is broken down completely.

• To take in enough oxygen to support aerobic respiration

• To remove the carbon dioxide produced during respiration

• Nasal cavity

• Trachea

• Bronchi

• Bronchioles

• Alveoli

• Lungs

• Diaphragm

• Ribs

• Intercostal muscles

The windpipe, which connects the nose and mouth to the lungs.

It warms and humidifies inspired air and removes airborne particles and debris before the air reaches the lungs.

Trachea → bronchi → bronchioles → alveoli

Tiny air sacs surrounded by a network of capillaries, which are the site of gas exchange in the lungs.

It is a sheet of muscle beneath the lungs that changes the volume of the thorax, allowing inspiration and expiration.

• The ribs surround and protect the lungs, and move to aid breathing

• The intercostal muscles between the ribs control this movement, causing inspiration and expiration

The bronchioles are the smallest tubes in the lungs, branching from the bronchi and connecting to the alveoli.

Mucus traps particles, dust and pathogens such as bacteria and viruses, preventing them from reaching the lungs and damaging the cells there.

Cilia are tiny hair-like structures that beat to push mucus up the airways towards the nose and throat, where it can be removed.

The airways are lined with cilia, which beat to move mucus upwards.

False.

Gas exchange takes place in the alveoli. The bronchi are simply large tubes that carry air towards them.

True.

Mucus traps particles and pathogens, and cilia sweep the mucus up and out of the airways.

So that oxygen can be delivered to respiring cells fast enough. Diffusion across the body surface alone would be too slow.

Breathing in. Air is drawn into the lungs because the pressure inside them falls below the pressure outside the body.

Breathing out. Air is forced out of the lungs because the pressure inside them rises above the pressure outside the body.

The diaphragm contracts and flattens.

This increases the volume of the thorax, so the pressure decreases and air is drawn in.

The diaphragm relaxes and moves back into its domed shape.

This decreases the volume of the thorax, so the pressure increases and air is forced out.

They contract, pulling the ribs up and out.

This increases the volume of the thorax, decreasing the pressure so air is drawn in.

They relax, so the ribs drop down and in.

This decreases the volume of the thorax, increasing the pressure so air is forced out.

The volume of the thorax increases, so the pressure inside the lungs falls below the pressure outside the body.

Air always moves from high to low pressure, so it flows into the lungs.

During inspiration the volume of the thorax increases and the pressure inside the lungs decreases.

The diaphragm is a sheet of muscle that separates the chest cavity from the abdomen.

The thorax.

False.

The diaphragm relaxes during expiration, returning to its domed shape. It contracts during inspiration.

True.

Inhalation and inspiration both mean breathing in. Exhalation and expiration both mean breathing out.

Differences in pressure between the inside of the lungs and the air outside the body.

The diaphragm contracts and flattens.

The intercostal muscles contract, pulling the ribs up and out.

The volume of the thorax increases.

The pressure in the lungs decreases, so air is drawn in.

The process of ventilation, illustrating inspiration and expiration in the human respiratory system.

• Glass tube → trachea

• Balloons → lungs

• Bell jar → thorax or chest cavity

• Rubber sheet → diaphragm

The volume inside the jar increases, so the pressure decreases.

Air is drawn in through the glass tube and the balloons inflate. This models inspiration.

The volume inside the jar decreases, so the pressure increases.

Air is pushed out and the balloons deflate. This models expiration.

So that air can only enter and leave through the glass tube. Otherwise the pressure inside the jar could not change.

In the bell jar model, the rubber sheet represents the diaphragm.

In the bell jar model, the balloons represent the lungs.

The glass tube is rigid, whereas the real trachea is flexible and can bend as the body moves.

The bell jar cannot move, whereas the real chest cavity and ribs move up and out during breathing.

The balloons are hollow and simply air-filled, whereas real lungs contain millions of tiny alveoli.

The rubber sheet is pulled down, whereas the real diaphragm contracts and flattens.

False.

The bell jar is rigid and cannot move, so the model cannot show the movement of the ribs and intercostal muscles.

False.

The balloons inflate because the pressure inside the jar falls, drawing air in through the glass tube. Nothing is blown in.

It makes the link between volume, pressure and air movement easy to see, which is difficult to observe directly inside the body.

At the end of the bronchioles.

