Lipids Flashcards

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Questions and Answers

What type of compound are lipids?

organic

What three elements are lipids composed of?

carbon, hydrogen, and oxygen

Lipids are large complex molecules called?

macromolecules

Why are lipids non-polar molecules?

<p>Their electrons in the outer orbitals that form bonds are more evenly distributed than those in polar molecules.</p> Signup and view all the answers

What property does being non-polar lead to?

<p>Insolubility in water</p> Signup and view all the answers

What are triglycerides?

<p>Lipids composed of fatty acids and glycerol.</p> Signup and view all the answers

What is glycerol?

<p>Small, simple alcohol</p> Signup and view all the answers

Glycerol is an alcohol that contains 3 carbon atoms joined by a?

<p>hydroxyl group</p> Signup and view all the answers

What happens when the hydroxyl group between the glycerol and fatty acid interact?

<p>3 water molecules are formed and bonds between the molecules occur.</p> Signup and view all the answers

What is this reaction called?

<p>esterification</p> Signup and view all the answers

What is the bond called formed during esterification?

<p>an ester bond</p> Signup and view all the answers

What type of reaction is esterification an example of?

<p>a condensation reaction</p> Signup and view all the answers

What is the formula of glycerol?

<p>C3H8O3</p> Signup and view all the answers

What is this particular glycerol's modern chemical name?

<p>propane 1,2,3 triol</p> Signup and view all the answers

What is the general formula of a fatty acid?

<p>CH3 (CH2)n COOH</p> Signup and view all the answers

What group of molecules do fatty acids belong to?

<p>carboxylic acids</p> Signup and view all the answers

Why are fatty acids called acids?

<p>They contain the carboxyl group -COOH, and this group is found in all organic acids.</p> Signup and view all the answers

What happens to the carboxyl group when in water?

<p>It dissociates to produce hydrogen ions, H+.</p> Signup and view all the answers

Give the equation for the dissociation of the carboxyl group.

<p>COOH → COO- + H+</p> Signup and view all the answers

What is the rest of the fatty acid composed of?

<p>carbon and hydrogen; it is called a hydrocarbon chain.</p> Signup and view all the answers

How can the hydrocarbon chain vary in fatty acids?

<ol> <li>The number of carbons; 2. The presence or absence of double bonds; 3. The position of such double bonds if they exist.</li> </ol> Signup and view all the answers

What gives a fatty acid its properties?

<p>The structure of the fatty acid.</p> Signup and view all the answers

When is a triglyceride formed?

<p>When each hydroxyl group on the glycerol molecule combines with a carboxyl group on a fatty acid molecule.</p> Signup and view all the answers

What is this reaction called?

<p>condensation reaction</p> Signup and view all the answers

What is removed and what is formed during triglyceride formation?

<ol> <li>Water; 2. An ester bond.</li> </ol> Signup and view all the answers

What is the umbrella term used to describe triglycerides?

<p>fats</p> Signup and view all the answers

How are triglycerides grouped?

<p>According to their physical state.</p> Signup and view all the answers

What are triglycerides called when liquid at room temperature (20 degrees C)?

<p>oils</p> Signup and view all the answers

What are triglycerides called when solid at room temperature?

<p>fats</p> Signup and view all the answers

What is each molecule of fat or oil made up of?

<p>1 glycerol molecule and 3 fatty acid molecules.</p> Signup and view all the answers

Fatty acids can be described as?

<p>saturated or unsaturated</p> Signup and view all the answers

What does saturated mean?

<p>Each carbon atom in the hydrocarbon chain is linked to a carbon atom on either side and also 2 hydrogen atoms, leading to no spare bonds.</p> Signup and view all the answers

Saturated fatty acids have only?

<p>single bonds in the hydrocarbon chain.</p> Signup and view all the answers

Explain the link between saturated triglycerides and the appearance of fats.

<p>Saturated fatty acids only have single carbon-carbon bonds, which makes the hydrocarbon chain relatively straight, allowing fatty acids to pack closely. Thus, triglycerides of saturated fatty acids tend to be solid at room temperature.</p> Signup and view all the answers

Name an example of an unsaturated fat.

