Biological molecules Flashcards
(87 cards)
1
Q
what is a monomer
A
small, single units that act as the building blocks to create larger molecules
2
Q
what is a polymer
A
made up of many monomers, usually thousands, chemically bonded together
3
Q
condensation reaction
A
bonds monomers together through the removal of a water molecule
4
Q
hydrolysis reaction
A
water molecule is added between two bonded monomers, breaking the chemical bond
5
Q
examples of monomers
A
nucleotides, monosaccharides, amino acids
6
Q
examples of polymers
A
polynucleotides (DNA/RNA), polysaccharides (starch), polypeptides (proteins)
7
Q
monosaccharides
A
glucose, fructose, galactose
8
Q
disaccharides
A
maltose (glucose+glucose)
sucrose (glucose+fructose)
lactose (glucose+galactose)
9
Q
polysaccharides
A
starch (alpha glucose)
glycogen (alpha glucose)
cellulose (beta glucose)
10
Q
general formula for a monosaccharide
A
CnH2nOn
11
Q
two structural isomers of glucose
A
alpha glucose and beta glucose
12
Q
alpha glucose
A
has H on top on both sides and OH on bottom on both sides
13
Q
beta glucose
A
H on top and OH on bottom on left
OH on top and H on bottom on right
14
Q
how is a disaccharide formed by condensation reaction
A
H and OH removed from hydroxyl groups on each molecule
15
Q
where is starch found
A
in plants
16
Q
purpose of starch
A
store of carbohydrates - made from excess glucose created during photosynthesis
17
Q
structure of starch
A
made up of alpha glucose
amylose - joined by 1,4-glycosidic bonds resulting in a spiral shaped polymer
amylopectin - joined by combination of 1,4 and 1,6-glycosidic bonds, resulting in a branched polymer
18
Q
properties of starch
A
large and insoluble so doesn’t impact the water potential of a cell nor cause osmosis to occur
amylose - spiral shaped and readily compacted
amylopectin - branched so greater surface area for enzymes to attach to, meaning it is readily hydrolysed back into glucose for respiration
19
Q
where is glycogen found
A
liver and muscle cells
20
Q
purpose of glycogen
A
stored in muscles and the liver to ensure they always have glucose to respire and release energy
21
Q
structure of glycogen
A
made up of alpha glucose
monomers are joined at 1,4 and 1,6-glycosidic bonds
it contains more 1,6-glycosidic bonds than amylopectin and therefore is more highly branched
22
Q
properties of glycogen
A
large and insoluble - doesn’t impact water potential of a cell nor cause osmosis
highly branched - greater surface area for enzymes to attach so is readily hydrolysed into glucose
it is more readily hydrolysed than starch as it is more highly branched - necessary as animals have a higher metabolic rate
23
Q
function of cellulose
A
to provide structural strength to plants
24
Q
where is cellulose found
A
in the cell wall of plants - prevents cells from bursting if they take in excess water
25
structure of cellulose
made up of beta glucose
joined by 1,4-glycosidic bonds
forms straight, unbranched chains which lie parallel to each other
the parallel chains are held together by many hydrogen bonds, forming a fibril
26
properties of cellulose
large and insoluble - doesn't impact water potential nor cause osmosis
very strong - many hydrogen bonds
27
where are polypeptides created
polypeptides synthesised on ribosomes and then further folded and modified in the Golgi apparatus
28
how many amino acids are there
20
29
general structure of an amino acid
central carbon
amine group - NH2
hydrogen atom on central carbon
carboxyl group - COOH
variable group represented by R
30
bonds between amino acids
peptide
31
primary structure of a protein
sequence of amino acids in a polypeptide chain
the order is determined by DNA
the sequence of amino acids determines the final 3D shape and function
32
secondary structure of a protein
bending/folding into alpha helix or beta pleated sheet
hydrogen bonds form between COOH of one amino acid and NH2 of another to hold the secondary structure in place
33
tertiary structure of protein
further twisting/folding to form 3D shape
held in place by hydrogen bonds between R groups, ionic bonds, and disulphide bridges between amino acids that have sulphur containing R groups
34
quaternary structure of a protein
only if the protein is made up of two or more different polypeptide chains
example is haemoglobin which also has prosthetic group haem
35
prosthetic group
non protein group present in a protein
36
how do enzymes act as biological catalysts
they lower the activation energy required for the reaction to occur, therefore speeding up the reaction
