Biological Molecules

Monosaccharides:

• The monomers of carbohydrates
• Trioses, pentoses and hexoses.
• Sweet, soluble and crystalline.
• Simple sugars with one 1 or chain of 3,5 or 6 carbon atoms. 
• Examples are ribose, glucose and fructose.
• The formula is Cn(H20)n
• The are used for energy and biological building blocks.
• If the OH at the first carbon is below, it is an alpha-glucose.
• If the OH at the first carbon is above, it is a beta-glucose.

Disaccharides:

• Sugars with 2 rings of 6 carbon atoms, joined by a glycosidic bond.
• Examples include sucrose, lactose and maltose.
• Glucose+ glucose= maltose.
• Glucose+ galactose=lactose.
• Glucose+ fructose=,sucrose.
• They are used to sweeten food.
• Formed by the condensation of 2 monosaccharides, usually hexoses.
• The reverse of condensation is hydrolisis (di/polysaccharide to monosaccharide).
• These reactions are controlled by enzymes.
• The bond formed in condensation is a glycosidic bond.
• 

Polysaccharides:

• Macromolecules with many rings of 6 carbon atoms joined by glycosidic bonds.
• In a glucose there are lots of bonds that release enrgy in the form of ATP.
• This breakdown is driven by shape-specific enzymes.
• Only alpha- glucose can be broken down in respiration as only those enzymes are present.
• Glucose monomers join through condensation and form glycosidic bonds.
• Amylose molecules form compact, coiled springs due to the way they bond.
• Large molecules like amylose are not soluble in water.
• Iodine molecules can get stuck in the coils, meaning it turns yellow to black.

Polysaccharides- continued:

Cellulose:

• Made from beta-glucose.
• Long unbranched chains.
• If present, Schulze's reagent will turn purple.
• Found in cell walls in plants.
• Its function is to support cells.

Polysaccharides- continued:

Starch:

• Made from alpha glucose.
• Amylose is made of long unbranched chains.
• Amylopectin is made of long branched chains.
• The branches form when one end of a chain joins to a glucose in another, forming a glycosidic bond.
• When present, iodine turns from yellow to black.
• Insoluble in water so does not affect the water potential of cells.
• Found in the cytoplasm/starch grains in plant cells.
• Used for energy storage.

Polysaccharides- continues:

Glycogen:

• Made of alpha glucose.
• Like starch, but shorter so more branched.
• Branching means faster breakdown in respiration and more ends which enzymes can start hydrolyisis from.
• Insoluble in water so does not affect the water potential of the cell. 
• Reacts with Lugol's reagent to give a brown-blue color. 
• Found in the muscles/ liver of animals.
• Used as energy storage.

• Provides energy storage.
• Provides insulation.
• Found in the cell membrane.
• Used for waterproofing in birds.
• The most common type are triglyerides, which are commonly known as fats and oils.
• Fats are solid at room temperature.
• Oils are liquid at room temperature.

Triglycerides:

• Made of three fatty acids bonded to a glycerol molecule.
• When a fatty acid combines with glycerol, it becomes a glyceride, so when all 3 fatty acids are added it becomes a triglyceride.
• Fatty acids have long tails made of hydrocarbons.
• Tails contain lots of chemical energy- lots of energy is released when they are broken down.
• Because of these tails, lipids contain twice as much energy per gram as carbohydrates.
• The tails are hydrophobic, so make lipids insoluble in water, meaning it doesnt cause water to enter the cell by osmosis.
• The bundle together as inoluble droplets, with the hydrophobic ends facing inwards, shielded by the glycerol heads.
• Glycerol is a type of alcohol.
• They are organic molecules with a -COOH group attached to a hydrocarbon tail. 
• Non- polar, insoluble in water, soluble in ether, chloroform and ethanol, and are hydrophobic.
• 

Phospholipids:

• 2 fatty acids and a phosphate bonded to a glycerol.
• One end is soluble in water becuase one of the three fatty acid molecules is replaced by a phosphate which is polar and can therefore dissolve in water.
• The phosphate group is hydrophilic which makes the head hydrophilic, although the two tails are still hydrophobic.
• Make up the bilayer in cell membranes.
• Form a double layer with heads on the outside and tails on the inside.
• The centre is hydrophobic so water-soluble products cant easily pass through it. It acts as a barrier to these kinds of substances.

