biological molecules Flashcards
(93 cards)
1
Q
what are monomers?
A
the smaller units from which larger molecules are made
2
Q
examples of monomers
A
monosaccharides, amino acids, nucleotides
3
Q
what are polymers
A
molecules made from a large number of monomers joined together
4
Q
examples of polymers
A
polysaccharides, protein, DNA
5
Q
how are polymers formed?
A
via a condensation reaction, which joins 2 molecules, creating a chemical bond and removing water
6
Q
condensation reaction
A
joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water
7
Q
different types of bonds from condensation reactions
A
glycosidic (monosaccharides), peptide (amino acids), ester (fatty acids + glycerol)
8
Q
hydrolysis reaction
A
breaks a chemical bond between two molecules and involves the use of a water molecule
9
Q
what are monosaccharides
A
the monomers from which larger carbohydrates are made
10
Q
examples of monosaccharides
A
glucose, fructose, galactose
11
Q
disaccharides
A
formed by a condensation reaction between two monosaccharides
12
Q
examples of disaccharides and their components
A
glucose+glucose=maltose+water
glucose+fructose=sucrose+water
glucose+galactose=lactose+water
13
Q
polysaccharides def
A
a carbohydrate which contains many monosaccharides bonded together by glycosidic bonds; created by condensation reactions
14
Q
examples of polysaccharides
A
starch, glycogen, cellulose
15
Q
isomers
A
same molecular formula but different structure (alpha-glucose and beta-glucose)
16
Q
starch
A
stores glucose in plants
17
Q
two types of starch
A
amylose and amylopectin
18
Q
structure of amylose
A
formed by a condensation reaction;
long, unbranched helix of alpha-glucose;
forms 1-4 glycosidic bonds;
coils up to form a helix (compact; stores a lot of energy-glucose)
19
Q
structure of amylopectin
A
formed by condensation reaction;
long, branched chain of alpha-glucose;
forms straight chains of 1-4 glycosidic bonds and branches out with 1-6 glycosidic bonds (increases surface area and allows enzymes to work simultaneously and hydrolyse it back into glucose)
20
Q
iodine test
A
add iodine dissolved in potassium iodide to sample
orange-brown–>neg result
blue-black–>pos result
21
Q
glycogen
A
store of glucose in animals
22
Q
structure of glycogen
A
formed from α-glucose;
more branches (1-6 gd bonds) than amylopectin (increases surface area and allows enzymes to work simultaneously and hydrolyse it back into glucose);
large and compact maximising the amount of energy it can store;
insoluble means it will not affect the water potential and cannot diffuse out of cells
23
Q
cellulose
A
for structural strength in plant cell wall
24
Q
structure of cellulose
A
formed from β-glucose;
each alternate glucose is inverted;
formed by many condensation reactions and 1-4 gd bonds;
creates a long, straight chain;
the chains line up parallel to each other, held in place by H bonds which are individually weak, but collectively strong (fibril)
25
test for reducing sugars
1. add 2cm3 of food sample (must be liquid)
2. add 2cm3 of benedicts reagent (copper (II) sulfate)
3. heat mixture gently in water bath for 5 mins
(green/yellow/orange/brick red-positive result)
(blue- negative result)
26
test for non-reducing sugars
if reducing sugar is NOT PRESENT.
