Biology chapter 5:99-100

What are the seven key classes of membrane proteins?

Transporters, enzymes, cell-surface receptors, cell-surface identity markers, cell-to-cell adhesion proteins, attachments to the cytoskeleton, and proteins that affect membrane structure.

What role do transporters play in cell membranes?

They selectively allow certain solutes to enter or leave the cell.

How do enzymes function in relation to the plasma membrane?

They carry out chemical reactions on the interior surface of the plasma membrane.

What is the function of cell-surface receptors?

They detect chemical messages from the environment.

What are cell-surface identity markers?

They are specific combinations of cell-surface proteins and protein complexes that identify cell types.

What is the role of cell-to-cell adhesion proteins?

They help cells stick to one another through temporary or permanent interactions.

How do proteins attach to the cytoskeleton?

Surface proteins interact with the cytoskeleton through linking proteins.

What effect do wedge-shaped proteins have on membranes?

They can cause membranes to bend and form tubes.

What is a transmembrane domain?

A membrane-spanning region of a protein, composed of hydrophobic amino acids, that anchors the protein in the membrane.

How many transmembrane domains can a protein have?

Proteins can have one or more transmembrane domains.

What is an example of a protein with a single transmembrane domain?

A linking protein that attaches the spectrin network of the cytoskeleton to the plasma membrane.

What is bacteriorhodopsin and its function?

A protein with seven transmembrane domains that pumps protons (H+) across the bacterial membrane using light energy.

What characterizes G protein-coupled receptors?

They all contain seven characteristic transmembrane domains.

What is a β barrel in transmembrane proteins?

A structure formed by β-pleated sheets that creates a polar environment for molecules to pass through the membrane.

How do reticulons affect membrane structure?

They cause membranes to bend and can help form tubular structures.

What is the significance of hydrophobic interactions in membrane stability?

They prevent transmembrane proteins from detaching from the membrane when cells move.

What is the fluid mosaic model?

A model describing how membranes are held together by hydrophobic interactions, allowing for flexibility and movement of proteins within the membrane.

Why do transmembrane domains consist of hydrophobic amino acids?

To ensure they remain embedded within the lipid bilayer, avoiding contact with water.

What are peripheral membrane proteins?

Proteins that are attached to the membrane surface, often anchored by modified lipids.

What is the role of phospholipid composition in membrane shape?

It affects the overall shape and structure of the membrane.

What are the two types of secondary structures found in transmembrane proteins?

α helices and β-pleated sheets.

How do proteins stabilize flattened regions of membranes?

By coating the membrane and holding adjacent folds together with adhesion proteins.

What is the primary function of membrane proteins?

To confer differences between membranes of different cells, facilitating various cellular functions.