Biology (Biological Molecules 1)

Covalent- Atoms share a pair of electrons in outer shell so both outer shells are full

Ionic- Ions with opposite charges have an electrostatic attraction to each other

Hydrogen bonding- electrons in molecule not evenly distributed and so spend more time in one place than another so molecule is polar (has uneven distribution of charge). Weak electrostatic bonds formed between polar molecules

Monomer sub-units

Polymerisation.

polysaccharides- monosaccharide or single sugar polynucleotides- mononucleotides

polypeptides- peptides which are made up of amino acids

Water

Condensation reaction

Water

Hydrolysis reaction

Carbons join to each other to create a back bone along which other elements can join

Organic molecule

Carbon, hydrogen, oxygen and nitrogen

Monosaccharide, disaccharide and polysaccharide

Sweet tasting, soluble, general formula (CH2O)n where n is any number from 3-7 and it can have isomers

All monosaccharides and some disaccharides

A sugar which can give electrons to another chemical

The Benedict's test.

Add 2cm3 of food sample to be tested in a tube in liquid or ground in water form

Add equal volume of Benedict's reagent

Heat mixture for five minutes in gently boiling water bath

If reducing sugar present solution turns orange-brown as when Benedict's reagent (alkaline solution of copperII sulphate) is heated with a reducing sugar it forms an insoluble red precipitate of copperI oxide

Maltose

sucrose

Lactose

Glycosidic

Add 2cm3 of the sample to 2cm3 of Benedict's reagent in a test tube and filter it

Put test tube in gently boiling water for 5 minutes.

If there is no colour change then no reducing sugars are present

Add another 2cm3 of food sample to 2cm3 of dilute hydrochloric acid and place in water bath for 5 minutes

This will hydrolyse any disaccharides present to monosaccharides

Add some sodium hydrogencarbonate solution to a test tube to neutralise acid so benedicts reagent will work. Test pH with pH paper to test solution is alkaline

Redo Benedict's test and solution will now turn orange if non-reducing sugars were there in original sample

Insoluble

Structural support

Alpha glucose

Found in small granules

place 2cm3 of sample in test tube and add a few drops of potassium iodide and shake and it will turn bluey black if starch is present

Seeds and storage organs

Branched or unbranched

In tight wound up coils as a helix meaning it is very compact

The inward pointing OH group form hydrogen bonds which hold the helix in place

Energy storage

Insoluble so no affect of WP of cell

Large so doesn't diffuse out of cell

Compact so lots can be stored in a small space

Forms alpha glucose when hydrolysed which is easily transported and readily used in respiration

Branched form has many ends which many enzymes can act on independently so monomers are released rapidly

No

Glycogen

Shorter chains

More highly branched

As small granules in liver or in muscle cells

Although glycogen stores majority of carbohydrate fat is our main storage molecule

Insoluble so doesn't effect WP of cell or diffuse out

Compact so lots stored in small space

Highly branched so rapidly broken down to glucose monomers used for respiration which is needed for animals as they have a higher metabolic and so respiratory rate than plants

Made of beta glucose monomers

The beta glucose forms straight unbranched chains rather than coils which run parallel to each other so hydrogen bonds can form cross linkages between adjacent chains.

Although one hydrogen bond adds little strength many means cellulose is a good structural material

Grouped into microfibrils which then for parallel groups called fibres

Provides rigidity to plant cells and cellulose cell wall stops cell bursting as water enters by osmosis by exerting inwards pressure to stop any further influx of water

This means cells are turgid and push against each other

This makes plants semi rigid which helps keep stems and leaves in turgid state giving max surface area

Contain carbon, oxygen and hydrogen

Proportion of oxygen to hydrogen and carbon smaller than in carbohydrates

Insoluble in water

Soluble in organic solvents such as ethanol

Triglycerides (fats and oils) and phospholipids

contribute to CM flexibility and transfer of lipid soluble products across membrane

Source of energy as they provide twice then energy of the same mass of carbohydrate and release water

Lipids insoluble in water so used in plants and insects for waxy lipid cuticle which conserve water and mammals produce an oily secretion through sebaceous gland in the skin

Fats slow conductors of heat and retain body heat when stored beneath surface

Insulate mylein sheath around nerves

Protect delicate organs

Oils are liquid fats are solid

They have three fatty acids and each one forms an ester bond with glycerol in a condensation reaction.

The different fatty acids the glycerol is always the same

70 with COOH group at the end

Saturated no C=C double bonds

Mono-unsaturated one C=C bond

Polyunsaturated many C=C bonds

Good source of energy- high ratio of energy storing C-H bonds to carbon atoms

Good storage molecules- low mass to energy ratio so lots of energy stored in little volume especially good for moving animals

Doesn't affect WP in cells- large non polar so insoluble

Good source of water- high hydrogen to oxygen ratio so release water when oxidised

One of the fatty acid molecules is replaced by a phosphate molecule

Phosphate molecules are hydrophillic so a phospholipid has hydrophillic head and hydrophobic tail

Polar

Heads as close to water as possible and tails as far away as possible

Molecules form a bilayer in an aqueous environment- due to hydrophobic tail and hydrophilic head e.g hydrophobic bilayer in a cell

Form gylcolipids used for cell recognition - by combining with carbohydrates

Take dry and grease free test tube

Add 5cm3 of ethanol to 2cm3 of sample

Shake to dissolve lipid in sample

Add 5cm3 of water and shake gently

White colour indicates lipid

Repeat using water instead of sample as a control

Lipids in the sample are finely dispersed in water and light refracts when passing through emulsion from oil to water droplets

