Brocks Chapter 2: Terms and Definition

Cell Envelope

Layer of structures that surround the cytoplasm and govern cellular interaction with the external environment

Function of the Cell Envelope

1. Govern transport of nutrients and waste into and out of the cell

2. Governs cell shape

3. Protects from mechanical stress

4. Help in attachment

5. Protect cell from attack

Component of Cell Envelope

1. Cytoplasmic membrane

2. Cell wall

3. Outer membrane

4. S-layer

Cytoplasmic membrane

Physically weak

Major function: selective permeability

Transportation of nutrients and waste occurs here

Phospholipid bilayer

Cytoplasmic membrane of ALL bacterial and eukaryal cells

Hydrophilic component of Bacterial/Eukaryal Cytoplasmic Membrane

Glycerophosphate and functional group (sugar, ethanolamine, or choline)

Integral Membrane Proteins

Proteins significantly embedded in the membrane

Transmembrane Proteins

Type of integral membrane protein that extends completely across the membrane

Peripheral Membrane Proteins

Loosely attached proteins in the membrane

Lipoproteins

Contains hydrophobic lipid tail that anchors the proteins into the membrane

Hydrophobic Component of the Archaeal Cytoplasmic Membrane

Isoprenoid tails bound to glycerol by ether bonds

construction of the cytoplasmic membrane of Archaea

Phosphoglycerol Diethers with C20 side chain (phytanyl group)

Diphosphoglyerol Tetraethers with C40 side chain (biphytanyl group) that form a lipid monolayer

Crenarchaeol (in Thaumarcheaota) with four C5 rings and one C6 ring

Major Functions of the Cytoplasmic Membrane

1. Permeability barrier

2. Protein anchor

3. Energy conservation

Proton Motive Force

Energize state of the cytoplasmic membrane. Created when protons (H+) are separated from hydroxyl ions (OH -) across the membrane surface.

Active transport

Process by which cells accumulate solutes against the concentration gradient

Simple transport

The movement of a solute is coupled with the dissipation of an electrochemical gradient such as the proton motive force

Symport and antiport reactions

Two main type of simple transport

Symport reactions

A solute and a proton are cotransported in the same direction

Antiport reactions

A solute and a proton are transported in opposite directions

Group translocation

The transported substance is chemically modified upon entering the cell and uses an energy rich organic compound that drives the transport event

ATP Binding Cassette (ABC) Transporter Systems

Modular (independent parts) systems that has three components: a binding protein, a transmembrane protein, and an ATP hydrolyzing protein