<p>oleic acid</p> Signup and view all the answers

What are fatty acids with one double bond called?

<p>mono-unsaturated fats</p> Signup and view all the answers

What are fatty acids with more than one double bond called?

<p>polyunsaturated fats</p> Signup and view all the answers

What are the 2 arrangements around a double bond called?

<ol> <li>Cis; 2. Trans</li> </ol> Signup and view all the answers

Triglycerides with a high proportion of cis-fatty acids tend to be what at room temperature?

<p>oils</p> Signup and view all the answers

What does the presence of one or more double carbon-carbon bonds cause?

<p>Kinks in the hydrocarbon chain.</p> Signup and view all the answers

Why are fats a more concentrated source of energy than protein and carbohydrates?

<p>Triglycerides have a higher proportion of hydrogen.</p> Signup and view all the answers

In mammals, what is extra fat laid down for?

<p>Storage of special connective tissue (adipose tissue).</p> Signup and view all the answers

What are phospholipids?

<p>Modified triglycerides</p> Signup and view all the answers

What elements do phospholipids contain?

<p>carbon, oxygen, hydrogen, and phosphorus.</p> Signup and view all the answers

Where are inorganic phosphate ions found in every cell?

<p>In the cytoplasm.</p> Signup and view all the answers

Why are phosphate ions negatively charged?

<p>They contain extra electrons.</p> Signup and view all the answers

What property does being negatively charged lead to?

<p>They are soluble in water.</p> Signup and view all the answers

Why are phospholipids called surfactants?

<p>They form a layer on the surface of water with phosphate heads sticking in the water and the fatty acid tails sticking out.</p> Signup and view all the answers

What is a bilayer and how is it formed?

<p>Phospholipids form bilayers which is a two-layered sheet formation. Hydrophilic tails point towards the centre of the sheet.</p> Signup and view all the answers

What is another name for sterols?

<p>steroid alcohols (complex alcohol structure)</p> Signup and view all the answers

Where are steroids found?

<p>Inside cells.</p> Signup and view all the answers

Steroids are not?

<p>fats and oils.</p> Signup and view all the answers

What is the complex alcohol structure based on?

<p>A four carbon ring structure with a hydroxyl group at each end.</p> Signup and view all the answers

What do steroids of phospholipids have in common?

<p>The hydroxyl group is polar and therefore the rest of the molecule is hydrophilic.</p> Signup and view all the answers

Name a sterol.

<p>cholesterol</p> Signup and view all the answers

Where is cholesterol manufactured in the body?

<p>In the liver and intestines.</p> Signup and view all the answers

What is cholesterol's important role?

<p>The formation of cell membranes.</p> Signup and view all the answers

Name 3 things manufactured using cholesterol.

<ol> <li>Vitamin D; 2. Steroid hormones; 3. Bile.</li> </ol> Signup and view all the answers

Due to their non-polar nature, name 4 biological roles of lipids.

<ol> <li>Membrane formation and the creation of hydrophobic barriers; 2. Hormone production; 3. Electrical insulation necessary for impulse transmission; 4. Waterproofing, for example, in birds' feathers and on plant leaves.</li> </ol> Signup and view all the answers

What are lipids (in particular triglycerides) roles around organs and under the skin?

<ol> <li>Thermal insulation to reduce heat loss; 2. Cushioning to protect vital organs such as the heart and kidneys; 3. Buoyancy for aquatic animals.</li> </ol> Signup and view all the answers

What laboratory test is used to determine if lipids are present?

<p>emulsion test</p> Signup and view all the answers

Method for emulsion test.

<ol> <li>Sample mixed with ethanol; 2. Resulting solution mixed with water and shaken; 3. If an emulsion forms as a layer on top of the solution, this indicates the presence of a lipid.</li> </ol> Signup and view all the answers

Flashcards

Lipids

Organic compounds primarily composed of carbon, hydrogen, and oxygen, with a lower oxygen content compared to carbohydrates.

Macromolecules

Large, complex molecules with a variety of biological functions.

Non-polar molecules

Molecules that repel water due to an even distribution of electrons.

Triglyceride

A type of lipid composed of one glycerol molecule and three fatty acid chains.

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Glycerol

A small alcohol with three carbon atoms connected by hydroxyl groups.