1. add 2cm3 of the same food sample and 2cm3 of dilute HCl
2. place in water bath for 5 mins (dilute HCl will hydrolyse the disaccharides and polysaccharides into their constituent monosaccharides)
3. add some sodium hydrogencarbonate to neutralise the test tube (benedicts reagent doesn't work for acids)--> use pH paper to check for neutralisation
4. retest with 2cm3 of benedicts reagent and place in water bath for 5 mins
5. will change to brick-red if non-reducing sugar is present
27
two types of lipids
triglycerides and phospholipids
28
triglycerides
one molecule of glycerol with three fatty acids attached to it (ester bond);
fatty acids are tails that are hydrophobic and insoluble
29
saturated lipids
found in animal fats;
single bonds (C-C)
30
unsaturated lipids
found in plants;
contain carbon-carbon double bonds allows molecule to bend;
cannot pack together tightly and are liquid at room temperature
31
triglycerides properties related to its function
energy storage molecules;
metabolic water source (release water if they are oxidised);
low mass---> a lot can be stored without increasing the mass;
long hydrocarbon tails of the fatty acids contain a lot of chemical energy;
insoluble in water (doesn't affect water potential);
bundle together as insoluble droplets in cells because the fatty acid tails are hydrophobic (the tails face inwards, shielding themselves from water with their glycerol heads)
32
what is a phospholipid
a lipid where one of the fatty acid molecules is replaced by a phosphate group (hydrophilic)
33
what is the difference between hydrophobic and hydrophilic
hydrophobic - repels water
hydrophilic - attracts water
34
properties of phospholipids related to its function
make up the bilayer of the cell membranes;
phospholipid heads are hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side;
the centre of the bilayer is hydrophobic so water-soluble molecules can't easily pass through--the membrane acts as a barrier
35
emulsion test
1. shake sample with ethanol for 1 min and pour the solution into water
2. lipid will show up as a milky white emulsion layer on top
36
proteins
chain of amino acids
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dipeptide
formed when two amino acids join together
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polypeptide
when more than two amino acids join together
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structure of amino acids
carboxyl group (COOH);
an amine/amino group (NH2);
and an R group (unique) attached to a central carbon atom
40
how are dipeptides and polypeptides formed
formed through a condensation reaction, a molecule of water is released, the bonds are called peptide bonds
41
primary structure of a protein
sequence of amino acids in the polypeptide chain
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secondary structure of a protein
hydrogen bonds form between the amino acids in the chain;
coils into alpha-helix or beta-pleated sheet
43
tertiary structure of a protein
the secondary structure is coiled and folded further to form a 3D structure where H bonds, ionic bonds and a disulfide bridge maintains the structure
44
H bonds (tertiary structure)
numerous and easily broken
45
ionic bonds (tertiary structure)
form between the carboxyl and amino groups not involved in the peptide bonds;
weaker than disulfide bridge
46
disulfide bond (tertiary structure)
whenever two molecules of cysteine (amino acid) come close together; the S atom in one cysteine bonds to the S atom in the other cysteine
47
quaternary structure of a protein
the quaternary structure is the way the polypeptide chains are assembled tg
48
biuret test
1. add a few drops of sodium hydroxide solution to make the sample alkaline
2. add some copper (II) sulfate
purple-positive result
blue-negative result
49
enzymes
proteins that speed up chemical reactions by acting as biological catalysts
50
how do enzymes speed up reactions
enzymes lower the activation energy by providing alternative pathway
51
lock and key model
active site is a fixed shape/doesn’t change shape;
it is complementary to one substrate;
after a successful collision, an enzyme-substrate complex forms leading to reaction
52
induced fit model
1. before reaction, enzyme active site not completely complementary to substrate/ doesn’t fit substrate
2. active site shape changes as substrate binds and enzyme-substrate complex forms
3. this stresses / distorts bonds in substrate leading to a reaction
53
how does temperature affect the rate of enzyme-controlled reactions
rate of reaction increases as particles gain more kinetic energy;
leading to more collisions;
if temperature is too high enzymes denature
54
how does pH affect the rate of enzyme-controlled reactions
at very acidic and alkaline pH values the shape of the enzyme is altered so that it is no longer complementary to its specific substrate
55
how does enzyme concentration affect the rate of enzyme-controlled reactions
there are more active sites for the substrates to bind to
however, its only applicable to a certain extent;
at some point, enzyme activity will plateau because there are too many active sites and not enough substrates
56
competitive inhibitors
have a similar shape to substrate;
compete with the substrate molecules to bind to the active site but no reaction takes place
57
what happens when there's a higher concentration of competitive inhibitors
if there's a higher conc of inhibitors, it will take up nearly all active sites and hardly any of the substrate will get to the enzyme
58
what happens when there's a higher concentration of substrates
if there's a higher conc of substrates, the substrates chance of getting to an active site before the inhibitor increases
*increasing substrate conc increases rate of reaction*
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non-competitive inhibitors
they bind to the enzyme away from its active site which causes the active to change shape so the substrate molecules can no longer bind to it
60
what happens when you increase the substrate concentration when non-competitive inhibitors are present
non-competitve inhibitors don't compete with the substrate molecules to bind to the active site because they are a different shape;
inhibits enzyme activity
61
what are DNA and RNA
types of nucleic acid
62
function of DNA
deoxyribonucleic acid;
used to store your genetic info (AGCT)
63
function of RNA
ribonucleic acid;
transfer genetic information from the DNA to the ribosomes (ACGU)
64
nucleotide
*DNA and RNA are polymers of nucleotides*
nucleotides are made from: a pentose sugar (sugar with 5 C atoms) and phosphate group (sugar-phosphate backbone and a nitrogen-containing base (ACGT)
65
polynucleotide structure
nucleotides join tg to form polynucleotides via a condensation reaction between phosphate group of one nucleotide and the sugar of another;
form a phosphodiester bond
66
DNA structure
double-helix;
composed of two polynucleotides joined tg by H bonds between complementary bases;
(a+t, c+g)
67
complementary base pairing
adenine pairs with thymine (2 H bonds)
guanine pairs with cytosine (3 H bonds)
equal amounts of A+T and C+G
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RNA structure
a pentose sugar (sugar with 5 C atoms) and phosphate group (sugar-phosphate backbone and a nitrogen-containing base (ACGU)
69
RNA function
transfer the genetic code from the DNA in the nucleus to the ribosomes
70
difference between DNA and RNA
1. deoxyribose/ribose
2. thymine/uracil
3. double strand/single strand
4. long/short
71
how does DNA replicate?
