Respiration In Organisms

The nasal cavity works hard to condition the air you breathe. In very cold weather, the air is dry and cold. Your nose increases blood flow and mucus production to add warmth and moisture. The excess mucus that is not needed drips out, giving you a runny nose.

When you inhale, the air pressure inside the trachea becomes lower than the pressure outside. Without the stiff C-shaped rings of cartilage to hold it open, the soft walls of the trachea would be sucked inward, causing it to collapse. This would block the flow of air and make breathing impossible.

A small flap called the epiglottis normally covers the trachea when you swallow, directing food and drink down the esophagus. If you laugh or talk while swallowing, the epiglottis may not close in time. Food or liquid enters the trachea, triggering a forceful cough reflex to clear the airway and prevent choking.

Newborn babies have a much higher metabolic rate relative to their body size. Their organs are small but need a lot of energy to grow and function. They also have less efficient lungs. Therefore, they breathe much faster than adults, often 30 to 60 times per minute, while adults breathe 12 to 20 times per minute.

Climbing stairs requires your leg and hip muscles to work hard against gravity. Their cells perform rapid cellular respiration to produce energy. This uses up oxygen from your blood and creates carbon dioxide. Your brain detects the low oxygen and high carbon dioxide and increases your breathing rate, which you feel as breathlessness.

Your brain has special sensors that monitor the pH of your blood, which becomes more acidic as carbon dioxide levels rise. When you hold your breath, carbon dioxide accumulates quickly. The brain sends very strong, urgent signals to your diaphragm and rib muscles to breathe. The urge is much stronger from high CO2 than from low O2.

Singers and flute or trumpet players train to exhale very slowly and steadily over a long period. They learn to control the diaphragm and intercostal muscles, preventing the chest from collapsing too quickly. This allows them to hold a note or a phrase for many seconds. This is called diaphragmatic or belly breathing.

Laughing is a complex reflex. When you laugh, your diaphragm and rib muscles undergo a series of quick, involuntary contractions. These contractions push air out of your lungs in short bursts, creating the “ha ha ha” sound. Between bursts, you take quick, small inhalations.

At rest, a person takes about 12 breaths per minute, and each breath moves about 0.5 liters of air. This equals 6 liters per minute. Over 24 hours (1440 minutes), that is 6 x 1440 = 8,640 liters. With light activity, it is often closer to 11,000 liters per day. That is enough to fill over 200 large bathtubs!

In a cockroach, the tracheae branch into finer and finer tubes called tracheoles that reach each and every cell. Oxygen travels through these air-filled tubes directly to the cells without needing to be carried by blood. The insect’s blood (hemolymph) only transports nutrients and waste, not oxygen.

Earthworms are not fish, but they can survive in oxygen-rich water because their skin can absorb dissolved oxygen directly from the water. However, if the water is stagnant and low in oxygen, or if the water contains chemicals, the earthworm will suffocate. This is why earthworms come out of the soil during heavy rain – the rainwater may have little oxygen, or it may flood their burrows.

The gill filaments are packed with thousands of tiny blood vessels (capillaries). The blood inside these vessels contains red blood cells, which are red due to hemoglobin. The thin walls of the gills allow the red color to show through, making the gills look bright red and very vascular.

Fish use up the dissolved oxygen in the water for respiration. If the tank is completely sealed with no air above the water, no new oxygen from the atmosphere can dissolve into the water. Once the fish uses up all the available dissolved oxygen, it will suffocate, even if the water is still there.

Dolphins and whales are not fish; they are marine mammals that evolved from land animals. They have lungs, not gills. They must come to the surface regularly to breathe air through a blowhole (which is a modified nostril). They can hold their breath for a long time (dolphins for 10-15 minutes, some whales for over an hour), but they cannot extract oxygen from water.

Mangroves live in muddy, waterlogged soil where there is very little oxygen. To solve this problem, they grow pencil-like roots upward out of the mud and water. These are called pneumatophores or breathing roots. They have small openings called lenticels that allow oxygen to enter and travel down to the underwater roots.

Overwatering fills all the air gaps in the soil with water. The roots need oxygen from these air gaps to perform cellular respiration and get energy. Without oxygen, the root cells cannot make ATP and they begin to die. This is called root rot, and the plant eventually cannot absorb water or minerals, leading to death.

Woody stems have a thick, dead bark that is impermeable to gases. Lenticels are small, raised, corky spots or pores on the bark. They act like breathing holes, allowing oxygen to reach the living cells in the stem’s interior (the cortex and pith) and allowing carbon dioxide from cellular respiration to escape.

Cellular respiration is not 100% efficient. About 60-70% of the energy from glucose is released as heat. This is why your body feels warm. In warm-blooded animals (mammals and birds), this heat is used to maintain a constant body temperature. In cold weather, shivering increases cellular respiration to produce more heat.

