Biology: Membrane Permeability and Transporters

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Questions and Answers

What is the primary function of the phospholipid bilayer in terms of communication?

To respond to signaling molecules

To enable the recognition of signaling molecules

To control the flow of information between cells and the environment (correct)

To facilitate the reception of signaling molecules

What is the percentage of lipids in a cell membrane?

40% (correct)

60%

50%

30%

What is the primary role of carbohydrates in membrane composition?

To increase membrane permeability

To provide structural support to the membrane

To facilitate cell recognition (correct)

To decrease membrane fluidity

What is the function of integral proteins in the cell membrane?

To facilitate transport of molecules across the membrane Signup and view all the answers

What is the result of van der Waals forces in the lipid bilayer?

Stability of the bilayer formation Signup and view all the answers

What is the function of peripheral proteins in the cell membrane?

To modify the activity of integral proteins Signup and view all the answers

What is the primary function of the mitochondrial membrane?

To conserve energy through oxidative phosphorylation Signup and view all the answers

What is the lipid mosaic model?

A model that describes the structure of the lipid bilayer Signup and view all the answers

What is the primary function of cholesterol in maintaining cell membrane fluidity?

To prevent excessive separation or tight packing of phospholipids Signup and view all the answers

What is the shape of an erythrocyte membrane?

Biconcave disc Signup and view all the answers

What type of bonds are present in unsaturated fatty acid chains?

Double bonds Signup and view all the answers

What is the primary function of Band 3 in the erythrocyte membrane?

To facilitate the exchange of Cl- and HCO3- Signup and view all the answers

What is the role of ankyrin in the erythrocyte membrane?

To link integral membrane proteins to the spectrin-actin cytoskeleton Signup and view all the answers

What is the effect of cold temperature on phospholipids in the cell membrane?

They come closer together Signup and view all the answers

What is the function of spectrin in the erythrocyte membrane?

To crosslink with actin Signup and view all the answers

What is the effect of saturated fatty acid chains on cell membrane fluidity?

They decrease fluidity Signup and view all the answers

Study Notes

Membrane Permeability and ATP-Dependant Pumps

Phospholipid Bilayer Function

Controls the flow of information between cells and the environment
Recognition of signaling molecules
Selective control of substance transport

Mitochondrial Membrane

Involved in energy conservation through oxidative phosphorylation

Membrane Composition

Phospholipids: amphipathic molecules with a glycerol backbone, two hydrophobic fatty acid chains, and a phosphate hydrophilic head group
Fatty acids are poorly soluble in water
Composition: 40% lipid, 60% protein, 1-10% carbohydrate

Lipid Mosaic Model

Van der Walls forces allow bilayer formation between hydrophobic tails, providing stability
Lipid bilayers have low permeability to ions and polar molecules

Membrane Proteins

Integral proteins: embedded within the phospholipid bilayer
Peripheral proteins: attached to the surface of the phospholipid bilayer

Carbohydrates in Membrane Composition

Attached to lipids and proteins on the exterior surface of the cell
Allow for cell recognition
Form glycoproteins (membrane proteins with a carbohydrate group) and glycolipids (modified lipids with a carbohydrate group)

Glycocalyx

Highly hydrophilic

Cell Membrane Fluidity

Influenced by three factors:
- Temperature: cold temperatures cause phospholipids to be closer together, while hot temperatures cause them to move farther apart
- Cholesterol: prevents excessive separation or tight packing of phospholipids, maintaining fluidity
- Saturated and unsaturated fatty acids: saturated fatty acids have straight chains and pack tightly, while unsaturated fatty acids have kinks in their chains, making them harder to pack tightly

Erythrocyte Membrane Model

Biconcave disc shape with a 120-day lifespan
Specialized cytoskeleton (spectrin and actin) provides flexibility and stability
Composed of lipids and proteins

Band 3, Ankyrin, Protein 4.2, and Spectrin

Band 3: a Cl-/HCO3- exchanger and integral protein that links to protein 4.2 and ankyrin
Ankyrin: a protein that links integral membrane proteins to the spectrin-actin cytoskeleton
Protein 4.2: an ATP-binding protein that may regulate the association of band 3 with ankyrin
Spectrin: a protein that crosslinks with actin

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Description

Learn about the function of phospholipid bilayer, ATP-dependent pumps, and transporters in membrane permeability, including communication, reception, and selectivity.