• End of bronchiole

• Wall of alveolus

• Moist lining of alveolus

• Wall of capillary

• Red blood cells and plasma

It is one cell thick and has a moist lining.

A network of capillaries containing red blood cells and plasma.

• Oxygen diffuses from the alveoli into the blood

• Carbon dioxide diffuses out of the blood into the alveoli

It gives a short diffusion distance between the air in the alveolus and the blood in the capillary, so gases diffuse quickly.

Gases dissolve in the moisture, which allows them to diffuse across the alveolar wall more easily.

It maintains the concentration gradient by constantly bringing blood that is high in carbon dioxide and low in oxygen, and carrying oxygenated blood away.

Breathing keeps the alveolar air high in oxygen and low in carbon dioxide, maintaining a steep concentration gradient for diffusion.

Many small sacs give a very large surface area to volume ratio, which maximises the rate of diffusion.

• Large surface area, because there are millions of alveoli

• Walls one cell thick, giving a short diffusion distance

• Moist lining, so gases dissolve

• Good blood supply and ventilation, which maintain the concentration gradient

The wall of an alveolus is only one cell thick, which gives a short diffusion distance.

Gas exchange in the alveoli takes place by the process of diffusion.

False.

Gas exchange happens by diffusion, which is a passive process and requires no energy.

True.

Alveolus is the singular and alveoli is the plural.

• Inspired air: 21%

• Expired air: 16%

• Inspired air: 0.04%

• Expired air: 4%

Oxygen is removed from the blood by respiring cells, so the blood returning to the lungs has a lower oxygen concentration and less oxygen diffuses back out.

Carbon dioxide is produced by respiring cells and diffuses into the blood. It is then carried to the lungs and diffuses into the alveoli to be breathed out.

78% in both inspired and expired air.

Nitrogen is not used by the body, so the same amount is breathed in and out.

Water evaporates from the moist lining of the alveoli into the air in the lungs, helped by the warmth of the body.

Limewater tests for carbon dioxide.

It is colourless, and turns cloudy or milky when carbon dioxide is bubbled through it.

The limewater the air is drawn through when breathing in stays clear.

The limewater blown into when breathing out turns cloudy.

This shows expired air contains more carbon dioxide than inspired air.

Limewater turns cloudy when carbon dioxide is bubbled through it.

The alveolar air has a high oxygen concentration and the blood in the capillaries has a low oxygen concentration.

Oxygen therefore diffuses down the concentration gradient into the red blood cells.

The blood arriving at the lungs has a high carbon dioxide concentration and the alveolar air has a low carbon dioxide concentration.

Carbon dioxide therefore diffuses down the concentration gradient into the alveoli.

Expired air contains about 16% oxygen, compared with about 21% in inspired air.

False.

Expired air still contains about 16% oxygen. Only some of the inhaled oxygen is absorbed into the blood.

True.

Nitrogen is inert and is not used by the body, so it stays at about 78% in both.

The chemicals in cigarette smoke paralyse the cilia, so they can no longer beat and sweep mucus out of the airways.

Small particles in the smoke clog the mucus, and the paralysed cilia cannot move it.

Mucus therefore builds up and blocks the smallest bronchioles.

It is an attempt to move the built-up mucus.

Repeated coughing damages the lining of the airways, which narrows them and makes breathing difficult.

The dirt and pathogens trapped in the mucus are not removed from the airways, because the cilia are paralysed.

Frequent lung infections attract phagocytes to the lung tissue.

The phagocytes release enzymes that damage the alveolar walls.

This creates large air spaces, reducing the surface area for gas exchange.

Breathlessness and wheezy breathing.

As the disease progresses, sufferers often need a constant supply of oxygen to stay alive.

Any three of:

• A persistent cough, or coughing up blood

• Coughing up an increased amount of mucus

• Wheezing and breathing difficulties

• Back or shoulder pain

• Sudden weight loss

They interfere with the normal working of the lungs, reducing how effectively gas exchange can take place.

The chemicals in cigarette smoke paralyse the cilia so they can no longer move mucus.

True.

The alveolar walls are broken down, creating large air spaces in place of many small alveoli.

The number of female smokers kept rising into the 1950s and 1960s after male smoking had started to fall.

Lung cancer takes years to develop, so the fall in female rates comes later.