After you eat, your digestive system breaks down food into glucose and other nutrients. These nutrients are absorbed into the blood and delivered to cells. The cells then increase their rate of cellular respiration to use this fuel. The extra energy released as heat makes you feel slightly warmer, a phenomenon called diet-induced thermogenesis.

A germinating seed is alive and very active. It needs a lot of energy (ATP) to break open the seed coat, grow the root and shoot. This energy comes from cellular respiration, which requires oxygen. Deep in the soil, air spaces are few, and oxygen levels are very low. The seed will suffocate and die.

Cilia are microscopic, hair-like projections on the surface of certain cells. In the trachea and bronchi, millions of cilia beat in a coordinated, wave-like motion about 10 to 20 times per second. They constantly sweep a thin layer of mucus (and trapped particles) upward toward the throat, where it can be swallowed or coughed out. This is called the mucociliary escalator.

Tobacco smoke contains chemicals that paralyze and eventually destroy the cilia in the airways. Without working cilia, mucus with trapped dust and germs builds up in the lungs. The only way the body can clear this excess mucus is by a forceful cough. This chronic coughing is the smoker’s attempt to clean the damaged airways.

Amoeba is a unicellular organism with no specialized organs. Oxygen from the surrounding water simply diffuses directly across its thin cell membrane into the cytoplasm. Inside the cell, the oxygen is used for cellular respiration. Carbon dioxide waste diffuses out the same way, directly through the cell membrane.

Fever raises the body’s core temperature. Chemical reactions, including the ones in cellular respiration, occur faster at higher temperatures. Therefore, the body’s cells perform cellular respiration more rapidly and need more oxygen. The breathing rate increases to supply this extra oxygen and to remove the extra carbon dioxide produced.

Cellular respiration requires oxygen as the final electron acceptor to efficiently break down glucose and release a large amount of energy. On the moon, there is no atmosphere and no oxygen. An astronaut’s space suit must supply a continuous flow of breathable oxygen to keep the cells in the astronaut’s body alive.

Spiracles are the only openings through which air enters the cockroach’s tracheal system. If you block all of them, no fresh oxygen can reach the cells, and carbon dioxide cannot escape. The cockroach will die from lack of oxygen for cellular respiration, similar to a human whose nose and mouth are sealed shut.

Earthworms breathe through their skin and need oxygen dissolved in the moisture on their skin. However, when heavy rain floods their burrows, the water often has low oxygen (especially if it’s stagnant). The earthworm cannot get enough oxygen from the floodwater and will suffocate if it stays underground. It comes to the surface to breathe the air, even though that exposes it to predators.

During the night, plants in the pond stop photosynthesizing (which produces oxygen) and continue respiring (which uses oxygen). By early morning, the dissolved oxygen in the water can become very low. Fish may come to the surface and gulp air, trying to get oxygen from the thin layer of water at the surface that is in contact with the air, or even gulp air bubbles.

Smaller animals have a much higher surface area to volume ratio, which means they lose body heat faster. To maintain their body temperature, they have a very high metabolic rate, requiring a lot of energy (ATP) per gram of body weight. This means they need much more oxygen for cellular respiration. A mouse’s resting breathing rate is about 80-230 breaths per minute, much faster than a human (12-20) or an elephant (5-10).

Bird lungs are connected to thin-walled air sacs. When a bird inhales, fresh air goes into the air sacs. When it exhales, that fresh air is pushed from the sacs through the lungs. So the lungs receive fresh, oxygen-rich air during both inhalation and exhalation. This provides a constant supply of oxygen needed for the high energy demands of flying.

Asthma is a common respiratory condition. During an asthma attack, triggers like pollen, dust, or cold air cause the muscles around the bronchioles to tighten (bronchospasm). The lining of the airways also becomes inflamed and swollen, and extra mucus is produced. This narrows the air passages, making it very difficult to exhale air, leading to wheezing and breathlessness.

Under high pressure in deep water, the diver breathes compressed air. Extra nitrogen dissolves in the blood. If the diver ascends too quickly, the pressure drops rapidly, and the dissolved nitrogen comes out of solution as bubbles (like opening a soda bottle). These bubbles can block blood vessels, causing joint pain, paralysis, or even death.

The glottis is the slit-like opening in the larynx (voice box) between the two vocal cords. When you breathe, the glottis is open, allowing air to pass from the pharynx into the trachea. When you speak, the vocal cords come together across the glottis, and air from the lungs forces them to vibrate, producing sound.

Cacti and other succulent plants use a special method called CAM photosynthesis. They open their stomata at night when it is cooler and less water will evaporate. At night, they take in carbon dioxide and store it. During the day, with stomata closed, they use the stored CO2 for photosynthesis. This also allows some gas exchange for respiration at night with minimal water loss.

