2.1.2 BIOLOGICAL MOLCULES

Question 1

MACROMOLECULES AND POLYMERS

Question 2

monomer

Answer 2

small, basic molecular unit that makes a larger molecule i.e glucose

Question 3

polymer

Answer 3

large, complex molecules made up of repeating monomers joined together i.e starch

Question 4

macromolecule

Answer 4

complex molecules with relatively large molecular mass, made up of diff polymers/monomers i.e triglyceride(1 glycerol and 3 fatty acids)

Question 5

condensation reaction

Answer 5

chemical process by which 2 molecules are bonded together to make a larger, more complex molecule with and eliminates a water molecule.
(basis for synthesising important macromolecules/proteins from sub-units)

Question 6

Hydrolysis

Answer 6

breaks down chemical bond between monomers using a water molecule.

Question 7

CARBOHYDRATES

Question 8

carbs structure

Answer 8

polymers made up of carbon, hydrogen and oxygen (formula:Cx(H2O)y)

Question 9

uses of carbs

Answer 9

-substrate for respiration to give energy(mainly glucose)
-storage of energy i.e glycogen/starch
-structural uses i.e cellulose makes up cell wall

Question 10

monosaccharides

Answer 10

a repeating sugar unit, monomers that make up larger carbohydrates

Question 11

glucose

Answer 11

hexose monosaccharide
has two isomers: alpha(OH group below) and beta(OH group above on condensation reaction side only) ABBA
USES: -main energy source in animals/plants(bonds have a lot of energy)
-soluble so can be easily transported, and respiration happens in cytoplasm which is aqueous (it is polar due to H bonds between hydroxyl groups and water molecules)

Question 12

glycosidic bond

Answer 12

a covalent bond between a carbohydrate molecule and a hydroxyl group on another molecule, resulting from a condensation reaction

Question 13

The 4 hexose monsaccharides

Answer 13

-galactose
-alpha glucose
-beta glucose
-fructose

Question 14

ribose

Answer 14

-pentose monosaccharide
-sugar component of RNA nucleotide

Question 15

Disaccharides

Answer 15

two monosaccharides joined together through condensation

Question 16

1-4 glycosidic bond

Answer 16

type of covalent bond
glucose condensation reaction
-carbon 1’s (H) reacts with adjacent carbon 4’s (HO) to form waste water molecule.
form disaccharide

Question 17

Maltose

Answer 17

(malt sugar) is formed from 2 glucose molecules joined together by an alpha 1-4 glycosidic bond.

Question 18

Sucrose

Answer 18

(table sugar) is formed from a glucose and a fructose molecule(hexose monosaccharide) joined together by an alpha 1-6 glycosidic bond.

Question 19

Lactose

Answer 19

(milk sugar) is formed from galactose and glucose joined together by an alpha 1=4 glycosidic bond.

Question 20

Polysaccharide

Answer 20

more than two monosaccharides joined together

Question 21

Starch

Answer 21

STRUCTURE: mixture of two polysaccharides of a-glucose=amylose and amylopectin
-stored as excess glucose by plants=can be broken down when needed for respiration
-insoluble in water so prevents water entering through osmosis and swelling up cell(doesn’t affect water potential)
-helical so compact

Question 22

Amylose and Amylopectin

Answer 22

amylose: coiled , long, unbranched chain of a-glucose
-angles of alpha 1-4 glycosidic bonds give coiled structure–}good for storage as its compact. is soluble in water
amylopectin: straight , long, branched chain of a-glucose that is insoluble in water because it is a large molecule (alpha 1-4 and alpha 1-6 glycosidic bonds) 1-4 create coils and 1-6 create branches
-branches make it easier for enzymes to break down molecules so glucose can be released quickly for respiration
-helical so it can be tightly packed
-long molecule so it cannot cross plasma membrane

Question 23

Glycogen

Answer 23

STRUCTURE: polysaccharide of a-glucose, similar to amylopectin with more side branches, created by high proportion of 1-6 glycosidic bonds (many ends for hydrolysing enzymes to attach)
PROPERTIES:
-compact so main energy store in animals for respiration
-branches release glucose quicker due to free ends
-can’t cross cell membrane because it is too large(good for storage bc it won’t escape cell)
-insoluble(doesn’t affect water potential of cell) so it won’t cause water to move in by osmosis

Question 24

Cellulose

Answer 24

STRUCTURE: long, straight, unbranched chain of b-glucose arranged in layers
-beta 1-4 glycosidic bonds(every second B glucose is flipped so OH’s are adjacent)
-straight chains are linked together by many H bonds to form strong fibres (microfibrils, which together form macro fibrils)
-they make cellulose a good structural support/rigidity for cells
-permeable but doesn’t burst due to strength of cellulose cell wall

