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A level biology > 2.1.2 Biological molecules > Flashcards

2.1.2 Biological molecules Flashcards

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1
Q

How does hydrogen bonding occur between polar molecules such as water?

A

the positive and negative regions of the polar molecules interact to form hydrogen bonds = electrons will be shared greater to the elements that has more electrons = electronegative

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2
Q

What is the structure of glycerol?

A

3 carbons bonding to hydrogens with 3 hydroxyl groups

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3
Q

What is a disaccharide?

A

two sugar units joined together

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4
Q

What is the bond called between amino acids?

A

peptide bond

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5
Q

What is the mobile phase in paper chromotography?

A

solvent

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6
Q

What are the properties of water?

A

1) high boiling point
2) denser as a solid
3) high surface tension
4) good solvent
5) good transport medium

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7
Q

How are peptide bonds formed between amino acids?

A

the hydroxyl group group bonds to the hydrogen from the amine group - releasing water and bond forming = condensation reactions

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8
Q

How can be break peptide bonds in amino acids?

A

add water - hydrolysis reaction = occurs by protease enzymes in the digestive system

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9
Q

How do you test for reducing sugars?

A

add a sample to a boiling tube;
add benedicts;
place boiling tube in beaker of boiling water;
leave for 5 mins;
remains blue = no reducing sugar;
colour changes to green/yellow/orange/red = reducing sugar present;

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10
Q

How does water provide transport for organisms such as pond skaters?

A

as water molecules are polar = attracted to each other = cohesion;

the attraction for water molecules means that some organisms can walk on top of water = high surface tension

water molecules attract other materials = adhesion

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11
Q

What is the function of glycogen?

A

storage molecule in animals and fungi;
highly branches;
highly compact;
more compact than amylopectin to store more glucose;
highly branches = more free ends to be added on or removed via condensation or hydrolysis = reactions occur more rapid;
glucose demand meets need of organism;

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12
Q

How do you calculate the Rf value?

A

distance travel by substance/distance travelled by solvent

max Rf value = 1

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13
Q

What are prosthetic groups?

A

non-protein parts of protein = help carry out the proteins role such as haem group in haemoglobin

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14
Q

How are ester bonds broken in triglycerides?

A

by lipase enzymes in digestive system;
hydrolysis reaction occurs;
one glycerol and three fatty acids are released;
three molecules of water needed for hydrolysis to break the ester bonds

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15
Q

How do you test for non-reducing sugars?

A

1) carry out the normal benedict test
2) add unknown solution in test tube and add dilute HCl
3) gently boil for 5 mins
4) add dilute alkali
(benedicts test doesnt work under acidic conditions)
5) add benedict reagent again
6) boil for 5 mins
7) if colour changes to green,yellow,orange,red after breaking glycosidic bond using HCl = present

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16
Q

What are the two types of proteins called?

A

globular and fibrous

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17
Q

What are cuvettes?

A

small cuboid test tubes with 2 transparent sides and 2 sides translucent
transparent sides goes towards the colorimeter

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18
Q

What are the cations you need to know?

A

Ca2+ = nerve impulse/muscle contraction

Na+ = nerve impulse/kidney function

K+ nerve impulse/stomatal opening

H+ = catalysis of reactions

NH4+ = production of nitrate ions by bacteria

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19
Q

What are the formulas and uses for the anions you need to know?

A

NO3- = nitrogen supply to plants

HCO3- = maintenance of blood pH

Cl- = balance positive charge of Na and K in cell

PO43- = cell membrane/ATP

OH- = catalysis of reactions

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20
Q

Why is water denser as a solid than a liquid?

A

this is due to hydrogen bonds
when water is cooled at 4 degrees the hydrogen bonds fix in a position further apart as they would than a liquid = creating a giant, rigid open structure

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21
Q

What are the functions of lipids?

A

1) energy storage
2) insulation
3) cell membrane structure
4) protection (adipose tissue around organs)

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22
Q

What is the structure of fatty acids?

A

one end = carboxylic acid
rest = carbon atoms bonded to hydrogen

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23
Q

How are hydrophobic and hydrophilic and hydrophobic interactions formed in proteins tertiary structure?

A

uncharged R group = hydrophobic = clusters together away from water molecules = hydrophobic interactions (found in the middle of proteins)

charged R groups = hydrophilic = include water molecules (found on the surface of proteins)

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24
Q

What is the structure of haemoglobin?