The air you exhale is warm (about 37°C) and is nearly saturated with water vapor. This water vapor is a byproduct of cellular respiration. When this warm, moist air hits a cool mirror surface, the water vapor condenses into tiny liquid water droplets, forming fog. This shows that water is indeed produced during cellular respiration.

Carbon dioxide produced by cells needs to be transported in the blood. Carbonic anhydrase is an enzyme in red blood cells that rapidly converts CO2 and water into carbonic acid (H2CO3), which then dissociates into bicarbonate (HCO3-) and hydrogen ions. This is how most CO2 is carried in the plasma. At the lungs, the same enzyme reverses the reaction, releasing CO2 to be exhaled.

The ribs are attached to muscles that lift them during deep inhalation. If a rib is fractured, any movement of the rib cage, especially a deep breath, will cause significant pain. To avoid pain, the person takes shallow, rapid breaths. This reduces the volume of air exchanged and can lead to incomplete lung expansion and a risk of pneumonia.

The water scorpion is an aquatic insect that breathes air through spiracles. It has a long, thin, tail-like tube called a siphon. It extends this tube to the water surface, like a snorkel, to draw in fresh air. This allows the insect to remain submerged, hidden from predators, while still breathing atmospheric oxygen.

The pleura is a smooth, slippery, double-layered membrane. One layer sticks to the lung, and the other lines the inside of the chest wall. Between the layers is a thin film of pleural fluid. This fluid acts like oil, allowing the two layers to slide against each other with very little friction as the lungs expand and contract during breathing.

Respiration is a continuous, life-sustaining process that does not require light. It occurs in all living cells at all times. A plant kept in the dark will not be able to photosynthesize, but it will still need energy to stay alive. It will use stored food (starch) for cellular respiration, breaking it down with oxygen to release energy, until the stored food runs out.

When you chop an onion, you break its cells. This releases enzymes that convert certain chemicals into a volatile, irritating gas. This gas rises and reaches your eyes, where it reacts with the water on your eye’s surface to form a mild acid. Your eyes produce tears to wash away the irritant. The sneeze or eye irritation is a protective reflex, not directly related to breathing, but it involves the nasal cavity.

Inside your lungs, there are stretch receptors. When you take a very deep breath and the lungs expand too much, these receptors send a signal via the vagus nerve to the brain. The brain then sends a signal to the diaphragm and rib muscles to stop inhaling. This protective reflex prevents over-stretching and damage to the lung tissue.

While we need oxygen, too much can be harmful. Breathing pure oxygen at pressures greater than normal (like in some diving situations) can cause inflammation, fluid buildup, and scarring in the lungs. It can also affect the brain, causing seizures. This is why divers use special gas mixtures, not pure oxygen, for deep dives.

The medulla oblongata is the part of the brainstem that controls automatic functions like breathing and heartbeat. It has a group of neurons called the respiratory center. This center generates rhythmic signals that travel down the phrenic nerve to the diaphragm and intercostal nerves to the rib muscles, causing them to contract (inhale) and then relax (exhale). You can override it voluntarily, but it will take back control if you hold your breath too long.

A spirometer is a medical device that measures the volume of air inhaled and exhaled by the lungs. A person breathes into a mouthpiece attached to the device, which records the different lung volumes and capacities, such as tidal volume, vital capacity, and total lung capacity. It is used to diagnose lung diseases like asthma and COPD.

Trees transport water and minerals upward through xylem vessels using physical forces like transpiration (water evaporating from leaves creates negative pressure). No pumping heart is needed. However, the living cells in the roots are not involved in this water transport. They are alive and need to perform cellular respiration to make ATP for growth and active transport of minerals. They get oxygen from air spaces in the soil.

The human lungs contain about 300 to 500 million alveoli. Because they are so numerous and tiny, their total combined surface area is enormous – roughly 70 to 100 square meters. That is about the size of half a tennis court or one side of a singles tennis court. This large surface area allows for very efficient gas exchange.

Carbon monoxide (CO) is a colorless, odorless gas. When you breathe it in, it attaches to the hemoglobin in your red blood cells much more tightly than oxygen does. This forms carboxyhemoglobin. Even if there is plenty of oxygen in the air, it cannot be transported to the tissues. The person dies from internal suffocation (lack of oxygen for cellular respiration) without feeling breathless.

Pranayama is a yogic breathing practice that involves slow, deep, controlled inhalation and exhalation. Over time, this can strengthen the diaphragm and intercostal muscles, increase the elasticity of the lungs, and improve the efficiency of gas exchange. It also activates the parasympathetic nervous system, which reduces stress and lowers heart rate and blood pressure.

This is related to the surface area to volume ratio. As an animal gets larger, its volume (number of cells needing oxygen) grows as the cube of its length, while the surface area of its lungs grows only as the square of its length. At some point, the lungs cannot provide enough oxygen for all the cells through cellular respiration. Very large animals like whales have evolved extremely efficient lungs and a slow metabolism, but there is still a physical limit.