semi-conservative replication
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what does semi-conservative replication mean?
half of the strands in the new DNA are from the original DNA molecule;
leads to genetic continuity
73
semi-conservative replication (process)
1. DNA helicase breaks the H bonds between bases on the two polynucleotide strands (helix unwinds)
2. each original single strand acts as a template for a new strand; complementary base pairing makes free-floating DNA nucleotides are attracted to their complementary exposed bases from original template strand
3. condensation reactions join the nucleotides of the new strands together catalysed by DNA polymerase; H bonds form between the bases
4. each new DNA molecule contains one strand from the original DNA molecule and one new strand
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semi-convervative
each replicated DNA molecule contains of the original DNA strands and one newly synthesised DNA strand
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conservative
original DNA remains intact following DNA replication and the two newly-synthesised strands of DNA join together
76
meselson+stahl experiment
used 2 isotopes of N to show that DNA replicates using semi-conservative replication
(heavy-15);(light-14)
1. grow 2 samples of bacteria (one in lightN broth and one in heavyN broth)
2. sample of DNA taken from each batch and spun in centrifuge
3. bacteria grown in heavyN broth taken out and put in lightN broth and left for one round of DNA replication
4. DNA settled in the middle, mixture of both heavyN and lightN
77
ATP
adenosine triphosphate;
immediate source of energy for metabolic reactions
78
what is ATP made up of?
one adenine base, ribose sugar and 3 phosphate groups
79
where is the energy in ATP stored?
stored in high energy bonds between the phosphate groups and is released via hydrolysis reactions
80
how is ATP released?
ATP is broken down into ADP and Pi (inorganic phosphate); hydrolysis reaction
phosphate bond in broken down and energy is released; catalysed by ATP hydrolase
81
ATP hydrolysis reaction
ATP+water-->ADP+Pi (energy)
82
how can ATP make other compounds more reactive?
transfers energy to different compounds; the released Pi can be bonded onto different compounds to make them more reactive (phosphorylation);
happens to glucose before respiration to make it more reactive
83
properties of ATP
1. released in small, manageable amounts so energy is wasted (cells do not overheat from wasted energy)
2. small and soluble and can easily be transported around the cell
3. only one bond needs to be broken to release energy (release is immediate)
4. can transfer energy to another molecule by transferring one of its phosphate groups (phosphorylation)
5. cannot leave the cell, always an immediate supply
84
is water polar or dipolar?
dipolar
85
5 properties of water
1. metabolite
2. solvent
3. high specific heat capacity; buffers temperature
4. large latent heat of vaporisation
5. strong cohesion
86
where do inorganic ions occur?
in the cytoplasm and body fluids of organisms, in a range of concentrations
87
hydrogen ions (H+)
lowers the pH of solutions;
impacts enzyme and haemoglobin function
88
iron ions (Fe2+)
binds to haemoglobin to transport oxygen
89
sodium ions (Na+)
involved in the co-transport of glucose and amino acids
90
phosphate ions (PO43-)
component of DNA (forms phosphodiester bonds with deoxyribose);
involved with ATP (makes ADP more reactive)
91
how does the structure of ATP make it a good source of immediate energy?
the bonds between the phosphate groups have a low activation energy; this means they can be easily broken; breaking the bonds releases energy
92
what is the structure of ATP?
a pentose sugar (ribose), a nitrogenous base (adenine) and three inorganic phosphate groups
93
what is the function of ATP?
an immediate source of energy for biochemical processes and synthesis of biological molecules
