A estrutura e função da membrana plasmática - Aula 17 - Módulo 1 - Prof. Guilherme

New Section

This section introduces the importance of understanding the structure and function of the plasma membrane in cells.

The Significance of Early Membrane Studies

• Górter and Grandel's experiment measured the surface area of a red blood cell, revealing that the membrane was a bilayer, not a single layer.

• The membrane's role in cell isolation and maintaining cellular balance is crucial for cell function.

Exploring Membrane Functionality

Delving into the functions of the plasma membrane and its significance in cellular processes.

Understanding Membrane Function

• The plasma membrane acts as an outer coating for cells, defining their boundaries and facilitating interactions.

• Its primary function includes isolating the cell from its surroundings and regulating substance entry and exit to maintain internal balance.

Permeability and Selectivity

Discussing how the plasma membrane controls substance movement through selective permeability.

Permeability Control Mechanisms

• The concept of selective permeability allows the membrane to regulate substances like water, ions, and gases based on cellular needs.

Fluid Mosaic Model

Exploring Singer and Nicholson's fluid mosaic model as a representation of the dynamic nature of the plasma membrane.

Fluidity in Membrane Structure

• The fluid mosaic model depicts a lipid bilayer with proteins embedded, showcasing fluidity essential for protein movement within the membrane.

New Section

In this section, the speaker discusses the polarity of the phospholipid bilayer in cell membranes and its interaction with water molecules.

Phospholipid Bilayer Polarity

• The phosphate head is negatively charged, while choline is positively charged, making the phospholipid bilayer polar. -

• Water is abundant in both extracellular and intracellular spaces due to its polarity. -

• The lipid layer isolates the external and internal cellular spaces due to its non-interaction with water. -

New Section

This section delves into the hydrophilic and hydrophobic nature of membrane components, emphasizing their role in cellular isolation.

Membrane Components

• Phospholipid heads are hydrophilic, interacting with water molecules. -

• The middle portion of the membrane, composed of lipids that do not interact with water, is hydrophobic. -

• Proteins embedded in the membrane play crucial roles such as peripheral proteins located on the exterior surface. -

New Section

Here, integral proteins and glycocalyx are introduced as essential components for cellular recognition processes.

Integral Proteins and Glycocalyx

• Integral proteins can span the entire membrane (transmembrane) facilitating substance transport. -

• Glycocalyx aids in cellular recognition processes by forming compounds that determine blood types. -

New Section

This part explores how glycocalyx influences cell-cell interactions through cellular recognition mechanisms.

Cell Recognition Mechanisms

• Glycocalyx plays a vital role in cell recognition between different cell types based on their structures. -

• Cells with similar glycocalyx structures tend to adhere together while those with different structures do not interact effectively. -

New Section

The functions of cell membranes are discussed focusing on spatial limitation and selective permeability controlled by various proteins.

Functions of Cell Membranes

• Cell membranes serve to limit cellular space through a lipid bilayer and control substance entry/exit via selective permeability facilitated by integral proteins. -