biological molecules (WHOLE)

2 amino acids

dipeptide

what are one or more polypeptides

proteins

what is polypeptide

lots of amino acids

how are peptides formed?

• via condensation reactions between an amine group of one amino group and the carbonyl group of another

• a molecule of water is realeased

• the bonds formed is called a peptide bond

• the reverse happens during digestion

what’s the enzyme that catalyses the condensation reaction between two amino acid called

peptidyl transferase

amino acids and their condensation reaction

why do the polypeptides fold into complex structures?

the different R groups of the amino acids interact with each other which form different bonds.

The different sequences of amino acids present lead to different structures with different shapes,

the primary structure of proteins

simple long chains with no intermolecular bonds or interactions

the secondary structure of proteins

• hydrogen bonds form causing the molecule chain to either fold or coil

• the primary sequence is what determines weather it folds or coils

what are the two secondary structure of protein?

• Alpha helix (α-helix) and beta pleated sheet (β-sheet)

• They form due to hydrogen bonding between the backbone atoms of the polypeptide chain

• These hydrogen bonds stabilize the structure and help the protein fold into regular, repeating patterns

the tertiary structure of proteins

• the 3D shape of the polypeptide chain.

• It creates a specific shape due to the sequence of amino acids in the haon

• hydrogen bonds, ionic one, disulphide bridges form between R groups

• a change to the sequence of amino acids would effect the secondary and tertiary structure as these bonds would form in different

• All enzymes, antibodies and some hormones have a tertiary structure

quaternary structure of proteins

• if proteins are made of more than one polypeptide chains they then are joined together to create quaternary structure.

• Antibodies and haemoglobin are examples.

why are lipids non polar

because elections are evenly distributed

what is the biological roles of lipids

• controlling fluidity of the cell membrane

• electrical insulation

• hormone production

• waterproofing

what are triglycerides made off

one glycerol and 3 fatty acids

what is the general formula of triglycerides

CnH(2n+1)COOH

what’s the function of triglycerides

• energy storage

• thermal insulation (buoyancy, and around vital organs cushioning)

• the long fatty acids chains release lots of energy when broken down.

what is glycerols

a small 3 carbon molecule with three alcohol groups (C3H8O3)

why are triglycerides good for energy store

they yield more energy per unit mass than other compounds so are good for energy storage

properties of fatty acids

1. fatty acids have a carboxyl group and a hydrocarbon chain

2. the chain can be from 14-22 carbon long

3. fatty acids have the same basic structure but the hydrocarbon tail varies

4. the tails are hydrophobic (they repel water molecules) therefore lipids are insoluble

what are saturated fats

• they have no C=C bonds in the chain

• this makes them saturated and straight chains

what are mono saturated fats

• they have one C=C bond in the chain

• this causes a kink and bends in the chain

• bending in the chains means they cannot pack closely together

• this makes them liquid at room temp

what are poly saturated fats

• they have several C=C bonds

• this makes them unsaturated

• this causes kinks and bends in the chain

• the bends lower the melting point

how are triglycerides formed

1. triglycerides are made of one glycerol and 3 fatty acids joined together

2. each hydroxyl group interacts to form an ester bond between the glycerol and each fatty acid

3. during the ester bond formation three water molecules are released

4. this reaction is called esterification

5. when triglycerides are broken down, 3 water molecules are needed to be supplied to reverse the reaction

structure of triglycerides

what are phospholipids

lipids with a phosphate group rather than a fatty acid chain.

what’s the property of the phosphate group in phospholipids?

it’s hydrophilic

what’s micelle

1. when mixed with water, phospholipids form droplet spheres

2. the hydrophilic head gave the water

3. the hydrophobic tails gave each other

4. this is called micelle

what’s a phospholipid bilayer

• Made of phospholipids (hydrophilic heads + hydrophobic tails)

• In water, tails hide from water, heads face water

• Two layers form: tails inside, heads outside → bilayer

• Basis of cell membranes; creates a semi-permeable barrier

what are sterols also known as

steroid alcohols

what are sterols

complex alcohol molecules based on a 4 carbon ring structure with a hydroxyl group at the end of

the hydroxyl group is polar and therefore hydrophilic

the rest of the molecules is hydrophobic

where is cholesterol made

it’s manufactured in the liver and intensifies.

what’s the function of cholesterol

it positions itself between the phospholipids in the membrane,

it adds stability to the membrane (fluid at low temp and not too fluid at high temp)

vitamins D, steroid, hormones and bile at

produced using cholesterol

what’s the steps for the emulsion test for lipids?

lipids do not dissolve in water but they do in ethanol to find out if there is fats in a sample, you do an emulsion test.

1. add ethanol to a test substance and shake throughly for about a minute so it dissolves

2. add water to the solution

3. if lipid is present, it will show as a milky emulsion. The more lipids, the more noticeable the milky colours will be.

