TRANSPORTE PASSIVO: Difusão Simples | Difusão Facilitada | Osmose

How Long Would It Take to Count to 100 Trillion?

Introduction to Cell Count in the Human Body

• The human body contains approximately 100 trillion cells, but only about 10% of these are human cells; the rest are microorganisms.

• These microorganisms reside in various parts of the body, including the gut microbiota, skin, mouth, and nasal passages.

Membrane Transport Mechanisms

Overview of Transport Types

• The video introduces three key types of membrane transport: passive transport, active transport, and vesicular transport.

Passive Transport Explained

• Passive transport does not require energy expenditure. It includes three subtypes: simple diffusion, facilitated diffusion, and osmosis.

Simple Diffusion vs. Osmosis

• In both simple and facilitated diffusion, solutes move across membranes; however, in osmosis, it is the solvent (water) that moves.

Detailed Look at Simple Diffusion

Characteristics of Simple Diffusion

• Simple diffusion occurs without energy use as solutes move from areas of higher concentration (hypertonic) to lower concentration (hypotonic).

Examples of Solutes in Simple Diffusion

• Common solutes include oxygen (O2) and carbon dioxide (CO2), which pass directly through the phospholipid bilayer.

Application in Gas Exchange

• An example provided is gas exchange in pulmonary alveoli where CO2 diffuses out into alveoli while O2 enters capillaries from alveoli.

Facilitated Diffusion Explained

Mechanism of Facilitated Diffusion

• Facilitated diffusion involves larger molecules or those lacking affinity for the lipid bilayer passing through protein channels called permeases.

Substances Transferred via Facilitated Diffusion

• This process can involve amino acids, vitamins, ions like calcium and sodium, glucose, and even water through specialized proteins called aquaporins.

Understanding Osmosis

Key Differences from Other Transport Types

Osmosis Explained Through Everyday Examples

Understanding Osmosis with a Simple Experiment

• The concept of osmosis is introduced using a simple setup involving a pot, tube, and semi-permeable membrane separating two solutions: one with sodium chloride (salt) and one without.

• Water moves from the hypotonic side (low solute concentration) to the hypertonic side (high solute concentration), equalizing osmotic pressure and reducing volume on the hypotonic side.

Real-Life Application: Salt and Slugs

• A humorous example illustrates how sprinkling salt on slugs causes them to lose water due to osmosis, demonstrating the effects of creating a hypertonic environment around them.

• When salt is applied externally, it creates a hypertonic solution outside the slug, leading to water leaving its cells, causing dehydration.

Reverse Osmosis Experiment

• An alternative experiment involves injecting saline into a slug and then placing it in freshwater. This results in water entering the slug's cells due to osmotic pressure differences.

• The slug swells as water moves from an area of lower solute concentration (freshwater) into an area of higher solute concentration (inside the slug).

Effects on Red Blood Cells

• The discussion shifts to red blood cells (hemácias), explaining their behavior in different solutions: they swell in hypotonic solutions and shrink in hypertonic ones.

• In isotonic conditions, there is no net movement of water; thus, red blood cells maintain their shape.

Plant Cells vs. Animal Cells

• Plant cells behave differently than animal cells when placed in hypotonic or hypertonic solutions due to their rigid cell walls. They swell but do not burst under hypotonic conditions.

• In hypertonic environments, plant cells undergo plasmolysis where they shrink away from their cell walls while remaining intact.

Summary of Key Concepts

• The session concludes by summarizing passive transport mechanisms: simple diffusion allows solutes through phospholipid bilayers; facilitated diffusion uses proteins for transport; osmosis specifically refers to water movement across membranes without energy expenditure.

• All discussed processes are classified as passive transport since they do not require energy input.