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A level biology > 2.1.2 Biological molecules > Flashcards

2.1.2 Biological molecules Flashcards

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
What is the structure of enzymes (lysozyme)
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
26
What are the properties and function of collagen?
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
27
What are the properties and function of elastin?
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
28
What occurs during a benedicts test when a reducing sugar is present?
benedicts solution gains an electron forming a 1+ ion = red ppt
28
What is a reducing sugar?
a sugar than can donate electrons to another molecules = all monosaccharides
28
How does water act as a solvent?
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
29
How does a colorimeter work for reducing sugars?
red filter is used the lighter the blue of the benedicts solution = the les red light is absorbed = more is transmitted
30
What does alpha glucose + alpha glucose form?
maltose + water
31
What does glucose and fructose form?
sucrose and water
32
What is the structure of amylose?
amylose consists of long, unbranched chains of alpha glucose subunits joined together by 1,4 glycosidic bonds
33
What is the structure if glycogen?
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
What is the function for starch?
plant storage molecules because compact = large quantaties can be stored insoluble = doensnt affect the cells water potential
35
What is the function of cellulose?
main structural component in cell walls = high structural strength = by hydrogen bonds between microfibrills = provide support to plant
36
What are the two groups of lipds?
triglycerides and phospholipids
37
What is the structure of a triglyceride?
glycerol and 3 fatty acids
38
How is a triglyceride formed?
one glycerol, three fatty acids = ester bonds = esterification 4 molecules of h20 produces as a condensation reaction occurs
39
Why ate triglycerides used for waterproofing for aquatic birds?
non-polar structure = insoluble and hydrophobic = wont dissolve
40
What is the different between a saturated and an unsaturated fatty acid?
saturated = single covalent bonds unsaturated = double covalent bonds lots of double covalent bonds = polyunsaturated
41
What is the structure of a phospholipid?
glycerol, two fatty acids and a phosphate phosphate group = polar = hydrophilic rest of phospholipid = non-polar = hydrophobic
42
What do phospholipids do in water?
hydrophilic heads near water content, hydrophobic tails away from water content = phospholipid bilayer
43
What is the structure of cholestrol?
hydroxyl group = hydrophilic rest of molecules = hydrophobic hydrocarbon
44
How can cholesterol enter cells?
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
What is the general structure of an amino acid?
amine group, R group , carboxyl group
46
What is the difference between a polypeptide chain and proteins?
in order for polypeptide to form protein = fold into a complex 3D shape = carry out its function e.g enzyme, hormone
47
What determines the primary structure of a polypeptide?
determined by the DNA sequence of the gene that encodes for that polypeptide
48
What is the secondary structure of the protein?
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
What is the tertiary structure of a protein?
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
What is the quaternary structure of a protein?
two or more polypeptide chains (subunits) and fit together to form a larger 3D structure
51
What are conjugated proteins?
proteins that contain prosthetic group to aid role
52
How are hydrogen bonds formed in proteins tertiary/quaternary structure?
amino acids R group is polar = causes attraction = hydrogen bonds = subunits fold into specific shape and 3D structure
53
How are hydrogen bonds broken in proteins?
high temperature pH change
54
How are ionic bonds in proteins formed in tertiary/quaternary structure?
charged and uncharged R groups = attract = form ionic bonds = hold different parts of the chain together
55
How are disulphide bonds formed in tertiary structure?
sulphur in R groups = form covalent bonds = disulphide bonds strong = not broken down by high temp and pH changes
56
How do you test for proteins? Results?
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
How do you test for lipids? Results?
add sample to test tube add ethanol and water add more water shake lipid = cloudy/milky emulsion no lipid = remains colourless
58
What type of test is the benedicts test?
semi-quantitative = because all humans perceive colours differently = only can tell approximate amount of reducing sugar present
59
How does a colorimeter work?
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
Before using a colorimeter for reducing and non-reducing sugars, what do you need to do?
filter the red ppt formed by the Cu+ ion.
61
How do you find the concentration of glucose using a quantitative method?
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
What is the structure of an alpha glucose molecule?
hydroxyls groups are both at the bottom
63
What are the two polysaccharides of starch?
amylose and amylopectin
64
What is the structure of cellulose?
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
What is the function of cholesterol?
control fluidity of cell membranes starting point for hormones make vitamin D
66
What are globular proteins?
spherical in shape soluble in water = surface later contains hydrophilic amino acids; centre contains hydrophobic amino acids
67
What is the structure of insulin?
globular protein two polypeptide chains = linked by disulphide bonds insulin binds onto receptor molecules = found on cell membrane of target cells
68
What are the properties and function of keratin?
fibrous protein found in hair, finger nails and skin strong and insoluble high proportion of amino acids = cysteine = disulphide bonds = strong covalent bonds
69
How do you test for starch?
add iodine starch present = blue black no starch = stays brown
70
What is the stationary phase of chromotography?
chromatogram
71
What is the structure of a beta glucose monomer?
hydroxyl group on opposite sides
72
What elements are in carbohydrates?
C, H, O
73
What elements make up proteins?
C, H, O, N
74
What elements make up lipids?
C,H,O
75
What elements make up nucleic acids?
C. H, O, N, P
76
How does water insulate ponds/lakes/rivers?
as ice forms a layer on the top, it insulates the water below allowing fish to survive
77
What ate condensation reactions?
two molecules combine to form a single molecules with a loss of a molecules = water
78
what does glucose and galactose form?
lactose and water
79
What is a hydrolysis reaction?
a reaction in which a bond is broken by an addition of a water molecule
80
How many amino acids are there?
20
81
What is the name of the gel used in TLC?
silica gel
82
Why is it important to handle the TLC with gloves?
so the amino acids on you hands don't contaminate the results
83
How does a biosensor work?
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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