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Esterification

The process of combining glycerol and fatty acids to form triglycerides, releasing water.

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Fatty acids

Carboxylic acids with a long hydrocarbon chain.

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Saturated fatty acids

Fatty acids containing only single bonds between carbon atoms.

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Unsaturated fatty acids

Fatty acids containing one or more double bonds between carbon atoms.

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Oils

Triglycerides that are liquid at room temperature.

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Fats

Triglycerides that are solid at room temperature.

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Phospholipids

Modified triglycerides containing phosphorus, forming bilayers in cell membranes.

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Hydrophilic head

The polar 'head' of a phospholipid, attracted to water.

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Hydrophobic tail

The non-polar 'tail' of a phospholipid, repelled by water.

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Surfactants

Molecules that can interact with both polar and non-polar substances.

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Sterols (Steroid alcohols)

Complex molecules based on a four-carbon ring with hydroxyl groups.

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Cholesterol

A key sterol found in cell membranes, involved in various biological processes.

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Emulsion test

A test to detect the presence of lipids in a sample.

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Emulsion layer

The formation of a cloudy layer indicating the presence of lipids in a sample.

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Lipids as membrane components

Act as structural components of cell membranes and other cellular structures.

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Lipids as hormone precursors

Serve as precursors for hormones, such as steroid hormones.

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Lipids for nerve insulation

Provide electrical insulation for nerve fibers, allowing efficient nerve impulse transmission.

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Lipids for waterproofing

Create waterproof surfaces in animals and plants, preventing water loss.

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Lipids for thermal insulation

Provide thermal insulation in mammals, helping to maintain body temperature.

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Lipids for organ cushioning

Act as cushioning for vital organs, protecting them from injury.

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Lipids for buoyancy

Contribute to buoyancy in aquatic species, allowing them to float more easily.

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Study Notes

Lipids Overview

  • Lipids are organic compounds primarily composed of carbon, hydrogen, and oxygen, with less oxygen than carbohydrates.
  • They are classified as macromolecules, indicating their large, complex structure.

Properties of Lipids

  • Lipids are non-polar molecules due to the even distribution of electrons, leading to insolubility in water.
  • The non-polar nature of lipids contributes to their biological functions.

Triglycerides

  • Triglycerides consist of one glycerol molecule and three fatty acids.
  • Glycerol is a small alcohol with three carbon atoms connected by hydroxyl groups.
  • Esterification is the reaction forming triglycerides, where three water molecules are produced and ester bonds are formed.

Fatty Acids

  • Fatty acids are carboxylic acids characterized by the general formula CH3(CH2)nCOOH.
  • They include hydrocarbon chains which vary in length, degree of saturation (single or double bonds), and position of double bonds.
  • Saturated fatty acids contain only single bonds, while unsaturated fatty acids have one (mono-unsaturated) or more (polyunsaturated) double bonds.

Physical States of Triglycerides

  • Triglycerides are categorized as oils when liquid at room temperature and fats when solid.
  • The structure of saturated triglycerides allows tight packing, making them solid, while unsaturated triglycerides tend to be liquid due to kinks in their structure from double bonds.

Phospholipids

  • Phospholipids are modified triglycerides containing carbon, hydrogen, oxygen, and phosphorus.
  • They form bilayers in cell membranes due to the hydrophilic heads and hydrophobic tails, acting as surfactants.

Sterols

  • Sterols, also known as steroid alcohols, have a complex structure based on a four-carbon ring with hydroxyl groups.
  • Cholesterol is a key sterol manufactured in the liver and intestines, essential for cell membrane formation and the synthesis of Vitamin D, steroid hormones, and bile.

Biological Roles of Lipids

  • Lipids play critical roles including:
    • Formation of membranes and hydrophobic barriers.
    • Production of hormones.
    • Providing electrical insulation for nerve transmission.
    • Waterproofing surfaces in animals and plants.
  • In mammals, lipids serve as thermal insulation, cushioning for vital organs, and buoyancy for aquatic species.

Testing for Lipids

  • The emulsion test is used to detect the presence of lipids, involving mixing the sample with ethanol followed by water, leading to an emulsion layer if lipids are present.

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