26 Questions
What is the outcome of the binding of biologically active substances to receptors?
The action is initiated within the cell
What is the function of the LDL receptor in the cell?
To facilitate the uptake of cholesterol from the bloodstream
What happens when there is an oversupply of cholesterol in the cell?
The LDL receptor protein is inhibited
What is the result of an insufficient number of LDL receptors in the cell?
Increased levels of LDL and cholesterol in the bloodstream
What is the function of the protein in the LDL molecule?
To carry cholesterol in the bloodstream
What is the characteristic of the binding sites of membrane receptors?
They have a good fit for the substrate
What type of membrane protein is embedded in a membrane and can be removed by treatment with detergents or extensive sonication?
Integral protein
What is the function of receptor proteins in a cell?
To contain specific binding sites for extracellular substances
What is the primary function of transport proteins in a cell?
To mediate the entry of specific substances into a cell
What type of protein is bound to the outside of a membrane by polar or electrostatic interactions?
Peripheral protein
What is the term used to describe the lateral motion of components in a membrane?
Membrane fluidity
What is the function of anchoring proteins in a cell?
To anchor proteins to membranes
What is the primary function of a lipid bilayer in a cell membrane?
To provide structural support to the cell
What is the term used to describe the process by which a molecule or ion moves through an opening or pore in a membrane?
Simple diffusion
What is the term used to describe the process by which substances enter a cell by binding to a carrier protein?
Facilitated diffusion
What is the term used to describe the model in which proteins and a lipid bilayer exist side by side without covalent bonds between them?
Fluid-mosaic model
What is the primary function of cell membranes in cells?
To separate cells from the external environment and transport specific substances
What is the main force driving the formation of lipid bilayers?
Hydrophobic interaction
What is the characteristic of the arrangement of hydrocarbon chains in saturated fatty acids?
Linear arrangement leading to rigidity
What is the effect of cholesterol on the order and rigidity of lipid bilayers?
It increases order and enhances rigidity
What is characteristic of animal membranes compared to plant membranes?
Presence of cholesterol
What is the effect of a phase transition on the surface area of a lipid bilayer?
It increases
What is the difference between the membranes of prokaryotes and eukaryotes?
Prokaryotes have more fluid membranes
What is the role of membrane proteins in biological membranes?
They facilitate the transport of specific substances
What is the characteristic of the enzymes found in biological membranes?
Their function depends on the membrane environment
What is the arrangement of lipid molecules in a lipid bilayer?
Polar head groups are in contact with water and the hydrophobic parts are not in contact with water
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