MMG 301: Cytoplasmic Membrane Overview

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Questions and Answers

Name the three reasons why a bacterial cell is efficient.

Growth, survival, and dispersal.

Overview of the locations of bacteria structures.

Surface appendages extend into the external environment, extracellular matrix (some bacteria), cell envelope surrounds the cell, internal matrix contains cytoplasm, nucleic acids, and other internal structures.

Bacterial membranes are mostly composed of _______.

phospholipids.

What are Phospholipids?

Phospholipids are made of fatty acids linked to glycerol phosphate by an ester bond. Signup and view all the answers

Name some properties of Phospholipids.

Some phospholipids contain charged groups; they form a lipid bilayer; they are amphipathic molecules; they can move within the bilayer. Signup and view all the answers

Bacteria and eukaryotes have ester lipids, while Archaea have several types of ______.

lipids. Signup and view all the answers

What do the membranes of Archaea contain?

Archaea contain membranes made of ether lipids, which can form lipid bilayers or monolayers. Signup and view all the answers

The cytoplasmic membrane acts as....

A barrier, an anchor for membrane proteins, and is the site of energy generation. Signup and view all the answers

What are the functions of the cytoplasmic membrane?

It surrounds the cell's contents, anchors proteins for various functions, and creates an energetically charged membrane. Signup and view all the answers

Bacterial membranes contain embedded...

Proteins and are impermeable to most chemicals (except water). Signup and view all the answers

List 3 properties of the fluid membrane.

Proteins can be on one side or span the bilayer; substances must be transported across; proteins can move relative to each other. Signup and view all the answers

What is needed to enter the inside of a cell?

Transport proteins are needed to facilitate the entry of chemicals into the cell. Signup and view all the answers

Are nutrients abundant in nature? How do they make it across the concentration gradient of a cell?

Many nutrients are present at very low concentrations and must be transported against a concentration gradient. Signup and view all the answers

Movement of solutes across the cell membrane (through transport proteins) can either release energy or require energy.

True (A) Signup and view all the answers

What is chemiosmosis?

Movement with a concentration gradient (high→low) releases energy. Signup and view all the answers

What type of movement across the concentration gradient requires energy? (movement against or with)

Movement against a concentration gradient (low→high) requires energy. Signup and view all the answers

Name the 3 general mechanisms used by transport systems.

Simple Transport, Group Translocation, ABC Transporter. Signup and view all the answers

What is Simple Transport?

Driven by the energy in the proton motive force. Signup and view all the answers

What is Group Translocation?

Chemical modification of the transported substance driven by phosphoenolpyruvate, such as glucose uptake in E. coli. Signup and view all the answers

What is an ABC Transporter?

Periplasmic binding proteins are involved, and energy comes from ATP. Signup and view all the answers

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Study Notes

Efficiency of Bacterial Cells

Bacterial cells are efficient due to their structural design supporting growth, survival, and dispersal.

Bacterial Structures Overview

Surface appendages extend into the environment.
Cell envelope surrounds each bacterial cell, providing protection.
Internal matrix holds cytoplasm, nucleic acids, and organelles.

Phospholipids in Bacterial Membranes

Bacterial membranes primarily consist of phospholipids.
Phospholipids are formed by fatty acids linked to glycerol phosphate via ester bonds.

Properties of Phospholipids

May contain charged groups on the phosphate.
Create a lipid bilayer structure.
Amphipathic nature with hydrophobic and hydrophilic regions.
Capable of movement within the bilayer.

Membrane Components of Different Domains

Bacteria and eukaryotes have ester lipids, while Archaea possess diverse lipid types.
Archaea have ether lipids that can form bilayers or monolayers.

Functions of the Cytoplasmic Membrane

Acts as a barrier and an anchor for membrane proteins, key for energy generation.
Encloses cell contents, critical for defining cell identity.
Proteins in the membrane enable energy generation, nutrient transport, and chemical sensing.
The cytoplasmic membrane maintains a charge difference essential for energy production.

Properties of Bacterial Membranes

Embedded proteins make the membrane selectively impermeable, only allowing water to pass freely.
Proteins can be situated on one bilayer side or span both.

Nutrient Transport Mechanisms

Nutrients are often present in low concentrations in nature.
Transport proteins are vital for moving nutrients against concentration gradients into the cell.
Simple diffusion is insufficient for nutrient uptake, necessitating specialized transport systems.

Energy and Solute Movement

Movement of solutes can either release or require energy depending on the direction.
Chemiosmosis describes the energy-releasing movement with the concentration gradient (high to low).
Moving solutes against the gradient (low to high) requires energy input.

Transport Systems in Bacteria

Three general transport mechanisms exist: Simple Transport, Group Translocation, and ABC Transporters.
Simple Transport relies on proton motive force for driving the transport.
Group Translocation chemically modifies the substance during transport, such as glucose uptake in E. coli.
ABC Transporters utilize periplasmic binding proteins and ATP for energy to transport molecules effectively.