Membrane Structure, Synthesis, and Transport - Lecture Notes

This set of flashcards covers key concepts, definitions, and processes related to membrane structure, synthesis, and transport based on the lecture notes.

What is the primary function of the plasma membrane?

It holds the contents of the cell in one place and regulates the traffic of substances into and out of the cell.

What does the fluid-mosaic model describe?

The plasma membrane is a mosaic of lipid, protein, and carbohydrate that resembles a fluid due to the movement of lipids and proteins.

What are phospholipids?

Amphipathic molecules that form the framework of the phospholipid bilayer.

What are glycolipids?

Carbohydrates attached to lipids that are found in the membrane.

Which type of molecules can move freely in the lipid bilayer?

Lipid molecules move freely laterally within the membrane leaflet.

What does 'asymmetrical' mean in the context of phospholipid bilayers?

Each leaflet of the bilayer faces a different environment, often with different compositions.

What role do membrane proteins play?

They participate in transport, energy transduction, cell signaling, secretion, and recognition.

What are transmembrane proteins?

Proteins that span from one side of the membrane to the other.

What are lipid-anchored proteins?

Proteins anchored to the membrane via a covalently attached lipid.

What are peripheral membrane proteins?

Proteins that are non-covalently bound to other membrane proteins or lipids.

How does temperature affect membrane fluidity?

Membranes are less fluid at low temperatures and more fluid at high temperatures.

What are the two types of transport proteins?

Channels and transporters.

What happens to cells in a hypertonic environment?

Cells will lose water and shrink.

What is osmosis?

The movement of water across membranes in response to solute concentration gradients.

Describe simple diffusion.

The movement of solutes down a concentration gradient without the aid of a transport protein.

What is facilitated diffusion?

The movement of solutes down a concentration gradient with the aid of a transport protein.

What is active transport?

Movement of molecules against a concentration gradient using energy, often from ATP.

What is the role of cholesterol in membranes?

Cholesterol stabilizes membranes and affects fluidity depending on temperature.

What is the structure of a membrane protein channel?

Transmembrane proteins that allow movement of specific ions and molecules across a membrane.

What are the two classes of transporters?

Uniporters and symporters.

What is primary active transport?

Transport that uses energy directly to move a solute against its concentration gradient.

What does an antiporter do?

Transports two or more different ions or molecules in opposite directions across the membrane.

How do plants respond to hypotonic environments?

They will take up water, generating osmotic pressure that prevents major expansion due to the cell wall.

What happens in a hypotonic environment for animal cells?

Animal cells will swell and may undergo lysis.

What is a chemical gradient?

A difference in the concentration of a solute across a membrane.

What is the significance of a sodium-potassium pump?

It exports Na+ and imports K+ against their gradients, generating an electrical gradient.

What alters lipid composition in membranes?

Organisms can adjust lipid types to ensure optimal fluidity.

How do double bonds in phospholipid tails affect membrane fluidity?

They create kinks, reducing interactions between adjacent tails and increasing fluidity.

What kind of molecules have the highest permeability across membranes?

Gases and small, uncharged molecules.

What effect does an increase in temperature have on membrane fluidity?

It generally makes membranes more fluid.

What is plasmolysis?

The process where the cell membrane pulls away from the cell wall in plant cells due to water loss.

What factors affect the ability of solutes to pass through a lipid bilayer?

Size, polarity, charge, and concentration.

What is the role of the hydrophobic interior of a membrane?

It acts as a barrier to the movement of ions and hydrophilic molecules.

What happens to cells placed in isotonic solutions?

They maintain normal shape and volume.

What are the roles of integral membrane proteins?

They help transport specific substances across the cell membrane.

What is the significance of maintaining membrane gradients?

Living cells must maintain a distinct internal environment relative to the external environment.

Describe the mechanism of the Na+/K+ pump.

It binds three Na+, hydrolyzes ATP for energy, releases them, then binds two K+ and releases them into the cytosol.

What are the two main types of passive transport?

Simple diffusion and facilitated diffusion.

Why can water cross the membrane while many solutes cannot?

The lipid bilayer is relatively impermeable to solutes but somewhat permeable to water.

What is selective permeability?

The property of membranes to allow certain molecules to pass while blocking others.

What do glycolipids and glycoproteins contribute to cell membranes?

They play essential roles in cell recognition and signaling.

Name a process that can use an existing gradient to transport another solute.

Secondary active transport.

In what manner do transport proteins operate?

They undergo conformational changes to move solutes across the membrane.

What defines a

The arrangement of components in a fluid-mosaic model refers to the dynamic and asymmetrical organization of lipids, proteins, and carbohydrates, similar to a mosaic.

What happens during facilitated diffusion?

Substances move across a membrane with the help of specific transport proteins, down their concentration gradient.