#Diffusion #diffusioninhumanbody #biology #textbook #igcse

Ch:- 3

Pg:- 41,42,43,44

Diffusion is a fundamental process in the human body that allows the passive movement of molecules, such as gases, ions, and nutrients, across cell membranes and tissues.

 Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. Molecules naturally move down their concentration gradient until equilibrium is reached, where the concentration of molecules is equal in both areas.  Diffusion does not require energy (ATP), as it relies on the natural kinetic energy of molecules.

• Lungs: In the alveoli (air sacs) of the lungs, diffusion is crucial for gas exchange. Oxygen diffuses from the high concentration in the alveoli into the lower concentration in the blood, while carbon dioxide diffuses from the high concentration in the blood to the lower concentration in the alveoli.

• Cells: Once oxygen-rich blood reaches body tissues, oxygen diffuses from the blood (higher concentration) into cells (lower concentration) for cellular respiration. Carbon dioxide, a byproduct of cellular respiration, diffuses in the opposite direction—from cells into the blood.

• Capillaries and Tissues: Nutrients like glucose and amino acids diffuse from the bloodstream (where their concentration is higher) into body cells (where their concentration is lower) to fuel metabolic processes.

• Waste Removal: Waste products from cells diffuse into the blood, where they are transported to organs such as the kidneys and liver for elimination or detoxification.

• Neurotransmitters: In the synaptic cleft (the space between neurons), neurotransmitters released from one neuron diffuse across the gap to bind to receptors on the next neuron. This transmission of signals allows communication between neurons.

• Ion Movement: The diffusion of ions like sodium (Na⁺) and potassium (K⁺) across neuron membranes is crucial for generating electrical impulses, which enable nerve signal transmission.

Small Intestine: After digestion, nutrients like glucose, amino acids, and fatty acids are in high concentration within the small intestine. They diffuse across the intestinal lining into the bloodstream to be distributed throughout the body.

Hormones and signaling molecules rely on diffusion to move from areas of higher concentration (such as glands where they’re produced) to areas of lower concentration, reaching their target cells or tissues to regulate body functions, like metabolism, growth, and immune responses.

Water Movement: Osmosis is the diffusion of water across a semipermeable membrane. In cells, water diffuses to balance solute concentrations inside and outside the cell. For example, cells absorb water from blood when the body is dehydrated, helping maintain hydration and proper cell function.

Factors Affecting Diffusion in the Body:

Several factors can impact the rate of diffusion within the human body:

• Concentration Gradient: A greater difference in concentration between two areas speeds up diffusion.

• Temperature: Higher temperatures increase molecular movement, speeding up diffusion.

• Membrane Permeability: Some membranes are selectively permeable, allowing certain molecules to diffuse while restricting others.

• Surface Area: Larger surface areas, such as the extensive alveolar surface in the lungs, facilitate greater diffusion.

• Distance: Diffusion is more efficient over shorter distances, which is why blood capillaries are very close to cells.