Temperature Transition in Lipid Bilayers and Biological Membranes

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What is the primary effect of cholesterol on membrane fluidity?

Decrease in fluidity due to the rigidifying effect of cholesterol (correct)
Cholesterol only affects the fluidity of the outer leaflet of the membrane
Increase in fluidity due to the disruption of the lipid bilayer structure
No effect on fluidity, as cholesterol is not an integral part of the membrane

What type of proteins are bound tightly to the interior of the membrane?

Receptor proteins
Enzyme proteins
Integral proteins (correct)
Peripheral proteins

What is the nature of the interaction between peripheral proteins and the membrane?

Covalent bonds
Hydrogen bonds
Electrostatic interactions (correct)
Hydrophobic interactions

What is the structural organization of the cell membrane, according to the fluid mosaic model?

A lipid bilayer with proteins embedded in it (A) Signup and view all the answers

What is the characteristic of the cell membrane that refers to the asymmetry of its structure?

Asymmetry of protein distribution (B) Signup and view all the answers

What is the role of kinks in the tails of phospholipids in the plasma membrane?

To maintain the fluidity of the membrane across a range of temperatures (A) Signup and view all the answers

What is the characteristic shape of steroid molecules?

Almost planar (C) Signup and view all the answers

What is the function of cholesterol in the animal cell membrane?

To provide structural support to the membrane (C) Signup and view all the answers

What is the difference between LDL and HDL cholesterol?

LDL is 'bad' cholesterol, while HDL is 'good' cholesterol (A) Signup and view all the answers

What is the characteristic of amphipathic molecules, such as steroids?

They have both polar and nonpolar groups (D) Signup and view all the answers

What is the primary characteristic of membrane lipids that allows them to form lipid bilayers?

Their amphipathic nature, having a non-polar end and a polar end (A) Signup and view all the answers

What is the main difference between saturated and unsaturated fatty acids?

The presence or absence of carbon-carbon double bonds (B) Signup and view all the answers

What is the function of cholesterol in cell membranes?

To decrease membrane fluidity (D) Signup and view all the answers

What is the term for the interaction between proteins and lipids in cell membranes?

Protein-lipid interaction (B) Signup and view all the answers

What is the characteristic of cell membranes that refers to the difference in lipid composition between the inner and outer leaflets?

Asymmetry (D) Signup and view all the answers

Which type of protein spans the membrane?

Integral protein (A) Signup and view all the answers

What is the primary mechanism of facilitated diffusion?

Carrying of molecules across the membrane by a carrier/channel protein (A) Signup and view all the answers

What is the primary function of HDL cholesterol in the body?

To absorb cholesterol in the blood and carry it back to the liver (A) Signup and view all the answers

Why do lipids form various structures in an aqueous environment?

Because they are not very soluble in water (D) Signup and view all the answers

What is the driving force behind secondary active transport?

Movement of a driving ion down an electrochemical gradient (C) Signup and view all the answers

What is the role of the sodium-potassium ion pump in primary active transport?

To transport Na+ ions out of the cell and K+ ions into the cell (C) Signup and view all the answers

What is the result of high levels of LDL cholesterol in the body?

Raised risk for heart disease and stroke (C) Signup and view all the answers

What is the role of the liver in regulating cholesterol levels?

To flush excess cholesterol from the body (C) Signup and view all the answers

What is the result of the binding of Na+ ions to the enzyme in the sodium-potassium ion pump?

Phosphorylation of the enzyme (A) Signup and view all the answers

What is the relationship between lipoproteins and cholesterol in the bloodstream?

Cholesterol is a component of lipoproteins (D) Signup and view all the answers

What is the characteristic of lipids that leads to the formation of lipid bilayers?

Insolubility in water (D) Signup and view all the answers

What is the result of high levels of HDL cholesterol in the body?

Lowered risk for heart disease and stroke (B) Signup and view all the answers

What is the role of lipid bilayers in biological systems?

To form the structure of biological membranes (B) Signup and view all the answers

What is the significance of lipid metabolism in the body?

It regulates cholesterol levels in the bloodstream (B) Signup and view all the answers

What is the relationship between cholesterol and heart disease?

High levels of LDL cholesterol increase the risk of heart disease (D) Signup and view all the answers

What is the effect of heat on membrane structure?

Membranes become more disordered and fluid (A) Signup and view all the answers

What is the role of hydrophobic interactions in lipid bilayer formation?

It is the major force driving the formation of lipid bilayers (C) Signup and view all the answers

Which type of membrane is more fluid due to a higher percentage of unsaturated fatty acids?

Plant membranes (B) Signup and view all the answers

What is characteristic of animal membranes?

Presence of cholesterol (A) Signup and view all the answers

What is the significance of lipid bilayer asymmetry?

It is important for many physiological cell functions (B) Signup and view all the answers

What is the characteristic of fatty acids in phospholipids that allows them to aggregate in a lipid bilayer?

They are non-polar and hydrophobic. (C) Signup and view all the answers

What is the function of the modified phosphate group in phospholipids?

To orient towards water (D) Signup and view all the answers

What is the result of the orientation of phospholipid molecules in a lipid bilayer?

A hydrophobic core and a hydrophilic exterior (B) Signup and view all the answers

What is the characteristic of unsaturated fatty acids that affects membrane fluidity?

They have one or more double bonds between carbons. (B) Signup and view all the answers

What is the difference between triglycerides and phospholipids?

Triglycerides have a glycerol molecule linked to three fatty acids, while phospholipids have a glycerol molecule linked to two fatty acids and a modified phosphate group. (A) Signup and view all the answers