BIO MOLECULES 2

facts about lipds and types of lipids?

• They have no affinity to water (insoluble) or hydrophobic

• Made up of lots of carbon and hydrogen but little amounts of oxygen.

  • Types of lipids: Triglycerides, Phospholipids and Cholesterol

USES OF LIPIDS IN BODY?

1. Energy store - major long-term energy store in humans; energy is released when lipids are respired.

2. Insulation - reduces heat loss from the body.

3. Water production - produces metabolic water when respired, important in animals such as camels.

3. Lubrication - reduces friction between surfaces.

4. Shock absorption - protects organs from physical damage.

5. Waterproofing - lipids form a water-resistant barrier, reducing water loss.

STRUCTURE OF TRIGLYCERIDE ?

• Made of carbon, hydrogen and oxygen

• One molecule of glycerol and three fatty acids

• The glycerol and fatty acids are joined by 3 ester bonds.

• The three fatty acids can have different hydrocarbon chains.

structure of glycerol?

• A 3 carbon molecule with 3 hydroxyl (OH) groups so an alcohol

• Each -OH group is bonded to a carbon atom.

structure of fatty acids

• Fatty acids contain a carboxyl group (-COОН) attached to a hydrocarbon chain.

• Fatty acids can be saturated or unsaturated.

• The carboxyl group is an acidic group.

describe the esterification process (or condensation) of fatty acids and glycerol to form a triglyceride

• A triglyceride is formed when one glycerol reacts with three fatty acids.

• The glycerol loses an hydroxyl (-OH) group and the fatty acids loses a hydrogen.

• This a condensation reaction.

• An ester bond forms between the glycerol and each fatty acid.

• One molecule of water is released for each ester bond formed.

• Therefore, forming one triglyceride produces three ester bonds and three water molecules.

Overall:

glycerol + 3 fatty acids - triglyceride + 3H₂O

describe the types of fatty acids

1. Saturated: Contains no carbon-carbon double bonds (C=C) in its hydrocarbon chain and each carbon atom is joined to the next by a single bond.

• Contains the maximum possible number of hydrogen atoms.

2. Unsaturated: Contains one or more carbon-carbon double bonds (C=C) in its hydrocarbon chain.

• Therefore contains fewer hydrogen atoms than a saturated fatty acid.

• C=C double bonds can cause the hydrocarbon chain to bend/kink.

describe the structure of a Saturated triglyceride

Glycerol bonded to three saturated fatty acids by three ester bonds.

The fatty acids contain no C=C double bonds.

The fatty acid chains are straight.

describe the properties of a saturated triglyceride

• Straight chains can pack closely together.

• This produces stronger intermolecular forces between molecules.

• Therefore, more energy is needed to separate the molecules, giving a high melting

point.

• Usually solid at room temperature (e.g. lard).

• Animal fats

• Generally considered the least healthy of saturated, monounsaturated and

polyunsaturated fats.

describe the structure of an unsaturated triglyceride

Glycerol bonded to three unsaturated fatty acids by three ester bonds.

The fatty acids contain one or more C=C double bonds.

The C=C double bonds cause kinks/bends in the fatty acid chains.

describe the properties of an unsaturated triglyceride

• The kinks mean the fatty acid chains cannot pack closely together.

• This produces weaker intermolecular forces between molecules.

• Therefore, less energy is needed to separate the molecules, giving a lower melting

point.

• Usually liquid at room temperature, e.g. olive oil.

describe the structure of polyunsaturated triglyceride

Glycerol bonded to three polyunsaturated fatty acids by three ester bonds.

Each fatty acid contains two or more C=C double bonds.

The multiple C=C double bonds cause more kinks/bends in the fatty acid chains.

describe the Properties of a Polyunsaturated triglyceride

• The multiple kinks mean the fatty acid chains cannot pack closely together.

• This produces weaker intermolecular forces between molecules.

• Therefore, less energy is needed to separate the molecules, giving a lower melting

point.

• Usually liquid at room temperature.

• Generally considered healthier than saturated and monounsaturated fats.

• e.g fish oil

describe the Breakdown of a triglyceride?

• Triglycerides are broken down by hydrolysis.

• Water is used to break the ester bonds.

This produces:

• glycerol

• three fatty acids

Overall:

triglyceride + 3H₂O - glycerol + 3 fatty acids

What is the structure of a phospholipid?

1 glycerol molecule

2 fatty acid molecules

1 phosphate-containing group

A simple organic molecule, such as choline

Therefore, a phospholipid has two fatty acid tails instead of the three found in a triglyceride.

hydrophilic head and a hydrophobic tail

describe the hydrophilic head and the hydrophobic tail of a phospholipid

Hydrophilic head

• Contains glycerol and phosphate group.

• The phosphate group is polar (charge) and interacts with water.

• Therefore, the head is hydrophilic.

• The head orientates towards water.

Hydrophobic tails

• Made from 2 fatty acids.

• Fatty acid tails are non-polar (no charge) and do not interact with water.

• Therefore, the tails are hydrophobic.

