biology biological molecules

covalent bonding?

atoms share a pair of electrons in their outer shells. as a result the outer shell of both atoms is filled and a more stable compound (molecule) is formed

ionic bonding?

ions with opposite charges attract one another. this electrostatic attraction is known as an ionic bond. these are weaker than covalent bonds

hydrogen bonding?

the electrons within a molecule arent evenly distributed but tend to spend more time at one position. this region is more negatively charged than the rest of the molecule. this molecule with uneven charge is said to be a polar molecule. the negative region and the positive region attract each other, forming a weak electrostatic bond - collectively form strong forces

polymerisation?

when lots of monomers join together to form long chains known as polymers

industrial polymers?

polythene and polyesters

natural polymers?

polysaccharides, polypeptides and polynucleotides

condensation reaction?

in the formation of polymers, each time a new subunit is attached a water molecule is formed

hydrolysis reaction?

polymers being broken down through the addition of water. the water molecules are used when breaking bonds that link the subunits of a polymer, thereby splitting the molecule into its constituent parts

metabolism?

all the chemical processes that take place in living organisms

what does 1 mole contain?

the same number of particles that there is in 12g of carbon12 atoms - 6.022×10²³

whats a molar solution?

a solution that contains one mole of solute in each litre of solution

what are organic molecules?

carbon containing molecules

monomer?

each individual molecule that makes up chains

what elements are polymers and monomers made of mainly?

C, H, N, O

whats the basic monomer in a carbohydrate?

sugar/ saccharide - single monomer = monosaccharide

monosaccharide x 2 =?

disaccharide

monosaccharide x n =?

polysaccharide

general formula of monosaccharides?

(CH2O)n

properties of monosaccharides?

-sweet tasting

-soluble

-3-7 carbons

examples of monosaccharides?

glucose, galactose, fructose

glucose info:

• hexose (6 carbon)

• sugar

• C6H12O6

• 2 isomers - alpha glucose and beta glucose

what is a reducing sugar?

a sugar that can donate electrons to another chemical

test for reducing sugar?

benedicts test (CuSO4) 

• add 2cm³ benedicts reagent to food sample

• heat above 70 degrees C

present result for reducing sugars?

green, yellow, orange, brick red (low to high conc)

glucose x 2 =?

maltose

glucose + fructose =?

sucrose

glucose + galactose =?

lactose

what is removed when 2 monosaccharides join?

water (condensation reaction)

what bond is formed when 2 monosaccharides join?

glycosidic bond

how do you hydrolyse a disaccharide?

add water. it will break the glycosidic bond and release the monosaccharides

how to test for NON reducing sugars?

1. liquidify the sample

2. add 2cm³ of benedicts reagent to 2cm³ sample 

3. place in water bath >70 for 5 mins (no colour change = no reducing sugar present)

4. add 2cm³ HCl and place in water bath again for 5 mins (HCl will hydrolyse any disaccharides)

5. add NaHCO3 until solution is alkaline

6. retest with benedicts reagent (colour change now = non reducing sugar present)

polysaccharide properties:

• insoluble

• suitable for storage/ strength

• break down into di/monosaccharides when hydrolysed

example of polysaccharide?

starch: many alpha glucose molecules joined together

test for starch?

1. 2 drops of iodine solution to food sample and mix gently

presence of starch result?

blue-black

how is starch found in plants?

small grains in seeds and storage organs

whats starch made up of?

chains of alpha glucose monosaccharides linked by glycosidic bonds formed from condensation reactions

what are the chains like in starch

some branched, some unbranched. the unbranched chain is wound into a tight coil → makes compact 

starch properties:

• insoluble → doesnt affect water potential 

• doesnt diffuse out of cells as large and insoluble

• compact

• can hydrolyse to form alpha glucose (easy to transport and use in respiration)

• the branched form has many ends which can be acted on by enzymes simultaneously meaning that glucose monomers are released rapidly

is starch found in animal cells?

no

wheres glycogen found?

animals and bacteria, NEVER plants

whats the difference in structure between starch and glycogen?

glycogen structure has shorter chains and is more highly branched

where is glycogen stored?

as small granules mainly in the muscles and the liver

glycogen properties and structure:

1. insoluble so doesnt tend to draw water into cells by osmosis

2. doesnt diffuse out of cells

3. compact

4. more highly branched than starch and so has more ends that can be acted on simultaneously by enzymes. It is therefore more rapidly broken down to form glucose monomers which are used in respiration - important to animals which have a higher metabolic rate 

how does cellulose differ from starch and glycogen?

made of monomers of B- glucose

cellulose structure and properties:

1. straight, unbranched chains which run parallel to each other, allowing hydrogen bonds to form cross linkages between adjacent chains

2. the mass number of the bonds adds a considerable amount of strength to cellulose, making it a good valuable structure

structure of a cellulose molecule diagram

what do cellulose molecules form when grouped together?

microfibrils, which in turn are arranged in parallel groups called fibres

what does cellulose provide form cell walls?

rigidity. it also prevents the cell from bursting as water enters it by osmosis, by exerting an inward pressure that stops any further influx of water

what is celluloses functions important for?

maintaining stems and leaves in a turgid state so they can provide the max surface area for photosynthesis

what properties do all lipids share?