Amino acids

100

20

Indirect evidence for evolution

Peptide bond from carbon of carboxyl group to nitrogen from amino group of another. Water made from OH of carboxyl group to H of amino group

Many hundred form polypeptides and the sequence of amino acids in a polypeptide chain forms primary sructure of a protein

DNA

100's of the 20 bases joined in in different sequences make a protein so almost limitless combinations

Lead to change in shape and stop it working as primary structure determines its ultimate shape

NH and C=O groups are either side of the peptide bond and the overall positive NH forms a weak hydrogen bond with the overall negative C=O causing the long polypeptide chain to twist into a 3D alpha helix coil

Twisting and folding of alpha helix to give even more complex and often specific 3D shape

Primary structure

Disulfide bridge- strong and not easily broken

Ionic bonds- between carboxyl and amino groups not in peptide bonds. Weaker than disulfide bridges and easily broken by pH changes

Hydrogen bonds- numerous but easily broken

It allows it to recognise and be recognised by other molecules so it can interact with them specifically due to each protein being distinctive

Can be a number of linked polypeptide chains or non-protein prosthetic groups associated with molecules e.g. iron containing haem group in haemoglobin

The biuret test which detects peptide bonds

Place sample in test tube and add equal volume of sodium hydroxide solution

Add few drops of 0.05% copper(II) sulfate solution and mix gently

Purple colour indicates peptide bonds are present so there's a protein

No proteins if solution stays blue

Globular-metabolic functions

Fibrous- Structural role

Long chains which run parallel to each other and are linked by cross bridges to form very stable molecules

Primary- unbranched polypeptide chain

Secondary- Tightly wound chain

Tertiary- Chain twisted into second helix

Quaternary- three tertiary polypeptide chains wound like rope fibres

Sucrose ans water molecules must collide with enough energy to to alter arrangement of their atoms to form glucose and fructose

Free energy of products must be less than that of substrates

Must have activation energy to begin reaction

Lower them

Metabolic reactions can occur rapidly at normal body temperature

Into a small depression on enzyme called the active site to form enzyme-substrate complex

By temporary bonds formed between certain amino acids of the active site and groups on substrate molecule

The active site forms as the enzyme and substrate interact. The proximity of the substrate s a change to the enzymes environment and so causes a change in the enzyme which leads to a functional active site forming.

The enzyme is flexible and so can mould itself around substrate similar to a glove- general shape stays the same but alters in presence of substrate.

As the enzyme changes shape it puts a strain on the substrate which distorts a bond or bonds lowing activation energy for to break bond

A substrate will only fit the active site of one particular enzyme

Enzymes are specific to reactions they catalyse

The enzyme is considered rigid but other molecules can bind to enzymes at sites other than active site and alter enzymes activity suggesting its shape was altered by molecule. Therefore its structure was not rigid but could be altered

Formation of products

Reduction of substrate

There are less and less products which means less chance for the products to come into contact with the enzymes and also product might get in the way of substrate and stop it reaching active site

Stops when no substrates left so no new product can be produced

Draw a line for the normal then a tangent to the curve then find gradient of that line

Complimentary not the same

Temperature increase increases KE of molecules so they move more rapidly and the substrates and enzyme will collide more often meaning more effective collisions forming more enzyme substrate complexes and increasing the rate of reaction

May cause hydrogen bonds to break in enzyme and change its shape and shape of the active site.

Initially at 45C this will cause reaction to slow as substrate fits less easily and at 60C will stop reaction all together

Denaturing

Permenantly

Would speed up reactions but more food would be needed to maintain temperature

Other proteins apart from enzymes may denature at higher temperatures

At 40*C any further rise e.g. illness may denature enzymes

-log10(H+ concentration)

Change reduces rate of enzymes action or if too large denatures enzyme

Change alters charges on amino acids which make up active site of enzyme

May cause bonds maintaining tertiary structure to break (ionic)

Change in H+ ions affects NH2-COOH bond which makes up protein changing shape of active site

Work even with low enzyme concentration as when it has catalysed one reaction it can do another immediately

Can do many substrates a minute

Increases it proportionally as long as there is an excess of substrates as there are more substrates than the active sites can cope with so increasing enzyme number means excess substrates can now also be acted upon until all active sites are filed with substrates

If enzyme concentration is constant then the rate of the reaction will increase proportionally to substrate increase until all active sites are full and they are working at full capacity

Substances which interfere with the functioning of an active site.

Can be....

Competitive inhibitors-bind to enzyme's active site

Non-competitive inhibitors- bind to enzyme at position other than active site

molecule with a similar shaped to the substrate of an enzyme which allows it to occupy the active site of an enzyme and so it competes with the substrate for available active sites.

Has large effect with low substrate concentration and less with a higher one as the inhibitor is not permanently bound so when it leaves another molecule will take its place and how long it takes for a substrate to get in depends on concentration of inhibitor

penicillin to transpeptidase

They attach to enzyme at binding site not at the active site which alters the shape of the enzyme and so the active site so that the substrate can no longer occupy it so enzyme is non-functional.

Non as substrate and inhibitor are not competing for the same site

A series of reactions in which every step is catalysed by an enzymes laid out in a structured order e.g in a precise sequence on the membrane of a cell organelle inside which the conditions are ideal for the reaction

By using the same chemical as an inhibitor at the start of the metabolic pathway and this is known as end product inhibition

Non- competitive

More will create greater inhibition of an enzyme earlier in the pathway and then less of the chemical will be produced so concentration