Question 25

lipids

Answer 25

macromolecules that contain carbon, hydrogen and oxygen. -NOT POLYMERS= just a mix of different, smaller molecules joined together

Question 26

triglycerides

Answer 26

-made up of one molecule of glycerol with three fatty acid chains -formed through 3 condensation reactions (waste product of 3 h20's) -esterification(type of con reaction) and 3 bonds formed are called ester bonds. -large molecules due to long hydrocarbon chains -non polar(insoluble in water), glycerol is polar but fatty acid chain is not

Question 27

fatty acids

Answer 27

-RCOOH -made up of carboxyl group, hydrocarbon chain(R) and methyl group -bonds in hydrocarbon 'tails’ are non polar so it is hydrophobic= make lipids insoluble in water -high ratio of hydrogens and carbons to oxygens -large due to its long hydrocarbon chains -tail varies in each fatty acid

Question 28

saturated fatty acids

Answer 28

-single bonds between carbons -molecules have many contact points -straight, parallel hydrocarbon chains can be tightly packed i.e solid animal fats -higher melting point(solid) -fully saturated with hydrogen(each carbon linked to a H molecule)

Question 29

unsaturated fatty acids

Answer 29

-at least one double bond between carbons -chain is ‘kinked’ so are not packed close together (fewer contact points) i.e plant oils -lower melting point(liquid) -not fully saturated with hydrogen because the number of double bonds reduces number of hydrogens present -monounsaturated/polyunsaturated

Question 30

Phospholipids

Answer 30

-outward facing hydrophilic head made up of a negatively charged phosphate group(polar) bonded to one molecule of glycerol -head joined by ester bonds to tails -inward facing hydrophobic tails repel water= two fatty acids -makes a bilayer arrangement(oxygen in phosphate group has strong negative charge so polar and non polar regions is equal) -may form oil droplets called micelle or bilayer

Question 31

cholesterol

Answer 31

-hydrocarbon ring structure attached to a hydrocarbon chain -ring has OH group attached to it

Question 32

functions of cholesterol

Answer 32

-to strengthen cell membrane -small, flat shape allows it to fit between bilayer and regulate fluidity -stimulates formation of steroid hormones -formation of bile -Vitamin D synthesis

Question 33

function of triglycerides

Answer 33

-short term energy storage(can be converted into glucose, chemical energy in C-C/C-H bonds) -energy source through respiration(high ratio of H+C:O) -more energy stores in less space(high energy value= low mass: energy ratio) -thermal insulation to reduce heat loss (slow heat conductor) -provide electrical insulation(some are wrapped around nerve cells to prevent escape of electrical impulses) -insoluble (so prevent water swelling the cells and won’t affect water potential) -too big to move across cell membrane -buoyancy for aquatic animals(less dense than water)

Question 34

function of phospholipids

Answer 34

-control movement of molecules -centre of the bilayer repels water-soluble substances from easily passing through -membrane acts as a barrier to those substances -make cell surface membrane flexible(mix of saturated and unsaturated fatty acids) -enable cell recognition(can form glycolipids)

Question 35

Proteins

Question 36

what are proteins made from?

Answer 36

-monomers= amino acid -dipeptide: two joined together -polypeptide: chain of more than two joined together

Question 37

amino acid structure

Answer 37

-amino group -variable region(gives amino acid it’s property) -carboxyl group -made up of C,H,O,N and S

Question 38

how do amino acids join together?

Answer 38

-through a condensation reaction between OH group and H group with water produced -produces peptide bonds(covalent bonds) occurs in RIBOSOMES (hydrolysis occurs in digestive system)

Question 39

primary structure

Answer 39

-sequence of amino acids in a polypeptide chain held together by peptide bonds

Question 40

secondary structure

Answer 40

- H bonds form between amino groups and carboxyl groups= sections coil and fold -coils= alpha helix -folds= beta pleated sheets (H bonds hold amino acids in place)

Question 41

tertiary structure

Answer 41

-determines 3D shape of protein R groups interact dependant on properties: -H bonds form between slightly (+) Rs and slightly (-) Rs -ionic bonds form between (-) Rs and (+) Rs(can hold parts of the polypeptide chain together) -hydrophilic/phobic interactions -disulfide bonds(type of strong covalent bond) between two cysteine molecules

Question 42

quaternary structure

Answer 42

-more than one polypeptide chain(subunit)i.e haemoglobin -determined by tertiary structure of the individual chains joining together to form a larger structure -can also contain prosthetic groups that help the protein carry out its function(conjugated proteins)

Question 43

Features of globular proteins

Answer 43

-spherical and (compact) -soluble in water and easily transported: due to r groups that are attracted to water(hydrophilic) on their surface Hydrophobic amino acids in centre of protein(complementary tertiary structure) -temp sensitive

