2nd October 2019

ncl

14

Why is the tail hydrophobic?

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Phospholipids are amphipathic molecules. This means that they have a hydrophilic, polar phosphate head and two hydrophobic fatty acid tails. These components of the phospholipids cause them to orientate themselves, so the phosphate head can interact with water and the fatty acid tails can't, hence forming a bilayer.

Likewise, is lipid hydrophilic or hydrophobic?

Lipids are fats, like oil, that are insoluble in water. There are two important regions of a lipid that provide the structure of the lipid bilayer. Each lipid molecule contains a hydrophilic region, also called a polar head region, and a hydrophobic, or nonpolar tail region.

What do the hydrophobic tails do?

In biological systems, the phospholipids often occur with other molecules (e.g., proteins, glycolipids, sterols) in a bilayer such as a cell membrane. Lipid bilayers occur when hydrophobic tails line up against one another, forming a membrane of hydrophilic heads on both sides facing the water.

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What is the function of the hydrophobic tails?

Phospholipids are the primary molecules found in the plasma membrane. A phospholipid is unique in that it has a hydrophilic region called the head, and a hydrophobic region known as the tail. The hydrophilic region can interact with water due to the presence of a phosphate group which is polar, like water.

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Which side of the phospholipid is hydrophobic?

A single phospholipid molecule has a phosphate group on one end, called the “head,” and two side-by-side chains of fatty acids that make up the lipid “tails. ” The phosphate group is negatively charged, making the head polar and hydrophilic, or “water loving.”

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Is triglyceride a lipid?

Although the term "lipid" is sometimes used as a synonym for fats, fats are a subgroup of lipids called triglycerides. Lipids also encompass molecules such as fatty acids and their derivatives (including tri-, di-, monoglycerides, and phospholipids), as well as other sterol-containing metabolites such as cholesterol.

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Which is the best definition of osmosis?

Definition of osmosis. 1 : movement of a solvent (such as water) through a semipermeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane.

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What is the definition of lipids?

Any of a group of organic compounds, including the fats, oils, waxes, sterols, and triglycerides, that are insoluble in water but soluble in common organic solvents, are oily to the touch, and together with carbohydrates and proteins constitute the principal structural material of living cells.

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Are triglycerides polar?

Introduction Triacylglycerols, also known as triglycerides, are the simplest lipids formed by fatty acids. Triacylglycerols are nonpolar, hydrophobic, and insoluble in water. This is due to the ester linked bond between the polar hydroxyls of glycerol and the polar carboxylates of the fatty acids.

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Is a lipid cholesterol?

Cholesterol and triglycerides are important fats (lipids) in the blood. Cholesterol is an essential component of cell membranes, brain and nerve cells, and bile, which helps the body absorb fats and fat-soluble vitamins.

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How does water go through the cell membrane?

Nonpolar and small polar molecules can pass through the cell membrane, so they diffuse across it in response to concentration gradients. Carbon dioxide and oxygen are two molecules that undergo this simple diffusion through the membrane. The simple diffusion of water is known as osmosis.

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What is meant by the term lipid bilayer?

phospholipid bilayer. Word Origin. a two-layered arrangement of phosphate and lipid molecules that form a cell membrane, the hydrophobic lipid ends facing inward and the hydrophilic phosphate ends facing outward.

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What aspect of the cell membrane makes it selectively permeable?

Cell membranes are selectively permeable. A few lipophilic substances move freely across the cell membrane by passive diffusion. Most small molecules or ions require the assistance of specific protein carriers to transport them across the membrane.

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Is glycerol a lipid or protein?

If this is for school, you should write that glycerol is a lipid. The building blocks of lipids are glycerol and fatty acids. You have to prove that you know that. In real life, glycerol is a sugar alcohol which makes it more like a carbohydrate than anything else.

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Why are phospholipids good emulsifiers?

Like a triglyceride, a phospholipid has a backbone of glycerol, but it contains two fatty acids rather than three. Phospholipids act as emulsifiers because they can surround droplets of oil, allowing them to remain suspended in a watery environment. Phospholipids are an important component of cell membranes.

13

What is the fluid mosaic model of the cell?

The fluid mosaic model explains various observations regarding the structure of functional cell membranes. The model, which was devised by SJ Singer and GL Nicolson in 1972, describes the cell membrane as a two-dimensional liquid that restricts the lateral diffusion of membrane components.

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What types of molecules can pass through the phospholipid bilayer?

Because of the chemical and structural nature of the phospholipid bilayer (hydrophobic core), only lipid-soluble molecules and some small molecules are able to freely pass through the lipid bilayer. Ions and large polar molecules cannot pass through the lipid bilayer.

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Are phospholipid tails saturated or unsaturated?

If saturated fatty acids are compressed by decreasing temperatures, they press in on each other, making a dense and fairly rigid membrane. If unsaturated fatty acids are compressed, the “kinks” in their tails push adjacent phospholipid molecules away, which helps maintain fluidity in the membrane.

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What is the role of a phospholipid?

Phospholipids consist of a hydrophilic (or 'water loving') head and a hydrophobic (or 'water fearing') tail. Phospholipids like to line up and arrange themselves into two parallel layers, called a phospholipid bilayer. This layer makes up your cell membranes and is critical to a cell's ability to function.

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What is meant by the phospholipid bilayer?

phospholipid bilayer. Word Origin. a two-layered arrangement of phosphate and lipid molecules that form a cell membrane, the hydrophobic lipid ends facing inward and the hydrophilic phosphate ends facing outward.

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What is the role of cholesterol in the cell membrane?

This helps slightly immobilize the outer surface of the membrane and make it less soluble to very small water-soluble molecules that could otherwise pass through more easily. Without cholesterol, cell membranes would be too fluid, not firm enough, and too permeable to some molecules.

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Why do phospholipids form a bilayer when placed in water?

When phospholipids are mixed with water, they spontaneously rearrange themselves to form the lowest free-energy configuration. This means that the hydrophobic regions find ways to remove themselves from water, while the hydrophilic regions interact with water. The resulting structure is called a lipid bilayer.

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Is a cholesterol molecule polar or nonpolar?

Consequently, in an animal cell membrane the polar hydroxyl group sticks into the aqueous environment (either extracellular water or intracellular water), and the rest of the cholesterol molecule, which is non-polar, is found among the non-polar fatty acid tails of the phospholipids.The image below depicts a section of

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