Biology Chapter 5: The Plasma Membrane

Questions and Answers

Which of the following are main components of the plasma membrane? (Select all that apply)

Phospholipid bilayer (correct)

Proteins (correct)

Nucleic Acids

Cholesterol (correct)

What is the chief component of the plasma membrane?

Phospholipid bilayer

What role does cholesterol play in the plasma membrane?

Keeps membrane at optimum level of fluidity

Integral proteins can span the entire membrane.

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What is the function of peripheral proteins?

Lying on either side of the membrane, they are usually attached to integral proteins. Signup and view all the answers

What do receptor proteins in the plasma membrane do?

Bind with signaling molecules. Signup and view all the answers

What are transport proteins responsible for?

Facilitating the movement of molecules or ions across the plasma membrane. Signup and view all the answers

What is the glycocalyx?

An outer layer of the plasma membrane composed of carbohydrate chains. Signup and view all the answers

What does the term 'fluid-mosaic model' refer to?

A conceptualization of the plasma membrane as a fluid phospholipid bilayer with a mosaic of proteins. Signup and view all the answers

Define diffusion.

Movement of molecules from a region of higher concentration to a region of lower concentration. Signup and view all the answers

What is a concentration gradient?

The difference in concentration of a substance between two regions. Signup and view all the answers

Study Notes

Components of the Plasma Membrane

Composed of a phospholipid bilayer, cholesterol, membrane proteins, and glycocalyx.

Phospholipid Bilayer

Major structure made of two layers of phospholipids with hydrophobic fatty acid tails facing inward.
Imparts fluidity to the membrane, allowing for flexibility.
Only hydrophobic or very small uncharged molecules can easily pass through; hydrophilic substances require assistance.

Cholesterol's Role

Embedded within the phospholipid bilayer in animal cells.
Acts as a stabilizer, preventing small molecules from passing through.
Prevents membrane from becoming too rigid or too fluid in response to temperature changes.

Membrane Proteins

Integral and peripheral proteins constitute the main types of membrane proteins.
Integral proteins can span the membrane entirely or partially, associated with the hydrophobic core.

Integral Proteins

Form channels and transport pathways for molecules across the membrane.

Peripheral Proteins

Positioned on the membrane's surface and are not embedded.
Often attached to integral proteins, supporting the cell's structure and stability.

Structural Support by Proteins

Peripheral proteins on the cytoplasmic side anchor to the cytoskeleton, contributing to cell shape and structural integrity.

Protein Function in Cell Recognition

Proteins on cell surfaces interact with immune cells; they can identify self versus invaders.
They can contain binding sites that convey information to immune cells.

Receptor Proteins

Bind signaling molecules such as hormones, enabling communication between cells and their external environment.

Transport Proteins

Integral proteins that facilitate the movement of ions and molecules across the membrane.
Can create channels or actively transport substances, ensuring necessary materials enter and exit the cell.

Glycocalyx

Composed of carbohydrates attached to proteins and phospholipids.
Functions as binding sites for signaling molecules and aids in cell lubrication and adhesion.

Overview of the Plasma Membrane

The outer boundary of many cells, characterized by a phospholipid bilayer interspersed with proteins and cholesterol, and covered by carbohydrate chains.

Fluid-Mosaic Model

Illustrates the plasma membrane as a fluid structure with a dynamic mix of stationary and mobile proteins.

Diffusion Process

Involves the movement of molecules from areas of higher concentration to lower concentration, driven by a tendency to distribute evenly.

Concentration Gradient

Refers to the difference in concentration of molecules across a space, influencing movement through diffusion.

Description

Test your knowledge on the plasma membrane with these flashcards. Chapter 5 focuses on its main components, including the phospholipid bilayer, cholesterol, and various proteins. Perfect for biology students looking to reinforce their understanding of cell membranes.