Question 44

haemoglobin

Answer 44

-carries oxygen around the body in red blood cells made up of 4 polypeptide chains each containing a haem group, 2 alpha and 2 beta subunits * has an attached prosthetic group(inorganic component in a protein) haem(contains iron) * so it's a conjugated protein i.e glycoproteins, lipoproteins * when oxygen attaches to haemoglobin changes quaternary structure making it easier for other oxygen molecules to bind onto haemoglobin

Question 45

Insulin

Answer 45

- regulates blood glucose levels -soluble: can be transported in the blood and diffuse through to the tissues where it acts two polypeptide chains • linked by disulphides bonds • globular protein • hormone • shape of insulin molecule means that it complimentary to target cells

Question 46

Amylase

Answer 46

-enzyme that catalyses the breakdown of starch in the digestive system -made of single chain of AA folds to form a groove along surface(active site) -secondary structure contains alpha helix and beta pleated sheets sections -most enzymes are globular proteins

Question 47

Fibrous proteins

Answer 47

-long tough and rope shaped molecules -insoluble due to hydrophobic R groups -structural proteins and fairly unreactive

Question 48

Collagen

Answer 48

• found in animal connective tissues i.e bone,tendons, muscles and walls of arteries • strong molecule due to structure • forms a triple helix= 3 polypeptide chains wrap around each other in a tightly wound rope •joined together by cross links + form microfibrils due to H bonds • the molecule is staggered so there are no weak spots • third amino acid is glycine which alleos collagen to wrap tightly making it strong

Question 49

Keratin

Answer 49

-found in many external structure of animals i.e skin, hair, nails - flexible/hard and tough due to fibrous shape -insoluble -high proportion of cysteine so have large number of disulfide bonds(very strong)

Question 50

Elastin

Answer 50

-found in elastic connective tissue i.e skin, large blood vessels and some ligaments -elastic so allows tissues to return to original shape due to fibrous shape -long strands with hydrophobic regions that can form cross links and interact so they group together

Question 51

WATER

Question 52

STRUCTURE OF WATER

Question 53

why is it a dipolar molecule?

Answer 53

-covalent bonds share electrons unevenly (-) electrons move away from hydrogen and towards oxygen

Question 54

what is a polar molecule?

Answer 54

has different charges across the molecule

Question 55

how are hydrogen bonds formed?

Answer 55

-between o and h of adjacent molecules slightly (-) oxygen attract the slightly (+) hydrogen of other water molecules

Question 56

PROPERTIES

Question 57

metabolite

Answer 57

-reactant in hydrolysis and photosynthesis -produces in condensation reactions and respiration

Question 58

how is water a solvent?

Answer 58

-dissolves hydrophilic polar molecules because it is polar(positive hydrogen will attract negative ion and negative oxygen will attract positive oxygen) -transport medium: dissolved substances like glucose can be carried around -medium for metabolic reactions: allows ionic compounds to separate

Question 59

high specific heat capacity

Answer 59

-requires LOTS(4.18J) of energy to break the large volume of energy held in H bonds -acts as buffer against rapid temp changes -keeps internal environment of organisms stable and optimum enzyme conditions for aquatic animals

Question 60

high latent heat of vaporisation

Answer 60

-lots of energy required to evaporate to gas because of H bonds -cooling effect: sweat means heat energy transferred to surface and evaporates/ plants release water vapour in transpiration

Question 61

strong cohesion

Answer 61

-the force of attraction between water molecules causing them to bond/stick together strongly and become very dense(surface tension) can transport in continuous columns of water(capillary action) -can become habitat to less dense organisms like pond skaters

Question 62

importance of water being a solvent

Answer 62

-transport medium: dissolved substances like glucose can be carried around -medium for metabolic reactions: allows ionic compounds to separate -organisms can take in minerals -able to dilute toxic substances

Question 63

what is an ion?

Answer 63

atom or group of atoms that have an electrical charge

Question 64

inorganic ions

Answer 64

doesn't contain carbon

Question 65

Calcium(ca2+)

Answer 65

-transmission of nerve impulses and release of insulin from the pancreas -acts a cofactor(non-protein compound required for enzyme activity)

Question 66

sodium(Na+)

Answer 66

-important for generating nerve impulses, for muscle contraction and regulating body fluid balance

Question 67

potassium(K+)

Answer 67

-same as sodium -activates essential enzymes for photosynthesis

Question 68

hydrogen(H+)

Answer 68

-affects pH of substances(more h=more acidic) -important for photosynthesis and respiration

Question 69

ammonium(NH4+)

Answer 69

-important source of nitrogen for plants (used to make amino acids, nucleic acids)

Question 70

nitrate(NO3-)

Answer 70

-same as ammonium

Question 71

hydrogencarbonate(HCO3-)

Answer 71

-buffer that helps maintain the pH of the blood

Question 72

chloride(Cl-)

Answer 72

-'chloride shift' maintains pH of blood during gas exchange -cofactor for amylase -involved in some nerve impulses

Question 73

phosphate(PO(4)3-)

Answer 73

-involved in photosynthesis and respiration reactions -needed for synthesis of many biological molecules i.e phospholipids, nucleotides

Question 74

hydroxide(OH-)

Answer 74

-affects the pH of substances(more OH=more alkali)

Question 75

BIOLOGICAL TESTS

Question 76

What is qualitative testing?

