What is the difference between the movement of oxygen and carbon dioxide in the alveoli?


Molecules of oxygen and carbon dioxide are passively exchanged, by diffusion, between the gaseous external environment and the blood. This exchange process occurs in the alveolar region of the lungs. AnswerParty!

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carbon dioxide

Carbonic acid gas
Carbonic anhydride
Carbonic oxide
Carbon oxide
Carbon(IV) oxide
Dry ice (solid phase)


Chemistry Matter Biology
Respiratory physiology

Respiratory physiology is the branch of human physiology focusing upon respiration.

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The respiratory system (or ventilatory system) is a biological system consisting of specific organs and structures used for the process of respiration in an organism. The respiratory system is involved in the intake and exchange of oxygen and carbon dioxide between an organism and the environment.

In air-breathing vertebrates, respiration takes place in the respiratory organs called lungs. The passage of air into the lungs to supply the body with oxygen is known as inhalation, and the passage of air out of the lungs to expel carbon dioxide is known as exhalation; this process is collectively called breathing or ventilation. In humans and other mammals, the anatomical features of the respiratory system include include trachea, bronchi, bronchioles, lungs, and diaphragm. Molecules of oxygen and carbon dioxide are passively exchanged, by diffusion, between the gaseous external environment and the blood. This exchange process occurs in the alveoli air sacs in the lungs.

Pulmonary alveolus

An alveolus (plural: alveoli, from Latin alveolus, "little cavity") is an anatomical structure that has the form of a hollow cavity. Found in the lung parenchyma, the pulmonary alveoli are the terminal ends of the respiratory tree, which outcrop from either alveolar sacs or alveolar ducts, which are both sites of gas exchange with the blood as well. Alveoli are particular to mammalian lungs. Different structures are involved in gas exchange in other vertebrates. The alveolar membrane is the gas-exchange surface. Carbon dioxide rich blood is pumped from the rest of the body into the alveolar blood vessels where, through diffusion, it releases its carbon dioxide and absorbs oxygen.

"Molecular diffusion", often simply called diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size (mass) of the particles. Diffusion explains the net flux of molecules from a region of higher concentration to one of lower concentration, but diffusion also occurs when there is no concentration gradient. The result of diffusion is a gradual mixing of material. In a phase with uniform temperature, absent external net forces acting on the particles, the diffusion process will eventually result in complete mixing.

Diffusive equilibrium is reached when the concentrations of the diffusing substance in the two compartments becomes equal.

Lung Oxygen
Gas exchange

Gas exchange is a biological process through which different gases are transferred in opposite directions across a specialised respiratory surface. Gases are constantly required and produced as a by-product of cellular and metabolic reactions so an efficient system for their exchange is extremely important. It is linked with respiration in animals, and both respiration and photosynthesis in plants.

In respiration, oxygen (O2) is required to enter cells whilst waste carbon dioxide (CO2) must be removed – the opposite is true for photosynthesis, where CO2 enters plants and O2 is released. The exchange of gases essentially occurs as a result of diffusion down a concentration gradient – gas molecules moving from an area of high concentration → low concentration.


Science of drugs including their origin, composition, pharmacokinetics,
pharmacodynamics, therapeutic use, and toxicology.

Pharmacology (from Greek φάρμακον, pharmakon, "poison" in classic Greek; "drug" in modern Greek; and -λογία, -logia "study of", "knowledge of") is the branch of medicine and biology concerned with the study of drug action, where a drug can be broadly defined as any man-made, natural, or endogenous (within the body) molecule which exerts a biochemical and/or physiological effect on the cell, tissue, organ, or organism. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function. If substances have medicinal properties, they are considered pharmaceuticals.


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