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A LEVEL BIOLOGY > 2.1.2 BIOLOGICAL MOLCULES > Flashcards

2.1.2 BIOLOGICAL MOLCULES Flashcards

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1
Q

MACROMOLECULES AND POLYMERS

A
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2
Q

monomer

A

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

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3
Q

polymer

A

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

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4
Q

macromolecule

A

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

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5
Q

condensation reaction

A

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)

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6
Q

Hydrolysis

A

breaks down chemical bond between monomers using a water molecule.

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7
Q

CARBOHYDRATES

A
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8
Q

carbs structure

A

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

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9
Q

uses of carbs

A

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

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10
Q

monosaccharides

A

a repeating sugar unit, monomers that make up larger carbohydrates

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11
Q

glucose

A

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)

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12
Q

glycosidic bond

A

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

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13
Q

The 4 hexose monsaccharides

A

-galactose
-alpha glucose
-beta glucose
-fructose

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14
Q

ribose

A

-pentose monosaccharide
-sugar component of RNA nucleotide

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15
Q

Disaccharides

A

two monosaccharides joined together through condensation

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16
Q

1-4 glycosidic bond

A

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

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17
Q

Maltose

A

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

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18
Q

Sucrose

A

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

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19
Q

Lactose

A

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

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20
Q

Polysaccharide

A

more than two monosaccharides joined together

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21
Q

Starch

A

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

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22
Q

Amylose and Amylopectin

A

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

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23
Q

Glycogen

A

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

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24
Q

Cellulose

A

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

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25
Q

lipids

A

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

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26
Q

triglycerides

A

-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

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27
Q

fatty acids

A

-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

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28
Q

saturated fatty acids

A

-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)

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29
Q

unsaturated fatty acids

A

-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

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30
Q

Phospholipids

A

-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

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31
Q

cholesterol

A

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

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32
Q

functions of cholesterol

A

-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

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33
Q

function of triglycerides

A

-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)

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34
Q

function of phospholipids

A

-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)

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35
Q

Proteins

A
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36
Q

what are proteins made from?

A

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

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37
Q

amino acid structure

A

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

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38
Q

how do amino acids join together?

A

-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)

39
Q

primary structure

A

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

40
Q

secondary structure

A
  • 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)
41
Q

tertiary structure

A

-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

42
Q

quaternary structure

A

-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)

43
Q

Features of globular proteins

A

-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

44
Q

haemoglobin

A

-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

45
Q

Insulin

A
  • 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
46
Q

Amylase

A

-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

47
Q

Fibrous proteins

A

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

48
Q

Collagen

A

• 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

49
Q

Keratin

A

-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)

50
Q

Elastin

A

-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

51
Q

WATER

A
52
Q

STRUCTURE OF WATER

A
53
Q

why is it a dipolar molecule?

A

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

54
Q

what is a polar molecule?

A

has different charges across the molecule

55
Q

how are hydrogen bonds formed?

A

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

56
Q

PROPERTIES

A
57
Q

metabolite

A

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

58
Q

how is water a solvent?

A

-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

59
Q

high specific heat capacity

A

-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

60
Q

high latent heat of vaporisation

A

-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

61
Q

strong cohesion

A

-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

62
Q

importance of water being a solvent

A

-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

63
Q

what is an ion?

A

atom or group of atoms that have an electrical charge

64
Q

inorganic ions

A

doesn’t contain carbon

65
Q

Calcium(ca2+)

A

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

66
Q

sodium(Na+)

A

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

67
Q

potassium(K+)

A

-same as sodium
-activates essential enzymes for photosynthesis

68
Q

hydrogen(H+)

A

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

69
Q

ammonium(NH4+)

A

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

70
Q

nitrate(NO3-)

A

-same as ammonium

71
Q

hydrogencarbonate(HCO3-)

A

-buffer that helps maintain the pH of the blood

72
Q

chloride(Cl-)

A

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

73
Q

phosphate(PO(4)3-)

A

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

74
Q

hydroxide(OH-)

A

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

75
Q

BIOLOGICAL TESTS

A
76
Q

What is qualitative testing?

A

non-numerical, observation based testing

77
Q

The biuret test for proteins

A

-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)

78
Q

The iodine test for starch

A

-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

79
Q

The emulsion test for lipids

A

-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)

80
Q

What are reducing sugars?

A

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

81
Q

Bendict’s test for reducing sugars

A

(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)

82
Q

Benedict’s test for non-reducing sugars

A

-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

83
Q

Test strip for glucose

A

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

84
Q

What is quantitative testing?

A

numerical testing

85
Q

Colorimetry benedicts test for sugars

A

-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

86
Q

biosensors

A

-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

87
Q

TLC

A

-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)

88
Q

What is Rf value?

A

distance of pigment/solvent

89
Q

why is Rf important?

A

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

90
Q

Adhesion in plants

A

-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

91
Q

how to tell what glycosidic bond it is on a diagram

A

-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

92
Q

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

A

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

93
Q

Protease

A

-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

A LEVEL BIOLOGY (21 decks)

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