Answer 76

non-numerical, observation based testing

Question 77

The biuret test for proteins

Answer 77

-add a few drops of sodium hydroxide solution to make solution alkaline -add some copper(II) sulfate solution -positive result=blue to purple (detects peptide bonds, if it was just amino acids it wouldn’t turn purple)

Question 78

The iodine test for starch

Answer 78

-add sample to test tube -mix in a few drops iodine dissolved in potassium iodide solution -positive result=brown-orange to blue-black (iodine separates out of solution and binds to the coiled chains of starch) *starch cannot be detected with benedict’s due to the minimal amount of reducing sugar molecules found only at the ends of carbohydrate chains

Question 79

The emulsion test for lipids

Answer 79

-add around 2cm3 of UNFILTERED food sample to test tube(dry and grease free) -Add around 5cm3 of ethanol into sample and shake it -pour solution into around 5cm3 of water -positive result= solution forms a milky emulsion (becomes emulsion because non polar region of lipids form micelles in water and shaking tube makes even smaller micelles and are distributed through water)

Question 80

What are reducing sugars?

Answer 80

sugars that donate electrons or reduce another molecule i.e all monosaccharides and lactose and maltose

Question 81

Bendict's test for reducing sugars

Answer 81

(benedicts is an alkaline solution of cu II sulfate) -grind sample with water -Add Benedict’s reagent to the sample (same volume as original mixture) and gently heat in a water bath for around 5 mins - positive result= blue to brick red/orange brown precipitate -due the addition of electrons to the blue Cu2+ ions reducing them to brick red Cu+ ions(can be green, yellow, orange then brick red)

Question 82

Benedict's test for non-reducing sugars

Answer 82

-confirm it is non-reducing by doing ordinary benedicts (now break down poly/disaccharide to a monosaccharide) -grind up sample and put in test tube with water -boil with a few drops HCl for around 5 mins -Neutralise with a few drops of sodium hydrogen carbonate and use pH paper to check if it is alkaline(benedict’s can’t work in acidic conditions) -Do Benedict’s Test for reducing sugars. -positive result= blue to brick-red

Question 83

Test strip for glucose

Answer 83

-Dip test strip in solution -Colour change will occur if glucose is present -Compare to chart of known colour changes to check for concentration

Question 84

What is quantitative testing?

Answer 84

numerical testing

Question 85

Colorimetry benedicts test for sugars

Answer 85

-make reducing sugar solutions of known concentrations using serial dilution technique -do a benedicts test on each solution + one water test tube(blue to brick red) -select the red filter on the colorimeter - calibrate using a cuvette ¾ filled with distilled water -use pipette to fill the cuvette ¾ with each sample and read the absorbance of light -plot absorbance against known conc in calibration curve to find conc

Question 86

biosensors

Answer 86

-device that uses a biological molecule to detect a chemical -produces a signal which is converted to an electrical signal by a transducer -processed and can be used to work out further info

Question 87

TLC

Answer 87

-Grind up the leaves using a pestle and mortar, with some anhydrous sodium sulphate and then add some propanone as a solvent -Draw a line on the TLC plate(made of silica gel) with a pencil about 2cm from the bottom -pipette some pigment and place in the middle of pencil line(wait till dry and keep going over the spot) -Add a small amount of solvent in a beaker(below pencil line) -mark the solvent front and the pigment spots(might fade)

Question 88

What is Rf value?

Answer 88

distance of pigment/solvent

Question 89

why is Rf important?

Answer 89

-can be compared to a standard value in a database to identify the pigment

Question 90

Adhesion in plants

Answer 90

-when water molecules are attracted to the impermeable walls of xylem tissue -the force of attraction between water and surfaces it is in contact with—> makes water molecules tend to stick to other things

Question 91

how to tell what glycosidic bond it is on a diagram

Answer 91

-count the first molecule’s carbons clockwise and the second inverted - 1-6 bond would be one molecule on top of the other because the 6th carbon is in the CH20H part

Question 92

Why can alcohol dissolve non polar substances like triglycerides and phospholipids?

Answer 92

-has both polar AND non polar regions so can mix with both types of regions

Question 93

Protease

Answer 93

-catalases the breakdown of peptide bonds between amino acids -soluble in water so it is able to diffuse through the cell and bind to its specific substrate