• The tails orientate away from water.

describe how phospholipids form a bilayer

• Phospholipids form a phospholipid bilayer in cell surface membranes.

• A bilayer forms because there is water outside the cell and water

inside the cell.

• The hydrophilic heads orientate towards the water on both sides of

the membrane.

• The hydrophobic fatty acid tails orientate away from water, towards

the middle of the membrane.

• This forms two layers of phospholipids, with the hydrophobic tails

facing each other in the centre.

• This forms the basic structure of cell surface membranes.

Q: How do phospholipids form cell membranes?

• Phospholipids have a hydrophilic head and

hydrophobic tails.

Because they have both regions, they are

amphipathic.

In water, they arrange into a bilayer with:

• hydrophilic heads facing the water

• hydrophobic tails facing inwards

• Phospholipid bilayers form the basic structure of cell surface membranes and membranes surrounding organelles.

Q: Why is the phospholipid bilayer useful

• The hydrophobic interior prevents many water-soluble and charged substances from

passing directly through the membrane.

• This contributes to the membrane's selective

permeability.

describe and explain the functions of triglyceride

1. Energy storage

Triglycerides are used as a respiratory substrate.

They release more energy per gram than carbohydrates when oxidised.

They can release water when metabolised, which is useful in some animals.

2. Do not affect water potential

Triglycerides are insoluble in water.

Therefore, they do not affect the water potential of cells.

3. Hormone production

Lipids are used in the production of some hormones.

4. Waterproofing

Lipids form waterproof layers on surfaces.

5. Buoyancy

Lipids can provide buoyancy because they are less dense than water.

6. Insulation and protection

Triglycerides form insulating layers that reduce heat loss.

They provide protection around organs.

Lipids are also associated with myelin sheaths around nerves.

7. Absorption of fat-soluble molecules

Dietary lipids aid the absorption of fat-soluble vitamins, such as vitamin A.

describe the basic structure of cholestrol

Cholesterol has a four-carbon-ring structure.

It has both hydrophilic and hydrophobic regions.

It fits between the phospholipids in cell membranes.

describe the role of cholestrol in cell membranes?

• Cholesterol regulates membrane fluidity and permeability.

• At high temperatures, it reduces membrane fluidity, helping prevent the membrane

becoming too fluid.

• At low temperatures, it prevents phospholipids from packing too closely together,

helping prevent the membrane becoming too rigid. At low temperatures, cholesterol increases membrane fluidity.

• Therefore, cholesterol helps maintain membrane stability.

define Amphipathic

Amphipathic = a molecule containing both hydrophilic and hydrophobic regions.

draw and label the general structure of an amino and then describe the structure in words

• carboxyl group

• amine group

• central carbon

• R side chain

facts about an amino acid?

• Amino acids are monomer units that form a polymer called a polypeptide. These polypeptides then combine to form proteins.

• The R group gives an amino acid its properties. The R group changes between the different amino acids.

• Changing the amino acid can lead to a change in the shape of the protein and may stop it from functioning.

what is a peptide bond and what is the simplest amino acid

A peptide bond is a bond that forms between a carboxyl group and and a amino acid group.

Glycine = simplest amino acid with it's R group just being hydrogen.

describe how a dipeptide is formed?

• One amino acid loses its -OH from it's carboxyl group and another amino acid loses it H from it's amine (or amino acid)

group.

• A peptide bond is formed.

• This forms water making it a condensation reaction.

Hydrolysis could also be used to reform the amino acid

monomers again by adding water.

describe the primary structure of a protein?

• The sequence of amino acids bonded by peptide bonds.

• Amino acids can be joined together to make a polypeptide in aprocess called polymerisation.

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• How is a polypeptide formed?

• Amino acids are joined by condensation reactions.

• Each condensation reaction forms a peptide bond and releases

one molecule of water.

• Repeated condensation reactions produce a polypeptide chain.

The sequence of amino acids determines the protein's ultimate/final 3D shape and therefore its function.

describe the secondary structure of a protein

• A polypeptide has -NH⁺ (positively charged) and -C=O^- (negatively charged) groups on either side.

• These two groups form a weak hydrogen bond.

• The hydrogen bonds hold the the folded polypeptide chain in place.

• This weak hydrogen bond causes the polypeptide chain to be twisted/folded into alpha helix or beta pleated sheet.

describe the tertiary structure of a protein

• The alpha helix or beta-pleated sheet folds further to form the protein's complex 3D structure.

• The tertiary structure is held in place by different bonds

and interactions:

• Disulfide bonds - fairly strong; form between -CH2-S-CH2 groups but the actual bond formed is S-S.

• lonic bonds - form between -NH3+ and -C=O-O groups; relatively easily broken but the actual ionic attraction is

between NH₂+ and O-.

• Hydrogen bonds - numerous but relatively easily broken; form between -NH and C=O groups but the actual hydrogen bond is between the H of -NH and the O of C=O.

• Amino acids with hydrophobic R groups orientate towards the centre of the protein.

• Amino acids with hydrophilic R groups orientate towards the outside of the protein.