Cholesterol:

• Cholesterol molecules help strengthen the cell membrane by interacting with the phospholipid bilayer.
• The small size and flattened shape allows cholesterol to fit inbetween the phospholipid molecules in the membrane.
• They bind to the hydrophobic tails of the phospholipids, causing them to pack more closely together.
• This helps make the membrane less fluid and more rigid. 

• Amino acids are monomers, proteins are polymers.
• The monomers (amino acids) are all different.
• There are around 20 amino acids.
• Examples are structural proteins, carrier proteins and enzymes.
• Proteins make antibodies.
• They contain N, S, C, H and O.
• Proteins are in muscles (protein fibres overlap as muscles shorten).

• Amino acids are monomers, proteins are polymers.
• The monomers (amino acids) are all different.
• There are around 20 amino acids.
• Examples are structural proteins, carrier proteins and enzymes.
• Proteins make antibodies.
• They contain N, S, C, H and O.
• Proteins are in muscles (protein fibres overlap as muscles shorten).

Amino Acids:

• A dipeptide is formed when 2 amino acids join.
• A polypeptide is formed when more than two amino acids join together.
• Proteins are made of one or more polypeptides.
• All amino acids have the same general structure- a carboxyl group (-COOH) and an amino group (-NH2).
• The difference between different amino acids in the variable R group.
• Amino acids are linked by peptide bonds to form di/ polypeptides.
• A dipeptide is formed by condensation.
• The reverse reaction adds a water molecule to break the peptide bond and is called hydrolysis. 

Primary Structure- The sequence of amino acids in a polypeptide chain.

Secondary Structure- Hydrogen bonds form between the amino acids in the chain. This makes it automatically coil into an alpha helix or fold into a beta pleated sheet.

Tertiary Strcuture- The coiled/ folded chain is often coiled/ folded further. More bonds form between different parts of the polypeptide chain. For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure.

Quaternary Structure- How the polypeptide chains are assmebled if there are more than one. 

Primary Structure- Held together by peptide bonds between amino acids.

Secondary Strcuture- Held together by weak hydrogen bonds that form between nearby amino acids. These bonds create alpha helix chains or beta pleated sheets.

Tertiary Structure- Held together by a few different bonds:

Quaternary Structure- this tends to be determined by the tertiary structure of the individual polypeptide chains being joined together, and can therfore be influenced by all above bonds.

Collagen:

• A fibrous protein that forms supportive tissues in animals, so it needs to be strong.
• Fibrous proteins are tough and rope- shaped.
• They tend to be found in connective tissues like tendons.
• Made of three polypeptide chains that are coiled in a tight strong triple helix.
• The chains are interlinked by strong covalent bonds.
• Minerals can bind to the triple helix to increase its rigidity.

Haemoglobin:

• Haemoglobin is a globular protein with an iron- containing haem group that binds to oxygen, carrying it around the body.
• A globular protein is round and compact.
• They are soluble, so are easily transported in fluids.
• Its structure is curled up so that hydrophilic side chains are on the outside of the molecule and hydrophobic side chains face inwards.
• This makes haemoglobin soluble in water, which makes it good for transport in the blood.

• biological catalysts
• proteins
• suited to one specific reaction only
• affected by PH
• affected by temperature
• affected by lack of metal ions (often found in vitamins)
• able to lower the activation energy barrier of a reaction

Each active site has a particular shape

Each substrate is designed for an enzyme

They fit together like jigsaw pieces