A

globular protein
four polypeptide chains
2 alpha subunits
2 beta subunits
each subunit contains a prosthetic group = haem
each haem group contains Fe2+ = where O2 binds
= one haemoglobin molecule can bind to 4 oxygen molecules

when O2 attaches to haemolglobin = it changes in quaternary structure = helps more O2 bind easier

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25
Q

What is the structure of enzymes (lysozyme)

A

globular protein
produced in tears and saliva
only react with specific substrate molecules
single polypeptide chain
chain folds to form a groove on the surface = active site

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26
Q

What are the properties and function of collagen?

A

fibrous protein
found in tendons, ligaments and skin
extremely strong due to structure
3 polypeptide chains wrapped together = form a triple helix
every 3rd amino acid = glyceine = (R groups is hydrogen) tightly wrap up together
hydrogen bonds form between the polypeptides

lots of triple helix structures join together to form larger structures = microfibrils and fibrils
molecules are staggered = stronger and no weak spot
crosslinking between the triple helix molecules

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27
Q

What are the properties and function of elastin?

A

fibrous protein
skin = high amount of elastin fibres = skin supple
elastic found in arteries = elastic fibres stretch when blood pulses through artery + recoil in between pulses = return to normal shape
long strands are crosslinked to each other = when stretched they move apart but remain attached at crosslinks = then strands reassociate = highly elastic

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28
Q

What occurs during a benedicts test when a reducing sugar is present?

A

benedicts solution gains an electron forming a 1+ ion = red ppt

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28
Q

What is a reducing sugar?

A

a sugar than can donate electrons to another molecules = all monosaccharides

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28
Q

How does water act as a solvent?

A

it allows for the dissolving and dissociation of substances due to its polar structure
polar solvents such as water can break down polar or ionic solutes

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29
Q

How does a colorimeter work for reducing sugars?

A

red filter is used
the lighter the blue of the benedicts solution = the les red light is absorbed = more is transmitted

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30
Q

What does alpha glucose + alpha glucose form?

A

maltose + water

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31
Q

What does glucose and fructose form?

A

sucrose and water

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32
Q

What is the structure of amylose?

A

amylose consists of long, unbranched chains of alpha glucose subunits
joined together by 1,4 glycosidic bonds

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33
Q

What is the structure if glycogen?

A

glycogen is long, branches chains of alpha glucose subunits
the subunits are joined by both 1,4 and 1,6 glycosidic bonds = branches
more compact than amylopectin = less space for storage

34
Q

What is the function for starch?

A

plant storage molecules because compact = large quantaties can be stored
insoluble = doensnt affect the cells water potential

35
Q

What is the function of cellulose?

A

main structural component in cell walls = high structural strength = by hydrogen bonds between microfibrills = provide support to plant

36
Q

What are the two groups of lipds?

A

triglycerides and phospholipids

37
Q

What is the structure of a triglyceride?

A

glycerol and 3 fatty acids

38
Q

How is a triglyceride formed?

A

one glycerol, three fatty acids = ester bonds = esterification
4 molecules of h20 produces as a condensation reaction occurs

39
Q

Why ate triglycerides used for waterproofing for aquatic birds?

A

non-polar structure = insoluble and hydrophobic = wont dissolve

40
Q

What is the different between a saturated and an unsaturated fatty acid?

A

saturated = single covalent bonds

unsaturated = double covalent bonds

lots of double covalent bonds = polyunsaturated

41
Q

What is the structure of a phospholipid?

A

glycerol, two fatty acids and a phosphate

phosphate group = polar = hydrophilic

rest of phospholipid = non-polar = hydrophobic

42
Q

What do phospholipids do in water?

A

hydrophilic heads near water content, hydrophobic tails away from water content = phospholipid bilayer

43
Q

What is the structure of cholestrol?

A

hydroxyl group = hydrophilic

rest of molecules = hydrophobic hydrocarbon

44
Q

How can cholesterol enter cells?

A

can enter into cell membranes as hydrophilic hydroxyl group interacts with hydrophilic phosphate head = hydrophobic end of cholesterol interacts with the fatty acid hydrophobic tails

45
Q

What is the general structure of an amino acid?

A

amine group, R group , carboxyl group

46
Q

What is the difference between a polypeptide chain and proteins?

A

in order for polypeptide to form protein = fold into a complex 3D shape = carry out its function e.g enzyme, hormone

47
Q

What determines the primary structure of a polypeptide?

A

determined by the DNA sequence of the gene that encodes for that polypeptide

48
Q

What is the secondary structure of the protein?

A

alpha helix or beta pleated sheet

hydrogen bonding occurs due to negative oxygen and positive charge from hydrogen = attraction = polypeptide chain twists and folds

49
Q

What is the tertiary structure of a protein?