4. (the rest can be improved by adding dye Sudan III, which will stain the lipids red)

what’s a carbohydrate

molecules which contain Hydrogen, carbon and oxygen only. The general formula is Cx(H2O)y

Molecular formula of glucose

C6H12O6

what are the two structures of glucose

• alpha glucose

• beta glucose

What happens to glucose in aqueous structures

forms a ring structure- a hexose monosaccharide.

alpha glucose

beta glucose

what are sugars that contain five carbon molecules called

pentose monosaccharides

ribose and deoxyribose

How are disaccharides formed

when two monosaccharides are joined together by a glycosidic bond

what is a glycosidic bond

a covenant bond between 2 monosaccharides

How does the condensation reaction occur between two sugars

It is formed when two hydroxyl groups on diffrent monosaccharides interact to form a strong covenant bond called glycosidic bond. (The oxygen link that holds the two molecules together) Every glycosidic bond results in one water molecule being removed.

The opposite is an hydrolytic reactions.

What are the two classification of sugars

• reducing sugar

• non-reducing sugar

what is a reducing sugar

• can donate electrons, the sugar becomes the reducing agent.

• they can be detected using benedict test

• the sugar reduces the soluble copper sulphate to insoluble copper oxide

• therefore turning it brick red

What are examples of reducing sugars?

1. glucose

2. fructose

3. galactose

4. galactose-fructose

what’s non-reducing sugar?

• sugars that cannot donate electrons

• therefore they cannot be oxidised

• to detect non reducing sugars you must first hydrolyse it to break the disaccharides

an example: sucrose

What is starch

glucose that’s photosynthesised and stored as starch in excess

starch is an energy store for plants and is insoluble.

Why is starch a good storage molecules?

• because its insoluble

• makes it an ideal storage molecule as it prevents water entering cells my osmosis which would make them swell

what are the two polysaccharides known as starch

1. Amylose

2. amylopectin

how is amylose formed

formed by alpha glucose molecules forming a 1-4 glycosidic bonds.

properties of amylose

• due to the angle of the bonds the long chains twists to form a helix

• it is further stabilised by hydrogen bonding

• therefore it is very compact, insoluble and good for storage.

amylose structure

twists and form a helix structure

how is amylopectin formed

by alpha glucose molecules forming a 1-6 and 1-4 glycosidic bond.

properties it amylopectin

• branched chains

• the branches occur every 25 units

• allows the enzyme to break down molecule to get to the glycosidic bonds easily.

What is glycogen

the equivalent energy storage molecule found in animal and fungi.

• animals store excess glucose as glycogen

• it’s stored in the liver and some muscles

properties of glycogen

• made of alpha glucose

• forms more branches- 10 every subunits

• the branching of glycogen makes it very compact, therefore ideal for storage

• branches means there is many free ends where glucose can be added or removed

• this speed up process of storing and releasing glucose molecules required by the cells.

what is cellulose

the major component of cell walls in plants

properties of cellulose

• made from beta glucose

• long unbranded chains

• 1-4 beta glycosidic bond

• the subunit are oriented alternatively upwards and downward

• therefore cellulose is a straight chain

• the straight chain are linked with hydrogen bonds.

amylopectin structure

glycogen structure

cellulose structure

What is an OH group called

hydroxyl group

Why does water have a high boiling point

Due to the hydrogen bonding between water molecules. It takes a lot of energy to increase the temperature and water and cause water to become gaseous

Why is water less dense in its solid state?

Water molecules are held further apart when they are solid than when they are liquid, therefore density decreases as water becomes solid. This is because as water cools the hydrogen bonds become fixed in position. Which produces a giant rigid but open structure.

What does polar mean?

A molecule with a uneven distribution of charge. with a positive pole<latex>\delta</latex>+ and a negative <latex>\delta</latex>-

Why does water have high electronegativity

Because it has higher affinity for electrons.

What is an advantage of oxygen being slightly negative and hydrogen slightly positive in water

it makes it polar which means it can form weak electrostatic associations with other polar molecules. This is called an hydrogen bond.

What is a property of hydrogen bonds

Hydrogen bonds are weak when they are few so they are constantly breaking and reforming. When a large number is present they form a strong structure.

properties of water: high specific heat capacity

• heat capacity is the energy needed to increase the temp of 1kg of water by 1 celcius.

• Hydrogen bonds between the water molecules absorb a lot of energy so the specific heat capacity of water is high

• this means there is no rapid temp changes

• This makes water a great habitat

• Also mean optimal temp is maintained within cells and bodies

properties of water: high latent heat of evaporation

• HLHE is the energy needed to make water evaporate.

• Hydrogen bonds use a lot of energy when water evaporates which makes it great for cooling

• an example: thermoregulation such as sweating

• allows for temp to be maintained in cellular environments since enzymes only work within a narrow range.

Property of water: cohesion

• Cohesion is the attraction between molecules of water.

• water flows, which shows water molecules stick together

• water is adhesive: it sticks to other polar molecules. The cohesion-adhesion properties of water are important in the transport of water in plants-capillary action.- in the transpiration stream.

• the cohesion nature of water also causss surface tension when a body of water meets the air.

• these hydrogen bonds occur between the top layer of water molecules to create a ‘ film’ on the body of water.

why is water a good solvent

water is polar so slightly. positive end of the water molecule will be attracted to negative ion and the slightly negative end of water will be attracted to the positive ion. In this way, ions will be completely surrounded by water molecule. (dissolve)

This allows chemical reactions to occur in cells and also molecules and ions to be transported