Plasma Membrane and Phospholipid Structure

Questions and Answers

A phospholipid has a 'head' made up of glycerol molecule attached to a single ________.

Phosphate Group

Because the phosphate group and its attachments are either charged or polar, the phospholipid head is ________.

Hydrophilic

A phospholipid has 2 'tails' made up of 2 _______ molecules.

Fatty Acid

The phospholipid shown in the figure has a _______ attached to phosphate.

Choline group Signup and view all the answers

Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are ______.

Hydrophobic Signup and view all the answers

What does a phospholipid consist of?

A hydrophilic head and hydrophobic tails. Signup and view all the answers

Which of the following statements about the plasma membrane is true?

Plasma membrane is hydrophobic. Signup and view all the answers

What type of molecules can easily cross the phospholipid bilayer of the plasma membrane?

Small, nonpolar molecules. Signup and view all the answers

What are ions and how do they cross the membrane?

Ions are hydrophilic and require transport proteins to cross efficiently. Signup and view all the answers

The motion of an individual dye molecule is random ______ whether or not a concentration gradient is present.

Random thermal motion Signup and view all the answers

Diffusion is the net movement of a population of dye molecules when a concentration gradient is present.

Net movement Signup and view all the answers

Study Notes

Phospholipid Structure

Phospholipids consist of a hydrophilic "head" and two hydrophobic "tails."
The head is made of a glycerol molecule linked to a phosphate group and another small molecule, such as a choline group.
The tails are composed of two fatty acid molecules, featuring carboxyl groups attached to long hydrocarbon chains.
The phosphate group and its attachments are polar or charged, leading to the hydrophilic nature of the head.
The C-H bonds in the fatty acid tails are nonpolar, resulting in a hydrophobic character that repels water.

Plasma Membrane Composition

The plasma membrane is structured as a phospholipid bilayer with hydrophilic heads facing towards the cytoplasm and extracellular fluid, and hydrophobic tails hidden within.
Membrane proteins possess both hydrophilic and hydrophobic regions, allowing them to integrate into the membrane's distinct regions.
Cholesterol molecules, which are hydrophobic, are interspersed among the hydrophobic tails, contributing to membrane fluidity.

Selective Permeability of Plasma Membrane

The plasma membrane selectively regulates substance transport into and out of the cell, being permeable to certain molecules based on their polarity.
Small, nonpolar molecules (e.g., hydrocarbons, O2, CO2) can cross the membrane easily without the need for transport proteins.
Polar molecules (e.g., water, sugars) and ions (e.g., Na+, K+, Cl-) struggle to cross the hydrophobic interior and often require transport proteins for efficient movement.
Water, while polar, can pass through the lipid bilayer slowly due to its small size; rapid transport occurs via specialized proteins called aquaporins.

Diffusion Concepts

Individual dye molecules exhibit random movement regardless of concentration gradients.
In contrast, a population of dye molecules shows net movement from areas of higher concentration to lower concentration in the presence of a concentration gradient, illustrating the principle of diffusion.

Description

Explore the key concepts of phospholipid structure with these flashcards. This quiz covers essential terms and definitions related to the plasma membrane's composition and properties, focusing on the hydrophilic nature of phospholipids. Perfect for students studying cell biology or biochemistry.