Mechanism of Solute Molecule Transport

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Questions and Answers

What is the main function of exocytosis in neurons?

Signal other neurons or muscle cells (correct)

Delivering proteins and carbohydrates to the outside of the cell

Ferry specific organic nutrient molecules

Taking in cholesterol for membrane synthesis

Which process delivers proteins and carbohydrates from Golgi vesicles to the outside of plant cells?

Receptor-mediated endocytosis

Endocytosis

Transport systems

Exocytosis (correct)

What type of nutrient molecules are ferried by transport systems across membranes?

Glucose (correct)

Cholesterol

Carbohydrates

Proteins

What is the function of electrically charged surface groups in membranes?

Creating a difference in electrical potential Signup and view all the answers

What do some membranes contain that have substrates outside and inside the membrane?

Enzymes Signup and view all the answers

Which phenomenon involves the recognition of certain molecular signals like chemotaxis in bacteria?

Specific recognition sites Signup and view all the answers

What happens to the rate of transport as the concentration of the substance to be translocated increases?

It increases until it reaches a maximum when the substance saturates the transporter Signup and view all the answers

What term describes transport proteins having a high degree of specificity for the substance they transport?

Structural and stereospecificity Signup and view all the answers

What type of mechanism leads to a charge separation across a membrane when a charged substance like K+ is translocated without a counter ion movement?

Electrogenic Signup and view all the answers

In what situation does a movement of an uncharged molecule occur spontaneously without the need for a driving force?

$C1>C2$ with negative $\Delta G$ Signup and view all the answers

When calculating the change in free energy for charged molecules like Na+ ions, what factors are considered?

Both electrical potential and concentration of the solute Signup and view all the answers

What is the term used to describe a situation where an opposite charged ion is moved to balance the charge during translocation?

Antiport Signup and view all the answers

What is the defining characteristic of passive transport?

Movement of solute occurs spontaneously Signup and view all the answers

In active transport, what is the source of energy used to drive the process?

Hydrolysis of ATP to ADP Signup and view all the answers

What types of molecules can pass through pores in the membrane?

Both organic and inorganic molecules Signup and view all the answers

What is a characteristic feature of channels and pores in membrane translocation systems?

They involve a conformational change in the channel protein Signup and view all the answers

What is the function of gap junctions between cells?

Create aqueous connections between two cells Signup and view all the answers

Compared to K+, how does the Na+ channel of plasma membrane permit rates?

At a rate 10X greater than K+ Signup and view all the answers

Which type of proteins are embedded within the lipid bilayer of the cell membrane?

Integral Proteins Signup and view all the answers

What is the main function of membrane carbohydrates in cell membranes?

Cell-cell recognition Signup and view all the answers

Which type of proteins are attached to the exterior side of the plasma membrane?

Peripheral Proteins Signup and view all the answers

What is the role of transmembrane proteins within cell membranes?

Signal transduction Signup and view all the answers

Which type of carbohydrates in membranes covalently attach to proteins to form glycoproteins?

Oligosaccharides Signup and view all the answers

What is the function of membrane proteins known as CD in the context of surface proteins and diseases?

Cell-cell recognition Signup and view all the answers

Which category of ionophores forms a channel that traverses the membrane for ions to diffuse through?

Channel formers Signup and view all the answers

What is the function of Valinomycin in ion transport?

Translocates K+ ions across the membrane Signup and view all the answers

How do large molecules like proteins and polysaccharides generally cross the plasma membrane?

By mechanisms involving packaging in vesicles Signup and view all the answers

Which process requires energy: exocytosis or diffusion through the lipid bilayer?

Exocytosis Signup and view all the answers

What is the main difference between mobile carriers and channel formers among ionophores?

The presence of a channel for diffusion Signup and view all the answers

Which antibiotic facilitates the movement of K+ ions across biological membranes?

Valinomycin Signup and view all the answers

Study Notes

Membrane Structure and Function

Membranes contain lipids, proteins, and polysaccharides in a bilayer structure.
Three types of proteins are present in membranes: Integral, Peripheral, and Transmembrane proteins.
Positioning of proteins depends on their hydrophobicity.
Membrane proteins serve six different functions: Transport, Enzymatic Activity, Signal Transduction, Cell-cell recognition, Intercellular Joining, and Attachment to the cytoskeleton and extracellular matrix.

Carbohydrates in Membranes

Carbohydrates in membranes are oligosaccharides covalently attached to proteins (glycoproteins) and lipids (glycolipids).
Mainly gangliosides, found on the exterior side of the plasma membrane.
Roles of membrane carbohydrates include cell-cell recognition, adhesion, and receptor action.

Mechanisms of Transport

Transport of solute molecules involves Recognition and Binding, Translocation or Transport, and Dissociation or Release.
Mechanisms of transport include Symport, Antiport, and Uniport.
Electrogenic transport occurs when a charged substance is translocated without an oppositely charged ion, leading to a membrane potential.
Neutral or electrically silent transport occurs when an oppositely charged ion is moved to balance the charge.

Energetics of Membrane Transport

The change in free energy (ΔG) for an uncharged molecule moving from a concentration of C1 to C2 is given by ΔG = 2.3 RT log (C2/C1).
Passive transport occurs when ΔG is negative, and the movement of solute occurs spontaneously.
Active transport occurs when ΔG is positive, and energy input is required to drive the transport.

Types of Membrane Translocation Systems

Channels are selective for specific inorganic cations and anions.
Pores are not selective and permit organic and inorganic molecules to pass through the membrane.
Channels and pores are intrinsic membrane proteins.
Gap junctions are clusters of membrane channels lined by proteins that create aqueous connections between two cells.
Nuclear pores cover two membranes, creating aqueous channels in the nuclear envelope.

Ionophores

Ionophores are antibiotics that facilitate the movement of monovalent and divalent inorganic ions across biological membranes.
Two major groups: Mobile carriers (e.g., valinomycin) and channel formers (e.g., gramicidin A).
Both types translocate ions by passive mediated transport mechanism.

Bulk Transport

Bulk transport across the plasma membrane occurs by exocytosis and endocytosis.
Exocytosis involves the release of vesicles from the cell, and endocytosis involves the uptake of vesicles into the cell.
Examples of exocytosis include the secretion of insulin from pancreatic cells into the extracellular fluid.

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Description

This quiz covers the mechanism of transport for solute molecules, including stages like recognition, binding, translocation, dissociation, and recovery. It also discusses the specificity and saturation of transporters. Learn about symport, antiport, and uniport mechanisms.