Biology Chapter 3 Flashcards

Questions and Answers

Define amphipathic.

A molecule that has both a hydrophilic region and a hydrophobic region.

Describe the structure of a phospholipid.

There is one head made up of glycerol linked to phosphorous and there are two carbon-hydrogen chains.

What parts of the phospholipids are hydrophobic and hydrophilic?

The head is hydrophilic and the two tails are hydrophobic.

Define hydrophobic.

Repelling, tending not to combine with, or incapable of dissolving in water. Also can be known as nonpolar. Signup and view all the answers

Define hydrophilic.

Having an affinity for water; readily absorbing or dissolving in water. Also can be known as polar. Signup and view all the answers

How do phospholipids react to water?

The hydrophilic head faces the water, while the hydrophobic tail faces away from the water. Signup and view all the answers

Describe the phospholipid bilayer.

Two sets of phospholipids form the inside and outside of the cell membrane. The heads face the inside and outside of the cell membrane which is surrounded by watery fluid, and the tails form a middle barrier. Signup and view all the answers

Why is the fluid mosaic model used to describe how the cell membrane works?

The cell membrane is always moving and is composed of many different things. Signup and view all the answers

Name the two primary things that make up the cell membrane as well as their function.

Phospholipids- keep water fluid on either side and create structure; Proteins- give the molecule its characteristics and allow material in and out of the cell. Signup and view all the answers

Name some other things in the cell membrane.

Glycoprotein, Glycolipid, Cholesterol. Signup and view all the answers

Name the watery fluid on either side of the cell membrane.

Cytoplasm- on the inside of the cell; Extracellular fluid- on the outside of the cell. Signup and view all the answers

How is cholesterol important to the phospholipids?

It keeps the two fatty acid tails of the phospholipids from touching each other when it is too hot and drifting from one another and touching their neighbors when it is too cold. Signup and view all the answers

How do molecules without a charge get into and out of the cell?

Diffusion. Signup and view all the answers

How do very large molecules or molecules with a charge get into the cell?

Using proteins, for example, aquaporins allow water into a cell. Signup and view all the answers

What four types of proteins are in the cell membrane and what are their functions?

Receptor proteins- Bind to molecules outside the plasma membrane and regulate cell processes; Recognition proteins- Mark cells as 'not foreign' so they will not be attacked; Transport proteins- Allow very large or very charged molecules into and out of the cell; Enzymatic proteins- Help chemical reactions occur more quickly. Signup and view all the answers

What is the major 'take home message' of section 3.5?

A cell membrane is in all cells, it is fluid (always in motion), and is made primarily of phospholipids and proteins. Signup and view all the answers

Study Notes

Key Definitions

Amphipathic: Molecules possessing both a hydrophilic (water-attracting) region and a hydrophobic (water-repelling) region.
Hydrophobic: Molecules that repel water, generally nonpolar substances that do not dissolve in water.
Hydrophilic: Molecules that are attracted to water, readily absorbing or dissolving, characterized as polar.

Phospholipid Structure

Basic Composition: Contains one hydrophilic head (glycerol linked to phosphorous) and two hydrophobic carbon-hydrogen tails.
Hydrophobic and Hydrophilic Regions: The head is hydrophilic, while the two tails are hydrophobic.

Phospholipid Behavior in Water

Reaction to Water: The hydrophilic heads orient toward water, while the hydrophobic tails orient away from it.
Phospholipid Bilayer: Formed from two layers of phospholipids with heads facing outwards towards the watery environments and tails creating an inner barrier.

Cell Membrane Model

Fluid Mosaic Model: Describes the dynamic nature of the cell membrane, which consists of various components that move within the lipid bilayer.

Composition of Cell Membrane

Primary Components:
- Phospholipids: Maintain fluidity and structural integrity of the membrane.
- Proteins: Provide specific functions, such as transport and communication across the membrane.

Additional Membrane Structure

Other Components:
- Glycoproteins: Proteins with sugar groups that serve as cell recognition molecules.
- Glycolipids: Lipids with sugar groups that play a role in cell recognition.
- Cholesterol: Helps maintain membrane fluidity by preventing the fatty acid tails of phospholipids from sticking together or drifting too far apart.

Transport Mechanisms

Diffusion: Process by which uncharged molecules pass freely through the membrane.
Proteins for Large or Charged Molecules: Utilize specific proteins to facilitate entry or exit, such as aquaporins for water.

Types of Membrane Proteins

Receptor Proteins: Bind extracellular molecules to regulate cellular processes.
Recognition Proteins: Identify cells as self to prevent immune attacks.
Transport Proteins: Allow passage of large or charged molecules.
Enzymatic Proteins: Catalyze chemical reactions within the cell.

Summary of 3.5

The cell membrane is a universal component of all cells, characterized by its fluid nature and composition primarily of phospholipids and proteins.

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Explore key concepts from Biology Chapter 3, focusing on sections 4-5. These flashcards cover important terms like amphipathic molecules and the structure of phospholipids. Perfect for quick review or study before a test.