1. contain carbon, hydrogen and oxygen

2. insoluble in water

3. proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates

4. soluble in organic solvents such as alcohols and acetone

what are the main groups of lipids?

triglycerides and phospholipids

what are the roles of lipids?

1. in cell membranes

2. source of energy

3. waterproofing

4. insulation

5. protection

role of lipids: cell membrances?

phospholipids contribute to the flexibility of membranes and the transfer of lipid-soluble substances across them

role of lipids: source of energy?

when oxidised, lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water

role of lipids: waterproofing?

lipids are insoluble in water and therefore useful as a waterproofing. both plants and insects have waxy, lipid cuticles that conserve water, while mammals produce an oily secretion from the sebaceous glands in the skin

role of lipids: insulation?

fats are slow conductors of heat and when stored beneath the body surface help to retain body heat. they also act as electrical insulators in the myelin sheath around nerve cells

role of lipids: protection?

fat is often stored around delicate organs, like the kidney

fats vs oils storage?

fats: solid at room temp

oils: liquids

why are triglycerides called triglycerides?

3 (tri) fatty acids combined with glycerol (glyceride)

what does each fatty acid form with glycerol?

an ester bond in a condensation reaction

what does hydrolysis of a triglyceride therefore produce?

glycerol and 3 fatty acids

what do differences in triglycerides come from?

the different properties of different fats and oils from the variations in fatty acids

how many fatty acids are there?

>70

what does each fatty acid have?

a carboxyl group with a hydrocarbon chain attached

saturated meaning?

no carbon=carbon double bonds - saturated with hydrogen atoms

mono-unsaturated meaning?

a single double bond

polyunsaturated meaning?

more than one double bond

why are triglycerides a good source of energy?

they have a high ratio of energy storing carbon-hydrogen bonds to carbon atoms

why are triglycerides good storage molecules?

they have a low mass to energy ratio, so lots of energy can be stored in a small volume. this is especially beneficial to animals as it reduces the mass they have to carry as they move

why are triglycerides insoluble in water?

they are large, non polar molecules, meaning their storage doesnt affect osmosis/ water potential as a result

why do triglycerides release water when oxidised?

they have a high ratio of hydrogen to oxygen atoms, providing an important source of water

whats a phospholipid?

similar to a lipid except one of the fatty acid molecules is replaced with a phosphate molecule

what is a phospholipid made up of?

2 parts as fatty acids repel water, while phosphate molecules attract water

whats the head?

a hydrophilic head: interacts with water (is attracted to it) but not with fat

whats the tail?

a hydrophobic tail which orients itself away from water but mixes with fat

what does this mean a phospholipid is called?

polar

what does the polarity of a phospholipid mean?

when placed in water they position themselves so that the hydrophilic heads are close to the water and the hydrophobic heads are far away from the water

what does the phospholipids polarity mean related to its properties?

in an aqueous environment, phospholipid molecules form a bilayer within the cell surface membranes. As a result, a hydrophobic barrier is formed between the inside and outside of a cell

what does the hydrophilic phosphate head help do?

hold at the surface of the cell surface membrane

what does the phospholipid structure allow?

glycolipids to form by combining with carbohydrates within the cell surface membrane

what are glycolipids important in?

cell recognition

what is the lipid test? (steps)

1. take a completely dry and grease free test tube

2. to 2cm³ of sample being tested, add 5cm³ of ethanol

3. shake test tube to dissolve any lipid in sample

4. add 5cm³ of water shake gently

5. a milky white emulsion indicates the presence of a lipid

6. as a control, repeat the procedure using water, which should remain clear

whats the lipid test also known as?

the emulsion test

why does lipids turn cloudy in the test?

the lipid is finely dispersed in the water to form an emulsion. light passing through this emulsion is refracted as it passes from oil droplets to water droplets, appearing cloudy

what are amino acids?

the basic monomer units which combine to make a polymer called a polypeptide

what can polypeptides be combined to form?

proteins

how many of the 100 amino acids identified occur naturally in proteins?

20

what does the fact that the same 20 amino acids occur in all living organisms provide evidence for?

evolution

what does every amino acid have?

a central carbon atom to which are attached 4 different chemical groups

what are these 4 chemical groups?

• amino group (NH2) 

• carboxyl group (COOH) 

• hydrogen atom (H)

• R (side) group) - variety of different chemical groups

whats the general structure of an amino acid?

what is the type of reaction that occurs when amino acids monomers combine to form a dipeptide?

condensation reaction ( water is lost )

how is the water made?

combining an -OH from the carboxyl group of one amino acid with an -H from the amino group of another amino acid

what do the 2 amino acids then become linked by?

a new peptide bond between the carbon atom of one amino acids and the nitrogen atom of the other

how can the peptide bond be broken down to give back its 2 constituent amino acids?

hydrolysis

what is the process by which many amino acid monomers join?

polymerisation- giving a long chain of amino acids called a polypeptide

what does the sequence of amino acids in a polypeptide chain form?

the primary structure of a protein

what is this sequence of amino acids determined by?

DNA

why are there limitless types of primary protein structure?

due to to mass number of possible sequences of the 20 naturally occuring amino acids