37
lock and key model (bad)
suggests that the enzyme is the lock and the substrate is the key that fits in due to complementary shape
forms an enzyme-substrate complex in the active site
38
induced fit model
suggests that the enzyme is not exactly complementary to the shape of the substrate but when the substrate binds, the enzyme active site slightly changes shape to mould around the substrate
the formation of the ESC puts a strain on the bonds in the substrate and therefore lowers the activation energy
39
factors affecting the rate of enzyme controlled reactions
teperature
pH
substrate conc
enzyme conc
inhibitors
40
how does temp affect enzymes
if temp too low, not enough kinetic energy for successful collisions so no ESC
if temp too high, enzymes denature and shape of AS changes so ESC can't form
41
how pH affects enzymes
too high or low interferes with charges in the Aino acids in the active site
this can break ionic and hydrogen bonds holding together the tertiary structure so AS changes shape and ESC can't form
42
how substrate and enzyme conc affects enzymes
if insufficient substrate, reaction slower as fewer collisions between enzyme and substrate
if insufficient enzymes, enzyme AS are saturated with substrate and unable to work any faster
43
competitive inhibitors
same shape as substrate and can bind to AS, preventing the substrate from binding and forming ESC
can be overcome by adding more substrate to out-compete the inhibitor
44
non-competitive inhibitors
bind to enzyme at allosteric site, causing the AS to permanently change shape so substrate can't bind and no ESC formed
cannot be overcome
45
triglycerides
formed via condensation between one molecule of glycerol and three molecules of fatty acids, forming ester bonds
46
saturated fatty acids
only C-C single bonds
47
unsaturated fatty acids
at least one C=C double bond in the fatty acid chain
48
properties of triglycerides
large ratio of energy storing C-H bonds to C atoms - lots of energy stored in molecule
high ratio of H to O atoms - act as metabolic water source and can release water if oxidised (useful for desert animals like camels)
large and hydrophobic - insoluble so don't affect water potential and osmosis
low mass - a lot can be stored without increasing mass and preventing movement
49
phospholipids
made of one glycerol molecule, two fatty acids, and a phosphate group (attached to glycerol)
two fatty acids bond to glycerol via condensation reaction to form ester bonds
50
head and tails of phospholipid
hydrophilic head attracts water as it is charged (phosphate is charged and repels other fats)
hydrophobic tails repels water but will mix with fats
51
properties of phospholipids and formation of bilayer
have two charged regions so are polar
in water they are positioned so their heads are exposed to water and tails are not
this forms a phospholipid bilayer which makes up the plasma membrane around cells
52
reducing sugars test
Benedict's reagent added
bright blue solution --> brick red precipitateadd to sampleheatif colour change of blue to yellow/green/red is observed, then reducing sugar is presentif solution remains blue, no reducing sugar present
53
non reducing sugars
sucrose
can't reduce Cu2+ as the chemical group needed for this is involved in the glycosidic bonds
glycosidic bond must be hydrolysed to give positive test
54
test for non-reducing sugars
first do reducing sugars test then test all remaining blue solutionsmix with HCl and boil (below boiling, there is not enough energy to break the glycosidic bond)cool the solution then add NaOH to make the solution alkaline as Benedict's only works in alkaline solutionsadd Benedict's heatcolour change of blue to yellow/green/red indicated positive result
55
test for starch
add iodine in potassium iodide solution
colour change from orange/brown --> blue/black indicates positive result
56
test for protein
add biuret reagent
colour change from blue --> purple indicates positive result
57
test for lipids
dissolve sample in ethanol and shake and distilled water and shakepositive result is milky white emulsion
58
nucleotide
deoxyribose sugar, nitrogenous base (adenine thymine cytosine or guanine), phosphate group
59
bonds between nucleotides
condensation reaction between deoxyribose sugar and the phosphate group, creating a phosphodiester bond - forms sugar-phosphate backbone
60
bonds between cytosine and guanine
three hydrogen bonds between
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bonds between adenine and thymine
forms 2 hydrogen bonds