A

over 3D shape
really important it folds into correct shape = e.g if active site of enzyme depends on specific tertiary structure = if active site changes = enzyme denatures

50
Q

What is the quaternary structure of a protein?

A

two or more polypeptide chains (subunits) and fit together to form a larger 3D structure

51
Q

What are conjugated proteins?

A

proteins that contain prosthetic group to aid role

52
Q

How are hydrogen bonds formed in proteins tertiary/quaternary structure?

A

amino acids R group is polar = causes attraction = hydrogen bonds = subunits fold into specific shape and 3D structure

53
Q

How are hydrogen bonds broken in proteins?

A

high temperature
pH change

54
Q

How are ionic bonds in proteins formed in tertiary/quaternary structure?

A

charged and uncharged R groups = attract = form ionic bonds = hold different parts of the chain together

55
Q

How are disulphide bonds formed in tertiary structure?

A

sulphur in R groups = form covalent bonds = disulphide bonds

strong = not broken down by high temp and pH changes

56
Q

How do you test for proteins? Results?

A

add sample to test tube
add biuret solution
protein present = lilac
no protein = remains blue

biuret tests for peptide bonds = present = lilac means peptide bond present if negative remains blue = amino acids

57
Q

How do you test for lipids? Results?

A

add sample to test tube
add ethanol and water
add more water
shake
lipid = cloudy/milky emulsion
no lipid = remains colourless

58
Q

What type of test is the benedicts test?

A

semi-quantitative = because all humans perceive colours differently = only can tell approximate amount of reducing sugar present

59
Q

How does a colorimeter work?

A

a colorimeter is a machine that passes light of a specific wavelength through a liquid and measures how much light is absorbed

opposite colour on the colour wheel is used

60
Q

Before using a colorimeter for reducing and non-reducing sugars, what do you need to do?

A

filter the red ppt formed by the Cu+ ion.

61
Q

How do you find the concentration of glucose using a quantitative method?

A

set a colorimeter to red filter
set colorimeter to measure absorption
place cuvette only containing distilled water
set to 0
test all other solutions
plot out calibration curve
work out unknown glucose con

62
Q

What is the structure of an alpha glucose molecule?

A

hydroxyls groups are both at the bottom

63
Q

What are the two polysaccharides of starch?

A

amylose and amylopectin

64
Q

What is the structure of cellulose?

A

cellulose consists of long straight chain of beta glucose subunits;
subunits joined by a 1.4 glycosidic bond;
the beta glucose molecules have to be rotated 180 degrees for 1,4 bonds = causing hydrogen bonds = high strength

65
Q

What is the function of cholesterol?

A

control fluidity of cell membranes

starting point for hormones

make vitamin D

66
Q

What are globular proteins?

A

spherical in shape
soluble in water = surface later contains hydrophilic amino acids;
centre contains hydrophobic amino acids

67
Q

What is the structure of insulin?

A

globular protein
two polypeptide chains = linked by disulphide bonds
insulin binds onto receptor molecules = found on cell membrane of target cells

68
Q

What are the properties and function of keratin?

A

fibrous protein
found in hair, finger nails and skin
strong and insoluble
high proportion of amino acids = cysteine = disulphide bonds = strong covalent bonds

69
Q

How do you test for starch?

A

add iodine
starch present = blue black
no starch = stays brown

70
Q

What is the stationary phase of chromotography?

A

chromatogram

71
Q

What is the structure of a beta glucose monomer?

A

hydroxyl group on opposite sides

72
Q

What elements are in carbohydrates?

A

C, H, O

73
Q

What elements make up proteins?

A

C, H, O, N

74
Q

What elements make up lipids?

A

C,H,O

75
Q

What elements make up nucleic acids?

A

C. H, O, N, P

76
Q

How does water insulate ponds/lakes/rivers?

A

as ice forms a layer on the top, it insulates the water below allowing fish to survive

77
Q

What ate condensation reactions?

A

two molecules combine to form a single molecules with a loss of a molecules = water

78
Q

what does glucose and galactose form?

A

lactose and water

79
Q

What is a hydrolysis reaction?

A

a reaction in which a bond is broken by an addition of a water molecule

80
Q

How many amino acids are there?

A

20

81
Q

What is the name of the gel used in TLC?

A

silica gel

82
Q

Why is it important to handle the TLC with gloves?

A

so the amino acids on you hands don’t contaminate the results

83
Q

How does a biosensor work?

A

detects the presence of a chemical
uses biological chemicals such as enzymes to produce a chemical signal
then converted to a electrical signal by transducer = processed

A level biology (17 decks)

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