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why is complementary base pairing important
helps maintain the order of the genetic code when DNA replicates, reducing the chance of mutations
63
how DNA structure links to function
stable structure due to sugar-phosphate backbone (covalent bonds)
double helix prevents damage
double stranded so semi-conservative replication can occur
weak hydrogen bonds for easy separation of the two strands during replication
large molecule to carry lots of genetic information
complementary base pairing allows identical copies to be made
64
RNA nucleotide
ribose sugar, nitrogenous base (adenine uracil cytosine or guanine), phosphate group
65
comparison of DNA polymer and RNA monomer
DNA contains thymine whereas RNA has uracil
DNA contains deoxyribose whereas RNA has ribose
66
function of RNA
to copy and transfer the genetic code from DNA in the nucleus to the ribosomes
some is combined with proteins to create ribosomes
67
where is mRNA found
created in the nucleus and leaves nucleus to carry the copy of the genetic code of a gene to a ribosome in the cytoplasm
68
why is mRNA used over DNA
DNA is too large to leave the nucleus and would be at risk of being damaged by enzymes
mRNA is shorter so small enough to fit through nuclear pores
mRNA is short lived as it is only needed temporarily to help create a protein so by the time enzymes could break it down, it has already carried out its function
69
structure of mRNA
single stranded
every 3 bases (codons) code for a specific amino acid
70
where is tRNA found
in the cytoplasm only
71
structure of tRNA
it is single stranded and folded in a cloverleaf shape, which is held in place by hydrogen bonds
72
function of tRNA
attach to one of the amino acids and transfer this amino acid to the ribosome to create the polypeptide chain
specific amino acids attach to specific tRNA molecules and this is determined by the anticodon (3 bases on the tRNA which are complementary to the 3 bases on mRNA)
73
rRNA
makes up the bulk of ribosomes (rest is made of protein)
74
difference between DNA and RNA polymer
DNA is larger as it has approx 23,000 genes where RNA has the length of only one gene
DNA is double stranded, RNA is single stranded
75
why is replication semi conservative
one strand of daughter DNA is from parental DNA and one strand is newly synthesised
76
stages of DNA replication
DNA helicase breaks the hydrogen bonds between the complementary base pairs, causing the DNA double helix to unwind
each of the separated parental DNA strands acts as a template
free floating DNA nucleotides within the nucleus are attracted to their complementary base pairs on the template strands
DNA polymerase causes adjacent nucleotides to be joined to form phosphodiester bonds by condensation reaction
77
how is water a polar molecule
oxygen is slightly negative and hydrogen is slightly positive
78
five key properties of water
metabolite - condensation and hydrolysis reactions
solvent - for all chemical reactions
high heat capacity - buffers temperature
large latent heat of vaporisation - cooling effect with loss of water through evaporation (sweating)
cohesion - between water molecules, supporting water columns and provides surface tension
79
structure of ATP
adenosine triphosphate
it has adenine as a nitrogenous bade
ribose sugar
three inorganic phosphate groups
80
how is ATP synthesised
made during respiration from ADP and Pi in a condensation reaction catalysed by ATP synthase
81
how is ATP hydrolysed
into ADP and Pi using ATP hydrolase
one of the bonds between the inorganic phosphate groups is broken in hydrolysis reaction which releases a small amount of energy
82
how does ATP transfer energy to different compounds
the inorganic phosphate released during the hydrolysis of ATP can be bonded onto different compounds (phosphorylation)
83
what properties of ATP make it a suitable immediate source of energy
it is released in small, manageable amounts - no energy is wasted and cells don't overheat from wasted energy
it is small and soluble - easily transported around the cell
only one bond is hydrolysed - energy release is immediate, glucose would need several bonds to be broken
it can be phosphorlyated - makes other compounds more reactive
ATP can't pass out of the cell - cell always has an immediate supply of energy
84
uses of hydrogen ions
to determine pH
85
use of iron ions
compound in haemoglobin
86
use of sodium ions
for co-transport of glucose and amino acids
87
use of phosphate ions
component of DNA and ATP
